bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex ratios of American alligators (Crocodylidae): male or female biased?
Authors: Lance Valentine A. , Elsey Ruth M. , Lang Jeffrey W.
Published: February 2006

Recent theoretical papers on temperature‐dependent sex determination in reptiles are based on the assumption that crocodilian populations, particularly adults, are markedly female biased. While there is evidence that some crocodile populations may conform to this expectation, there is no compelling evidence that American alligator populations are female biased anywhere in the species' range. Previous data had indicated that some populations of juvenile and/or adult alligators were significantly male biased. However, these studies were criticized for sampling errors. Adult males typically occupy a different habitat from that of females, and males frequent areas where they are more likely to be caught. In contrast, in juveniles, both sexes occupy the same habitat. We determined the sex ratios of c. 3000 juvenile alligators collected from 11 sites over 6 years in south Louisiana. Our results indicate a significant sex bias (58% male), but variation was evident among samples. Sex ratios varied by year and site, and the interaction of these factors was significant. At one site in one year, there was a female bias (71%), but in no year was there an overall female bias across sites. From this study and earlier reports, we conclude that there is no evidence at present of female‐biased sex ratios in the juvenile and/or adult alligator populations, and consequently, that certain models of temperature‐dependent sex determination in reptiles require re‐evaluation. Furthermore, our data suggest a pattern of differential mortality of females vs males during the first years of life, a pattern consistent with a key prediction of several differential fitness models for the adaptive significance of temperature‐dependent sex determination in reptiles.
Costs of reproduction in introduced female Canadian beavers (Castor canadensis)
Authors: Ruusila Vesa , Ermala Aslak , Hyvärinen Heikki
Published: February 2006

In iteroparous organisms, maximum lifetime reproductive success is achieved through multiple successful breeding attempts. Therefore one of an individual's major life‐history decisions is the allocation of resources between current and future reproduction. We studied the production of foetuses in the introduced female Canadian beaver Castor canadensis in Finland in 1992–93. The number of foetuses produced in 1993 was negatively correlated with the number produced in the previous year, irrespective of female age. Females that bred only in 1993 tended to produce more foetuses in that year than females that had reproduced in both years. However, the total number of foetuses produced was higher in females that had young in both years, stressing the importance of multiple breeding attempts in maximizing lifetime reproductive success. Despite the small size of the founder population in Finland, mean litter size and pregnancy rates were not different from North American populations.
Lace corals (Bryozoa: Phidoloporidae) from Australia and the tropical south‐west Pacific
Authors: Hayward P. J.
Published: February 2006

Twenty‐three species of erect, fenestrate bryozoans belonging to the family Phidoloporidae Gabb & Horn 1862, popularly termed lace corals, are described from the coasts of Australia, Torres Strait and Fiji, and illustrated by scanning electron microscopy. Nine species of Triphyllozoon are re‐examined, including seven originally described by Harmer (1934). Seven new species are described in Reteporella and one each in Schizoretepora and Reteporellina. Of the remaining four species, two species of Reteporellina are reported for the second time since their original description and two first described by MacGillivray (1883) are redescribed from additional materials.
Correlates of population density and body weight of raptors in the family Accipitridae: a comparative study
Authors: Krüger Oliver
Published: February 2006

This study is the first attempt to use both independent contrasts and cross‐genera correlation for the family Accipitridae to see if population density and body weight are associated with other ecological or morphological variables. Using literature data on nine variables for 189 species of 35 genera, significant associations between contrasts in population density and reproductive rate and hunting method were found. Cross‐genera correlation results differed because all morphological variables were negatively correlated with population density while none of these correlations was significant using independent contrasts. Contrasts in body weight were positively correlated with mean prey weight and negatively with range size. Overall, reproductive rate had the highest correlations with population density.
On some veretillid pennatulaceans from the eastern Atlantic and western Pacific Oceans (Anthozoa: Octocorallia), with a review of the genus Cavernularia, and descriptions of new taxa
Authors: López‐González Pablo J. , Gili Josep‐Maria , Williams Gary C.
Published: February 2006

Examination of recent pennatulacean material collected during several cruises off the Atlantic coast of Africa has allowed the taxonomic reassessment of several taxa of veretillid sea pens that were previously poorly known. The holotype of Cavernularia elegans (Herklots, 1858) is redescribed with the result that all previous records of the species from western Africa should be considered incorrect, as the taxon is here considered to be limited in distribution to Japan. A new species of the genus Cavernularia is described and compared with its congeners and a new veretillid genus and species are described. New taxa are based on specimens from western Africa.
Seasonal regression in testicular size and histology in harbour porpoises (Phocoena phocoena, L.) from the Bay of Fundy and Gulf of Maine
Authors: Neimanis Aleksija S. , Read Andrew J. , Foster Robert A. , Gaskin David E.
Published: February 2006

Seasonal regression of testes and epididymides is described for 161 mature harbour porpoises Phocoena phocoena, L. from the Bay of Fundy and Gulf of Maine from June to December 1984–1995. Based on histological appearance and size of gonads, testes are fully active from late June until at least the end of July, spanning the estimated period of conceptions. During testicular regression, spermatocytes and round spermatids disappeared first from the lumina of seminiferous tubules, followed by the gradual disappearance of spermatozoa. Ultimately, all signs of spermatogenesis were absent, but tubules retained an alternating lining of Sertoli cells and spermatogonia. Testicular and epididymal mass, testicular length and seminiferous tubular diameter decreased approximately 3.5, 1.5 and 1.5 times, respectively, from peak production to full regression and this decrease was best described by a quadratic function. During early July when most females are ovulating, all males had active testes; variation in the degree of regression among males increased as the season progressed. This may reflect a trade‐off between the costs of maintaining active testes at 4% body mass and the probability of successful fertilization. Testes are completely regressed during the winter, suggesting that few reproductive opportunities exist during this season. Unlike some other odontocete species, testicular mass of porpoises is a good indicator of breeding season.
Evolution of viviparity in squamate reptiles (Sceloporus spp.): a variant of the cold‐climate model
Authors: Andrews Robin M.
Published: February 2006

An alternative to the cold‐climate model for the evolution of viviparity is that the impetus for the initial transition from oviparity to viviparity is not an increase in the duration of egg retention but a shift in the location of nests to more superficial and thus warmer locations in the soil profile as temperature declines with increasing altitude or latitude. Shallower nest placement, however, would lead to increased egg mortality as a result of physiological stress or predation, and enhanced egg mortality would thus provide the initial benefit of extended egg retention. To test this hypothesis, I examined the thermal biology of three species of Sceloporus lizards living at high altitudes: S. virgatus (1800 m), S. aeneus (2800 m), and S. bicanthalis (3200 m). The oviparous S. virgatus and S. aeneus females laid eggs at depths of 6 and 2 cm, and mean body/nest temperatures were 24.6/25.2 °C and 19.9/20.8 °C, respectively. Because the initial increment in the duration of egg retention is presumably short, females of these oviparous species cannot initially keep their eggs appreciably warmer than they would be in nests. In contrast, mean temperatures of simulated nests (17.6 °C) of the viviparous S. bicanthalis were similar to the 17 °C low temperature threshold for development, and temperatures in some nests fell below freezing at night and rose to lethal levels during the day. Mean body temperatures of S. bicanthalis females were 20.1 °C; eggs retained during the entire developmental period would hatch 17 days sooner than they would if laid in a nest. Extended egg retention at the highest elevation site would thus provide two benefits: reduced mortality of eggs and accelerated development relative to that in a nest. These benefits, however, accrue because of the initial shift of nests from deeper to more superficial depths in the soil profile.
Development of adhesive toe‐pads in the tree‐frog (Phyllomedusa trinitatis)
Authors: Ba‐Omar T. A. , Downie J. R. , Barnes W. J. P.
Published: February 2006

Toe‐pad development in Phyllomedusa trinitatis is described using light microscopy, SEM and TEM. Pad development in forelimbs was slightly in advance of hindlimbs. The first sign of a difference between pad (ventral) skin and dorsal skin occurred at Gosner stage 37 as a convolution of the basal side of the epidermis. By stage 39, pad basal cells were elongated in shape, with highly convoluted basal sides, whereas the dorsal epidermis had a basal layer of cuboidal cells with relatively straight bases. Mucous glands developed from pad epidermis earlier than at the dorsal side, and penetrated deeply into a matrix‐rich dermis with a sparse cell population. Specialization of digit tip shape first became apparent at stage 38, with appearance of the distal circumferal groove. Widening of toe tips occurred at stage 39. Surface cells of the digital pads began to be shed by stage 40, in advance of epidermis elsewhere. Specialized pad surface cells were fully developed by stage 46, the end of metamorphic climax. During growth to adulthood, pads increased in overall area, but pad surface cells did not alter their dimensions. However, pad epidermis did become several cell layers thicker, much more so than in most other species described so far. Pad cells also had a surface area higher than in many other described species. The value of developmental studies in aiding our understanding of the multiple origins of adhesive pads in different anuran lineages is discussed.
Post‐breeding migrations of newts (Triturus cristatus and T. marmoratus) with contrasting ecological requirements
Authors: Jehle R. , Arntzen J. W.
Published: February 2006

Two newt species with contrasting ecological requirements (Triturus cristatus and T. marmoratus) were radio‐tracked after leaving a shared breeding pond in western France. Movements of 30 individuals were recorded over 491 days. During the first terrestrial night, the newts migrated with high directionality up to 137 m to their refuges. Burrows of small mammals were among the favourite refuges. Movements after the first night were mostly underground and over shorter distances (< 6.8 m). Sixty‐four per cent of all tracked newts stayed within 20 m of the pond edge, and migrations were recorded up to 146 m away from the pond. Both species preferred areas with bushes, hedgerows and trees, and avoided pastures and open areas. Migration in the direction of a habitat type characterized by trees and underground shelters was favoured over migrations in other directions. A clear terrestrial niche separation between the two newt species was not observed. The results are discussed in relation to previous findings that T. cristatus supersedes T. marmoratus as a consequence of anthropogenic change to the terrestrial environment, affecting the species differentially.
Limited use of stored energy reserves for reproduction by the tropical loliginid squid Photololigo sp.
Authors: Moltschaniwskyj Natalie A. , Semmens Jayson M.
Published: February 2006

This study sought to determine if the tropical loliginid squid Photololigo sp. stores energy in the form of lipid, carbohydrate or protein for reproductive investment. Individuals were examined for changes in morphometry, mantle muscle structure and concentrations of water, lipid, carbohydrate and protein in muscle tissue and the digestive gland, associated with the stage of reproductive maturation. Muscle mass was affected by reproductive maturation in females. Mature individuals were lighter for their length compared with females in the early stages of maturation. Concentrations of lipid and carbohydrate in the muscle tissue were very low, and female Photololigo sp. showed equivocal evidence of declining lipid and carbohydrate levels with egg production. There was no evidence of dramatic changes in protein concentration in the mantle muscle with reproductive maturation. Male Photololigo sp. showed a change in the digestive gland with maturation, with water content increasing and protein concentrations decreasing. The digestive gland of both male and female Photololigo sp. increased in size and contained less water with growth. There was little evidence that the storage and transfer of energy for reproduction occurred in Photololigo sp. Instead, it is probable that energy for reproduction is predominantly sourced directly from consumed food.
Interspecific differences in prey captured by associating saddleback (Saguinus fuscicollis) and moustached (Saguinus mystax) tamarins
Authors: Smith Andrew C.
Published: February 2006

The present study provides comparative data on the types and microhabitats of animal prey captured by associating saddlebackSaguinus fuscicollisand moustachedSaguinus mystaxtamarins. The main prey items were katydids (Tettigoniidae, Orthoptera), stick grasshoppers (Proscopiidae, Orthoptera) and spiders (Araneida), although lizards (Squamata) and frogs (Anura) were also taken. The tamarins foraged for, and captured prey from, significantly different substrates. This resulted in a significant partitioning of the prey spectrum between the two species. Sylvan katydids (Pseudophyllinae) accounted for most of the prey of both species, but the moustached tamarins captured more bush katydids (Phaneropterinae) than the saddlebacks. The degree of dietary overlap was less for animal prey than the plant‐based portion of the tamarins' diet.
Population density and adult sex ratio of the tortoise Testudo hermanni in Greece: evidence for intrinsic population regulation
Authors: Hailey A. , Willemsen R. E.
Published: February 2006

The idea that the size of animal populations may be regulated by factors intrinsic to them, such as behaviour, has a long history in ecology. Although this idea is now rejected as a general mechanism, it may apply in some species where females are damaged during courtship attempts, such as the Mediterranean tortoise Testudo hermanni. The sex ratios (adult males: adult females) of most dense Greek populations were more extreme (over 1.5:1) than could be accounted for by the earlier age at maturity of males, and some ranged to over 6:1. The sex ratio was correlated with the population density of adult males and the frequency of courtship attempts on females, and negatively correlated with the longevity of females. A high population density of males limits the density of adult females. This intrinsic regulation of population size is a consequence, rather than a goal, of a particular type of courtship behaviour (persistent thrusts by the male using a tail with a sharp terminal spur) in T. hermanni. Existing population densities at many Greek sites are probably unnaturally high, owing to the reduction of natural predators.
Influence of landscape and land‐use on the distribution of breeding birds in farmland in eastern England
Authors: Mason C. F. , Macdonald S. M.
Published: February 2006

The relationships between landscape, land‐use and the number of territories of eight species of birds, most with declining populations, were studied over 3 years in an area of largely arable agriculture in eastern England. Two species, skylark Alauda arvensis and yellow wagtail Motacilla flava, established territories within crops. More than half of skylark territories were in autumn‐sown cereals, but densities were higher in set‐aside and spring‐sown crops, while a conservation grassland cut for hay in late July held the highest density. Skylarks did not switch territories in winter cereals for other crops as the breeding season progressed. Weak preferences were found for spring‐sown crops and weak avoidance of autumn‐sown crops (i.e. there were fewer territories than expected from the area under autumn‐sown crops). Skylarks showed preferences for set‐aside and conservation grassland but other grassland was avoided. Skylark numbers were negatively associated with hedgerow length within tetrads. Most yellow wagtails nested in spring‐sown crops, especially potatoes, for which there was a strong preference; most territories were in the largest fields. More than 75% of territories of turtle dove Streptopelia turtur were associated with residential areas, scrub and woodland, with hedges used much less often than expected from their occurrence. Grass was a strongly preferred land‐use. Linnets Carduelis cannabina were mainly located in small areas of scrub and there was an association with winter oil‐seed rape. Common whitethroats Sylvia communis showed preferences for hedges, especially for tall hedges, though many territories were situated in field boundaries with only scattered shrubs. Lesser whitethroats S. curruca preferred only tall hedges. Both species had more territories adjacent to grass than expected, with common whitethroat also showing a preference for winter oil‐seed rape. Yellowhammers Emberiza citrinella declined over the 3 years of the study. Territories were strongly associated with tall hedges, but preferences for crops were weak. The small number of reed bunting E. schoeniclus territories were almost all by water, with a preference for adjacent grass. Possible mechanisms for reversing the downward trends of bird populations on farmland are discussed.
Sperm length is heritable and sex‐linked in the yellow dung fly (Scathophaga stercoraria)
Authors: Ward Paul I.
Published: February 2006

Sperm length varies considerably amongst closely related species and the variation can be positively related to interspecific variation in the risk of sperm competition. In addition, a comparative study has shown that traits involved in sexual selection may often be sex linked. This study examined the quantitative genetics of sperm length in the yellow dung fly Scathophaga stercoraria (L.). There was a significant heritability of sperm length, h2= 0.673. In addition, a significant non‐linear epistatic interaction between determinants on the X chromosome and on the autosomes was identified in a three‐generation breeding experiment. The ratio of the additive to epistatic components was approx. 5: 1, though this is probably an overestimate, and the total proportion of the variance in sperm length accounted for by these genetic factors was > 80%. I argue that selection acting in both males and females is relevant for the evolution of this trait.
A comparative study of ultrasound‐triggered behaviour in tiger beetles (Cicindelidae)
Authors: Yager David D. , Cook Aaron P. , Pearson David L. , Spangler Hayward G.
Published: February 2006

This study examines the behavioural responses to ultrasound in 52 species from the family Cicindelidae using both tethered flight and non‐flight assays. Tethered flying tiger beetles respond to trains of bat‐like ultrasonic pulses with a short‐latency, multi‐component behaviour. There was no variation in the nature of the behavioural responses regardless of geographical distribution or phylogenetic position. Lowest mean behavioural thresholds lie predominantly between 30 and 45 kHz. Sensitivity, however, varies widely, and several species do not respond at all in these assays. The lowest thresholds for responders are most often between 70 and 80 dB SPL. Almost all subgenera of North American tiger beetles in the genus Cicindela have at least some species with low‐threshold acoustic behaviour. The single exception is the large subgenus Cicindela where all species are completely unresponsive or have very high thresholds. There was little relationship between habitat and responsiveness to ultrasound, but there is a strong correlation with seasonal activity – species with adults active in the spring and autumn (all in the subgenus Cicindela) do not show ultrasound‐triggered behaviour whereas summer‐active species generally do. Superimposing these data on a current phylogeny of the North American tiger beetles suggests that acoustic behaviour (and hearing) is a shared primitive trait among the taxa examined here and that there have been at least five independent losses of this character.
Differential microdistributions and interspecific interactions in coexisting native and introduced Gammarus spp. (Crustacea: Amphipoda)
Authors: MacNeil Calum , Prenter John
Published: February 2006

In Northern Ireland, the native Gammarus duebeni celticus and introduced Gammarus tigrinus occur in the same river and lake systems. This study examined the outcome of encounters between the two amphipod species in the same patch of lake/pooled area of river. A laboratory simulation of a lake/river habitat indicated that G. d. celticus and G. tigrinus differed in distribution within the same complex habitat. Cannibalism was low for both species in single and mixed species treatments. However, G. tigrinus suffered heavy intraguild predation (IGP) from G. d. celticus in mixed species treatments, with 22% of the laboratory population of G. tigrinus being eliminated within 4 days. There was negligible reciprocal predation of G. d. celticus by G. tigrinus. It is proposed that IGP may account for G. tigrinus occurring more frequently and in greater abundance in patches of lotic and lentic systems where predatory G. d. celticus is absent or scarce.
Food selection by beavers (Castor fiber albicus) in relation to plant chemicals and possible effects of flooding on food quality
Authors: Ganzhorn Jörg U. , Harthun Mark
Published: February 2006

The goal of this study was to investigate whether or not beavers Castor fiber albicus improve the quality of their food plants by dam construction, resulting in periodic flooding associated with the deposition of mud and nutrients on their feeding grounds. For this, food selection of beavers was studied in relation to plant chemicals in the Spessart mountains (central Germany). The concentrations of the preferred plant chemicals were compared between individuals of the same plant species growing in areas that were flooded periodically and areas that were edaphically dry. Plants eaten by beavers contained higher concentrations of nitrogen and lower concentrations of neutral detergent fibre and hemicellulose than neighbouring plants that were not eaten. Neither nitrogen concentrations nor neutral detergent fibre contents differed significantly between plants from the dry and wet sites. Thus, beaver activities did not improve the chemical quality of their food plants.
Individual signatures in scent gland secretions of Eurasian deer
Authors: Lawson R. E. , Putnam R. J. , Fielding A. H.
Published: February 2006

Evidence for individuality of odour profile, coding for individual identity, was sought in scent profiles derived from natural secretions of the preorbital gland of red deerCervus elaphus(n= 26), sika deerC. nippon(15), fallow deerDama dama(50), Chinese muntjacMuntiacus reevesi(23) and Chinese water deerHydropotes inermis(53); from metatarsal secretions from red deer (n= 35), sika (30), fallow (193) and roe deerCapreolus capreolus(26), and from roe deer interdigital glands (n= 48). Volatiles were eluted from sample materials at body temperature, to restrict analysis to those elements that would occur within the natural odour signal; the different volatile elements were then separated by gas chromatography. For each species considered, secretions from at least one scent gland were individually distinct and sufficiently complex to code for identity. Within our samples no two individuals produced identical odour profiles; yet in analysis of metatarsal gland secretions of individual fallow deer sampled in successive years, odour signatures of individuals remained consistent over time. The wider potential for individual coding was assessed through calculation of the number of different possible combinations of all volatiles recovered in any species×gland system. Every secretion considered seems to have the potential to provide individually characteristic signals (with the exception of secretions from the fallow deer preorbital gland, which notably contained no odour information under any analytical system). Complexity of signals differed markedly between species as did the gland‐type responsible for production of the most complex or distinctive signal. No simple evolutionary patterns are apparent to account for this variation and we suggest that the form of gland selected for production of a signal carrying information about individual identity is a function of habitat type and sociality.
Between‐year differences in the feeding ecology of highland marmosets (Callithrix auritaandCallithrix flaviceps) in south‐eastern Brazil
Authors: Corrêa H. Kátia M. , Coutinho Paulo E. G. , Ferrari Stephen F.
Published: February 2006

The behaviour of free‐ranging groups ofCallithrix auritaandCallithrix flaviceps, small‐bodied omnivorous marmosets, was monitored at two sites (Cunha and Caratinga, respectively) in south‐eastern Brazil during equivalent periods in consecutive years. Quantitative behavioural data were collected using a standard scan‐sampling protocol, with scans being taken at 5‐min intervals throughout the daily activity period. Data were collected during the wet season months of January and February at Cunha in 1993 and 1994, and during the dry season months of July and August at Caratinga in 1985 and 1986. In both cases, wet‐season precipitation levels were considerably higher during the first year. Activity budgets, daily ranging and the foraging behaviour of both species were compared between years. Significant between‐year differences were observed in several behaviour categories in both species, and were consistent with seasonal and longitudinal variation in resource abundance. InC. aurita, apparent changes in fruiting patterns resulted in a significant increase in exudate feeding in the second year, both in relative and absolute terms, but little change in prey foraging. By contrast, a marked reduction in arthropod prey in 1986 resulted in major changes in most aspects ofC. flavicepsbehaviour, with the exception of plant feeding. While consistent with behaviour patterns in other marmoset species, the numerous significant differences observed in the present study further highlight the problems associated with the evaluation of intertaxon differences in the behaviour and ecology of primates, in particular marmosets, on the basis of relatively short‐term studies of a few individuals, often at only a single study site.
Daily and seasonal activity of the mountain tapir (Tapirus pinchaque) in the Central Andes of Colombia
Authors: Lizcano Diego J. , Cavelier Jaime
Published: February 2006

Daily and seasonal activity of the mountain tapir Tapirus pinchaque was measured along trails and at two salt licks in mature and secondary montane forests of the Central Andes of Colombia using active and passive infrared monitors. Daily activity of the mountain tapir showed a clear bimodal pattern, with maxima during the early hours of the day (5:00–7:00) and early hours of the evening (18:00–20:00). This bimodal activity pattern has also been found in radio‐tracking studies of T. terrestris and T. bairdii. Overall, there was more activity in mature than in secondary forest and at lower (3100 m) than higher altitudes (3600 m). Night‐time activity was higher during full moon than during quarter and new moons. There was no correlation between monthly rainfall and seasonal activity. The time the mountain tapir was at the salt licks varied between 1 and 190 min. Daily activity at Quebrada Paraiso salt lick (3400 m) showed a clear bimodal pattern with maxima around midnight (0:00–2:00) and midday (11:00–14:00). These patterns of diurnal and nocturnal activity of the mountain tapir could be used in combination with future radio‐tracking studies to better understand habitat use by this species.
Pituitary sensitivity to exogenous GnRH in giant Zambian mole‐rats, Cryptomys mechowi (Rodentia: Bathyergidae): support for the ‘socially induced infertility continuum’
Authors: Bennett N. C. , Molteno A. J. , Spinks A. C.
Published: February 2006

The giant mole‐rat Cryptomys mechowi exhibits an extreme reproductive division of labour. Reproduction in the colony is restricted to a single breeding pair. Non‐reproductive individuals do not breed unless removed from the colony and paired with unfamiliar conspecifics. Circulating basal concentrations of luteinizing hormone (LH) as well as LH levels measured in response to a single exogenous gonadotropin hormone (GnRH) challenge are not significantly different between the reproductive and non‐reproductive groups of either sex. Neither non‐reproductive males nor females are physiologically suppressed at the level of the pituitary, as they do not exhibit a reduced pituitary secretion of LH or decreased sensitivity to hypothalamic GnRH. Rather, reproductive skew seems to result from an inhibition to mate with familiar conspecifics. Familiar individuals housed in the absence of the breeding pair did not breed, whereas pairing unfamiliar individuals of the opposite sex resulted in sexual activity and recruitment. The results from the giant mole‐rat suggest that reproductive skew may result from a predominantly behavioural repression in non‐reproductive females arising from an incest avoidance mechanism.
Plasma fatty acids, triacylglycerol and cholesterol of the tuatara (Sphenodon punctatus punctatus) from islands differing in the presence of rats and the abundance of seabirds
Authors: Blair T. A. , Cree A. , Skeaff C. M.
Published: February 2006

Northern tuatara Sphenodon punctatus punctatus survive on about 26 islands off the north‐east coast of the North Island, New Zealand. These rare, lizard‐like reptiles include seabirds in their diet. The presence of the Pacific rat Rattus exulans on some islands has been implicated in the decline of tuatara populations through predation and competition for food. Pacific rats and tuatara eat similar dietary items, including seabirds. Seabirds have high levels of the long chain n‐3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The potential contribution of seabirds to the diet of tuatara was investigated by measuring the composition of plasma fatty acids and the concentrations of triacylglycerol and cholesterol of adult tuatara from Green Island (rat‐free, numerous seabirds) and Coppermine Island (rat‐inhabited, relatively few seabirds). The composition of plasma fatty acids differed between islands and sexes. Specifically, tuatara from rat‐free Green Island had higher levels of the long chain PUFAs arachidonic acid, EPA and DHA compared to tuatara on rat‐inhabited Coppermine Island, and males had significantly higher levels of DHA than females on both islands. Concentrations of plasma triacylglycerol and cholesterol were higher in tuatara from Green Island than Coppermine Island. Males had higher cholesterol but lower triacylglycerol concentrations than females. Differences in fatty acid composition and lipid concentrations between groups of tuatara imply differences in diet. Tuatara on the rat‐free island evidently had a higher intake of n‐3 PUFAs compared with tuatara on the rat‐inhabited island. This is probably due to higher seabird consumption, or perhaps to the presence of other dietary items containing EPA and DHA. High concentrations of plasma triacylglycerol and cholesterol may be the result of a high intake of insect larvae. We recommend the direct investigation of the diets of northern tuatara and the consequences of differences in the composition of plasma fatty acids for reproduction.
Foraging behaviour of Cape clawless otters (Aonyx capensis) in a marine habitat
Authors: Somers Michael John
Published: February 2006

The foraging behaviour of Cape clawless ottersAonyx capensiswas investigated. Factors included: duration of dives, recovery times, processing times, hunting success, per cent time at the surface, and time foraging before each catch. Observations were made during the day on solitary adultA. capensisin a marine environment in False Bay, South Africa. There were significant differences in duration of unsuccessful dives, recovery times, and processing times as well as successful dives with various depths.Aonyx capensisprefer hunting at depths of 0.5–1.5 m. This is despite having a higher hunting success, catching larger, more energy‐rich prey (fish), and shortest time foraging per catch, at depths of 1.5–2.5 m. Some of the data presented support the optimal breathing hypothesis, which predicts that both surface and dive times should increase for dives of greater depths. However, diving efficiency does not decrease with increasing depth, and percentage time at the surface does not increase with increasing depth. These are contrary to the optimal breathing hypothesis.
Embryonic and larval development of a substrate‐brooding cichlid Cichlasoma dimerus (Heckel, 1840) under laboratory conditions
Authors: Meijide F. J. , Guerrero G. A.
Published: February 2006

There is a vast literature on the reproductive behaviour of cichlid fishes, most of which describes spawning strategies and parental care. However, descriptive information on the early development of cichlids is scarce. In this study, embryos and larvae of laboratory‐reared Cichlasoma dimerus are described. The early ontogeny is documented from oocyte activation until the beginning of the juvenile period. At a water temperature of 25 ± 0.5 °C and a 12:12 h photoperiod, cleavage is finished in 10 h and the first somites appear at 26 h of development. The larvae hatch during the beginning of the third day and are deposited by both parents in a pit they have dug out in advance. Yolk‐sac larvae present three pairs of adhesive glands over the head, these transient larval organs being characteristic of substrate‐brooding cichlids. After another 5 days, the fry swim freely and begin to feed exogenously. Since the yolk‐sac is not completely reabsorbed until 2 or 3 days later, there is a period of combined endogenous and exogenous food supply. The juvenile stage is reached on the 42nd day from spawning.
Ecomorphological patterns related to migration: a comparative osteological study with passerines
Authors: Calmaestra Ricardo G. , Moreno Eulalia
Published: February 2006

An analysis of forelimb and hindlimb skeletal morphology of 15 passerine genera was performed to investigate the likely existence of an ecomorphological pattern relating morphology to migratory behaviour. Each genus was represented by a pair of species, one being sedentary and another migrant. Using a phylogenetic comparative method we found migrant species having longer sternum, deeper keel and longer coracoids than non‐migrant species. Hindlimb morphology was not related to migration. These results are interpreted as adaptations for migrants favouring flight ability, as the larger the sternum and the coracoids the greater the surface available for attachment of the main muscles involved in active flight.
Interplay between acclimation time and diet quality on basal metabolic rate in females of degus Octodon degus (Rodentia: Octodontidae)
Authors: Veloso Claudio , Bozinovic Francisco
Published: February 2006

The effect of diet quality on basal metabolic rate (BMR) over time was studied in female Octodon degus. Degus fed on a low‐quality diet maintained a constant BMR over time, while those fed on a high‐quality diet showed an increased BMR after 30 days. After 120 days of dietary acclimation, individuals fed on a high‐quality diet exhibited comparatively higher BMRs. Thus, we hypothesize that when environmental food quality is high, degus are able to increase their BMR quickly, allowing high rates of biosynthesis.
Body weights in grey and red squirrels: do seasonal weight increases occur in conifer woodland?
Authors: Lurz P. W. W. , Lloyd A. J.
Published: February 2006

Seasonal body weight changes were investigated in red and grey squirrels in spruce‐dominated conifer plantations in the north of England. Annual seed food availability, particularly in the spruce plantations, varies markedly and is characterized by years with large cone crops (‘mast crops’) followed by several years of intermediate or low crops. The last mast crop in Kielder Forest District occurred in 1991 and we studied the two squirrel species when food availability was intermediate and low between 1992 and 1999. Neither red nor grey squirrels in the conifer plantations significantly increased their body weight for the autumn or winter. The responses of red and grey squirrels to the different foraging conditions in deciduous and conifer woodlands and the accumulation of seasonal fat stores may have to be seen in the context of habitat type and the pattern and predictability of seed availability. Our findings suggest that fat accumulation is likely to be less pronounced in conifer habitats where autumn and winter food supplies are more predictable, and manoeuvrability to feed on cones in the canopy is important.
Allozyme variation in the Eurasian badgerMeles melesin Denmark
Authors: Pertoldi Cino , Loeschcke Volker , Madsen Aksel Bo , Randi Ettore
Published: February 2006

Genetic diversity in four populations of the Eurasian badgerMeles melesfrom Denmark was estimated by allozyme electrophoresis. Low genetic variability was found within populations as compared to the variability found in badger populations from other countries, whereas significant genetic differentiation was found between populations. The low genetic variability and the differentiation between populations is explained by the fragmentation of the Danish landscape, which reduces the effective population size of local populations and the gene flow between them. Low genetic variability found for Danish badgers also supports the hypothesis of a rapid recolonization following the last glaciation.
Varieties of attention in neutral trials: Linking RT to ERPs and EEG frequencies
Authors: Jongen Ellen M.M. , Smulders Fren T.Y. , van Breukelen Gerard J.P.
Published: February 2006

It is often assumed that when a neutral cue is presented in a spatial cueing task, attention remains at fixation until target onset. We hypothesized that variance in nonspatial attention and switches of attention toward target locations can account for variance in reaction times of neutral trials. Lateralized event‐related potentials (ERPs) and changes in electroencephalogram (EEG) frequency bands served as predictor variables in a single‐trial logistic regression analysis to predict the direction of spatial attention in cued and neutral trials. The contingent negative variation (CNV) and nonlateralized changes in the alpha band served as markers of nonspatial attention. The direction of attention in cued trials was reliably predicted from single‐trial lateralized ERP components. In neutral trials, only evidence for nonspatial attention was found, indicated by increases in the CNV and decreases in alpha preceding targets to which responses were relatively fast.
Reduced baroreflex cardiac sensitivity predicts increased cognitive performance
Authors: Yasumasu Tomiya , Reyes del Paso Gustavo A. , Takahara Kazuo , Nakashima Yasuhide
Published: February 2006

This study evaluated the relationship between baroreceptor reflex sensitivity and cognitive performance. Twenty normal subjects performed the Uchida–Kraepelin test, a serial arithmetic task. Baroreceptor reflex sensitivity during a 5‐min Uchida–Kraepelin test was assessed in minute periods by spectral analysis using the maximum‐entropy method. During the task, baroreceptor reflex sensitivity was significantly reduced. There was an inverse between‐subjects association between baroreceptor reflex sensitivity and the level of performance (number of additions completed) both at different time periods of the Uchida–Kraepelin test and during the whole task (r=−.51). This finding supports the existence of a pathway mediating mutual cardiovascular–central nervous system influences through the baroreceptors, establishing an essential mechanism facilitating adaptive reactions to stressful conditions.
Now you feel it—now you don't: ERP correlates of somatosensory awareness
Authors: Schubert Ruth , Blankenburg Felix , Lemm Steven , Villringer Arno , Curio Gabriel
Published: February 2006

We investigated correlates of somatosensory awareness for supratheshold stimuli using event‐related potentials in a masking paradigm: Conscious perception of a weak, but suprathreshold “target” stimulus was suppressed in a significant number of trials when followed by a higher‐intensity “mask” stimulus. ERPs were compared for trials with perceived versus unperceived target stimuli. Early ERPs (P60, N80), generated in the contralateral S1, were found independent of stimulus perception. In contrast, for consciously perceived target stimuli, amplitude enhancements were observed for the P100 and N140. Thus, early activation of S1 is not sufficient to warrant conscious stimulus perception. Conscious stimulus processing differs significantly from unconscious processing starting around 100 ms after stimulus presentation when the signal is processed in parietal and frontal cortices, brain regions crucial for stimulus access into conscious perception.
Effects of picture content and intensity on affective physiological response
Authors: Bernat Edward , Patrick Christopher J. , Benning Stephen D. , Tellegen Auke
Published: February 2006

This study evaluated the effects of affective intensity and thematic content of foreground photographic stimuli on various physiological response systems. This was accomplished by assessing responses to pictures that varied systematically in these parameters. Along with overall effects of picture valence reported in previous work, we found effects of thematic content (i.e., specific nature of objects/events depicted) for all measures except heart rate. In addition, we found that the magnitude of startle blink, skin conductance, and corrugator muscle reactions increased with increasing affective intensity of pictures. Additionally, for these three measures, intensity effects also interacted with effects of picture content. These results indicate that stimulus parameters of intensity and thematic content exert separate—and in some cases interactive—modulatory effects on physiological reactions to emotional pictures.
Early N400 development and later language acquisition
Authors: Friedrich Manuela , Friederici Angela D.
Published: February 2006

Recent developmental research on word processing has shown that mechanisms of lexical priming are already present in 12‐month‐olds whereas mechanisms of semantic integration indexed by the N400 mature a few months later. In a longitudinal setting we investigated whether the occurrence of an N400 at 19 months is associated with the children's language skills later on. To this end children were retrospectively grouped according to their verbal performance in a language test at 30 months. Children with later age‐adequate expressive language skills already displayed an N400 at 19 months. In contrast, children with later poor expressive language skills who have an enhanced risk for the development of specific language impairment (SLI) did not show an early N400. The results imply that children who have deficits in their expressive language at the age of 30 months are already impaired in their semantic development about one year earlier.
Return to Cyberia: technology and the social worlds of transnational migrants
Authors: PANAGAKOS ANASTASIA N. , HORST HEATHER A.
Published: February 2006

AbstractThis special issue on ‘Return to Cyberia’ is an attempt to evaluate the contemporary moment of new cultural and social forms influenced by rapidly evolving technologies in their first critical decade. It contains five case studies that highlight the range of transnational experiences ‐ from temporary migrants and refugees to the second generation. The contributors address how and why transnational populations use particular communication technologies and the ways in which these practices are influenced by factors such as generation, history of settlement and dispersal, cultural values, class and access. In addition to addressing a wide variety of study populations, the case studies highlight the variety of available ICTs including email and the Internet, teleconferencing, telephones and mobile phones. Collectively, the articles address issues such as geographic identity and connectivity, different use patterns based on gender and generation, authenticity and representation on the Internet, methodology and the intricacies of interpersonal dynamics across transnational social fields.
The blessings and burdens of communication: cell phones in Jamaican transnational social fields
Authors: HORST HEATHER A.
Published: February 2006

Abstract
Although much mention has been made of the importance of ICTs for transnational migrants, we know relatively little about how these technologies affect or change everyday transnational communications. Tracing the shift from community phone boxes to individually owned mobile (cell) phones in rural Jamaica, in this article I focus on the integration of mobile phones in Jamaican transnational communication. Equipped with a mobile phone, rural Jamaicans no longer rely on collect phone calls and expensive calling cards to initiate the connections between their friends and relatives living abroad. For many Jamaicans without access to a regular or reliable phone service prior to 2001, the mobile phone is viewed as an unadulterated blessing, transforming the role of transnational communication from an intermittent event to a part of daily life. For others, however, the mobile phone remains an object of ambivalence, bringing unforeseen burdens and obligations.
Diaspora, cyberspace and political imagination: the Eritrean diaspora online
Authors: BERNAL VICTORIA
Published: February 2006

Abstract
In this article I analyse the Eritrean diaspora and its use of cyberspace to theorize the ways transnationalism and new media are associated with the rise of new forms of community, public spheres and sites of cultural production. The struggle for national independence coincided with the rise of the Internet and the Eritrean diaspora has been actively involved in the new state. Eritreans abroad use the Internet as a transnational public sphere where they produce and debate narratives of history, culture, democracy and identity. Through the web the diaspora has mobilized demonstrators, amassed funds for war, debated the formulation of the constitution, and influenced the government of Eritrea. Through their web postings, ‘Internet intellectuals’ interpret national crises, rearticulate values and construct community. Thus, the Internet is not simply about information but is also an emotion‐laden and creative space. More than simply refugees or struggling workers, diasporas online may invent new forms of citizenship, community and political practices.