bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mesenchytraeus antaeus, a new giant enchytraeid (Annelida, Clitellata) from the temperate rainforest of British Columbia, Canada, with a revised diagnosis of the genus Mesenchytraeus
Authors: Rota Emilia , Brinkhurst Ralph O. 
Published: February 2006

Abstract Mesenchytraeus antaeus sp. n., an unpigmented giant enchytraeid inhabiting Carmanah valley (48°37′N, 124°44′W), Vancouver Island, is described. With its 102–127 segments and the size of fixed specimens reaching 61×2.9 mm (diameter maximal at midbody), this species qualifies as one of the largest members of the Clitellata family. The body wall comprises: a surprisingly thin cuticle (0.002 mm), the epidermis (0.02–0.04 mm), circular muscles (0.02 mm), plus thick longitudinal muscles (eight‐layered, totally 0.16–0.18 mm) divided into seven unequal fields. The chaetae are grouped in bundles of two to seven but show some unusual traits which suggest interesting convergences with the lumbricids. For instance, the most lateral chaeta in a bundle is always the largest; the larger chaetae exceed in length one‐third of a millimetre; the ectal tips of the chaetae are oriented in opposite directions in the anterior and posterior halves of the body. The spermathecal pores are prominent and open laterally in the middle of V, an unprecedented location among enchytraeids. The nature of the spermathecal ampullae (free, diverticulate and greatly elongate) indicates a close relationship to a group of species that seems to be confined to the Pacific coast of North America and the Arctic coast of Siberia. This amphi‐Beringean lineage includes other gigantic forms such as M. harrimani Eisen, 1904 and M. maculatus Eisen, 1904, from which, however, M. antaeus is clearly differentiated by the lack of pigmentation, the different size distribution of the chaetae within bundles, and the unique arrangement of the male apparatus. The latter includes unusually long sperm funnels (extending over 10 segments) and two groups of large accessory glands opening through two circular papillae at the base of each penial bulb, independently of the penial pores. All other congeners known to possess this type of glands (e.g. M. franciscanus Eisen, 1904) are at most only half as large as M. antaeus. The chaetal muscles of M. antaeus are heavily infested by encysted nematodes.
Developmental responses to pond desiccation in tadpoles of the British anuran amphibians (Bufo bufo, B. calamita and Rana temporaria)
Authors: Brady L. D. , Griffiths R. A. 
Published: February 2006

AbstractTadpole development was compared in three amphibian species (Bufo calamita, B. bufo and Rana temporaria) that suffer different risks of pond desiccation in nature. Using a replicated pond system, development was monitored in desiccating and non‐desiccating ponds, and in vertical‐sided and gently shelving (‘shoreline’) ponds. In desiccating ponds, tadpoles suffered from crowding effects and metamorphosed at a smaller size, but development was not accelerated in response to desiccation in any of the three species. Desiccating ponds had higher maximum temperatures but also lower minimum temperatures, which may explain the lack of any difference in development time between desiccating and non‐desiccating ponds. Although shoreline ponds were slightly warmer than vertical‐sided ponds, development under these conditions was also consistent with a crowding, rather than a temperature, effect. In shoreline ponds, metamorphosis generally took longer, was less synchronized between individuals, and resulted in a smaller size at metamorphosis, compared to development in vertical‐sided ponds. The lack of species‐by‐desiccation interactions indicated that there were no differences between the three species in developmental plasticity. Developmental constraints may place a limit on the degree of plasticity that can evolve in a species such as B. calamita, which breeds only in ephemeral ponds with a variable hydroperiod. Alternatively, low genetic variability within British populations of B. calamita may have constrained the evolution of adaptive plasticity in this species.
Sex ratios of American alligators (Crocodylidae): male or female biased?
Authors: Lance Valentine A. , Elsey Ruth M. , Lang Jeffrey W. 
Published: February 2006

AbstractRecent 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

AbstractIn 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

AbstractTwenty‐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

AbstractThis 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

AbstractExamination 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

AbstractSeasonal 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

AbstractAn 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

AbstractToe‐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

AbstractTwo 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractSperm 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.