bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of social interactions on tadpole activity and growth in the British anuran amphibians (Bufo bufo, B. calamita, and Rana temporaria)
Authors: Griffiths R. A. , Foster J. P. 
Published: February 2006

AbstractTadpoles of different species of frogs and toads display different tendencies to aggregate. We investigated some of the costs and benefits of aggregating in three British species by examining their behavioural responses to the presence of conspecifics, and by monitoring the performance of tadpoles under different levels of social interaction with other individuals. The common toad (Bufo bufo), an aggregating species, displayed higher levels of activity than the natterjack toad (B. calamita) and common frog (Rana temporaria), two species that form aggregations less frequently. Moreover, out of the three species, only B. bufo increased activity in the presence of conspecifics. In all three species, increased interaction between individuals resulted in increased variation in size. However, average growth rate was affected only in B. bufo, which grew faster when raised in isolation and not interacting with other individuals. Under certain conditions intraspecific competition therefore seems to be more important than social facilitation, but may lead to average size at metamorphosis being larger within the population. The consequences of intraspecific competition within aggregations may therefore be different for individuals and populations.
Behavioural response of wild rodents to the calls of an owl: a comparative study
Authors: Hendrie Colin A. , Weiss Scott M. , Eilam David 
Published: February 2006

AbstractEffective anti‐predator defence mechanisms depend on efficient recognition of possible predators. However, nocturnal aerial predators, such as owls, present very few stimuli to enable their detection by potential prey. The most prominent of these are their territorial calls which are believed to provide sufficient stimuli to activate anti‐predator defence mechanisms in species heavily predated upon by owls. To test this hypothesis, the behaviour of voles (Microtus socialis), dormice (Eliomys melanurus), jerboas (Jaculus jaculus), and spiny mice (Acomys cahirinus) was analysed during and following exposure to playback of tape recorded calls of the tawny owl (Strix aluco). In response, voles crouched, and retreated to a small burrow present in the test arena; dormice also reduced the distances they travelled in the arena, and spent an increased amount of time around the burrow; jerboas crouched and froze during the playback of the owl call but not thereafter; spiny mice, however, displayed enigmatic behaviour in apparently ignoring the owl calls. The results, which demonstrate an induction of defensive behaviours to recorded owl calls, support the results of others who have examined the effects of exposing wild rodents to live owls.
Predation risk as an influence on group size in cercopithecoid primates: implications for social structure
Authors: Hill R. A. , Lee P. C. 
Published: February 2006

AbstractPredation pressure has long been proposed as a determinant of mammalian social systems. Group size and composition were compared for 121 populations of cercopithecoid primates, from 39 species of 13 genera, living under low, moderate or high predation risk. In confirmation of previous studies, predation risk was found to have a major effect on group size, with populations under high predation pressure living in significantly larger groups than those at lower risk. However, there were differences in social structure between the predation risk categories. Unimale groups were smaller, had fewer females than multimale groups and were infrequently found under conditions of high predation risk. Predation risk had marked effects on the composition of multimale groups. Under conditions of high predation risk there was a disproportionate increase in the number of adult males over that predicted by the number of females present or by group size. At low predation risk there were fewer males than predicted on the basis of female group size. Together, these results suggest that male strategies to monopolize females depend both on the females' grouping patterns and on the needs of both sexes to maximize group size under high predation pressure.
Habitat selection by Dall's sheep (Ovis dalli): maternal trade‐offs
Authors: Rachlow Janet L. , Bowyer R. Terry 
Published: February 2006

AbstractHabitat selection by female Dall's sheep (Ovis dalli dalli) during lambing was studied in interior Alaska, U.S.A., in 1988 and 1989. Selection of habitat changed with the chronology of lambing. During the pre‐lambing period, maternal females selected sites with forage and avoided snow‐covered areas. During peak lambing, food and steep slopes continued to be selected. Distance to escape terrain was a critical component of habitat selection by females throughout lambing. Maternal bands that ventured farther from escape terrain were in larger groups. Abundance of forage also increased in areas that were farther from this terrain.Habitat selection by females also differed between years. In 1989, a late spring storm resulted in deep snow and delayed phenology of plants; forage was of lower quality, and the growing season was much shorter in 1989 than in 1988. Births of lambs also occurred later and less synchronously in the second year. Females selected terrain characteristics that were related to avoiding predators in 1988 when forage was more plentiful, but selected sites with forage in 1989 when food was less abundant.Group size of maternal bands was larger in 1988 than in 1989, and females foraged most efficiently during 1988. Large groups may not have occurred in 1989 because lambs were born asynchronously, preventing cohesive movements of maternal bands with lambs of differing ages.Both the chronology of lambing and a variable environment affected habitat selection by females. Maternal females made trade‐offs between the requirements for forage to meet the high energetic costs of lactation and the risk of predation.
Diet of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae)
Authors: Chiarello Adriano G. 
Published: February 2006

AbstractThe diet of maned sloths was studied throughout 14 months in an Atlantic forest reserve of south‐eastern Brazil. Three adult sloths were observed for a total of 680 h and located monthly by radio‐telemetry. Data were collected on diet, recording the actual time the sloths spent eating plant species. Overall, the diet was composed of 99% leaves, with young leaves (68%) preferred to mature ones (7%) throughout the year. A higher proportion of tree leaves (83%) than liana leaves (16%) were included in the diet. When analysed together, the diet of the three animals included a total of 21 plant species (16 tree and 5 liana), but each individual made up its diet with an even smaller number of species (7–12) and with a particular subset of the local flora. This is a very small portion of the total number of tree and liana species available to the sloths; furthermore, the top species consumed were present at very low population densities in the forest. Thus, B. torquatus, like other congeneric species studied elsewhere in the Neotropics, is a strictly arboreal folivore with a highly selective diet, probably resulting from evolving physiological adaptations to cope with a smaller range of plant secondary compounds. This is possible for the species of this genus through a combination of low basal rates of metabolism, which enable the sloths to survive on an energy‐poor diet, and a very long passage time of digesta, which, in turn, aids the digestion of a fibre‐rich diet while possibly contributing to the degradation of secondary compounds.
The reproductive potential and strategy of Scorpio maurus fuscus (Scorpiones: Scorpionidae): anatomical clues in the ovariuterus
Authors: Warburg M. R. , Elias Rivka 
Published: February 2006

AbstractThe reproductive potential of scorpions is difficult to assess since several stages of their life histories cannot be clarified under natural conditions. The female's age when she first reproduces, the frequency of parturitions, litter size, and longevity cannot be known with accuracy. A new approach to such questions is suggested, whereby clues in the female's ovariuterus can be used to shed some light on previous and forthcoming litter sizes.The ovariuterus of a female scorpion is unique among invertebrates in that past and forthcoming parturitions can be traced in its structure. Degenerated post‐partum diverticulae and the scars remaining after these have been completely resorbed indicate past parturitions, whereas young rudimentary diverticulae provide an estimate for future generations.It is estimated that Scorpio maurus fuscus (Scorpionidae), matures in its second year, and first reproduces when 3 years old. Ovariuterus structure shows that it can have at least four and perhaps up to eight litters. If parturition takes place every year this would imply that a female scorpion can reach a minimum age of 6 years or perhaps up to 10 years. Evidence based on population analysis of females indicates that it is unlikely that all females reproduce in consecutive years; more probably they reproduce every other year. Thus, longevity may reach 9 years and perhaps as much as 17 years.
A new family of cyclopoid copepods (Fratiidae) symbiotic in the ascidian (Clavelina dellavallei) from Cádiz, Spain
Authors: Ho Ju‐shey , Conradi Mercedes , López‐González Pablo J. 
Published: February 2006

Abstract Fratia gaditana, n. gen., n. sp., is described based on the specimens obtained from the atrium of the ascidian, Clavelina dellavallei (Zirpolo), collected at Tarifa Island in Cádiz, Spain. The new species belongs to a new family of Cyclopoida. Cladistic analysis revealed that phylogenetically it is closer to the Ascidicolidae than to the two other ascidicolous families, Archinotodelphyidae and Notodelphyidae.
The dynamics of growth in naked mole‐rats: the effects of litter order and changes in social structure
Authors: O'Riain M. J. , Jarvis J. U. M. 
Published: February 2006

AbstractIn this study factors that influence the plasticity in growth and adult body mass in the naked mole‐rat (Heterocephalus glaber) are explored. Growth functions (Gompertz transformation) revealed that naked mole‐rat pups have the slowest mean maximum growth rate (0.207 g.day−1) of all the Bathyergidae. Growth functions varied significantly between litters and there was an inverse trend between asymptotic body mass and litter order. Similarly, the magnitude of the growth response following the death of the breeding male or older siblings was greater for older litter members. There was a significant correlation between body mass and age at all stages of the colony's history although this relationship weakened with time. It is suggested that dominance interactions between old and young mole‐rats within the colony are important factors influencing the growth and reproductive potential of all colony members. Changes in body mass were linked to the behaviour of the individual within the colony providing a mechanism for the apparent match between large body size and colony defence and small body size and work frequency. Despite low genetic variation within colonies there is considerable variation in the size of colony members suggesting that plasticity in growth is the product of different ontogenetic histories of colony members that may serve as the basis for variation in size amongst adults.
Reproduction in the male Cape fur seal Arctocephalus pusillus pusillus: age at puberty and annual cycle of the testis
Authors: Stewardson C. L. , Bester M. N. , Oosthuizen W. H. 
Published: February 2006

AbstractSeasonal changes in the reproductive anatomy and histology of the male Cape fur seal Arctocephalus pusillus pusillus were examined. Studies were based on 99 specimens collected between Algoa Bay on the south‐east coast of South Africa, and Cape Frio, Namibia, during 1974 to 1990. Reproductive organs are briefly described. The presence of sperm in the seminiferous and epididymal tubules indicates that males attain puberty between 3 and 4 years of age. Quantitative measurements of testis weight, testis volume, and the diameter of the seminiferous and epididymal tubules were analysed on a monthly basis and spermatogenesis documented. Although some males may remain in breeding condition until March, the absence of spermatozoa in the epididymis during February to June, when mean testis mass and mean tubule diameter reached a minimum, clearly showed reproductive quiescence following the rut. Four stages of spermatogenesis were observed: (1) inactive (February/March–June); (2) early spermatogenesis (July); (3) late spermatogenesis (July/August–December/January); and (4) epithelial regression (February–June). Individual variation between males, possibly differences in social status and body condition, may influence the duration of spermatogenesis, hence the overlap in duration between epithelial regression and inactivity. It appears that photoperiod may act as an obligatory proximate factor initiating spermatogenesis 3–4 months before the relatively short breeding season from November to December.
Short‐ and long‐term resistance to desiccation in a minute litter‐dwelling land snail Lauria cylindracea (Pulmonata: Pupillidae)
Authors: Arad Zeev , Goldenberg Shoshana , Heller Joseph 
Published: February 2006

AbstractThis study examines the water economy and resistance to desiccation in a minute (5 mg snail mass; 3 mm shell height) litter‐dwelling land snail Lauria cylindracea (Pupillidae). As expected from its small size and from its moist habitat, L. cylindracea exposed to normothermic desiccation lost water at the highest rate revealed so far in our studies of resistance to desiccation in some 30 Israeli species and populations of land snails—22.7% of the whole snail mass within 5 days. This high water loss was selectively contributed by the extra‐pallial (free) compartment while soft body water content was closely maintained, without catabolism of body tissue as a source of metabolic water. Surprisingly, however, samples of L. cylindracea survived long periods (2–4 months) of aestivation when left undisturbed in the laboratory, sustaining a mass loss of 25–40%. This long‐term aestivation revealed a different pattern of water compartmentalization, as the snails also lost water from the soft body tissue. Samples of these snails were rehydrated for 48 h and then exposed to an identical desiccation regime as the original, field‐collected snails. Most of the water taken up during rehydration was lost within the first 24 h of desiccation, after which the rate of water loss dropped sharply. We conclude that short‐term water regulatory responses to experimental desiccation differ from long‐term responses to aestivation. We suggest that during long‐term aestivation, a new set‐point of water economy is established, in association with a metabolic depression, and that an extended period of contact with moisture is needed to change this set‐point.
Tooth breakage and diet: a comparison of bats and carnivorans
Authors: Fenton M. B. , Waterman J. M. , Roth J. D. , Lopez E. , Fienberg S. E. 
Published: February 2006

AbstractSpecies of carnivorans that eat bone are believed to break teeth more often than those eating mainly meat. Two predictions that arise from this hypothesis are that bats, which do not eat bone, will have a lower incidence of broken teeth than carnivorans and that smaller carnivorans, which often feed heavily on arthropods and other insects, will exhibit less tooth damage than larger carnivorans. We found no difference between bats and carnivorans in the proportion of skulls with broken or missing teeth in a sample including 10 species of carnivorans from ermines to bears, and 13 species of bats including some that eat insects, fruit, nectar and pollen, and blood. When the sample is expanded to include larger carnivorans studied by Van Valkenburgh (1988), there is a significant difference in the incidence of tooth breakage, indicating that the selection of species in the sample affects the results. Tooth breakage was strongly influenced by body size in carnivorans but not in bats. This evidence suggests that factors other than diet influence tooth breakage in mammals. We propose that lifespan, which increases with body size in carnivorans but not in bats, is a better predictor of tooth breakage than diet.
Morphology of the otoliths of Barbus sclateri (Pisces: Cyprinidae)
Authors: Escot Carmelo , Granado‐Lorencio Carlos 
Published: February 2006

AbstractThis is the first description of the otoliths (sagitta, asteriscus, and lapillus) of the European barbel (Barbus sclateri, Pisces: Cyprinidae), as well as the location, the procedure for extracting them and preparing them for age and growth studies. The otoliths were observed by light and scanning electron microscopy. With this last technique each otolith had a variable external crystalline morphology which may be related to different growth rates of the crystals. When seen through reflected light, the lapillus and the asteriscus showed opaque and translucent radial bands, and those in the lapillus were more clearly defined than in the other otolith.
Allozyme homozygosity and phally polymorphism in the land snail Zonitoides nitidus (Gastropoda, Pulmonata)
Authors: Jordaens K. , Backeljau T. , Ondina P. , Reise H. , Verhagen R. 
Published: February 2006

AbstractGenetic variation in the pulmonate land snail Zonitoides nitidus was examined by means of allozyme electrophoresis in 17 European populations. We observed no heterozygotes, indicating that Z. nitidus consists of several homozygous multilocus genotypes (strains) probably produced by self‐fertilization. Nine strains were detected. Strains appeared not to be equally distributed over the regions considered. One strain was strongly differentiated from the others, which is suggestive of a taxonomic differentiation. Anatomically, two major phally types were distinguished: euphallics, with well‐developed male reproductive organs, and hemiphallics, with weakly developed male reproductive organs. Both phally types were found together in natural populations, but euphally ratios were very low (0–19%; overall mean = 7.79%) and differed between geographical regions (Belgium, Germany, and Sweden). In some populations, hemiphallic individuals were smaller compared to euphallic individuals although the difference is small and its biological significance remains to be established. We found no clear relation between phally type and allozyme data.
A systemic secondary vessel system is present in the teleost fish Tandanus tandanus and absent in the elasmobranchs Carcharhinus melanopterus and Rhinobatos typus and in the dipnoan Neoceratodus forsteri
Authors: Chopin Lisa K. , Amey Andrew P. , Bennett Michael B. 
Published: February 2006

AbstractA system of secondary vessels emerging from the primary vessels as numerous coiled capillaries has been described in numerous teleost and holost fishes. The systemic secondary vessels of the teleost Tandanus tandanus are typical of this system and are described in this study. The existence of a secondary vessel system has been postulated in the elasmobranch group. No secondary vessel origins, as seen in the teleosts, are present in the elasmobranchs Rhinobatos typus and Carcharhinus melanopterus. Vessels with a similar distribution to secondary arteries are observed but these are venous rather than arterial in nature and do not connect with the primary arteries. Like the secondary veins in teleosts, the cutaneous veins in R. typus contain blood with a low haematocrit. There is no morphological evidence for a secondary vessel system in the dipnoan Neoceratodus forsteri.
Functional morphology of the gizzard of the domestic goose: design of an artificial gizzard
Authors: Moore S. J. , Lill C. A. , Sanson G. D. 
Published: February 2006

AbstractAn artificial gizzard was developed to investigate the functional basis of the asymmetry of the gizzard muscles of herbivorous birds, such as the domestic goose (Anser anser). Two types of gizzard muscle morphology were modelled: asymmetric muscles that generated a translational movement; and symmetric muscles that generated a compressional movement. The extent of breakdown of grass in the artificial gizzard was estimated by measuring nitrogen loss from blades of wheat (Triticum aestivum). The effect of grit and its interaction with the two types of gizzard muscle movement were also explored. In the artificial gizzard, translational movements caused more damage to grass than compressional movements and the damaging effect of grit was greatest when there was a translational movement. This type of movement was found to be particularly important as it prepares plant material for subsequent processing by stripping the matrix cells from the fibre bundles. Without such preparation, the breakdown of grass is limited.
Use of an artificial gizzard to investigate the effect of grit on the breakdown of grass
Authors: Moore S. J. 
Published: February 2006

AbstractHow geese break down food in their gizzards was investigated using an artificial gizzard that was loaded with grass (blades of wheat Triticum aestivum) and different quantities of four types of grit; large and small quartzite particles and large and small glass beads. Measuring nitrogen loss from the grass indicated the extent of damage to the grass. It was found that grass breakdown in the gizzard was most effective when it contained a small quantity of quartzite particles. In contrast, glass beads in the gizzard often resulted in less damage to grass than if they were absent. This suggests that there is a trade‐off between the damaging effect of grit on grass and the damaging translational movement of the gizzard lumen walls generated as the gizzard contracts. The damaging force produced by the gizzard is distributed across the gizzard contents. Thus with an increase in grit quantity in the gizzard, the force experienced by each grass particle will be reduced, resulting in reduced breakdown.