Three maned sloths were observed for a total of 680 h throughout 14 months in an Atlantic forest reserve of south-eastern Brazil. The study animals were located in the forest, monthly by radio-telemetry, and data on daily activity budgets were collected recording the actual time they spent in major activities. Individual home ranges were very small (0.5–6 ha, depending on the method used) and the sloths travelled an average of only 24 m during the 24 h period. A comparison between day- and night-range lengths suggests that maned sloths ranged more during daytime (17 m) than at night (5 m), indicating a predominantly diurnal period of activity. They rested, on average, for 74% of daytime, but a substantial variation was found between individuals (range 60–80%). Although a lack of synchrony was observed in activity pattern between study animals monitored simultaneously, all three sloths tended to start feeding and moving at the same time of the day (07:00–08:00), and the time that elapsed between the start of these activities on consecutive days was about 24 h, indicating a circadian rhythm of activity for the species. This finding contradicts previous studies on congeneric sloths, in which suggestions that Bradypus does not show cyclic patterns of activity were based on qualitative rather than quantitative data. Given the species' highly folivorous diet and the characteristic low basal rate of metabolism in this genus, the rather high levels of activity and the predominantly diurnal period of activity observed for maned sloths are probably related to the lower ambient temperatures found in the Atlantic forest when compared to other more equatorial localities of the Neotropics. Further studies with additional sloths are necessary, however, to ascertain the validity of this conclusion.

The 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.

Many spiders include conspicuous designs of white silk called stabilimenta in the centre of their orb webs. Stabilimenta are highly variable in their form and frequency and are hypothesized to function in either defence against predators or attraction of prey. These hypotheses generate different predictions about the effect of foraging success on variation in the form and frequency of stabilimenta. If stabilimenta serve as prey attractants, then starved spiders should invest more in them than well-fed spiders, while the opposite pattern is expected if stabilimenta function as a predator defence mechanism. This study examines the effect of variation in foraging success of the yellow garden argiope Argiope aurantia and the banded argiope Argiope trifasciata on variation of their stabilimenta and orb webs. Both species built smaller stabilimenta when fed less, even though a stabilimentum accounts for only 10% of the dry weight of an orb web. Poorly fed A. trifasciata also included stabilimenta in their webs less often than did well-fed A. trifasciata. Differences in stabilimenta were independent of differences between treatments in the orb webs themselves. These results argue against the prey attraction hypothesis, but not the predator defence hypothesis, since well-fed spiders invested more in stabilimenta.

The 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.

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.

In 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.

In Britain, the water vole (Arvicola terrestris) has declined in numbers and distribution (Jefferies, Morris & Mulleneux, 1989; Strachan & Jefferies, 1993). This species now enjoys a higher profile than hitherto and many local surveys have been initiated, following published methods. To monitor the status of the population or the effectiveness of habitat restoration projects, a method for estimating numbers of water voles is often needed, preferably based on latrines (a characteristic field sign of this species). Unfortunately, the published literature includes two potentially misleading components. In view of the significance of population size in a declining species, and the heightened interest in this animal, we felt it would be helpful to publish clarification and corrections in the hope of forestalling erroneous reports and conclusions in future investigations.

Seasonal 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.

This 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.

Species 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.

This 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.

Genetic 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 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.

An 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.

How 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.