Time-depth recorders were used to investigate the diving performance and behaviour of two bimodally respiring turtle species, Rheodytes leukops and Emydura macquarii, known to have a high and low reliance on aquatic respiration, respectively. Significant differences in diving performance between R. leukops and E. macquarii were observed in the number of dives/day (39.3±5.38 vs 112.2±11.73 dives/day; mean±se), mean dive length (33.1±7.33 min vs 9.6±2.26 min) and maximum dive length (623±104.74 min vs 67.1±8.14 min), respectively. Differences in diving performance between R. leukops and E. macquarii are attributed to the species' reliance (or lack thereof) upon aquatic respiration. Rheodytes leukops displayed a weak bimodal pattern of increased surfacing frequency in the early morning (05:00–07:00) and late afternoon (14:00–18:00), while E. macquarii displayed a strong bimodal pattern of elevated surfacing frequency over similar time periods. Daily patterns of increased surfacing frequency for both species failed to correlate with fluctuating aquatic Po2 levels or water temperature, and may instead be explained by the heightened activity levels of both species during twilight.

Morphological variation was investigated in hatchling squid Loligo forbesi Steenstrup 1856 reared at three constant temperatures. Twenty-seven morphometric and chromatophore characters were measured on 180 hatchlings. Hatchlings were randomly sampled from 15 egg strings, representing six egg mops and spread across two spawning seasons. Size at hatching varied inversely with temperature and was significantly reduced at 16°C (mean mantle length 2.87±0.04 se mm) compared to 8°C (3.26±0.03 se mm). Hatchlings reared at 12°C developed significantly narrower mantles than those reared at 8 or 16°C. Principal components, stepwise elimination and canonical variates analyses performed using all 27 measured characters revealed that nine characters were vital in discriminating between temperature groups. Canonical structure values associated with eight of these characters were used in the construction of a canonical equation. By measuring the same eight characters on field-sampled L. forbesi, this equation can be used to estimate mean thermal history of wild hatchlings. Field-application of the techniques developed during the present study may allow assessment of realized thermal niche in a mobile marine invertebrate.

Enhanced oxygen reserves in the blood facilitate diving in marine mammals. For pinnipeds (seals and sea lions), a developmental period of 4 to 24 months is required for blood oxygen stores to reach adult capacities. We investigated whether a similar developmental period for the blood occurs in cetaceans (dolphins and whales), a group of mammals that are exposed to diving immediately after birth. Blood samples were collected from wild and zoological park bottlenose dolphins Tursiops truncatus aged 0–12 years. Red blood cell number (RBC), haemoglobin content (Hb), haematocrit (Hct), mean corpuscular volume (MCV), mean cell haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC) were determined for each sample. We found that during postnatal development, RBC, Hb and Hct decreased from 0 to 1.5 months and then increased from 1.5 to 6 months, reaching adult levels by 3 years. MCV and MCH both increased from birth. MCHC decreased from 0 to 3.2 months and then increased. Adult levels for MCV were attained as early as 2 months of age while adult levels for MCH and MCHC were attained by 6 months of age. These results indicate that, for bottlenose dolphins, the development of the blood and its capacity to store oxygen is not complete with weaning, which generally occurs at 1.5 years old. The lower oxygen storage capacity of immature dolphins is likely to limit dive capabilities. Calculated aerobic dive limits (cADLs) for 0- to 2-year-old dolphin calves are 1.9–3.6 min, compared to 4.8–5.4 min for 3- to 12-year-old dolphins. Increases in cADLs from 0 to 3 years are attributed to increases in both body mass and mass specific oxygen stores while body mass alone explains the increases in cADLs from 3 to 9 years. The limited diving capacity of young dolphins may influence the foraging behaviours of newly weaned juveniles and females accompanied by calves.

In ungulates, females typically need to reach a critical threshold body weight in order to reproduce. Females born in ‘poor’ years may lose 1 year of reproduction, as they reach the critical body mass 1 year later. Some studies report also a lasting effect of low initial body weight into prime age, while several other studies have shown that nearly all prime-age females ovulate or are pregnant. However, the quality of the offspring (as measured by offspring body weight) is often not considered. We tested whether female ungulates with an initially low body weight (at around weaning) reach the same reproductive output as females with higher initial weights, and thus whether or not they are able to compensate for their initial low weight. Data on body weight of 123 533 lambs of domestic sheep Ovis aries from 73 299 litters that in turn derived from 32 359 different ewes were used. All ewes and lambs had been free-ranging on outlying pastures in Norway during the entire summer season. Ewes with an initially low body weight produced smaller offspring throughout their lifespan. Ewes with an initially low body weight also produced fewer lambs at first and second parturition, but lifetime number of offspring was not related to ewes' initial weight. We concluded that bigger was better: the smaller offspring of ewes with a low initial weight demonstrate a lasting cost on reproductive effort, with consequences for animal production systems and management of wild ungulates.

Miniature radio-transmitters were used to follow movements over a 10-day period of the 10 g honey possum Tarsipes rostratus, and the areas covered were compared with home-range estimates calculated from long-term mark-and-recapture records using pitfall traps. The study was carried out in the Scott National Park, in the extreme south-west of Western Australia, and shows that honey possums may move far greater distances than is apparent from trapping records. The overall mean area used determined by radio-tracking was significantly larger at 0.54±0.19 ha than the apparent home range of 0.03 0.01 ha determined by trapping. The area used by males was significantly greater than that of females when measured by radio-telemetry (0.79±0.24 ha vs 0.14±0.08 ha, P = 0.058), but did not differ significantly when estimated from trapping records (0.03±0.01 ha vs 0.01±0.01 ha). These data suggest that honey possums frequent plant assemblages at night where they are vulnerable to pitfall trapping, but that males, particularly, spend the day in other areas that may be as far as 200 m distant.

Time for metamorphosis and metamorph size of moor frogs Rana arvalis and common frogs R. temporaria were measured in 22 ponds for 1–8 years. Environmental data in these ponds were also measured. Metamorphosis of the frogs took place from the beginning of June to the beginning of August. When both species were found in one pond, the common frogs metamorphosed up to 20 days earlier than the moor frogs. Most variation in time for metamorphosis, among ponds and years, is explained by temperature effects, but a causal relationship was not established. Within a pond, metamorphosis was later in cold summers than in warm summers. Size at metamorphosis was affected by tadpole density; at high densities metamorphs were smaller. Size at metamorphosis was not related to time for metamorphosis. There was an effect of pond drying; if ponds were about to dry up, metamorphosis was accelerated by about 2.4 days. Tadpoles from ponds with a late metamorphosis in the field had tadpoles that metamorphosed early in a common garden experiment, suggesting counter gradient selection.

Mandrill Mandrillus sphinx hordes in the Lopé Reserve, Gabon, the approximate centre of the mandrill species range, were studied over 3 years from 1996 to 1999. Part of the study site included gallery forests within savanna areas, allowing observation of entire hordes, hitherto impossible in dense forest habitat. Horde size and composition (sex and age classes) were documented using exact records on video film whenever a horde or subgroup crossed an open space. Mean horde size was 620, and hordes of up to 845 individuals were documented, probably the largest stable group size found in any wild, unprovisioned primate population. Hordes were cohesive throughout the study period and did not seem to be aggregations of smaller units. Mandrill societies seem to be quite different from the baboon societies, to which they have been compared to date. Mature, breeding-age males were not resident members of hordes, but entered at the onset of seasonal cycles in the females (as deduced by the presence of sexual tumescence) and emigrated once female sexual cycles ceased. The number of breeding males present in the horde at any one time is best explained by the number of sexually attractive females. It is postulated that the extreme coloration of males and strong sexual dimorphism in mandrills may have evolved through an enhanced need for competitive signals in a situation where no long-term social bonds between breeding partners exist.

Metabolizable energy intake and changes in body mass was measured in the desert gerbil Gerbillus dasyurus when parasitized by the flea Xenopsylla ramesis. We hypothesized that energy requirements for maintenance, or average daily metabolic rate, of parasitized gerbils would be higher than those of non-parasitized gerbils. We also hypothesized that the efficiency of utilization of energy for maintenance would be the same for parasitized and non-parasitized gerbils, as this measurement is dependent mainly on dietary quality. Fifty fleas feeding on a gerbil consumed 3.68±1.19 mg blood, in total. This amounted to 34.3±1.8% of body mass of a starving flea and only about 0.17% of the blood volume of the host. The absolute amount of blood consumed by X. ramesis is the lowest reported for fleas in other studies. This suggested that the pressure of parasitism of X. ramesis on G. dasyurus in terms of blood consumed was relatively low. Both our hypotheses were confirmed. Average daily metabolic rate of the parasitized gerbils (7.75 kJ g−0.54d−1) was 16% higher than that of non-parasitized gerbils (6.69 kJ g−0.54d−1). In addition, at zero metabolizable energy intake, the parasitized gerbils lost body mass at a faster rate than the non-parasitized gerbils (4.34 vs 3.95% body mass d−1). The efficiency of utilization of energy in the parasitized and non-parasitized gerbils was similar.

Aspects of the skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni Herklots and Marshall, and host size and type selection by the symbiotic shrimp Spongicola japonica Kubo were investigated using field-collected material. Two phases, flexible and stiff, were observed in the framework of the sponges. In the flexible sponges, the circular, longitudinal and oblique systems of the skeletal beams that constitute the principal framework were not fused to each other, and the parietal ledges running circularly, or sometimes obliquely, on the wall were not developed. The skeletal wall was fragile in texture, readily torn by any external force. The wall was much sturdier in the stiff sponges, in which the systems of the skeletal beams were coarse, fused to each other to make the principal framework tough in texture, and pareital ledges developed so as to reinforce the sponge wall. The flexible phase is mainly seen in smaller and younger sponges, while the stiff phase was seen in the larger (or dead) ones. Almost all the solitary and young pairs of shrimps were collected from flexible sponges.

Many orb-web building spiders add conspicuous, white silk decorations termed stabilimenta onto the central portion of the webs. Stabilimenta are known to vary greatly in form and quantity from species to species, and also within a species. In the present study, stabilimentum variations in form and quantity are described, and the factors influencing stabilimentum variations in Argiope versicolor from Singapore, in both the field and the laboratory, are examined. Our results from field survey and laboratory experiments show that: (1) the form and occurrence of stabilimenta varied with developmental stage of spiders: A. versicolor juveniles (body length: < 0.6 cm) built disc-like (discoid) stabilimenta while adults spun cross-like (cruciform) stabilimenta; (2) the quantity of stabilimenta (percentage of stabilimentum area covering the web to the web area) decreased with increasing web size and spider size; (3) light intensity affected the density and percentage cover of stabilimentum on the web: A. versicolor tend to build more and denser stabilimenta in dim conditions than in bright surroundings; (4) well-fed A. versicolor adults added more stabilimenta than starved spiders. These findings suggest that A. versicolor may adjust the frequency and quantity of stabilimenta to suit multiple functions, specifying the circumstances under which to use each function (conditional stabilimentum-building strategies).

We examined the relationship between intrinsic and extrinsic variables and variation in size at birth and rates of postnatal growth in the big brown bat Eptesicus fuscus at maternity roosts in central Massachusetts and southern New Hampshire. Body mass and length of forearm at birth were lowest when precipitation in the month preceding births was relatively high. In addition, body mass at birth was significantly lower when ambient temperatures during late pregnancy were relatively low. Pups born to middle age mothers were heavier than pups born to young or old mothers. When evaluated using mark–recapture data (longitudinal method), postnatal growth in length of forearm and body mass was greater for pups born to middle age and older mothers and change in body mass was greater for female pups than for male pups. When growth data were evaluated using the trajectory method, the rate of growth for length of forearm was greatest when ambient temperature was highest. Age prediction equations were improved when maternal age was incorporated into predictive equations. We recommend considering both intrinsic and extrinsic variables in studies where maternal effort is evaluated and age prediction equations are used for estimating postnatal growth rates in free-ranging bats.

The epidermis of snakes produces two types of keratinocytes containing an alpha (soft) and a beta (hard) form of keratin. During epidermal renewal, which allows body growth, six types of epidermal layers are produced before moulting: oberhautchen, beta-, mesos, alpha-, lacunar, and clear. The precise layers in which beta-keratin, alpha-keratin and matrix proteins (loricrin and filaggrin) are produced, have been studied by light and ultrastructural immunocytochemistry. An antibody against chick scale beta-keratin recognizes also snake beta-keratin only in the oberhautchen and beta-layer. This confirms the phylogenetic relationships between avian and reptilian hard (beta) keratins. Beta-keratin rapidly disappears in mesos-cells, where little beta-keratin is present. Antibodies that recognize alpha-keratins (AE1, AE2, AE3) show that acidic keratins (AE1 positive) mainly localize in the most basal layers and basic keratins (AE3 positive) in all layers but disappear in those layers that are keratinized, especially in the beta-layer. The AE2 immunolabelling (a marker of keratinization in mammalian epidermis) is localized in the compact alpha-layer. This pattern is similar to that for loricrin and filaggrin, although in the latter the reaction is less intense and located mainly in the hinge regions among scales. Alpha-keratins and associated proteins disappear in the oberhautchen and beta-cells where beta-keratin is produced instead. This study suggests that the shedding mechanism in snakes evolved after the hard beta-keratin was compartmentalized beneath the soft alpha-keratin to create an intra-epidermal weakness region. The study also suggests that some common mechanism of alpha-keratinization is present in snakes, and the other amniotes in general.

Cranial variability was studied in 307 Eastern hedgehogs Erinaceus concolor Martin, 1838 from central and south-eastern Europe, the Near East, Middle East, and the Caucasus. The maxillary bone always contacted the nasal bone in European samples, forming a naso-maxillary suture which was mainly long (>2 mm). In contrast, the suture was usually short (<1–2 mm) in hedgehogs from the Near East and Middle East, and sometimes the maxillary failed to reach the nasal bone. In the latter case, the premaxillary formed a suture with the frontal bone (length = 2.5 mm in extreme cases). Two morphotypes could be distinguished on this basis: the roumanicus morphotype (with a long suture) and the concolor morphotype (with the naso-maxillary suture short or absent). Discriminant function analysis of nine geographic samples, and based on 14 linear log-transformed skull measurements, revealed two clusters: one included four European samples of the roumanicus morphotype and the other contained three Asiatic samples of the concolor morphotype. Specimens of the roumanicus morphotype from Asia were classified as having either the concolor or roumanicus morphotype; however, on average their skull morphology suggested closer affinities with the former.

Seven Euplotes spp. were investigated using amplified ribosomal DNA restriction analysis (RFLP, riboprinting). This involved the use of the polymerase chain reaction (PCR) to amplify a segment of the ciliate genome, followed by restriction digestion to yield restriction fragment length polymorphisms among the seven euplotids. Distinctly different restriction digestion haplotypes and similarity indices among the seven species (0.15–0.78) were obtained, which were used to separate the seven species and construct a distance tree among them. Seven species were separated into three clusters: i.e. E. rariseta, E. eurystomus–E. woodruffi–E. octocarinatus–E. charon and E. minuta–E. vannus. The present investigation demonstrates that RFLP riboprinting is a useful technique for species separation. Some limitations of this method for inferring the relationships above species level are discussed.

Limnognathia maerski, class Micrognathozoa, so far known only from Arctic Greenland, is reported from the subantarctic Crozet Islands. Fine morphology of the trophi is redescribed using scanning electron microscopy. Results show that the trophi are composed of the same functional units, i.e. incus, paired mallei and epipharynx, as found in Rotifera Monogononta. The zoogeography of the species is briefly discussed.

The seasonal and spatial pattern of diet composition of a population of wild rabbits Oryctolagus cuniculus L. occupying a southern Portuguese montado was estimated using the n-alkane technique. The diet was analysed in terms of components that are relevant to habitat management. The dietary categories considered were gum cistus leaves and flowers, cork oak and holm oak seedlings and acorns, cereals, olive tree regrowth and grass-forb species. The objectives were to assess the changes in diet across seasons in relation to the reproductive cycle of the rabbits, and to relate these changes to herbaceous biomass availability and to habitat structure, in terms of density of scrub cover and accessibility to arable crops. The results demonstrated that the diet was dominated by grass-forbs, and cereals when they were available. Browse was an important component of the diet and became more important in a year of low herbaceous biomass availability and in areas dominated by dense scrub. A similar phenomenon was observed in relation to consumption of acorns in winter. Seasonal and spatial variation in diet composition suggested a strategy aimed at maintaining a high quality diet. This was supported by the observed high dry matter digestibility of the diet during most of the year. The relevance of growing arable crops and providing fodder, as a means of increasing the carrying capacity of montados for rabbits and protecting the natural regeneration of trees, is discussed.

The cross-sectional geometric properties of the crocodylian humerus were examined in order to assess the effects of differential locomotor behaviour and habitat use on osteological properties. Several biomechanical properties of the humerus were calculated, including resistance to compression and tension, bending and torsion resistance. The biomechanical properties of the crocodylian humerus reflect little variation attributable to locomotor behaviour or natural habitat use (terrestrial vs aquatic habitat). However, the biomechanical properties of captive individuals differed from those of wild conspecifics. The results of this research suggest that crocodylian humeri maintain sufficient resistance to all loading conditions throughout life with little remodelling, though both resorption and remodelling of bone are known to occur. Consequently, crocodylian humeri do not respond to stresses incurred during life as predicted by Wolff's Law.

The Editors are pleased to report that the Journal of Zoology had another successful year in 2001. The submission of high-quality papers has continued to increase in numbers, and although these are most welcome, it means that far more papers are received than we are able to publish. We therefore have to make hard decisions about the selection of topics to be covered and we have to keep a balance between vertebrate and invertebrate taxa. In August, it was agreed that the focus of the Journal should be re-directed to the publication of hypothesis-driven research that is of interest to the general reader in zoology. Although we will continue to publish original research and reviews within the whole field of zoology, and provide information on the latest trends and developments, papers on the systematics of a restricted number of taxa, or on topics of specialist interest only, will not normally be accepted. We have also introduced a mechanism for accelerated publication for papers that are considered to be of topical interest or those that describe innovative research.