Homing and Egg Discrimination in the Western Slimy Salamander,Plethodon albagula(Caudata: Plethodontidae)

In some species of vertebrates egg brooding is a costly form of parental care. Therefore, misdirection of parental care can significantly lower a female’s fitness. Because of the maternal investment and increased survivorship to offspring from egg guarding, a brooding female should home to her nest site after being displaced a short distance and discriminate between her own eggs and eggs from other females. In this study, we experimentally tested, in the field, alternative hypotheses concerning homing ability and egg discrimination in a population of nesting western slimy salamanders (Plethodon albagula). Fourteen brooding females were displaced 1 m to the left or right of their nest sites (determined randomly) for the homing experiment. Furthermore, brooding females (n = 13) were presented with their own clutches, which were displaced 50 cm to the left or right (determined randomly), and unfamiliar egg clutches at their original nest sites. The females were released at an equal distance from both egg clutches. After 24 hours, 12 displaced females (86%) had returned to their own nest sites and were brooding their egg clutches. Also, after 24 hours, nine test females had returned to their own nest sites and were brooding the unfamiliar egg clutches. No control or test females were present at the other new nest site locations. Therefore, we suggest that brooding femaleP. albagulado home to their nest sites and exhibit indirect egg discrimination.

Egg mass ventilation by caridean shrimp: similarities to other decapods and insight into pheromone receptor location

Egg clutch brooding and larval release behaviour are common among decapods and involve pheromone communication between the developing embryos and the brooding female. We tested caridean shrimps to determine whether their behaviour was similar to other decapods. In tests with aqueous extracts of crushed eggs and peptide pheromone mimic shrimps responded similarly to brachyurans and lobsters. The elongate body form of shrimps enabled us to focally stimulate body locations with the goal of determining the location of pheromone receptors. The receptors for the pheromones are likely located on the bases of the walking legs or on the gills, not on the pleopods, first walking legs, antennae or antennules. Shrimps are another example of organisms that use peptides generated by trypsin-like serine proteases as pheromones and signal molecules.

Population dynamics and reproductive output of the non-indigenous crab Charybdis hellerii in the south-eastern Caribbean Sea

Charybdis hellerii is one of several poorly known non-indigenous crabs in the Caribbean. In this study we report on the reproductive dynamic of a shallow subtidal population that invaded Isla Margarita, Venezuela, south-eastern Caribbean Sea > 15 years ago and has persisted in the region up to date. Male and female crabs, both large and small, were found year-round at the study site. The size–frequency distribution indicated a lifespan of 2–3 years. Charybdis hellerii reproduces continuously but with very low intensity during the year. Small individuals (<25 mm carapace length) were uncommon and intermittently found during the study period. Sex-ratio varied between 0.1 and 0.65 (mean ± SD = of 0.46 ± 0.14) and did not differ significantly from 1:1 ratio during most of the year. The size of the smallest brooding female was 36.81 mm carapace width (CW). Behavioural size at first maturity (movable abdomen) in males and females was estimated to be 22.39 mm CW (confidence limits: 18.35–24.72) and 37.43 mm CW (35.55–39.09), respectively. Reproductive output, estimated as the ratio of embryo to female body dry mass, varied between 0.052 and 0.084 (0.07 ± 0.008). Also, reproductive output was size-dependent with large females allocating proportionally less resources to egg production than small females. The reproductive schedule here reported for C. hellerii disagrees with the generalized idea of exotic populations ‘thriving’ in an environment free of natural enemies (e.g. predators, competitors and diseases).

Roosting behaviour of the endangered Sichuan Hill-partridge Arborophila rufipectus during the breeding season

Roosting behaviour in diurnal ground-dwelling birds is important to their conservation as they are particularly vulnerable to predation when on their roosts. In 2005, we studied the roosting behaviour of the globally ‘Endangered’ Sichuan Hill-partridge (Arborophila rufipectus) in Laojunshan Nature Reserve, southwest China, a site dominated by evergreen broadleaf forest. Our study showed that the birds roosted on elevated perches and roosting behaviour was associated with social organization. Breeding males roosted alone within their territories before mating or during the female's involvement in incubation, but at other times they roosted with the female bird. After hatching of the brood, the adult males roosted on the ground close to the brooding female for about two weeks. After this time the male left the female and chicks to roost elsewhere in the territory. High vegetation cover around the perch site was a key predictor of roosting sites for the partridges. Only six out of 84 tree and shrub species were typically used by the roosting birds, although individual roosting plants varied from night to night. The median height of roosting plants was 6.9 (3.8–10.5) m, which was significantly lower than many shrubs within the breeding territory. Perches were 1.7–6.4 (median = 2.7) m from the ground and independent of roost tree height, suggesting an optimum roosting height. The partridges preferred roosting sites with denser shrub vegetation. In terms of the species' conservation, our results highlight the importance of protecting primary forest that contains suitable roosting trees and shrubs.

The reproductive cycle and development of Crepipatella fecunda (Gastropoda: Calyptraeidae) from southern Chile

Crepipatella fecunda is a benthic, primarily suspension-feeding gastropod that occurs in great abundance along the Chilean coast. It is a protandrous species whose reproduction involves brooding of an encapsulated embryonic stage followed by the release of free-living planktotrophic larvae. Because its close sister species, C. dilatata, co-occurs with C. fecunda, understanding the details of reproduction in this species might shed light on differences in reproductive features that correlate with divergences in mode of development. In southern Chile, brooding occurs throughout the year except for May and June, and each female produces 3–7 broods. The smallest brooding female was 28·2 mm in shell length and the largest was 56·3 mm. All full-grown eggs from the ovary are deposited at one time in a single brood, and only smaller oocytes remain in the gonad after the female finishes ovopositing. Those females that host pinnotherid crabs do not deposit eggs. All the eggs develop into embryos whose intracapsular development is similar to Crepidula fornicata and Crepipatella lingulata. Planktotrophic larvae hatch at a mean shell length of 329·5 μm (SD=27·09) after 4–5 weeks. During the pelagic stage the shell and velum of the larvae grow, but little other morphological development is visible externally. The pelagic stage lasts for 15–16 days at 17°C, during which the larvae grow ∼20·7 μm d−1. Observations of cultured larvae and protoconchs of field-collected juveniles show that settlement occurs when the larvae reach a shell-length of 650 μm (SD=28·3 μm).

Respiration rates in late eggs and early hatchlings of the common octopus, Octopus vulgaris

Respiration rates during late embryonic development and hatchlings of Octopus vulgaris were measured at 20 °C. Oxygen consumption rates increased suddenly at hatching, in response to the increase in energetic expenditure due to their constant swimming activity by means of jet propulsion. Estimates indicate that hatchlings consumed three times more oxygen than the embryos at late stages. Chemical composition analysis revealed a relatively high nitrogen content (11%) in O. vulgaris hatchlings with an energy content of 1.09±0.03 J mg dry matter−1. Specific oxygen consumption in unfed O. vulgaris hatchlings reached values around 0.18 nmol O2 μg−1 h−1. It was estimated that the oxygen consumption of a medium-size egg mass of O. vulgaris is approximately twice than the oxygen uptake of the respective brooding female.

Gastric Brooding - a New Form in a Recently Discovered Australian Frog of the Genus Rheobatrachus

The phenomenon of gastric brooding and oral birth displayed by the Australian frog Rheobatrachus silus has not previously been observed in the Animal Kingdom. This report describes another example of gastric brooding in a recently discovered, closely related species, Rheobatrachus vitellinus. The stomach of a female R. vitellinus that had given birth to 22 froglets revealed morphologic changes which were quite different to those described in R. silus. Unlike the atrophy of the mucosa and acid-secreting oxyntic cells in the latter species, there was no evidence of major structural changes in the brooding stomach of R. vitellinus. Furthermore, no differences were observed in the light microscopic appearances of the stomach in the brooding female and that from a non-brooding female and male R. vitellinus. A striking finding not observed in the non-brooding stomachs of R. vitellinus nor in R. silus was the presence of widespread and numerous apoptotic bodies in the gastric epithelium. The apoptotic bodies were recognized as phagocytosed fragments of eosinophilic cytoplasm and pyknotic nuclear material. Ultrastructurally, well preserved organelles were observed in the phagocytosed fragments. This diffuse deletion of cells and the striking absence of major structural changes in the brooding stomach may indicate a dichotomy in the evolution of this bizarre and unique reproductive habit.

The Disputed Feeding Behaviour of a Paedophagous Haplochromine Cichlid (Pisces) Observed and Discussed

Aquarium-observations on a new paedophagous haplochromine species (Pisces, Cichlidae) showed that engulfing the snout of a brooding female to extract the brood, is a possible technique of gathering food, as was suggested by GREENWOOD (1959, 1974). Considering morphological information from various authors (GREENWOOD, 1959, 1974; BAREL et al., 1976, 1977) and notwithstanding some doubt expressed by FRYER & ILES (1972) and FRYER (1977), this snout-engulfing may be a widespread technique among the "larger mouthed" paedophages (i. e. in Lake Victoria: 6 out of 8 spp. described plus at least 8 new spp.). Snout-engulfing is the climax of a performance which resembles a fight, during which the paedophage also can force a brooding female to disgorge its brood by chasing and repeated attacks. The origin of snout-engulfing may be thought to lie in a modification of the fighting behaviour of a piscivorous ancestor, hunting on already jettisoned young still guarded by the female.