The trematode fauna of Potamopyrgus antipodarum, an introduced and invasive gastropod mollusc species native to New Zealand, was studied in Mont Saint Michel Bay (France). The study revealed, for the first time in Europe, the occurrence of larval digenean species, Sanguinicola sp., a blood fluke of fish never previously recorded in this prosobranch. Phase contrast and scanning electron microscopy was used to investigate the morphology of the parasite. Hypotheses on the origin of the P. antipodarum–Sanguinicola sp. association are discussed in relation to the history of invasion of the gastropod into brackish and fresh waters and the structure of local gastropod communities.

The knowledge of the ability of a species to adapt to a human-altered environment is important for developing wildlife management plans and, in turn, for conservation of the species. Radio-tracking was used to examine the effects of partial food or cover removal (owing to agricultural changes) on the spacing patterns and habitat use of adult roe deer Capreolus capreolus in a mixed wood/agricultural Mediterranean area, during spring–summer 1996–97. For both sexes, there were no changes in home-range and core-area sizes, or in inter-fix distances, after food (field ploughing) or cover (crop harvesting) removal. After food removal, both sexes shifted their home ranges and core areas, spending more time in woodland and less time in the ploughed field. This suggests a change in feeding habits. In addition, similar responses by males and females indicate that their energetic requirements are comparable during the territorial/reproductive period. After removal of cover, males neither shifted their home ranges and core areas, nor changed their habitat use, whereas females responded with significant shifts (by c. 90%) of the core area, and a significant decrease in the proportion of daytime spent in the harvested field. Thus, crop harvesting in this period (May/June) has different effects on the two sexes, with adult females being much less tolerant than males. Differential responses to cover removal were related to the different security requirements of the two sexes around the period of parturition.

The most familiar examples of erectile tissue are the genitalia of mammals, notably the penis and clitoris. Among the soft-bodied invertebrates, erectile tissue is virtually unknown, even in sex organs. Here we report that the ligula, the copulatory organ that is a modification of an arm tip of male octopuses, is erectile in Octopus bimaculoides. The normally minute ligula was observed during an unsuccessful mating attempt to be engorged. Histological sections of the ligula reveal striking structural convergences with mammalian erectile tissue: large, well-vascularized internal cavities subdivided by networks of collagen fibres and enclosed by an array of collagen fibres. This internal structure differs markedly from the dense, three-dimensional array of muscles and connective tissues seen in the other octopodid ligulae examined. Erectile tissue may represent an evolutionary compromise between opposing selective forces. Small ligulae may be advantageous because O. bimaculoides hunts in daylight and the white-faced ligula may be conspicuous to predators. Large ligulae, however, may be advantageous if the intense sexual selection thought to occur among octopodids selects for large ligulae, which can transfer larger spermatophores that carry more sperm. An erectile ligula may minimize the impact of these opposing selective forces.

5th International Symposium on Tropical Biology: African Biodiversity – Molecules, Organisms, Ecosystems 2–6 May 2004

The factors that affect the selection of feeding sites by giant pandas Ailuropoda melanoleuca in the Longxi-Hongkou Nature Reserve were explored in winter from 2000 to 2002, by using strip transects. It was reported in the literature that giant pandas prefer to forage on the edges of bamboo patches because these edges offer them more food than the interiors. The number of feeding sites and the corresponding vegetation indices (including the basal diameter of bamboo stem, height and density of bamboo or bamboo shoot; density and canopy density of trees) were compared close to and far away from the edges of bamboo patches to detect the patterns of feeding habitat selection by giant pandas. Giant pandas preferred to forage at the sites near edges rather than in the interiors of bamboo patches. Such a tendency was independent of bamboo species and individual pandas. By comparing the density, basal diameter of bamboo stem and shoot, tree density and available dry biomass of bamboo, we detected no significant differences between the edges and the interiors of bamboo patches. The possible explanations were analysed and it was deemed that the selection of food habitat near edges by the giant pandas could be attributed to the direct effects of edges, which facilitate movement of the giant pandas in the otherwise dense bamboo patches.

Subterranean mammals inhabit an environment that is normally devoid of light and are therefore deprived of photoperiodic information that can be used to time important life-history events. An assessment was made of whether melatonin secretion in a strictly subterranean rodent, the Damaraland mole-rat Cryptomys damarensis, can be modified by photoperiod. In experiment 1, a clear diurnal rhythm of melatonin secretion in animals housed under a neutral photoperiod (12L:12D) was observed, with significantly higher melatonin concentrations in the dark compared to the light phase. The same diurnal melatonin rhythm was found 1 day after animals were transferred to either continuous light or continuous dark, suggesting that a circadian rhythm was maintained under acute exposure to light and dark. In experiment 2, melatonin secretion was monitored in a long (14L:10D) and short day (10L:14D) photoperiod and was found to be modified by the photoperiodic change. We therefore suggest that the Damaraland mole-rat possesses a circadian melatonin rhythm that can be physiologically modulated in response to photoperiod.

The amphipod Gammarus pulex is an intermediate host to the acanthocephalan fish parasite Echinorhynchus truttae. Gammarus pulex has a wide trophic repertoire, feeding as a herbivore, detritivore and predator. In this study an examination was made of the effects of E. truttae parasitism on components of the G. pulex diet: stream-conditioned leaves, dead chironomids and live juvenile isopods Asellus aquaticus. Over 21 days, parasitism had no effect on daily feeding rates or wet weights of G. pulex fed on leaves or chironomids. Parasitism had a significant effect on the number of A. aquaticus killed by G. pulex, with parasitized individuals killing significantly fewer than their unparasitized counterparts. In addition, unparasitized amphipods killed all size classes of A. aquaticus indiscriminately, whereas parasitized animals tended to kill the smaller size classes. The impacts of the parasitism of G. pulex throughout the wider freshwater community are discussed.