We describe the digenean fauna of one of the dominant intertidal hosts, the common cockle Cerastoderma edule, in terms of biomass, off north-eastern Atlantic shores. Using published and unpublished literature we have prepared an identification key and provide an up-date of the large-scale distributional patterns of digenean species of the common cockle. At least sixteen digenean species, belonging to seven families, use cockles as intermediate host. Among these species two utilize cockles as first intermediate host only, whereas two species utilize cockles as both first and second intermediate host. The remaining eleven species have cockles as their second intermediate host. Water birds and fish are the definitive hosts to twelve and four species, respectively.Cockles are infected with digeneans along the latitudinal gradient from southern Morocco to the western region of the Barents Sea often with high infection levels. Whereas some of these digenean species occur along most of the latitudinal gradient others show a more restricted northern or southern distribution mostly caused by an underlying latitudinal gradient of host species.Knowledge of digenean species and their large-scale distribution pattern may serve as a baseline for future studies dealing with the effects of climate change on parasite-host systems. For such studies the cockle and its digenean community could be an ideal model system.

In the Bay of Saint-Brieuc, a 3,110-ha tidal bay in NW France, English Channel, the cockle Cerastoderma edule has been collected by traditional fishing methods for many decades without any evaluation or management of this resource taking place. Since 2001, the National Natural Reserve of the bay of Saint-Brieuc has carried out an evaluation of the stock and a mapping of the cockle fishing grounds each year. Analysis of the spatial structure of the population is approached by cartography through interpolation of the data using the kriging method. The recruitment zones are geographically quite well defined and located in areas limited to the mean-tide zone. The distribution of the population was affected by passive displacement of juvenile cockles. Evaluation using the matrix of individual numbers for each age group found the interannual mortality rates to be about 60%. Somatic production was estimated and expressed in ash-free dry weight. The average annual production ranged from 7.4 to 14.5 g/m 2 . In the autumn of 2006, the minimum legal fishing size changed from 30 to 27 mm (corresponding to individuals aged about 2.5 years). The model developed shows that this change has led to a doubling of the fishable stock.

Weighting of different orientation sources in conflict experiments in Blattella germanica (L.

WOS:A1994QA02600002International audienceThe aim of these experiments was to investigate the type of cues used in homing processes by young Blattella germanica L. larvae. Several types of stimuli were tested: path integration with kinesthetic cues and visual orientation with landmark cues. Tests measured the escape direction of larvae from the food box after disturbance. Either type of cue alone, path integration or visual landmarks, was sufficient to allow larvae to orient towards their shelters, but they oriented more precisely when both types of cue were used. When several landmark cues (proximal and distal) were present, their relative angular position seemed important in the orientation process. Macroscopic shapes in the environment appeared to be used as a global image, memorized to reach the shelter

International audienceChanges in spatial orientation related to aging were investigated during the first two instars in Blattella germanica (L). Spatial orientation was tested through shelter return under various experimental conditions in order to understand how kinesthetic path integration and visual cues intervene in the construction of this behaviour. We were able to distinguish two types of changes: experience during the first instar and maturation between instars. Young larvae need 2–3 d to develop the appropriate shelter-return behaviour when they can only use visual cues. By contrast, they can use kinesthetic path-integration cues efficiently to return to the shelter as soon as they hatch