A strain of Cyclotella meneghiniana was isolated from the River Danube. The optimum irradiance and temperature for growthwere determined in batch cultures. The optimum temperature for growth was 25 °C. The estimated saturated irradiance wasnear 125 µE m-2 s-1. The calculated Ik for growth and photosynthesis were 30 ± 3 and 44 ± 6 µE m-2 s-1 respectively. A continuousculture technique was used to test the growth and cell composition at the transition state between batch, nutrient sufficiency, anda low rate of nutrient supply. Algal response was characterized by high intracellular N and C with negative growth rate. At a lowdilution rate (0.06 d-1), the continuous culture theory was not followed. This critical rate is characterized by low chlorophyll-acontent per cell and may depend on the mode of nutrition.

Les recherches écologiques concernant la nouvelle espèce marocaine de Phreodrilidae en provenance du sous-écoulement dedivers oueds et de puits du Haut Atlas de la région de Marrakech nous ont permis de confirmer son statut d'espèce stygobie, sapréférence pour les biotopes hyporhéiques et les sédiments sableux ainsi que le rôle déterminant de la texture des sédiments surson mode de répartition.Une étude conjointe du bol alimentaire des représentants du genre Astacopsidrilus et du genre Trichodrilus qui cohabitent autitre de formes dominantes de la faune totale d'Oligochètes dans le sous-écoulement de l'Oued Makhfaman, affluent de l'OuedN'Fis (Haut Atlas, région de Marrakech) a été réalisée sur la base notamment du calcul du nombre et de la taille des particulessableuses ingérées. Cette analyse a révélé la plus grande capacité d'absorption de l'appareil digestif de la nouvelle espèce dePhreodrilidae, comparativement aux représentants du genre Trichodrilus, considérés comme des limivores sensu stricto et permisd'aborder le comportement alimentaire de ces taxons en termes de compétitivité.

The epithelia of the main organs likely to be involved in contaminant uptake, viz. mantle and gill were studied in the Asiaticclam Corbicula fluminea as a base for future ecotoxicological studies. On its margin, the mantle epithelium displays three foldsseparated by two grooves. The outer epithelium made of cubic cells, and the periostracal groove are involved in the formation iscomposed of the shell, secreting crystals and the periostracal lamella respectively. In the median area, the inner epithelium iscomposed of three cell types: ordinary epithelial cells, ciliated cells and mucocytes. The gill epithelium displays two structurallyand functionally different areas: a respiratory area in the interlamellar chamber and, on the opposite side, a ciliated epithelium.The respiratory epithelium is composed of thin pavement epithelial cells. The ciliated epithelium is made of different cell types:lateral ciliated epithelial cells, secretory cells, latero-frontal ciliated cells and ciliated frontal cells. The role of the secretory cellsis particularly discussed in relation to their structural similarity with lower vertebrate chloride cells (ionocytes) involved in iono- andosmoregulation processes.

The life cycle of a brackish-water population of Palaemonetes argentinus, a normally freshwater shrimp from the warm temperateregion of eastern South America, was studied in Mar Chiquita coastal lagoon, Argentina. In 1995, recruitment took placein January, followed by two growth periods, the first at the beginning of summer and the second from the end of winter throughmost of spring. Females reached a larger size than males. Ovigerous females, probably belonging to two cohorts, were foundfrom October 1995 to February 1996, with a maximum number in November (93 %). Their average size and fecundity varied duringthe breeding period. The sex ratio did not significantly differ from 1:1 except in November. Evidence of mature oocytes inthe ovaries was found in ovigerous and postovigerous shrimps, suggesting that they breed twice a year. However, only some femalesof the first cohort produced a second hatch in 1995. The maximum number of undifferentiated embryos carried by a femalewas 250; there was a positive relationship between fecundity and size. Larvae were collected together with adults from Novemberto March. The life history is similar to that described in several freshwater populations. Differences are restricted to chronologicalaspects such as a shorter unimodal breeding period and are probably related to climatic factors, since Mar Chiquita is nearthe southern limit of the geographic range of the species. Data presented here suggest interannual variations in reproductive patternsthat lead, sometimes, to a longer bimodal breeding period.

Edmulmeatus grandis, n. gen. and sp. (Ephemeroptera : Baetidae) is described from larvae collected from eastern Madagascar.The genus is distinguished primarily by having a relatively very large head capsule, large and robust mandibles with specializedarmature, and gills on abdominal segments 2-7 only. The relatively massive mandibles suggest that larvae have unusual feedinghabits compared to other baetids, being probably a macrovore-herbivore adapted for cutting and crushing plant food items. Edmulmeatusis possibly related to other Afrotropical genera having two rows of denticles on the tarsal claws.

A new corer is described which may be used in sediments of shallow standing waters, such as in rice fields, and which facilitatesthe study of the vertical distribution of the invertebrate fauna at 2 cm depth intervals. Its small surface area permits quantitativesampling of the sediment-dwelling fauna, particularly the chironomid larvae, around the roots of rice-plants. Results arepresented and the efficiency of the sampling method is discussed.