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In order to establish the distribution and abundance of demersal fishes and of some other benthic organisms on the continental shelf of French Guiana (western central Atlantic), ninety-five bottom trawls were effected at depths ranging from 0 to 60 m in October 1993. A total of one hundred and ten different species were identified including eight decapod crustaceans, two cephalopods, one sea turtle and ninety-nine fishes. Despite the high species richness in benthic macrofauna, most species showed a low count, and only twelve of them comprised more than 80% of total captures. This study has mainly highlighted the existence of a well-pronounced bathymetric zonation. This phenomenon would appear to be linked to environmental factors, especially salinity and substrate granulometry, which are greatly conditioned by fresh water and sediment flowing in large rivers such the Amazon River. The results revealed three distinct faunistic assemblages: a littoral (or shallow-water) community (0-30 m) distributed in coastal estuarine waters characterized by muddy bottoms, a middle-shelf community (30-50 m), and a lower-shelf community (depths > 50 m) distributed in deeper marine waters characterized by sandy bottoms.

The study of the cymothoid isopod parasites on marine fishes from Tunisian localities has allowed us to distinguish eight species, seven of which have already been recorded and one, Mothocya epimerica which is new to the region. New hosts for Cerathotoa parallela and Nerocila orbignyi are reported. For each parasite species collected, the host fish, the parasitic specificity and the parasitological index are given.

A genetic analysis realized, on Tunisian coasts, within and between two populations of a Teleostean (Sardina pilchardus) on one hand, and two populations of their parasitic Copepods (Peroderma cylindricum) on the other hand, reveal that: (l) the 14 loci analysed are monomorphic in the Teleostean populations; (II) 3 loci among 13 investigated are polymorphic in the Copepod populations. Statistical tests from deviations of Hardy-Weinberg equilibrium and genotypic homogeneity show the existence of strong gene flows within and between Copepod populations. Thus, it seems that the Teleostean (Sardina pilchardus) and the Copepod (Peroderma cylindricum) constitute at least on Tunisian coasts, two homogeneous taxinomic units.

In polytypic Idotea chelipes species, the slow esterase constitutes a subspecific biochemical marker which discriminates, without ambiguity, each of three subspecies. Amylase 2 is a diagnostic locus which separates I. chelipes bocqueti from the two other subspecies where each is characterized by particular frequencies of the most frequent allele. The analysed electrophoretic zymogram and the intersubspecific cross-breeding results attribute a monomeric structure for this enzyme which depends on diallelic gene.

Hemocyanin has been used as a protein marker for Crustacea speciation. The specificity of the hemocyanin fractions of two Idotea species has been confirmed by mono and bidirection electrophoresis. Four protein fractions have been found in the two Idotea species. However, the molecular weight of each Idotea chelipes fraction is slightly higher. The two fractions of high molecular weight are strongly associated. We assumed a molecular weight of 240,000 for I. chelipes and 230,000 for I. balthica basteri. The two other protein fractions are well separated and have a weight of 130,000 and 77,000 in I. chelipes; 120,000 and 75,000 for I. b. basteri. In contrast, the subspeciation of I. chelipes has not been clearly demonstrated by electrophoresis of the hemocyanin.

Out of 29 species of fish from the Kerkennah Islands examined, 30 species of parasitic copepoda were collected which belong to seven families and nine different genera. Among them three new species have been found and ten were reported for the first time in Tunisia.

Twenty-five species of parasitic copepods are presented, collected on fishes living in the Montenegro sea coasts. Among these species, belonging to ten families and sixteen different genera, fifteen are new records for the Adriatic Sea.