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Five genetically distinct and reproductively isolated species have been detected previously within the morphospecies Pseudoterranova decipiens from the Arctic-Boreal, Boreal and Antarctic. Morphological analysis was carried out on male specimens identified by genetic (allozyme) markers, allowing the detection of significant differences at a number of characters between two members of the P. decipiens complex, namely P. decipiens A and B. On the basis of such differences, the nomenclatural designation for the two species is discussed. The names Pseudoterranova krabbei n. sp. and P. decipiens (sensu stricto) are proposed for species A and B, respectively. Morphological and genetic differentiation between the two species is shown using multivariate analysis. Allozyme diagnostic keys for routine identification of the four members of the P. decipiens complex, namely P. decipiens (s.s.), P. krabbei, P. bulbosa and P. azarasi, irrespective of sex and life-history stage, are provided.

Biochemical keys based on the electrophoretic patterns of nine enzymatic loci diagnostic between Dirofilaria repens and D. immitis were used to examine an immature female of Dirofilaria removed from a 32-year-old woman resident in Caserta, Italy. The worm, tentatively assigned on a morphological basis to D. conjunctivae-D. repens, showed at all the loci examined the same electrophoretic pattern as an Italian dog strain of D. repens. This genetic evidence is in substantial agreement with the hypothesis, already supported by morphological and epidemiological data, that D. conjunctivae (Addario, 1885) Desportes, 1939-1940 and D. repens Railliet and Henry, 1911 should be considered as synonyms. According to the law of priority D. conjunctivae should be the valid name for the species; however, it is proposed to preserve the name repens, well-established for the dog subcutaneous filaria. Multilocus electrophoretic analysis appears to be a valuable tool for the identification of aetiological agents of human zoonotic filariae, particularly in areas where more than one species of the subgenus Nochtiella are present.

A multilocus genetic analysis based on protein electrophoresis was carried out on 39 adult specimens of Dirofilaria repens and 31 of D. immitis. Seventeen enzymatic loci provided reliable electrophoretic patterns which were compared in the two species. All loci except one were monomorphic. Fixed alternative allozymes were found at 13 loci while only 3 loci shared apparently the same allozyme in the two species. The polymorphic locus, Pgm, also showed alternative allozymes. This remarkably high genetic divergence, which presumably reflects a very old speciation process, allows an easy characterization of D. repens and D. immitis and supports their classification in the subgenera Nochtiella and Dirofilaria, respectively.

Anguillicola australiensis Johnston and Mawson, 1940 is redescribed and reported for the first time from Anguilla anguilla of Lake Bracciano (Rome-Italy). It is suggested that the appearance of Anguillicola australiensis in european eels might be in relation with intercontinental live eels transfers.

Data on the occurrence of larvae of Anisakis simplex A and Anisakis physeteris in marine fishes from Italian waters are reported. The larvae have been identified by multilocus electrophoresis using biochemical keys. Considerations on the life-history pattern of these species in the Mediterranean Sea are advanced.

On the basis of electrophoretic studies carried out on 15 gene-enzyme systems, 80 Anisakis sp. larvae from the herring Clupea harengus, fished in South Baltic Sea and Gdanisk Bay, were identified as Anisakis simplex B. This is the first record of Anisakis simplex B in the Baltic Sea. The spawning migration of the herrings from the North Sea to the Baltic Sea and the distribution of A. simplex B are briefly discussed.

As a further contribution to the systematics of species belonging to the genus Crassostrea, electrophoretic studies of gene-enzyme system have been carried out on five populations of oysters regarded as either Crassostrea gigas or Crassostrea angulata species. Two populations of C. gigas from Japan (Karakawa and Hiroshima), one of C. gigas from France (Fouras), one of C. angulata from Portugal (Sado) and one of Crassostrea sp. from Italy (Chioggia) have been examined. The electrophoretic study of 20 enzyme loci and the genetic distance value showed no significant genetic divergence among the Crassostrea sp. populations. Thus the results of this study seem to confirm and extend to other populations what obtained by Buroker et al. (1979), that is a remarkable genetical identity between the two species Crassostrea gigas and Crassostrea angulata.