No abstract

Genetic variation at 21 gene-enzyme systems was studied in a sample of an adult population of Anisakis typica (Diesing, 1860) recovered in the dolphin Sotalia fluviatilis from the Atlantic coast of Brazil. The characteristic alleles, detected in this population, made it possible to identify as A. typica, Anisakis larvae with a Type I morphology (sensu Berland, 1961) from various fishes: Thunnus thynnus and Auxis thazard from Brazil waters, Trachurus picturatus and Scomber japonicus from Madeiran waters, Scomberomorus commerson, Euthynnus affinis, Sarda orientalis and Coryphaena hippurus from the Somali coast of the Indian Ocean, and Merluccius merluccius from the Eastern Mediterranean. Characteristic allozymes are given for the identification, at any life-stage and in both sexes, of A. typica and the other Anisakis species so far studied genetically. The distribution of A. typica in warmer temperate and tropical waters is confirmed; the definitive hosts so far identified for this species belong to delphinids, phocoenids and pontoporids. The present findings represent the first established records of intermediate/paratenic hosts of A. typica and extend its range to Somali waters of the Indian Ocean and to the Eastern Mediterranean Sea. A remarkable genetic homogeneity was observed in larval and adult samples of A. typica despite their different geographical origin; interpopulation genetic distances were low, ranging from D(Nei)=0.004 (Eastern Mediterranean versus Somali) to D(Nei)=0.010 (Brazilian versus Somali). Accordingly, indirect estimates of gene flow gave a rather high average value of Nm = 6.00. Genetic divergence of A. typica was, on average, D(Nei)=1.12 from the members of the A. simplex complex (A. simplex s.s, A. pegreffii, A. simplex C) and D(Nei)=1.41 from A. ziphidarum, which all share Type I larvae; higher values were found from both A. physeteris (D(Nei)=2.77)

Seventy-four genera comprising approximately 140 named and 75 undetermined species of adult and larval nematodes are associated with about 330 named and 50 undetermined species of marine, brackish and freshwater fishes from Brazilian waters. These are listed with information on their hosts, habitat, distribution and records. A key to these parasites at the generic level is provided.

Pseudorhabdosynochus sulamericanus n. sp. from the gills of Epinephelus niveatus has a reniform proximal region of the cirrus-bulb which is divided in four chambers and contains a large, round reservoir of the male accessory glands, a partly sclerotised vagina which is enclosed in a muscular funnel cap and squamodiscs with 15-16 open concentric rows of elements. P. beverleyburtonae (Oliver, 1984) is redescribed from E. marginatus with additional morphological data. These are the first reports of Pseudorhabdosynochus spp. in South American Atlantic waters, where the potentiality for the mariculture of Epinephelus spp. is currently being evaluated. Pseudorhabdosynochus hargisi (Oliver & Paperna, 1984) n. comb. is proposed for Diplectanum hargisi.

Anisakid nematode larvae from Trichiurus lepturus off coast of Rio de Janeiro were studied using light, laser confocal and scanning electron microscopy, in addition to a molecular approach. Mitochondrial cytochrome c-oxidase subunit 2 (mtDNA cox-2), partial 28S (LSU) and internal transcribed spacers (ITS-1, 5.8S, ITS-2) of ribosomal DNA were amplified using the polymerase chain reaction and sequenced to evaluate the phylogenetic relationships between the nematode taxa. The morphological and genetic profiles confirmed that, of the 1,030 larvae collected from the 64 fish examined, 398 were analysed, of which 361 were Hysterothylacium sp. and 37 were Anisakis typica. Larvae of Hysterothylacium sp. were not identified to the species level due to the absence of similar sequences for adult parasites; however, the ITS sequence clustered in the phylogenetic tree with sequences of H. deardorffoverstreetorum, whereas an mtDNA cox-2 and LSU concatenated phylogenetic analysis demonstrated the presence of two clades, both of them under the same name as the larval H. deardorffoverstreetorum. Data on the occurrence of parasites during the winter and summer months were compared using the t-test. The greatest prevalence and intensity of infection were recorded for larval Hysterothylacium, with a prevalence of 51.56% and an intensity of up to 55 parasites per fish. The larval Anisakis exhibit a higher abundance and intensity of infection in the winter months, and those of Hysterothylacium during the summer. However, the t-test indicated no significant differences between the abundance and intensity of infection recorded during the months of collection for either of these larval nematodes. All sequences generated in this study were deposited in GenBank.