Ana L. Lanfranchi

Similarity in parasite communities of the teleost fish Pinguipes brasilianus in the southwestern Atlantic: infracommunities as a tool to detect geographical patterns.

Patterns of distance decay in similarity among communities of the fish Pinguipes brasilianus (Teleostei: Pinguipedidae) from five areas in the southwestern Atlantic were investigated to determine whether the rate of decay varied depending on the community level or the parasite guild analyzed (ectoparasites, adult endoparasites and larval endoparasites). Similarities in species composition were computed at both the component community and infracommunity levels. Similarity indices were calculated between all possible pairs of assemblages from different zones. Infracommunity similarity values between and within host populations were averaged. Significance of linear regressions for similarity values against distance was assessed using randomization tests. Different patterns were observed for each guild, and similarity among infracommunities within host populations varied accordingly. Decay in similarity over distance was recorded for most communities. The slopes differed significantly between infracommunities and component communities in all cases, and stronger decay was always observed for infracommunities. Different geographical patterns in parasite communities were a consequence of variability in parasite availability in the different regions, modulated by oceanographic conditions, as well as variation among species in terms of host specificity and life-cycles strategies. Infracommunities showed a stronger effect of distance than component communities, probably due to the influence of short term and local variability of oceanographic conditions.

Seasonal stability and spatial variability of parasites in Brazilian sandperch Pinguipes brasilianus from the Northern Argentine Sea: evidence for stock discrimination

The use of parasites as biological tags allowed the identification of two stocks of Brazilian sandperch Pinguipes brasilianus, in the Bonaerense region of the Argentine Sea. A total of 156 adult specimens of P. brasilianus were examined for parasites. Temporal variability in parasite burdens was assessed from fish caught seasonally in coastal waters of two zones, south Bonaerense (during autumn and winter) and north Bonaerense (during summer). Additional data from a previous study, comprising P. brasilianus caught during spring in these two zones, as well as in two populations from north Patagonian gulfs were used for comparative analyses of spatial variability. A total of 14 193 metazoan parasites belonging to 19 species were found. Comparisons of seasonal variability in pooled samples and within each locality showed that locality effects exceeded seasonal ones, suggesting the possible existence of two discrete stocks in the Bonaerense region. These findings were strongly supported by discriminant analyses and comparisons of prevalence and abundance between zones, after pooling seasonal samples within each zone. Further evidence of the discreteness of both stocks was assessed by inclusion of samples from Patagonian gulfs in the discriminant analysis, confirming that their differences were at a inter-population level. The parasite species that contributed most to the separation of the samples were generally those identified as biological markers in previous studies. Differing oceanographic conditions are discussed as potential causes of inter-population variation of parasite burdens.

Molecular identification, morphological characterization and new insights into the ecology of larval Pseudoterranova cattani in fishes from the Argentine coast with its differentiation from the Antarctic species, P. decipiens sp. E (Nematoda: Anisakidae).

Larvae of the genus Pseudoterranova constitute a risk for human health when ingested through raw or undercooked fish. They can provoke pseudoterranovosis in humans, a fish-borne zoonotic disease whose pathogenicity varies with the species involved, making their correct specific identification a necessary step in the knowledge of this zoonosis. Larvae of Pseudoterranova decipiens s.l. have been reported in several fish species from off the Argentine coasts; however, there are no studies dealing with their specific identification in this region. Here, a genetic identification and morphological characterization of larval Pseudoterranova spp. from three fish species sampled from Argentine waters and from Notothenia coriiceps from Antarctic waters was carried out. Larvae were sequenced for their genetic/molecular identification, including the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2), the first (ITS-1) and the second (ITS-2) internal transcribed spacers of the nuclear ribosomal DNA, and compared with all species of the P. decipiens (sensu lato) species complex (sequences available in GenBank). Further, adults of Pseudoterranova spp. from the definitive host, the southern sea lion, Otaria flavescens, from Argentine and Chilean coasts were sequenced at the same genes. The sequences obtained at the ITS-1 and ITS-2 genes from all the larvae examined from fish of Argentine waters, as well as the adult worms, matched 100% the sequences for the species P. cattani. The sequences obtained at mtDNA cox2 gene for Antarctic larvae matched 99% those available in GenBank for the sibling P. decipiens sp. E. Both MP and BI phylogenetic trees strongly supported P. cattani and P. decipiens sp. E as two distinct phylogenetic lineages and depicted the species P. decipiens sp. E as sister taxon to the remaining taxa of the P. decipiens complex. Larval morphometry was similar between specimens of P. cattani from Argentina, but significantly different from those of P. decipiens sp. E, indicating that larval forms can be distinguished based on their morphology. Pseudoterranova cattani is common and abundant in a variety of fish species from Chile, whereas few host species harbour these larvae in Argentina where they show low levels of parasitism. This pattern could arise from a combination of factors, including environmental conditions, density and dietary preferences of definitive hosts and life-cycle pathways of the parasite. Finally, this study revealed that the life-cycle of P. cattani involves mainly demersal and benthic organisms, with a marked preference by large-sized benthophagous fish.

A NEW SPECIES OF CUCULLANUS (NEMATODA: CUCULLANIDAE) PARASITIZING CONGER ORBIGNIANUS (PISCES: CONGRIDAE) FROM ARGENTINEAN WATERS

In total, 17 specimens of Conger orbignianus Valenciennes, 1847 from waters off Mar del Plata, Argentina (38°08′S, 57°32′W) were examined for parasitic nematodes. A new nematode species, Cucullanus pedroi n. sp., is described (prevalence 76.5%, x̄ intensity ± SD = 3.8 ± 2.7). The new species closely resembles some species parasitizing other anguilliform fishes; however, it can be distinguished from most of its congeners by the distribution pattern of caudal papillae (particularly fourth and eight pairs) and phasmids. Those congeners with similar pattern of papillae differ from the new species by the length of the spicules and gubernaculum and by the position of the excretory pore and deirids.

Fish trophic level and the similarity of non-specific larval parasite assemblages

Whereas the effect of parasites on food webs is increasingly recognised and has been extensively measured and modelled, the effect of food webs on the structure of parasite assemblages has not been quantified in a similar way. Here, we apply the concept of decay in community similarity with increasing distance, previously used for parasites in geographical, phylogenetic and ontogenetic contexts, to differences in the trophic level (TL) based on diet composition of fishes. It is proposed as an accurate quantitative method to measure rates of assemblage change as a function of host feeding habits and is applied, to our knowledge for the first time, across host species in marine waters. We focused on a suite of 15 species of trophically-transmitted and non-specific larval helminths across 16 fish species (1783 specimens, six orders, 14 families) with different sizes and TLs, gathered from the same ecosystem. Not all host species harboured the same number and types of parasites, reflecting the differences in their ecological characteristics. Using differences in TL and body length as measurements of size and trophic distances, we found that similarity at both infracommunity and component community levels showed a very clear decay pattern, based on parasite abundance and relative abundance, with increasing distance in TL, but was not related to changes in fish size, with TL thus emerging as the main explanatory factor for similarity of parasite assemblages. Furthermore, the relationships between host TL and assemblage similarity allowed identification of fishes for which the TL was under- or over-estimated and prediction of the TL of host species based on parasite data alone.

A new species of Capillaria (Nematoda: Capillariidae) parasitizing Conger orbignianus (Pisces: Congridae) from Argentina.

Capillaria (Procapillaria) navoneae n. sp. is described from the congrid fish Conger orbignianus from waters off Mar del Plata, Argentina (38°08′S, 57°32′W) (prevalence 29.17%, mean intensity ± SD 6.07 ± 6.59). The new species is assigned to the subgenus Procapillaria Moravec, 1987, despite the absence of vulvar appendages in gravid females. Of the 3 species so far known in the subgenus, the new one most closely resembles C. (P.) margolisi, from which it is distinguished by lacking a medial expansion in the spicule and a slightly elevated anterior lip of vulva, and by having a shorter esophagus, a larger number of stichocytes, and a shorter tail.

A NEW SPECIES OF PARACAPILLARIA (NEMATODA: CAPILLARIIDAE) PARASITIZING THE BRAZILIAN SANDPERCH, PINGUIPES BRASILIANUS (PISCES: PINGUIPEDIDAE), FROM ARGENTINA

A new species, Paracapillaria argentinensis n. sp., is described from the pinguipedid fish Pinguipes brasilianus Cuvier, 1829 from waters off Mar del Plata, Argentina (38°08′S, 57°32′W) (prevalence 22.2%; mean intensity ± SD, 4.42 ± 5.19). The new species is assigned to the subgenus Paracapillaria Moravec, 1987. Of the 10 species so far known in the subgenus, the new species more closely resembles P. (P.) plectroplites, from which it is distinguished by having a spicule with an expanded anterior end and a slender medial section. A similar spicular morphology is observed in P. (P.) epinepheli; however, it shows shorter spicules and a highly reduced caudal bursa. This is the first record of Paracapillaria in the southwestern Atlantic Ocean.

Redescription of Neobrachiella spinicephala (Ringuelet, 1945) parasitic on Pinguipes brasilianus Cuvier, 1829 from Argentina, with the first description of the male

Neobrachiella spinicephala (Ringuelet, 1945) (Copepoda, Siphonostomatoida, Lernaeopodidae) is redescribed based on newly collected material from the Brazilian sandperch, Pinguipes brasilianus Cuvier, 1829, (the type host) from Mar del Plata, Argentina (the type locality). A description of the male is given for the first time. Although some differences were observed between the original description and the specimens examined in this study, these differences do not warrant a change in the taxonomic status of this species. Indeed, the generic status of the species is confirmed, especially based on characteristics of the male.

The mesoparasitic copepod Trifur tortuosus Wilson, 1917 (Pennellidae): Redescription with notes on its congeners

The genus TrifurWilson, 1917 (Siphonostomatoida, Pennellidae) comprises relatively large and conspicuous parasitic copepods infecting the body surface and gills of several marine fishes. Variations in the gross morphology have been used to discriminate between the existing species of Trifur, however all previous descriptions of these species are brief, lacking many important characteristics, especially those of the head and trunk appendages, which usually were lost in the described specimens. In this paper, T. tortuosus is redescribed based on newly collected material from three species of fishes from Argentinean coasts. A detailed description of appendages morphology is given and the validity of T. merluccii Talice, 1936; T. puntaniger Thomé, 1963; T. physiculi Heegaard, 1962 and T. lotellae (Thomson, 1890) is herewith discussed.

Ecotonal marine regions – ecotonal parasite communities: helminth assemblages in the convergence of masses of water in the southwestern Atlantic Ocean

With the aim of evaluating the utility of marine parasites as indicators of ecotonal regions in the marine environment, we analysed data on assemblages of long-lived larval parasites of Zenopsis conchifer inhabiting the region of convergence of three masses of water in the southwestern Atlantic Oceans. These masses of water with different origins are expected to affect the structure of parasite communities by acting as sources of infective stages of helminth species typical of adjacent zoogeographical regions. Multivariate analyses at both infracommunity and component community levels, including data of four other species recognised as harbouring parasite assemblages representatives of these zoogeographical regions, were carried out to corroborate the existence of repeatable distribution patterns and to provide further evidence of the utility of parasites as zoogeographic indicators in the region. Results showed a tight correspondence with the existing zoogeographical classification in the study region, namely two zoogeographical provinces, one of which is subdivided into two districts demonstrating the ecotonal nature of parasite assemblages from the convergence region, which were characterised by a species rich component community but depauperate and heterogeneous infracommunities. The borders of biological communities have been suggested as priority areas for conservation where a fully functioning ecosystem can be protected and parasite communities can be considered as reliable indicators to define such transitional regions.