RESUMO
Egg cases of the narrowmouthed catshark Schroederichthys bivius were recorded entangled with sponges, corals and tubeworms at different sites in the south-west Atlantic Ocean. This work sheds light on the importance of benthic invertebrates in the life cycle of oviparous chondrichthyan species.
Assuntos
Invertebrados , Óvulo/fisiologia , Tubarões/fisiologia , Animais , Oceano Atlântico , Cruzamento , Ecossistema , PeixesRESUMO
The fish fauna of the Pampa Plain, the southernmost distribution range of many Neotropical species, was barcoded in this study. COI sequences were analysed by means of distance (K2P/NJ) and character-based (ML) models, as well as the Barcode Index Number (BIN). K2P/NJ analysis was able to discriminate among all previously identified species while also revealing the likely occurrence of two cryptic species that were further supported by BIN and ML analyses. On the other hand, both BIN and ML were not able to discriminate between two species of Rineloricaria. Despite the small genetic divergence between A. cf. pampa and A. eigenmanniorum, a tight array of haplotypes was observed for each species in both the distance and character-based methods. Deep intraspecific divergences were detected in Cnesterodon decemmaculatus (5%) and Salminus brasiliensis (6%). For Salminus brasiliensis, these findings were further supported by character-based (ML) evidence and meristic and morphological data. Our results also showed that Pampa Plain representatives of Salminus brasiliensis, Rhamdia quelen, Hoplias malabaricus, Synbranchus marmoratus, Australoheros facetus, Oligosarcus jenynsii and Corydoras paleatus differed by more than 3% from their conspecifics from other parts of South America. Overall, this study was able to highlight the likely occurrence of a cryptic species in Salminus brasiliensis and also illustrate the strong geographical structure in the COI sequence composition of seven fish species from South America.
Assuntos
Biodiversidade , Peixes/classificação , Peixes/genética , Animais , Argentina , Análise por Conglomerados , Código de Barras de DNA Taxonômico , Complexo IV da Cadeia de Transporte de Elétrons/genética , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNARESUMO
Morphologically, both classic and landmark-based morphometry and meristic analyses of 241 specimens of Merluccius, along with the re-examination of six paratype specimens of Merluccius hubbsi, the holotype and three paratypes of Merluccius patagonicus and the syntype of Merluccius australis revealed the presence of only two species of Merluccius in Argentinean waters. Internal structures (hyomandibula, urohyal and sagitta otolith) of M. hubbsi were compared to those reported for M. patagonicus and were shown to have identical morphology. Type specimens of M. patagonicus showed a complete overlap in morphometric and meristic characters with M. hubbsi, whereas M. australis had a greater number of second dorsal and anal-fin rays, and more lateral-line scales. In addition, M. australis had a smaller eye and longer snout than M. hubbsi and M. patagonicus. The results indicate that there is no evidence for a third hake species in Argentinean waters. Merluccius patagonicus is a synonym of M. hubbsi.