RESUMO
Two new species of Acanthobothrium Blanchard, 1848 were collected from rajiform batoids along the coast of Argentina. They are Acanthobothrium carolinae sp. n. from Bathyraja magellanica (Philippi) and Acanthobothrium domingae sp. n. from Dipturus brevicaudatus (Marini). Both belong to category 1 and 2 because their total length is lower than 15 mm, they have fewer than 50 proglottids, fewer than 80 testes and a symmetric or asymmetric ovary. Acanthobothrium carolinae sp. n. differs from all congeners by the following combination of features: proglottid apolysis, hook morphology, microthrix pattern on the cephalic peduncle and distribution of the vitelline follicles. Acanthobothrium domingae sp. n. is unique in the combination of proglottid apolysis, total length, number of proglottids, hook and septal morphology, microthrix pattern on the cephalic peduncle, number and distribution of testes, cirrus sac length, distribution of the vitelline follicles and genital pore position. The discovery of these species increases the number of species of Acanthobothrium parasitising rajiform batoids off Argentina from one to three. All three species have a unique pattern of distribution of the gladiate spinitriches along the length of the cephalic peduncle, i.e., gladiate spinitriches being interrupted in a medial line both dorsally and ventrally.
Assuntos
Cestoides/classificação , Cestoides/fisiologia , Infecções por Cestoides/veterinária , Doenças dos Peixes/epidemiologia , Rajidae , Animais , Argentina/epidemiologia , Cestoides/anatomia & histologia , Cestoides/ultraestrutura , Infecções por Cestoides/epidemiologia , Infecções por Cestoides/parasitologia , Feminino , Doenças dos Peixes/parasitologia , Masculino , Microscopia Eletrônica de Varredura/veterinária , Ovário/anatomia & histologia , Ovário/ultraestrutura , Prevalência , Testículo/anatomia & histologia , Testículo/ultraestruturaRESUMO
Overexploitation of marine communities can lead to modifications in the structure of the food web and can force organisms like elasmobranchs to change their feeding habits. To evaluate the impact that fisheries have on food webs and on the interactions between species, it is necessary to describe and quantify the diet of the species involved and follow it through time. This study compares the diet of five skate species using the data obtained from the by-catch of the Argentine hake (Merluccius hubbsi) fishery in north and central Patagonia, Argentina. Diet composition was assessed by analysing the digestive tract contents and trophic overlapping between species of the genus Bathyraja: Bathyraja albomaculata, Bathyraja brachyurops, Bathyraja macloviana, Bathyraja magellanica and Bathyraja multispinis. A total of 184 stomachs were analysed. The diets of B. albomaculata and B. macloviana mainly comprised annelids, whereas that of B. brachyurops primarily comprised fish, including hake heads discarded by the fishery. The diets of B. magellanica and B. multispinis were largely based on crustaceans. Despite the morphological similarities and their shared preference for benthic habitats, no complete diet overlaps were found between the different species. These results suggest that these skate species have undergone a process of diet specialisation. This is a common feeding strategy that occurs to successfully eliminate competition when resources are limited, which corresponds to the conditions found in an environment being affected by the pressures of overfishing.
Assuntos
Dieta , Ecossistema , Rajidae/classificação , Rajidae/fisiologia , Animais , Argentina , Conservação dos Recursos Naturais , Pesqueiros , Cadeia Alimentar , Gadiformes , Conteúdo Gastrointestinal , Estado Nutricional , Rajidae/anatomia & histologiaRESUMO
BACKGROUND: Parasites of deep-sea fishes from the South-East Pacific (SPO) are poorly known. Of c.1030 species of fish found in this area, 100-150 inhabit the deep-sea (deeper than 200 m). Only six articles concerning metazoan parasites of fish from deep-waters of SOP are known, and nine monogenean species have been reported. Currently, ten species are known in Acanthocotyle Monticelli, 1888 (Monogenea) and when stated, all of them are found in shallow waters (10-100 m). Acanthocotyle gurgesiella Ñacari, Sepulveda, Escribano & Oliva, 2018 is the only known species parasitizing deep-sea skates (350-450 m) in the SPO. The aim of this study was the description of two new species of Acanthocotyle from two Rajiformes. METHODS: In September 2017, we examined specimens of two species of deep-sea skates (Rajiformes), Amblyraja frerichsi (Krefft) and Bathyraja peruana McEachran & Myyake, caught at c.1500 m depth off Tocopilla, northern Chile, as a by-catch of the Patagonian tooth fish Dissostichus eleginoides Smitt fishery. Specimens of Acanthocotyle were collected from the skin of the skates. Morphometric (including multivariate analysis of proportional measurements, standardized by total length), morphological and molecular analyses (LSU rRNA and cox1 genes) were performed in order to identify the collected specimens. RESULTS: The three approaches used in this study strongly suggest the presence of two new species in the genus Acanthocotyle: Acanthocotyle imo n. sp. and Acanthocotyle atacamensis n. sp. parasitizing the skin of the thickbody skate Amblyraja frerichsi and the Peruvian skate Bathyraja peruana, respectively. The main morphological differences from the closely related species Acanthocotyle verrilli Goto, 1899 include the number of radial rows of sclerites, the non-discrete vitelline follicles and the number of testes. CONCLUSIONS: The two species of monogeneans described here are the only recorded parasites from their respective host species in the SPO. Assessing host specificity for members of Acanthocotyle requires clarifying the systematics of Rajiformes.
Assuntos
Doenças dos Peixes/parasitologia , Platelmintos/classificação , Rajidae/parasitologia , Infecções por Trematódeos/veterinária , Animais , Teorema de Bayes , Chile , DNA de Helmintos/química , DNA de Helmintos/isolamento & purificação , Complexo IV da Cadeia de Transporte de Elétrons/genética , Genes Mitocondriais , Especificidade de Hospedeiro , Funções Verossimilhança , Cadeias de Markov , Método de Monte Carlo , Análise Multivariada , Oceano Pacífico , Filogenia , Platelmintos/anatomia & histologia , Platelmintos/genética , Análise de Componente Principal , RNA Ribossômico/genética , Pele/parasitologia , Infecções por Trematódeos/parasitologiaRESUMO
Pseudanisakis argentinensis n. sp. is proposed to accommodate parasitic nematodes found in six skate species (Rajidae and Arhynchobatidae) examined from southern Southwest Atlantic waters. The new species differs from its congeners by the following combination of characters: a cupola on each lip, males with 8-12 pairs of precloacal genital papillae, a larger size for both males and females, a greater length-to-breadth ratio of the ventriculus and the presence of a small knob on the tip of the tail. Allometric growth was observed for several morphometric features; however, the slopes of the allometric relationships across host species exhibited non-significant differences and were considered as a strong evidence for conspecificity. Congruent results were obtained after the genetic characterization of the mitochondrial cytochrome c oxidase subunit 1 gene of worms obtained from different skate species, whose values of genetic divergence (1.3) lay within the range of intraspecific variation. Previous records of specimens referred to as Pseudanisakis tricupola in skates from South American waters are regarded as conspecific with P. argentinensis n. sp.