Alimentação de Xenomelaniris brasiliensis (Quoy & Gaimard): (Pisces - Mugiloidei - Atherinidæ)

• Autor(a) principal: Carvalho, J. de Paiva
• Data de Publicação: 1953
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Boletim do Instituto Oceanográfico
• Texto Completo: https://www.revistas.usp.br/biocean/article/view/27656

This work is based on the study of 12 samples of specimens of Peixe-Rei, Xenomelaniris brasiliensis (Quoy & Gaimard), that were caught, one sample per month, in the waters in front of the Base that the Institute maintains in Cananéia, in the south coast of S. Paulo State. Of the total catch 240 specimens were separated, that is, 20 specimens each month, and the gastro-intestinal contents were studied. As per page 134 the principal components found were the following, by order of importance: 1) Vegetal organic matter and vegetal detritus; 2) Crustacea; 3) Fishes; 4) Several Algæ; 5) Insecta; 6) Mollusca; 7) Protozoa and 8) Worms. Sand was computed in some extent, the percentage of amorphic matter completely digested and not liable of determination being relatively low. The author expends his opinions about each one of the components found presenting in one table and two graphs their mean relative frequency. This mean relative frequency was found to be very irregular. A conclusion is drawn that the species is a great consumer of vegetal organic matter and vegetal detritus, which were, otherwise, prominently found in all planctonic collections made at the same period, in the same region. In second place are the crustacea, mainly represented by Copepoda and the occurrence, although not very frequent, of a few young and adult shrimps from the genus Peneus (P. schmitti Burkenroad?). The more or less sporadic appearance of Crangon sp., C. armillatus, Palæmonetes (Paleander) northropi and Periclemenes sp. is also recorded. Besides a few Isopoda probably swallowed together with their hosts, some Amphipoda and Tainaidacea were found although in small quantities. A few samples showed substantial quantities of Cypris of Cirripedia, evidently from the genera Balanus and Cthamalus commonly found in the region. Fish remains were abundant only during two months, being scarce the rest of the time. Greater occurrence of specimens belonging to the genus Xenomelaniris was evident, showing that the school's individuals devour each other. Although monocellular algæ were always very abundantly found in the plancton collections made during the period under study, their mean frequency in the stomach contents never reached a high mark. Concerning the species under study it is therefore not possible to apply the usual conception of researchers that "all fish is diatoms". The average frequency of Insecta, Mollusca, Protozoa and Worms in general was also found to be very low. Insecta seem to happen only by accident their ingestion occurring probably while fluttering about on the water surface; in relation to Hemiptera the author believes that these were draggled together with stems of dry vegetais swept out by the tides movements from the mangrove margin. Mollusca and Protozoa were always very rare. Regarding worms only a few Polichæta may have been ingested intentionally. The Nematoda and Trematoda occasionally found are evidently endo-parasits of the species itself or from any other that may have been ingested. Xenomelaniris brasiliensis is therefore an omnivorous species, great consumer of vegetal detritus, which is, certainly, a character that typifies very well the group to which belong the other components of sub-order Mugiloidei.