Latest Articles from Zoologia Latest 3 Articles from Zoologia https://zoologia.pensoft.net/ Thu, 28 Mar 2024 21:19:03 +0200 Pensoft FeedCreator https://zoologia.pensoft.net/i/logo.jpg Latest Articles from Zoologia https://zoologia.pensoft.net/ Gonadal development and reproductive period of the characin Astyanax aff. bimaculatus (Characiformes: Characidae) in a tropical reservoir in southeastern Brazil https://zoologia.pensoft.net/article/30610/ Zoologia 36: 1-14

DOI: 10.3897/zoologia.36.e30610

Authors: Francisco G. Araújo, Aparecida A. Nascimento, Iracema D. Gomes, Armando Sales, Beatriz A. Chagas de Oliveira

Abstract: The gonadal development of the characin Astyanax aff. bimaculatus from Funil Reservoir, an impoundment in the middle reaches of the Paraiba do Sul River in southeastern Brazil was analysed through histological, histochemical and histometric techniques, and the spawning season was determined. Unbalanced sex ratio was found, with females outnumbering and reaching larger sizes than males. The following stages of oogenic cell development were identified for females: primary growth, pre-vitellogenic (cortical alveolar) and vitellogenic. In males, the following stages were determined: spermatogonia primary and secondary, spermatocyte primary and secondary, spermatid and spermatozoa. The spawning occurs most of the year, peaking in January-February, as indicated by the gonadosomatic index. In the peak of the spawning period, the condition factor and hepatosomatic indices decreased suggesting use of stored body energy reserves during the reproduction. Spawning in batches, small-sized oocytes and a long reproductive season suggest that Astyanax aff. bimaculatus fits to an opportunist strategy. Such strategy may facilitate the use of a wide range of lentic and lotic body waters in the Neotropical region.

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Research Article Wed, 30 Oct 2019 22:52:39 +0200
Changes in trophic characteristics of two fish species of Astyanax (Teleostei: Characidae) in response to aquatic pollution https://zoologia.pensoft.net/article/30445/ Zoologia 36: 1-12

DOI: 10.3897/zoologia.36.e30445

Authors: Mirella B. Alonso, Débora R. de Carvalho, Carlos B. M. Alves, Marcelo Z. Moreira, Paulo S. Pompeu

Abstract: The trophic plasticity of most fish species of Astyanax Baird & Girard, 1854 in response to environmental changes and resource availability is high. This work evaluates the differences in the trophic characteristics of two congeneric species, Astyanax taeniatus (Jenyns, 1842) and Astyanax lacustris (Lütken, 1875), in Rio das Velhas Basin, which is highly impacted by the discharge of sewage from the Metropolitan Region of Belo Horizonte (MRBH). Eight sites were sampled and grouped into three regions: upper course (two sites upstream of the MRBH); middle course (three sites located in the middle portion of the Rio das Velhas, region with greater influence of the MRBH), and lower course (three sites downstream of the MRBH). Samples of fish and food resources were collected from all sites to obtain the isotopic composition of nitrogen (δ15N) and carbon (δ13C), and the stomach contents of the two species was analized. The most common items in the stomach of A. lacustris and A. taeniatus, respectively, were from plants and insects, followed by algae/periphyton (especially at the low course of Rio das Velhas). In contrast, stable isotope analyses indicated that algae (in polluted sites) and periphyton (in least-disturbed sites) were best assimilated both species. Both analyses indicated that the trophic niches of the two species overlap more in more polluted sites relative to less polluted sites. Astyanax taeniatus and A. lacustris only presented different isotopic composition of carbon and nitrogen in the upper course of the Rio das Velhas, probably in response to the greater diversity of food items consumed by each species. In the other regions, the species presented similar isotopic signatures, with δ15N and δ13C notably enriched in the most polluted regions (middle and low course). Our results suggest that pollution acts by increasing trophic niche overlap of these species, altering the type of resources most assimilated, and promoting a greater enrichment of δ15N in fish and resources.

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Research Article Fri, 5 Jul 2019 16:00:01 +0300
Astyanax taurorum a new species from dos Touros River, Pelotas River drainage, an upland southern Brazilian river (Characiformes: Characidae) https://zoologia.pensoft.net/article/20174/ Zoologia 34: 1-8

DOI: 10.3897/zoologia.34.e20174

Authors: Carlos Alberto S. de Lucena, Amanda Bungi Zaluski, Zilda Margarete Seixas de Lucena

Abstract: A new species of Astyanax belonging to the Astyanax scabripinnis complex is described from dos Touros River, tributary of the Pelotas River, Uruguay River basin. Astyanax taurorum sp. nov. is distinguished from other species of the Astyanax scabripinnis species complex by having two humeral spots, the first vertically elongated; teeth of inner row of premaxilla with three to five cusps; 2–3 (modes 2 or 3) maxillary teeth; 20–23 (mode 22) branched anal-fin rays; 13–15 (mode 14) gill rakers on lower branch of the first branchial arch; 20–23 (mode 21) total gill rakers in first branchial arch; 33–36 (mode 35) perforated lateral line scales. Astyanax taurorum sp. nov. is similar to Astyanax paris; nevertheless, it can be readily distinguished from it by having a smaller head depth (73.6-83.1% vs. 86.4–95.6%) and smaller interorbital width (24.1–28.0% vs. 30.8–32.8%). In addition, it differs from A. paris by the presence a posttemporal hook-shaped posterodorsal margin.

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Research Article Mon, 18 Sep 2017 15:22:37 +0300