Comparative histology of the vocal sac in three species of hylid frogs with comments on its functional correlates

The vocal sacs of frogs are elastic structures responsible for the circulation of air during vocalization, amplifying the sounds produced by these animals during multimodal communication. Vocal sacs present a wide array of morphologies among species and may be single, paired, or absent in adult males. Most studies on vocal sacs in Anura deal with their external morphology, and not with their internal structure, which has been explored in only a handful of species. The aim of this study was to assess vocal sac structure in three hylid species, Dendropsophus haddadi, D. elegans, and Scinax fuscovarius, using histological techniques. These species differ greatly in the degree of development and histological properties of the gular skin and submandibular musculature. In particular, elastic fibers are abundant in the thick m. interhyoideus and the relatively tight gular skin of S. fuscovarius. In contrast, in both species of Dendropsophus (although more evident in D. elegans), the m. interhyoideus is extremely thin and expanded, with a negligible number of elastic fibers that appear as a loose, pleated sheet when deflated. We analyzed videos of calling males of the three species and their close relatives, which show two different patterns of inflation/deflation. These patterns are strongly correlated with the histological properties of the vocal sac wall. The three species have different vocal sac shapes and rely differently on elasticity for vocal sac function.Os sacos vocais dos anuros são estruturas elásticas responsáveis pela circulação do ar durante a vocalização, amplificando os sons produzidos por esses animais durante a comunicação multimodal. Os sacos vocais apresentam uma ampla gama de morfologias entre as espécies, podendo ser únicos, pareados ou ausentes em machos adultos. A maioria dos estudos sobre sacos vocais em Anura trata de sua morfologia externa, não incluindo dados sobre sua estrutura interna, que foi explorada em apenas algumas espécies. O objetivo deste estudo foi avaliar a estrutura do saco vocal de três espécies de hilídeos, Dendropsophus haddadi, D. elegans e Scinax fuscovarius, por meio de técnicas histológicas. Essas espécies diferem muito no grau de desenvolvimento e nas propriedades histológicas da pele gular e da musculatura submandibular. Em particular, as fibras elásticas são abundantes no músculo interioidal espesso e pele gular relativamente esticada de S. fuscovarius. Ao contrário, em ambas as espécies de Dendropsophus (embora mais evidente em D. elegans), o músculo interioidal é extremamente fino e expandido, com conteúdo não-significativo de fibras elásticas, aparecendo como uma folha solta e pregueada quando desinflado. Analisamos vídeos de vocalizações de machos das três espécies e parentes próximos, que mostram dois padrões bem diferentes de inflação/deflação. Além disso, estes estão fortemente correlacionados com as propriedades histológicas da parede do saco vocal, uma vez que as três espécies têm diferentes formatos de saco vocal e dependem diferentemente da elasticidade para a função do saco vocal

Records of chironomidae larvae living on other aquatic animals in Brazil

In this study, we report forty-nine cases of Chironomidae larvae living on other animals in Brazilian aquatic ecosystems, including a wide range of hosts, such as hydrozoans, snails, insects and fish. We also discuss some empirical difficulties to establish the ecological interactions between chironomids and their hosts

Population structure and reproductive biology of Cichla kelberi (Perciformes, Cichlidae) in Lobo Reservoir, Brazil

The structure of Cichla kelberi population was characterized regarding the sex ratio, total length composition and some reproductive characteristics. The specimens were collected in two periods, from November 2002 to November 2003 and from December 2004 to May 2006. The sex ratio was significantly different than 1:1. The total length varied from 3.4 to 40.1 cm, with individuals in the shortest length classes occurring throughout the year, but with greater incidence in the warmer periods. Females and males reached similar lengths and there was no difference between the sexes regarding the length-weight relationship. The estimated values of condition factor were near the central value of 1.0 and decreased during the cooler months, coinciding with periods of lower reproductive activity. Individuals with mature or semi-spent gonads occurred from November to April, indicating that Cichla kelberi reproduces for a long period of time. The spawning is partitioned, with an average absolute fecundity of 6072 oocytes (from 5220 to 6908 oocytes). The high relative condition factor values, long reproductive period, large output of fingerlings and high fecundity are biological conditions that indicate the species is well adapted in this reservoir

Population structure and reproductive biology of Cichla kelberi (Perciformes, Cichlidae) in Lobo Reservoir, Brazil

The structure of Cichla kelberi population was characterized regarding the sex ratio, total length composition and some reproductive characteristics. The specimens were collected in two periods, from November 2002 to November 2003 and from December 2004 to May 2006. The sex ratio was significantly different than 1:1. The total length varied from 3.4 to 40.1 cm, with individuals in the shortest length classes occurring throughout the year, but with greater incidence in the warmer periods. Females and males reached similar lengths and there was no difference between the sexes regarding the length-weight relationship. The estimated values of condition factor were near the central value of 1.0 and decreased during the cooler months, coinciding with periods of lower reproductive activity. Individuals with mature or semi-spent gonads occurred from November to April, indicating that Cichla kelberi reproduces for a long period of time. The spawning is partitioned, with an average absolute fecundity of 6072 oocytes (from 5220 to 6908 oocytes). The high relative condition factor values, long reproductive period, large output of fingerlings and high fecundity are biological conditions that indicate the species is well adapted in this reservoir