Comparative morphology of gill glands in externally fertilizing and inseminating species of cheirodontine fishes, with implications on the phylogeny of the family Characidae (Actinopterygii: Characiformes)

Abstract

The structure and form of gill gland among inseminating and externally fertilizing species of the Cheirodontinae are described under light microscopy, scanning electron microscopy, and transmission electron microscopy, and compared to other members of the family Characidae. At least one species from thirteen cheirodontine genera were analyzed, totaling seventeen species. Gill glands were found in all analyzed mature males of Cheirodontinae and were always absent in females, being located on the anteriormost portion of the lower branch of the first gill arch, extending posteriorly through a variable number of gill filaments. Gill glands of all cheirodontines and of all characid species in which this organ has been described possess the same structure, being considered homologous and supporting a single origin of the structure in a common ancestor to Clade A and Clade B characids.A estrutura e forma da glândula branquial de queirodontíneos inseminadores e de fecundação externa são descritas com base em análises de microscopia óptica, microscopia eletrônica de varredura e microscopia eletrônica de transmissão, e comparadas com outros membros da família Characidae. Pelo menos uma espécie de treze gêneros de Cheirodontinae foram analisadas, num total de dezessete espécies. Glândulas branquiais foram encontradas em todos os machos maduros analisados de Cheirodontinae, localizadas na parte mais anterior do ramo inferior do primeiro arco branquial, estendendo-se posteriormente por um número variável de filamentos branquiais, estando sempre ausentes nas fêmeas. As glândulas branquiais de todos os queirodontíneos analisados e de todas as espécies de Characidae em que este órgão foi descrito possuem a mesma estrutura, sendo consideradas homólogas e suportando uma origem única em um ancestral comum aos Clados A e B de Characidae.

Two new species and a review of the inseminating freshwater fish genus Monotocheirodon (Characiformes: Characidae) from Peru and Bolivia

“…These preliminary findings suggest that these five genera are more closely related among themselves than to any other stevardiin genus and probably represent a separate clade within the subfamily; however, a more comprehensive analysis of characters is required to confirm this hypothesis. Oliveira et al (2012) state that gill glands were found via histological preparations in mature inseminating males of Monotocheirodon species. No histological sections were conducted in this study to detect the presence of such structures.…”

Gill‐derived glands in species of Astyanax (Teleostei: Characidae)

“…; Oliveira et al . ). The development of such glands probably responds to an increase in testicular hormones and is apparently progressive with age, starting from the anteriormost filaments (Burns and Weitzman ).…”

“…Each chamber is limited anterior and posteriorly by gill filaments and laterally by a stratified squamous epithelial tissue (Oliveira et al . ), and it communicates to the exterior through openings in their distal region (Burns and Weitzman ; Bushmann et al . ).…”

“…In the most comprehensive study to date about gill‐derived glands in the Characidae, Oliveira et al . () reported the presence of a gill‐derived gland in Phenacogaster franciscoensis (they did not examine P. tegatus ), many Stevardiinae and all the species of the Cheirodontinae examined by them. When present, the gill‐derived glands of all the species examined by Oliveira et al .…”

“…When present, the gill‐derived glands of all the species examined by Oliveira et al . () had the same structure; therefore, these authors proposed that the glands were homologous, appeared in the phylogeny of the Characidae only once and had multiple reversions to absence.…”