Evidence of secondary sexual dimorphism in King Tiger Plecos Hypancistrus sp, Loricariidae, of the Amazon River basin

Abstract

The aim of the present study was to describe the secondary sexual characteristics of adult Hypancistrus sp. A total of 120 specimens were used to evaluate the morphometric characters, to confirm the morphometric data, histological identification of sex and maturation stages of gonads was performed. The results showed that males had higher median total and standard body lengths, open fin length, right and left fin lengths, head length and width and inter‐eye width than females. However, the females showed a high median abdominal width. Both sexes presented odontodes along the body, with thick odontodes present near the interopercular region and pectoral fins. In mature males, small odontodes were present along the snout. Scanning microscopy analysis confirmed that odontodes in females had a thicker base than those in males, conferring the former with a “cone” morphology. Additionally, it was observed that males had a long and broad head with a triangular shape and "V"‐shaped genital papilla, while females had a round head and "U"‐shaped genital papilla. Thus, we conclude that Hypancistrus sp. had secondary sexual characteristics, being possible to differentiate the sex by the size of the body, abdominal width, shape of the head, size of the odontodes and distinct morphology of the ovipositor. This study will serve as a basis for the development of breeding protocols, as it aims to identify sexually mature males and females of Hypancistrus sp. for breeding in captivity.

Sexual dimorphism in an invasive population of suckermouth armored catfish: Implications for management

“…Our work supports the pattern of larger body size in males for congeneric H. hermanni documented by Nomura and Mueller (1980) as well as the >100-year-old report by Miranda Ribeiro (1918) of enlarged fins in males of H. albopunctatus (Zawadzki et al 2020). Differences in total body size may cause other morphometrics to increase in size due solely to correlation with total size; thus, it is common to calculate ratios of morphometric measures to total or standard length as we did in our study (Reis et al 2022). When we adjusted measurements to account for differences in TL, we found evidence of proportionally larger dorsal-, anal-, and pectoral-fin lengths for the population of Hypostomus sp.…”

“…Our work also provides insight into sexually dimorphic characters that inform aquaculture of Hypostomus sp. during the future development of trojan genes as a form of biological control (Reis et al 2022). The analyses of existing data and field validation of the GBM model suggest that sex classification of Hypostomus sp.…”

“…Differences in total body size may cause other morphometrics to increase in size due solely to correlation with total size; thus, it is common to calculate ratios of morphometric measures to total or standard length as we did in our study (Reis et al. 2022). When we adjusted measurements to account for differences in TL, we found evidence of proportionally larger dorsal‐, anal‐, and pectoral‐fin lengths for the population of Hypostomus sp.…”

“…2014; Reis et al. 2022). However, there is limited evidence for sexual dimorphism within the globally invasive genus Hypostomus (Hoover et al.…”

“…Rapp Py- Daniel and Fernandes (2005) reviewed sexual dimorphism among siluriform fishes from the Amazon and noted that there were differences in body size, fin size, urogenital papilla shape, odontode number and size, and buccal teeth arrangement. More recently, obvious sexual dimorphism was noted among a newly described genus and species of SAC, Hirtella carinata, involving differences in total length (TL), head and mouth morphology, odontode size, and fin length and width (Pereira et al 2014;Reis et al 2022). However, there is limited evidence for sexual dimorphism within the globally invasive genus Hypostomus (Hoover et al 2014;Blanton et al 2020).…”