Gill dimensions in near-term embryos of Amazonian freshwater stingrays (Elasmobranchii: Potamotrygonidae) and their relationship to the lifestyle and habitat of neonatal pups

Abstract

This comparative study of gill morphometrics in near-term embryos of freshwater stingray potamotrygonids examines gill dimensions in relation to neonatal lifestyle and habitat. In embryos of the potamotrygonids Paratrygon aiereba, Plesiotrygon iwamae, Potamotrygon motoro, Potamotrygon orbignyi, and cururu ray Potamotrygon sp. the number and length of filaments, total gill surface area, mass-specific surface area, water-blood diffusion distance, and anatomical diffusion factor were analysed. In all potamotrygonids, the 3 rd branchial arch possessed a larger respiratory surface than the other gill arches. Larger embryos had more gill surface area and large spiracles, which are necessary to maintain the high oxygen uptake needed due to their larger body size. However, the higher mass-specific gill surface area observed in near-term embryos may be advantageous because neonates can use hypoxic environments as refuges against predators, as well as catch small prey that inhabit the same environment. As expected from their benthic mode of life, freshwater stingrays are sluggish animals compared to pelagic fishes. However, based on gill respiratory morphometry (such as gill area, mass-specific gill area, the water-blood diffusion barrier, anatomical diffusion factor, and relative opening of the spiracle), subtypes of lifestyles can be observed corresponding to: active, intermediate, and sluggish species according to Gray's scale.Este estudo realizado com embriões a termo de arraias de água doce (Potamotrygonidae) compara e analisa as dimensões branquiais em relação ao estilo de vida e habitat dos neonatos. Nos embriões de Paratrygon aiereba, Plesiotrygon iwamae, Potamotrygon motoro, Potamotrygon orbignyi e Potamotrygon sp. (arraia cururu) foram analisados número e comprimento dos filamentos, área branquial, área superficial branquial massa-específica, barreira de difusão água-sangue e fator de difusão anatômico. Em todos os potamotrigonídeos estudados, o 3º arco branquial possui uma superfície respiratória maior que os demais arcos. Embriões de espécies de maior porte possuem grandes espiráculos e maior área de superfície branquial. Isso ajuda a manter a taxa de absorção de oxigênio proporcional ao requerimento do animal. No entanto, a grande área de superfície branquial massa-específica observadas nos embriões a termo pode ser vantajosa, pois os neonatos podem usar ambientes hipóxicos como refúgios contra predadores, bem como capturar pequenas presas que habitam o mesmo ambiente. Devido ao modo de vida bentônico, as arraias de água doce são nadadoras lentas comparadas aos peixes pelágicos. No entanto, com base na morfometria branquial (área de superfície branquial, área branquial massa-específica, barreira de difusão água-sangue, fator de difusão anatômico e abertura relativa do espiráculo), subtipos de estilos de vida podem ser observados: ativas, intermediárias e lentas, conforme escala definida por Gray.

Sniffing at the river bottom: Influence of olfactory organ morphology on the life habits of freshwater stingrays (Potamotrygoninae)

“…The integration of all sensory systems in freshwater stingrays is indeed an important characteristic for the success of this group in a diversity of freshwater habitats, such as lakes, streams, shallow and deep waters such as beaches and river channels (Duncan et al 2015;Shibuya 2022). The synchronized performance of different sensory modalities plays an essential role in feeding behavior, with each sensory element having a primary function in different phases of foraging (search, location, and the phase prior to prey apprehension).…”

X-Ray Radiological Study for Skeleton of Rounded Fantail Stingray Taeniura grabata from Susah, Libya

“…The ventral bronchial skeleton consists of an enlarged central medial plate, which resulted from the fusion of the basibronchial copula and the basibronchial components (De Carvalho et al, 2004), a short and transversely directed basihyal, a pair of short and anteriorly directed hypobronchials, and five pairs of ceratobronchials. Duncan et al (2015) indicated to the gills are a multifunctional organ involved in gas exchange, acid-base, and ion regulation; where the structure and dimensions of gills of the potamotrygonid are important to assess their function. Gill measurements include gill filament's length and abundance, number of respiratory lamellae on the filaments, surface area of lamellar bilateral, total gill surface area, mass-specific gill area, and the water-blood diffusion barrier, are species-specific as reported from Hughes et al (1986).…”

Fisiologia do parto induzido por captura em Potamotrygon amandae (Elasmobranchii: Myliobatiformes: Potamotrygonidae)

“…Charvet-Almeida em 2001, em trabalho sobre ocorrência, biologia e uso de raias de água doce na Baia de Marajó (Pará, Brasil), com ênfase na biologia de Plesiotrygon iwamae, constatou que todas as raias capturadas abortavam os embriões. O mesmo padrão de parto induzido por diferentes artes de pesca (espinhéis, arrasto e tarrafas) foi verificado por Duncan et al, (2015)…”