Morphological variations of the three otoliths of some species of the family Loricariidae (Ostariophysi: Siluriformes)

Abstract

Otoliths are three pairs of calcareous structures found in the inner ear of bony fish. In many cases they display a speciesspecific morphology. The present study describes morphological variations of otoliths, namely lapillus, asteriscus and sagitta, of eleven species belonging to four loricariid subfamilies. Otolith structures that characterize the Loricariidae and some of its subfamilies are presented. The sagitta exhibit a specific morphology that is not found in other siluriform families; it is claviform with a tapered posterior region and a flared anterior one. In the latter, central elevations are observed and the dorsal wings are continuous with lateral expansions named basal wings. Hypoptopomatinae and Loricariinae as well as Hypostominae and Ancistrinae can be grouped by two morphological patterns of the lapillus: An ovoid pattern, in which the lapillae are elongated in its supero-inferior axis and the mond hardly exceed the anterior edge of the otolith and, an oval pattern, where the lapillae are elongated in their antero-posterior axis and the mond always exceeds the anterior edge in an obvious way. The patterns proposed here could be diagnostic of certain subfamilies.Keywords: Armored catfishes, Asteriscus, Lapillus, Morphology, Sagitta.Los otolitos son tres pares de estructuras calcáreas que se encuentran en el oído interno de los peces óseos. En muchos casos ellos muestran una morfología específica para cada especie. El presente estudio describe las variaciones morfológicas de los otolitos, lapillus, asteriscus y sagitta, de once especies pertenecientes a cuatro subfamilias de loricáridos. Se presentan estructuras que caracterizan los otolitos de Loricariidae y a algunas de sus subfamilias. El sagitta exhibe una morfología específica que no se encuentra en otras familias siluriformes: es claviforme con una región posterior cónica y una anterior ensanchada. En esta última, se observan elevaciones centrales; las alas dorsales que se continuan con expansiones laterales denominadas alas basales. Hypoptopomatinae y Loricariinae, así como las subfamilias Hypostominae y Ancistrinae se pueden agrupar por dos patrones morfológicos de la lapillus: Un patrón de forma ovoide, en el que los lapillae son alargados en su eje superior-inferior y el mond difícilmente sobrepasa el borde anterior de los otolitos. El otro es un patrón oval, donde los lapillae son alargados en su eje antero-posterior y el mond siempre sobrepasa el borde anterior de una manera notoria. Los patrones propuestos aquí podrían ser diagnósticos de ciertas subfamilias.

The developmental variations of the sagitta otolith in the young and mature male of a hermaphrodite polynemidae fish, Eleutheronema tetradactylum (Shaw, 1804)

“…The otolith is a calcareous anatomical structure in the inner ear of fish and assists in the sensation as well as the body balancing by stimulation of inner ear hair cells (Sanchez & Martinez, 2017). In the taxonomic field, the fish species identification is significantly supported by the structural characteristics of the otolith due to its longer time of degradation (Rodríguez Mendoza, 2006;Vilizzi, 2018;Mitsui et al, 2020).…”

“…The sagitta has two surfaces which are the lateral (outer) and medial surface (inner). The medial surface of the sagitta is well-decorated with different morpho-structural features (Smale et al, 1995;Jawad et al, 2018;Bardhan et al, 2021), which characteristically varies with the fish groups and various environmental factors in their respective habitats (Kumar et al, 2012;Omar & AMohamed, 2016;Abdulsamad, 2017;Sanchez & Martinez, 2017;Jawad et al, 2018;Pracheil et al, 2019). Several studies have dealt with the morphological descriptions of the sagitta of marine Perciformes fishes (Hunt, 1992;Smale et al, 1995;Gierl et al, 2018;Jawad et al, 2018), but no ultrastructural studies on the sagitta are available in the hermaphrodite perciformes fishes.…”