Social and reproductive physiology and behavior of the Neotropical cichlid fish Cichlasoma dimerus under laboratory conditions

Abstract

In this work we describe for the first time the social and reproductive behavior of the Neotropical fish Cichlasoma dimerus (Heckel, 1840) [Perciformes: Cichlidae], endemic to the Paraná River basin, using a comprehensive-integral approach, including morphological and physiological features. This substrate breeding fish has biparental care of the fry and presents a dominance hierarchy that determines access to breeding territories among males, and to males with territories among females. Gregarious behavior associated with a pale body color, was observed before reproductive behaviors started. Afterwards, a dominance hierarchy was established through aggressive interactions. Territorial individuals had bright body color patterns and non territorial an opaque grey one. Black ventral coloration was associated with reproductive individuals. Courtship displays, which were similar to threatening displays, had the common effect of increasing the visible area of the individual. The dominant male was always the largest one suggesting that size is probably a major factor determining the hierarchy establishment and that these intra-sexually selected traits may have been reinforced by inter-sexual selection. Reproductive males had higher pituitary levels of -follicle stimulating hormone (-FSH) and somatolactin (SL) than non reproductive ones, while no differences were found among females. No differences were found among male gonadosomatic indexes. Non reproductive individuals had higher plasma cortisol levels for both sexes. It is possible that dominant reproductive individuals may be inhibiting reproduction of subordinate fish through physical contact, increasing their cortisol levels and diminishing FSH and SL pituitary content. However, this was not reflected as an inhibition at the gonadal level in our experimental design.En este trabajo se describen por primera vez el comportamiento social y reproductivo del pez cíclido neotropical Cichlasoma dimerus (Heckel, 1840) [Perciformes: Cichlidae], endémico de la cuenca del Paraná, desde un enfoque integral y abarcador, incluyendo características morfológicas y fisiológicas. Éste pez incubador de substrato, tiene cuidado biparental de las crías y presenta una jerarquía de dominancia que determina el acceso a territorios reproductivos entre los machos, y a machos con territorios entre las hembras. Se observó un comportamiento gregario con una coloración corporal pálida característica, antes que comenzaran los comportamientos reproductivos. Luego, una jerarquía de dominancia se estableció a través de interacciones agresivas. Los individuos territoriales presentaron patrones de coloración corporal brillantes y los individuos no territoriales uno gris opaco. Una coloración ventral oscura fue observada asociada a individuos reproductivos. Los despliegues de cortejo fueron similares a los de amenaza y tuvieron la característica común de aumentar el área visible de los peces. El macho dominante fue siempre el más grande, sugiriendo que probablemente la fuerza (tamaño) es un facto...

The interrenal gland in males of the cichlid fish Cichlasoma dimerus: Relationship with stress and the establishment of social hierarchies

“…Similar results were obtained in subordinate male green swordtails (Xiphophorus helleri) (Scott and Currie, 1980). The South American cichlid fish, Cichlasoma dimerus (Heckel, 1840), inhabits the Parana and Paraguay Rivers' basins and has recently been used as a laboratory model to study teleost reproduction, neuroendocrinology and behavior (Alonso et al, 2011(Alonso et al, , 2012Fiszbein et al, 2010;Pandolfi et al, 2009;Ramallo et al, 2012;Tubert et al, 2012). In this species, under laboratory conditions, the largest male usually emerges as the dominant and reproductively active male of the group.…”

“…Subordinate males usually exhibit higher plasma cortisol levels than dominant ones (Alonso et al, 2011;Øverli et al, 1999;Pottinger and Pickering, 1992;Winberg and Lepage, 1998). If these levels are elevated for a prolonged period of time, subordinate individuals might be subjected to chronic stress, which has a detrimental effect on the animal's physiological state .…”

Description of the reproductive behavior of Symphysodon aequifasciatus (Cichlidae) in captivity

“…Both males and females of S. aequifasciatus performed cleaning of the substrate chosen to lay their eggs, similar to that observed in Cichlasoma dimerus Heckel, 1840 (Alonso et al 2011).…”

“…The care for the spawning was done by both sexes, similarly to C. dimerus (Alonso et al 2011). The observation of shifts by the male and female in relation to cleaning care and aeration of the spawning and later in the care of the larvae was also observed for other species of cichlids maintained and observed in captivity such as the Laetacara sp.…”

“…Males in many cichlid species (Cacho et al 1999;Câmara 2004;Alonso et al 2011) commonly perform territorial defense. In cichlids in captivity Archocentrus nigrofasciatus (Günther, 1867) curiously only the female performs territorial defense (Alonzo et al 2001).…”