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Abstract

The preference for melanistic males was studied in two populations of eastern mosquitofish (Gambusia holbrooki, Pisces: Poeciliidae), one from Florida and one from northern Italy. Melanism in the eastern mosquitofish is a Y--linked character, expressed in males only. Melanistic males have black spots varying in size and number. In the Florida population, melanistic males are common, whereas in the Italian population they have never been observed. Females were male-deprived for at least 2 months before being tested in a dichotomous choice chamber. Italian females showed a significant preference for unpigmented males from their own population, whereas Florida females preferred melanistic males. When given the choice between males with few (< 10% of the body surface) and males with many (> 50%) black spots, Italian females preferred males with few black spots and Florida females those with many black spots. The preference of the Italian females for unpigmented males was confirmed in females reared from birth to maturity in the presence of only melanistic males. The preference of Florida females for melanistic males was also confirmed in females reared from birth to maturity in the presence of only unpigmented males. Altogether, these results demonstrate that in the eastern mosquitofish there is polymorphism in female preference and that this preference does not have an environmental basis.

Mosquitofish (Gambusia affinis) Preference and Behavioral Response to Animated Images of Conspecifics Altered in Their Color, Aspect Ratio, and Swimming Depth

“…Specifically, dominant mosquitofish males can be visually identified based on the abundance of yellow pigment on their dorsal fin and along the dorso-lateral region of the body [32]. Social hierarchy in males is also a determinant of the attraction of mosquitofish females for them [26], which also rests upon melanism [64]. Mosquitofish females tend to avoid sexual harassment of subordinate males (by reducing their inter-individual distance) [25],[26],[54],[69], while they are attracted towards dominant males.…”

“…Further insight into the interaction between fish and animated images was garnered by analyzing the behavior of mosquitofish using a dedicated software (The Observer 2.0, Noldus, Wageningen, The Netherlands). Based on the literature on the behavior of this species [15],[18],[19],[25],[54],[64], as well as preliminary observations, we scored the following behavioral patterns: “swimming” (the fish moved while not in contact to the stimulus walls), “freezing” (the fish remained completely motionless), and “thrashing” (the fish was moving back and forth against the stimulus walls while its head was physically in contact with the glass).…”

The Colorful Sex Chromosomes of Teleost Fish

“…Mark-recapture and mesocosm studies have demonstrated that the melanic phenotype provides a survival advantage when predators are present as long as the phenotype is rare [ 122 , 123 , 125 ]. Female eastern mosquitofish prefer melanic males if they are derived from populations where such males occur [ 128 ].…”

Genomic organization of duplicated short wave-sensitive and long wave-sensitive opsin genes in the green swordtail, Xiphophorus helleri

“…This has allowed many species to evolve opsin repertoires and accompanying visual systems that best exploit the photic environments in which they live [12-14]. Furthermore, it is well established in many species that color vision plays a direct role in mate choice and sexual selection [15-18]. …”