Genetic and Environmental Basis of Variable Sex Ratios in Laboratory Strains of Poeciliopsis lucida

Abstract

Skewed sex ratios are common among several species of Poeciliopsis, a viviparous fish from northwestern Mexico. Since previous, unrelated studies from this laboratory (Angus and Schultz, 1983) suggested that deviation from a 1:1 sex ratio might be influenced by temperature, two inbred strains of P. lucida were tested for temperature-dependent sex determination by comparing sex ratios of offspring from pregnant females held at different water temperatures. Different sex ratios were produced by the two strains at the same temperature: one strain produced almost all-male offspring at 30°C and female-biased sex ratios at 24°C, while the other strain produced a 1:1 sex ratio at both temperatures. At intermediate temperatures, the labile strain produced sequentially fewer males with decreasing temperatures. The other strain produced a consistent sex ratio regardless of temperature. Poeciliopsis lucida apparently has a genetic polymorphism for temperature-influenced sex determination. An hypothesis is offered for the evolutionary origin of environmental sex determination.

The importance of parentage in assessing temperature effects on fish early life history: a review of the experimental literature

“…because of the desire to rear more profitable monosex populations (Baroiller et al 1995;Abucay et al 1999;Tessema et al 2006). In contrast, many other ITPI sex ratio studies were conducted under the premise of understanding the evolutionary complexity of temperature and genetically influenced sex determination mechanisms (Conover and Kynard 1981;Sullivan and Schultz 1986;Lagomarsino and Conover 1993;Baroiller et al 1996;Strussmann et al 1996;Bezault et al 2007). The mechanistic details and overall significance of how parentage and temperature determine progeny sex outcomes has been reviewed by several authors (Baroiller and D'Cotta 2001;Piferrer et al 2005;Baroiller et al 2009), but in the context of this review, the aforementioned ITPI studies lend weight to the argument that there is a great diversity of offspring traits that are affected both by individual parentage and the early incubation thermal environment.…”

Seasonality and the scheduling of life history at different latitudes

“…menidia, but its functional significance in other groups (if any) is not always clear (Bull, 1983). Besides atherinids, strong evidence of ESD in fishes has been found so far only in poeciliids (Sullivan & Schultz, 1986). Given that other forms of sex lability are prevalent in fishes, and that the life-history traits associated with ESD in silversides are common (protracted breeding seasons, sexual size dimorphisms, early maturity), ESD probably occurs in numerous fishes.…”

Thermolabile Sex Determination in honmoroko

“…Sex ratios of the progeny of males produced at 34 C determination differs with the genetic constitution of the parents. Thus, sex determination in honmoroko is under the control of both genetic factors and temperature levels, as in Menidia menidia (L.) (Conover & Kynard, 1981;Conover & Heins, 1987a), Oreochromis niloticus L. (Baroiller et al, 1995;Abucay et al, 1999) and Poeciliopsis lucida Miller (Sullivan & Schultz, 1986;Schultz, 1993). Fujioka (1998) suggested that the maternal parent in honmoroko can occasionally affect the sex ratio of its offspring despite the general rule of sex determination by female homogamety, because the sex ratios in gynogenetic diploids observed depends on the maternal parent.…”