Differences in life-history traits in two clonal strains of the self-fertilizing fish, Rivulus marmoratus

Abstract

SynopsisWe compared life-history traits such as fecundity, sex ratio, reproductive cycle, age at sexual maturity, embryonic period, egg size, early growth and morphology in two clonal strains (PAN-RS and DAN) of the mangrove killifish (Rivulus marmoratus) under constant rearing conditions. We found a positive relationship between growth and reproductive effort. Fecundity was significantly higher in the PAN-RS strain than in the DAN strain. Sex ratio was significantly different, with DAN producing more primary males than PAN-RS. Spawning and ovulation cycle did not clearly differ between the strains. PAN-RS showed a significantly higher growth rate than DAN from 0 to 100 days after hatching, however, age at sexual maturity, embryonic period, egg size, and morphometric and meristic characteristics (vertebral and fin-ray counts) did not differ between the two strains. The high fecundity of PAN-RS may provide an increased chance of offspring survival, while the attainment of sexual maturity at a smaller size in DAN may allow them to invest earlier in reproduction to increase breeding success.Variations in the life-history traits of PAN-RS and DAN may be adaptive strategies for life in their natural habitat, which consists of mangrove estuaries with a highly variable environment. 2 IntroductionThe individual traits of organisms and their interaction with the environment define the dynamics of populations, the structure of ecological communities, and the functioning of ecosystems (Tessier et al. 2000). Identifying trends in life-history traits and interpreting the adaptiveness of such variation has always been a challenge for biologists (Stearns 1992). It is generally believed that observed differences in life-history traits result from genotypic variation and/or from the effect on a plastic phenotype of variation in the environment (Belk 1995). One of the most important issues in evolutionary biology is defining whether differences in life-history traits can be attributed to genetic or environmental variation.In the present study, we used two clonal strains of mangrove killifish (Rivulus marmoratus, Family Rivulidae) to identify differences in life-history traits and determine whether these variations are the result of genetic or environmental differences.The mangrove killifish is distributed from Southern Florida, U.S.A. to Brazil (Davis et al. 1990). It inhabits mangrove areas, which are exposed to alternate flooding and desiccation; thus, it is necessarily tolerant of a wide range of environmental conditions (Taylor 2000). There are three recognized sexual types: hermaphrodites, which have a marbled brownish color pattern usually including a caudal ocellus, and are capable of internal synchronous self-fertilization, and thus are capable of producing clonal lineages (Kallman & Harrington 1964, Harrington & Kallman 1968; primary males, which have an orange body coloration usually without caudal ocellus and remain male throughout their lives; and secondary males, which arise from hermaphrodites following the loss o...

Fish embryos on land: terrestrial embryo deposition lowers oxygen uptake without altering growth or survival in the amphibious fishKryptolebias marmoratus

“…As predicted, adults released more embryos in air relative to water, suggesting a preference for terrestrial environments. The clutch size was relatively low, consistent with previous reports in K. marmoratus (0.7-2.2 embryos per week; Grageda et al, 2005). Previous literature described anecdotal observations of adult K. marmoratus that released embryos terrestrially in a terrarium (Abel et al, 1987;Taylor, 1990) or in the wild near crab burrows (Taylor, 2012).…”

Gonadal morphology in the self-fertilizing mangrove killifish, Kryptolebias marmoratus

“…They showed that this species secretes estrogen (17β-estradiol), androgen (11-ketotestosterone), and progestin (17α-20β-dihydroxy-4-pregnen-3-one) synchronously, which is unusual in teleosts. Moreover, the mangrove killifish does not have clear diel rhythms in terms of spawning and ovulation (Grageda et al 2005). Therefore, the triggering mechanisms of ovulation, self-fertilization, and spawning (oviposition) are still unclear and will be the subject of future research.…”

Embryonic development of the self‐fertilizing mangrove killifish Kryptolebias marmoratus

“…It is difficult to assess the exact fertilization time of K. marmoratus embryos, as ovulated eggs are fertilized within the gonadal lumen (Sakakura et al, 2006). Thus, all timings expressed as hours post fertilization are back-calculated estimations based on previous literature (Koenig and Chasar, 1984;Grageda et al, 2005).…”