Experimental test of the effect of maternal hormones on larval quality of a coral reef fish

Abstract

Maternal hormones can play an important role in the development of fish larvae. Levels of the stress hormone, cortisol, in females are elevated by social interactions and transferred directly to the yolk of eggs, where they may influence developmental rates. In some vertebrates, prenatal exposure to high levels of testosterone determine early growth rates, social status and reproductive success. The present study examined whether post-fertilization exposure of eggs of the tropical damselfish, Pomacentrus amboinensis (Pomacentridae), to natural levels of cortisol or testosterone directly affects larval morphology at hatching. Maternal and egg levels of cortisol and testosterone varied widely among clutches of eggs from local populations around Lizard Island on the Great Barrier Reef. The morphology of larvae produced by these local fish populations also varied widely and differed significantly among sites (e.g., standard length: 2.6-3.4 mm; yolk sac area: 0.01-0.13 × 10 mm). Laboratory experiments showed that elevated cortisol levels in the egg reduced larval length at hatching, while slight elevations in testosterone increased yolk sac size. The influence of testosterone, and to a smaller extent cortisol, on larval morphology differed among egg clutches. These differences were partly explained by differences in initial egg hormone levels. Morphological changes induced by experimental hormonal regimes encompassed the entire range of variability in body attributes found in field populations. It is unclear whether cortisol influences growth alone or development rate or both. Testosterone appears to influence yolk utilization rates, and has no significant effect on growth, in contrast to its role in later developmental stages. Maternally derived cortisol and testosterone are important in regulating growth, development, and nutritive reserves of the embryo and larvae of this fish species. Factors that influence the maternal levels of cortisol and testosterone may have a major impact on larval mortality schedules and, therefore, on which breeding individuals contribute to the next generation.

Influence of the type of management system on corticosterone transfer into eggs in laying hens

“…The blood plasma corticosteroid concentrations of vertebrates may be influenced by certain environmental and in vivo neurohormonal circumstances (McCormick, 1999). The circulating levels of glucocorticoids often vary with environmental impacts such as the change of weather conditions, habitat quality, predator frequency, and environmental noise load.…”

“…Consequently, changes of the maternal physical environment can influence steroid deposition in the egg yolk. In fishes, yolk corticosterone has been linked to the reduced length of larvae at hatching, an increased proportion of abnormal larvae and higher egg/larval mortality (McCormick, 1999).…”

Larval growth predicts the recruitment success of a coral reef fish

“…Both maternal (Kerrigan 1997;McCormick 1999) and environmental factors can influence these characteristics Molony 1992, 1995). However, the influence of this variability on settlement or recruitment has rarely been examined and, consequently, these studies do not explicitly test predictions of the growth-predation hypothesis.…”

Costly steroids: egg testosterone modulates nestling metabolic rate in the zebra finch

“…Clark & Galef 1995;McCormick 1999;Uller & Olsson 2003;Groothuis et al 2005a). In oviparous species, hormones transferred from the mother to the egg vary remarkably within as well as among clutches (e.g.…”