Eicosanoids and Egg-Hatching Synchrony in Barnacles: Evidence Against a Dietary Precursor to Egg-Hatching Pheromone

Paternal care regulates the timing, synchrony and success of hatching in a coral reef fish

In oviparous species, the timing of hatching is a crucial decision, but for developing embryos, assessing cues that indicate the optimal time to hatch is challenging. In species with pre-hatching parental care, parents can assess environmental conditions and induce their offspring to hatch. We provide the first documentation of parental hatching regulation in a coral reef fish, demonstrating that male neon gobies (Elacatinus colini) directly regulate hatching by removing embryos from the clutch and spitting hatchlings into the water column. All male gobies synchronized hatching within 2 h of sunrise, regardless of when eggs were laid. Paternally incubated embryos hatched later in development, more synchronously, and had higher hatching success than artificially incubated embryos that were shaken to provide a vibrational stimulus or not stimulated. Artificially incubated embryos displayed substantial plasticity in hatching times (range: 80-224 h post-fertilization), suggesting that males could respond to environmental heterogeneity by modifying the hatching time of their offspring. Finally, paternally incubated embryos hatched with smaller yolk sacs and larger propulsive areas than artificially incubated embryos, suggesting that paternal effects on hatchling phenotypes may influence larval dispersal and fitness. These findings highlight the complexity of fish parental care behaviour and may have important, and currently unstudied, consequences for fish population dynamics.

Possible Mechanisms of Hatching from Egg Capsules in the Gastropods Crepipatella dilatata and Crepipatella peruviana, Species with Different Modes of Early Development

Many invertebrates enclose their embryos within egg capsules, from which the offspring hatch. In marine gastropods that brood their egg capsules, hatching could involve radular activity by the mother or by unhatched stages, increased osmotic concentration of the intracapsular fluid, or production of hatching enzymes. The present research sought to determine whether mechanical action by the brooding female or by the encapsulated embryos was involved in the hatching for two sympatric and closely related species of calyptraeid: Crepipatella dilatata, which exhibits direct development without free-living larvae, and Crepipatella peruviana, which releases free-living veliger larvae. We also considered the role that enzymatic action or osmotic changes in the intracapsular fluid might play in hatching. Using scanning electron micrograph analyses, we found no evidence that the well-developed, pre-hatching juvenile radula of C. dilatata played any role in the hatching process and that the radula of C. peruviana did not even develop until long after hatching; so there was no evidence of radular activity involved in the hatching of either species. For C. peruviana, the intracapsular fluid osmolality was always higher than that of the surrounding seawater, suggesting that there is a strong natural water inflow during development. Moreover, when egg capsules of C. peruviana were exposed to lower ambient salinities, the substantial entry of water correlated well with high percentages of hatching, particularly for egg capsules containing advanced veligers, suggesting that an osmotic mechanism may be involved in the hatching process of this species. In contrast, hatching in C. dilatata appeared to be enzymatically mediated.