Intertidal Breeding and Aerial Development of Embryos of a Stickleback Fish (Gasterosteus)

Abstract

Males of the newly discovered 'white' stickleback disperse their embryos over the filamentous algae in which they nest and, unlike any other stickleback, they provide no subsequent parental care. Previously known populations of white sticklebacks nest only in shallow subtidal waters where filamentous algae are abundant. Our purpose in this paper is to describe highly divergent populations at Spry Bay, Nova Scotia, Canada, in which males build nests on bare rock in the subtidal and intertidal zones, and disperse their embryos over bare rock. Intertidal embryos are exposed to air and are vulnerable to desiccation at low tide. Field studies reveal that nests are built from locally available materials directly on the rock substrate. They are constructed very quickly and tend to be less substantial than subtidal nests. Internest distances are shorter in the intertidal zone than in adjacent subtidal areas. Dispersed intertidal embryos tend to settle into crevices between stones where the microenvironment remains moist and temperate between tides due to the presence of organic detritus and shade. Such embryos survive, develop, and hatch. Similar behaviours occur at other sites in Nova Scotia, and we know that it has persisted for at least four years at Spry Bay. We conclude that breeding and dispersing embryos over bare rock substrate, and intertidal breeding, are novel but stable breeding repertoires. We hypothesize that they have evolved secondarily to the evolution of emancipation from parental care in the white stickleback.

Parenting behaviour is highly heritable in male stickleback

“…Indeed, it is intriguing to consider how paternal care behaviour might have facilitated the adaptive radiation of stickleback because fathers might be able to buffer their offspring from environmental variation, thereby allowing colonists to persist in a new environment [40]. We know surprisingly little about variation in parenting among populations of stickleback, but males in certain populations of stickleback build nests but do not provide care for their embryos and fry [54][55][56][57][58][59]. Our findings suggest that this variation is tractable for further genetic dissection.…”

Long-term environmental stability does not erode plasticity in nest building responses to changing ambient conditions

“…sand, gravel) using a glue-like protein -'spiggin'produced by the kidney [61,62]. In natural populations, whether male sticklebacks build nests at all can vary between populations [63] and depends on the level of predation risk [64]. When they do build nests, sticklebacks show a strong preference for particular nesting sites [53,[65][66][67], and such preferences can vary according to habitat of origin [68].…”