Parental care and reproductive strategies in notothenioid fishes

The adoption of parental care behaviours is the distinctive reproductive characteristic associated with the diversification and divergence of notothenioid fishes into an array of habitats in the subzero shelf and upper slope waters around Antarctica and sub-Antarctic environments. These include a variety of pre- and post-fertilization activities, including courtship behaviour and mate choice, linked to the development of sexually dimorphic traits, nest construction and egg guarding until hatch. Using published literature and new data, this review synthesizes and evaluates, in a phylogenetic context, information related to parental care, specifically sex-specific morphological adaptations, nest location and structure, sexual differences in egg guarding and post-spawning mortality, duration of egg incubation times and larval size at hatch. The existence of parental care in phylogenetically basal notothenioids is not documented and unlikely; however, the derived lineages of the Antarctic clade (cryonotothenioids), especially bathydraconids and channichthyids, clearly exhibit a trend towards larger egg size and reduced fecundity that are considered proxies for parental care behaviours. In addition, the reproductive strategies of cryonotothenioids exhibiting parental care show latitudinal patterns at intra- and inter-specific levels. Antarctic species spawn in spring-summer and have low fecundity, large egg size at spawning and large larvae at hatching. Sub-Antarctic species spawn in autumn-winter and have moderate to high fecundity, moderate egg size and larval size at hatching, whereas non-Antarctic species spawn in winter and possess high fecundity, small egg size at spawning and small larvae at hatching.