Parental care and reproductive strategies in notothenioid fishes

Abstract

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.

Spatial patterns and behaviour of notothenioid fishes off the northern Antarctic Peninsula

“…As previously reported from the Weddell Sea (Ekau and Gutt 1991;La Mesa et al 2019), C. antarcticus and C. mawsoni both displayed a unique posture, perching on the extremely long pelvic fins or assuming a defensive or S-shaped position of the trunk, respectively. The adoption of parental care is a reproductive characteristic shared by species of all five notothenioid families occurring in the Southern Ocean (La Mesa et al 2021). During the survey, two species of channichthyids (C. wilsoni and P. macropterus) were observed guarding eggs laid on glacial dropstones, as previously reported (Kock et al 2008;Ziegler et al 2017;La Mesa et al 2019).…”

A vast icefish breeding colony discovered in the Antarctic

“…Neopagetopsis ionah breeding colony discovery Nest building and egg guarding is a common parental care behavior of channichtyids, previously observed in isolation or in clusters of a few tens of nests, in the Weddell Sea and elsewhere. [1][2][3][4][5] Here, we report the first observations of a Neopagetopsis ionah (Nybelin 1947) 6 breeding colony (Figures 1A and 1B) where brooding was observed occurring simultaneously across tens of thousands of nests, arrayed over many square kilometers of seafloor (Figures 2A and 2B). N. ionah exhibits a broad, potentially circumpolar Antarctic and sub-Antarctic distribution.…”

“…Though associated epifauna abundances were low, the locally elevated biomass, primarily made up of N. ionah, as well as the heavy reworking of the upper sedimentary structures by the nesting fish (excavation of $20 liters of sediment from each nest during nest construction, or $1.2 million cubic meters of excavated material across the surveyed area) may fuel the local benthic microbial loop 23,24 with the elevated carcass concentrations observed within the 0.04 dead fish containing nests m À2 (standard deviation = 0.013) 25 regularly observed to be covered by microbial mat (Figure 1B), and provide new habitat for sessile invertebrates, elevating local blue carbon concentrations 26,27 following nest abandonment (see ''Abandoned fish nests'' section below). Although there is no published evidence that N. ionah is strictly semelparous, post-spawning individuals are known to have poor and dissipated body conditions, 3 which after several months of egg tending could result in high mortality rates. 28 The shallow slope angle of the eastern slope of the Filchner Trough and low abundance of drop stones or other naturally occurring hydrodynamic structural traps renders the biogenic depressions produced by nesting fish the most efficient local hydrodynamic traps.…”

Decoupled spectral tuning and eye size diversification patterns in an Antarctic adaptive radiation

“…Continual ecological investigations focused on how notothenioids are utilizing their habitat are needed to place our analyses into a more refined ecological context, as it is currently not possible to accurately contrast patterns of eye size or opsin evolution relative to these aspects of water column niches. Fortunately, continual advances in imaging technology hold the promise of overcoming traditional logistical challenges of observing notothenioids in the Antarctic (Jones and Near 2012; La Mesa et al 2021; Purser et al 2022) and providing these critically needed insights into the ecology of this adaptive radiation in the near future.…”