Ecomorphological Differentiation of Feeding Structures within the Antarctic Fish Species Flock Trematominae (Notothenioidei) from Terra Nova Bay (Ross Sea)

Abstract

The Antarctic endemic fish genus Trematomus (Trematominae, Notothenioidei) includes 15 species very diverse in morphology, lifestyle and feeding ecology. Co-occurring on the continental shelf, they occupy different habitats and a wide range of ecological niches as the result of adaptive radiation during their evolutionary history. Ecomorphological differentiation is a key feature of adaptive radiations, with a general trend for specialization following divergence. Here, we investigated the trophic adaptive morphology and ecology of six Trematomus species from Terra Nova Bay (Ross Sea) through feeding apparatus metrics and geometric morphometrics. The suction index (SI), the mechanical advantage in jaw closing (MA), the relative surface of the adductor mandibulae muscle and nine morphological traits related to feeding structures were analysed. Head shape clearly differentiates the benthic (T. bernacchii, T. hansoni and T. pennellii) from the pelagic (T. eulepidotus and T. borchgrevinki) species. The position of the eyes and the orientation of the mouth also contribute to specific morphological differences and specialization. Interestingly, T. newnesi stands at an intermediate position and the mouth is clearly oriented upwards compared to the other congeneric species.

Feeding Behaviour of Seven Icefish Species (Channichthyidae) in the Ross Sea, Antarctica

“…These provide valuable information on feeding performance and potential resource use. Although many studies are available on the diet of Antarctic fish, ecomorphological studies relating morphology to diet are few [13,[38][39][40][41][42], and especially rare for icefish [43]. To evaluate fish feeding strategies, various biomechanical indices can be used, including the suction index (SI) and the mechanical advantage of jaw closure (MA) [31,35].…”

Morphology and diet are decoupled in nearshore notothenoids from King George Island, West Antarctica

“…External morphological features related to sensory perception, such as size of the eye and the mouth, are very suitable for ecomorphological studies, with Antarctic fish not being the exception (Colombo et al, 2015; Hu et al, 2016; Lombarte et al, 2003). For example, those morphological features as well as head shape may differentiate benthic from pelagic species within Trematomus genus (Carlig et al, 2022). In Nototheniidae, species with benthic feeding habits have lower jaws with a powerful biting force, capable of manipulating (grasping or crushing) prey (Bansode et al, 2014), whereas in pelagic species there is poor capability for the jaw to produce force (Carlig et al, 2018).…”

“…The morphological differences among Antarctic species are mainly the result of the lateral movement of growth trajectories, suggesting the importance of larval development above allometric growth (Klingenberg & Ekau, 1996). Therefore, the fish morphospace shows variability, and it is sensitive to environmental and ecological processes (Bernal‐Durán et al, 2017; Bower & Piller, 2015; Vignon, 2012), particularly in Antarctic fishes (Carlig et al, 2022; Frédérich et al, 2022; Wilson et al, 2013). In this sense, the diversification in the notothenioid radiation is linked to the operculum shape change along the benthic‐pelagic axis (Wilson et al, 2013), meanwhile, head shape, the position of the eyes, and the orientation of the mouth contribute to specific morphological differences among Trematomus species (Carlig et al, 2022).…”

Biodiversity, Adaptation Strategies, and Opportunities in Extreme Marine Environments

“…In this Special Issue, we also published several papers on macroorganisms, which mainly focused on Antarctic fishes. In particular, Carlig et al [7] studied six Trematomus species from Terra Nova Bay (Ross Sea) through feeding apparatus metrics and geometric morphometrics, showing how shape of the head differs between benthic and pelagic species; Amelio et al [8] focused on the hemoglobin-less Antarctic teleost Chionodraco hamatus (icefish) and in particular, on involvement of nitric oxide in the Frank-Starling response, an intrinsic heart property; Bakiu et al [9] studied the evolution of metallothioneins in notothenioid fish, which evolved under the selective pressure of relatively high oxygen partial pressures, cold Antarctic seawaters, and relatively high concentrations of metal ions-Cd and Cu in particular. Their analysis indicated the presence of two metallothioneins clades, suggesting that the evolution of these genes has been characterized by purifying selection.…”