Trophic Niche and Diversity of a Pelagic Squid (Dosidicus gigas): A Comparative Study Using Stable Isotope, Fatty Acid, and Feeding Apparatuses Morphology

Abstract

Commercially important pelagic squid such as jumbo squid Dosidicus gigas play a key role in energy and nutrient transfer in marine ecosystem. Geographic variations in the foraging strategy of D. gigas can provide valuable information on cephalopod trophic diversification and adaption to natural and anthropogenic impacts. Here, we used a novel combination of stable isotope (SI) and fatty acid (FA) analyses of muscle tissues and morphometric measurements of feeding apparatuses to evaluate spatial patterns of habitat and resource use of D. gigas collected from three main fishing grounds in the tropical and southern temperate Pacific Ocean. Results showed that the δ 13 C and δ 15 N values were different among geographic stocks within D. gigas, possibly because of site-specific dietary sources and isotopic baseline values. Spatial variabilities in FA profiles/biomarkers, combined with SI results, suggests two foraging patterns: utilization of resources mainly from oceanic food webs or from both neritic and oceanic food webs. This behavior likely promotes the site-specific trophic niche width, increases adaptation to inhabiting oceanographic conditions, and could be driven by differences in feeding apparatuses morphology, body size, and trophic position. These results emphasize the dietary flexibility of D. gigas and their important ecological roles in ecosystems as cross-biome trophic linkages. Trophic diversification of pelagic squid like D. gigas may have important implications for their population dynamics, ecological associations, and subsequent management.

Energy acquisition strategy for reproduction in a semelparous squid

“…The strategy of energy acquisition for reproduction is independent from body size that has been considered as an important factor linked to feeding ability [ 15 , 25 ]. LMMs results indicated that reproductive energy was not correlated with mantle length (Additional file 1 : Tables S2, S3).…”

“…Such energy expenditures should theoretically be saved when the consumer forages for small prey species to gain a comparative energy resource [ 24 ]. It is also assumed that the reason why squid species shift feeding habits ontogenetically is because they become better at hunting as they grow rather than the increased need of energy for reproduction [ 15 , 25 ]. It is still unclear how reproductive energy needs are met for semelparous animals, which is important for understanding their life-history.…”

Combining bulk stable H isotope (δ2H) measurements with fatty acid profiles to examine differential use of aquatic vs. terrestrial prey by three sympatric species of aerial insectivorous birds

“…In combination with δ 2 H, fatty acid profiles confirm diet differences among species across locations and can be used to infer diet quality. We created a matrix for δ 2 H values of feathers and relative abundance of 8 notable plasma fatty acids (palmitic acid, stearic acid, oleic acid, LA, ALA, ARA, EPA, and DHA) that were standardized (Routti et al, 2012;Gong et al, 2020) to a mean of zero and a standard deviation of one using the vegan R package (Oksanen et al, 2019). Using Euclidean distances, a redundancy analysis compared δ 2 H values and FA percentages among species and between locations using the vegan package.…”

Beaks And Gladii of Oegopsid Squids to Understand Their Trophic Ecology Around American Waters: A Review of The Stable Isotope Analysis

“…The isotope analysis in squids has been performed using mantle muscle tissue [17,[29][30][31] beaks [32][33][34][35][36], gladii [37][38][39], statoliths [40], and eye lenses [41][42][43]. Each tissue allows the isotope analysis in a determinate time; two months approximately for muscle tissue, and life history for beaks, gladii, and eye lenses [29,41,44].…”