2026/01/21 by Alexey V. Golikov, Natasha Vokhshoori, Rushan M. Sabirov +3 · 1 voice
Environmental Science · Agricultural and Biological Sciences · #Isotope Analysis in Ecology #Cephalopods and Marine Biology #Marine and fisheries research
paper · doi:10.3354/meps15107
openalex publication_date 2026/01/21 · openalex created_date 2026/01/22 · openalex updated_date 2026/07/02
Cephalopod paralarvae are an abundant and globally widespread component of marine zooplankton, whose trophic ecology is not yet well understood. Here, we applied compound-specific stable isotope analyses of amino acids (CSIA-AA) to paralarvae of oceanic squids (Oegopsida) collected in 2015 in the Sargasso Sea to understand their ecological role in the food web. Paralarvae were divided into 5 morpho-functional groups: Onychoteuthidae, enoploteuthids (3 families), Ommastrephidae, Cranchiidae and chiroteuthids (2 families). We hypothesized that paralarvae of Onychoteuthidae and enoploteuthids with adult-like morphologies occupy trophic positions (TPs) and niche spaces (estimated from δ 15 N AA and δ 13 C AA , respectively) distinct from each other, and even more so from Ommastrephidae rhynchoteuthions and ammoniacal Cranchiidae and chiroteuthids with their distinctive morphologies. TP was the highest in Onychoteuthidae and enoploteuthids (2.7-3.4), intermediate in Ommastrephidae and chiroteuthids (2.5-2.9), and lowest in Cranchiidae (1.6-2.3). Onychoteuthidae and enoploteuthids are significantly different in centroids of δ 13 C AA niche spaces. However, probabilistic measures of niche overlap reveal substantial dietary overlap (52-67%), indicating that significant differences in group means do not necessarily reflect complete ecological separation. Moreover, these paralarvae with adult-like morphologies seem to rapidly assume ecological roles akin to adults of these taxa. Ammoniacal paralarvae of Cranchiidae and chiroteuthids are the most distinct in AA composition from other taxa. TP of Cranchiidae was lower than expected, possibly due to ammonium altering δ 15 N AA fractionation. This study provides the first CSIA-AA evidence of trophic differentiation among oceanic squid paralarvae, addressing a critical gap in understanding early life-phase ecology of cephalopods.