Assessing the trophic ecology of Southern Ocean Myctophidae: the added value of DNA metabarcoding

Abstract

Lanternfishes (Myctophidae) are key components of mesopelagic fish communities globally. In the Southern Ocean, incomplete information on myctophid diets limits our understanding of their energetics, interactions and wider ecosystem impact. Traditional microscopic methods of diet analysis have relatively coarse prey resolution and possible taxonomic and observer biases. DNA metabarcode sequencing promises higher taxonomic and temporal resolution, but uncertainty remains in comparing this is with microscopy-based analyses. Here, we applied 18S DNA metabarcode sequencing to stomach contents from twenty Electrona antarctica individuals which had previously been examined via microscopic analysis. Across all fish, crustacean and gastropod taxa dominated the prey identified via both methods, with broad agreement between methods on the relative abundance of different prey items. DNA metabarcode sequencing recovered greater taxonomic diversity and resolution, particularly for soft-bodied prey items and small crustaceans. DNA sequencing results also more clearly differentiated diet between individuals collected from different environments. Overall, our findings illustrate how DNA based methods are complementary to, and consistent with, traditional methods and can provide additional, high-resolution data on a range of trophic interactions.

Unlocking Antarctic molecular time-capsules – recovering historical environmental DNA from museum-preserved sponges

“…Interestingly, one notably absent taxonomic group, besides two signals of Gymnoscopelus sp., from sponge specimens collected in deeper waters are the myctophids, the most diverse and abundant group of mesopelagic fishes globally, including in the Southern Ocean (Duhamel et al 2014;Woods et al 2023;Vasiliadis et al 2024). The lack of myctophid detection could potentially have stemmed from their occupancy of the mesopelagic zone (Catul et al 2011;Christiansen et al 2018).…”

“…The Antarctic fish community constituted 64 taxa ranging from Nototheniidae (cod icefishes) and Channichthyidae (icefishes), to Bathydraconidae (Antarctic dragonfishes), all of which are known to occur in the Ross Sea according to Antarctic toothfish bycatch records (Pinkerton and Bradford-Grieve 2014; Jeunen et al 2024). Interestingly, one notably absent taxonomic group, besides two signals of Gymnoscopelus sp., from sponge specimens collected in deeper waters are the myctophids, the most diverse and abundant group of mesopelagic fishes globally, including in the Southern Ocean (Duhamel et al 2014; Woods et al 2023; Vasiliadis et al 2024). The lack of myctophid detection could potentially have stemmed from their occupancy of the mesopelagic zone (Catul et al 2011; Christiansen et al 2018).…”

“…Environmental DNA (eDNA) surveys have revolutionised how scientists monitor the Earth’s marine biome (Takahashi et al 2023). The capacity to discern biodiversity and ecological processes utilising genetic material extracted from environmental samples, such as water (Cecchetto et al 2021), soil (Olmedo-Rojas et al 2023), sediment (Kuwae et al 2020), air (Lynggaard et al 2022), or gut content (Vasiliadis et al 2024), obviates the necessity for direct species observations, a challenging accomplishment for the inaccessible and vast marine environment (Takahashi et al 2023). Hence, eDNA metabarcoding surveys detect a significantly larger proportion of the marine biological community compared to traditional approaches, such as diver surveys (Robinson et al 2023), baited remote underwater video (Stat et al 2019), and trawling (Maiello et al 2022).…”