Notacanthus elongatus, a new deep-sea spiny eel (Notacanthiformes: Notacanthidae) from the Arabian Sea, southwest coast of India

Information on spiny eels of the family Notacanthidae from Indian waters remains limited. Examination of deep-sea trawl bycatch obtained from shrimp fisheries and exploratory surveys in the Arabian Sea revealed the presence of an undescribed species of Notacanthus. The new species differs from its congeners in possessing 13 or 14 dorsal-fin spines, 28–32 anal-fin spines, 38–66 anal-fin soft rays, and a relatively slender, laterally compressed body with a long dorsal-fin base (71.5–78.0% of gnathoproctal length). Molecular analysis based on the mitochondrial cytochrome c oxidase subunit I (COI) gene further supports its distinctiveness, showing a genetic divergence of 4.8%–16.4% from other species of Notacanthus. Phylogenetic analyses indicate that Notacanthus elongatus n. sp. is most closely related to Notacanthus indicus, although it differs from that species in several key morphological characters. The discovery increases the number of valid species of Notacanthus to 8 and represents a significant step forward in deep-sea research in the Indian Ocean, while also highlighting the potential of trawl bycatch as a valuable resource for species discoveries when logistical constraints limit targeted deep-sea sampling.