Killer Whale Parasite Redescribed from Stranded Orca in Indonesia with First DNA Sequences

Scientists have redescribed Orcinocyamus orcini, a tiny whale-louse amphipod found only on killer whales, using specimens collected from the skin lesions of an Orcinus orca stranded in East Java, Indonesia. The study, published in Acta Parasitologica, combines detailed microscopy with genetic analysis and delivers the first DNA sequences ever recorded for the species.

Whale lice are not true lice but cyamid amphipods, crustaceans that live on the skin of certain whales and dolphins, often within lesions. O. orcini was originally described in 1970, and its association with killer whales makes it a host-specific parasite. The Indonesian specimens were examined under both light and scanning electron microscopy, confirming their identity and revealing diagnostic features including anterodorsal epaulette-like processes, ventral abdominal spines, and paired double, sausage-shaped, non-fasciculate gills on segments 3 and 4.

The researchers obtained two COI sequences for O. orcini, deposited in GenBank under accession numbers PX513872 and PX513873. When compared with sequences from ten other cyamid species, these differed by 17.8 to 21.3 percent, and phylogenetic analysis placed O. orcini on a distinct lineage of its own. This genetic separation supports the morphological evidence that the species is distinct from its relatives.

Beyond the taxonomic detail, the findings carry a geographic significance. The study expands the documented distribution of O. orcini to the tropical Indo-Pacific, adding Indonesia to the record of where this killer whale-associated amphipod has been found. The authors note that the updated morphological characterization and the first molecular reference data will facilitate future identification of the species. Because the specimens came from a single stranded animal, the report reflects one documented occurrence rather than a survey of parasite prevalence in the region, and the description rests on material from that individual host.

Subject of Research: Redescription and first molecular characterization of the killer whale cyamid amphipod Orcinocyamus orcini from Indonesia

Article Title: Redescription of Orcinocyamus orcini (Amphipoda: Cyamidae) from Orcinus orca Stranded at East Java Island, Indonesia

Article References: Hassan, M., Yudhana, A., Ulkhaq, M. F., Mazelan, S., Ishak, A. N., Yusoff, N. A. H., Abdullah, F., Shukor, N. A., Zalati, C. W. S. C. W., & Peng, T. L. (2026). Redescription of Orcinocyamus orcini (Amphipoda: Cyamidae) from Orcinus orca Stranded at East Java Island, Indonesia. Acta Parasitologica, 71(6), Article 253. https://doi.org/10.1007/s11686-026-01436-5

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01436-5

Keywords: Orcinocyamus orcini, whale lice, cyamid amphipods, killer whale, Orcinus orca, COI barcode, taxonomy, Indonesia, parasitology, Acta Parasitologica, Redescription, Orcinocyamus