A first record of digenean parasites of the dwarf sperm whale Kogia sima with morphological and molecular information.

Abstract

Two species of digenean trematodes of the family Brachycladiidae were obtained from two male dwarf sperm whales Kogia sima that stranded along the island of Kyushu, southern Japan in 2017. From the liver of the first animal, a single, large gravid specimen of a digenean species was collected. The morphological features were consistent with those of the genus Brachycladium. The worm had a large body and was characterized by anterior caeca without lateral diverticula, the shape of testes, ovary, and eggs. Molecular analyses using gene sequences of the 28S rRNA and the mitochondrial NADH dehydrogenase subunit 3 also supported the inclusion of this specimen into the genus Brachycladium. The identity of this worm is undetermined due to the lack of information on the genus and is reported as Brachycladium sp. From the cranial sinuses of the second animal, 33 specimens of digeneans were collected that were morphologically identified as Nasitrema gondo. This report documents a new host record for N. gondo, and the sequence information is provided for this digenean for the first time. This is the second record of digenean parasites for the family Kogiidae, and the first record with morphological and molecular information. The possibility of digenean infection in the liver and cranial sinus should be kept in mind during the necropsy of stranded kogiids.