An unidentified species of Leucochloridium (Trematoda: Leucochloridiidae) found in an Amber snail (Succinea lauta) from Chiba Prefecture, Honshu, Japan

Abstract

Leucochloridium spp. are intriguing parasites due to their colorful, pulsating larval broodsacs in amber snails' eyestalks. The unusual appearance is believed to mimic caterpillars to attract insectivorous birds. Sporocysts of Leucochloridium sp. were discovered in an amber snail (Succinea lauta) in Chiba, located in the central region of Honshu, Japan. The broodsacs displayed a distinctive pattern, characterized by large dark brown spots, bands of the same color at the anterior end, and light brown vertical stripes running through them. Phylogenetic analyses were conducted based on DNA sequences of the nuclear 28S ribosomal RNA gene (28S rDNA) and the mitochondrial cytochrome c oxidase subunit 1 gene (cox1). Although the 28S rDNA sequence of the present species was closely related to that of Leucochloridium problematicum from North America, morphological differences in the broodsacs suggest that it is likely a distinctive species. A ML tree based on the cox1 sequences indicated that the Leucochloridium species analyzed in this study and L. subtilis form a clade separate from other Leucochloridium species in Europe and Asia. However, the p-distance between the cox1 sequences of the present species and L. subtilis was 0.24, supporting their distinction at the species level. Although definitive identification of Leucochloridium sp. was not achieved in this study, the DNA barcodes generated here and in related research may facilitate future direction and identification of adult Leucochloridium sp. in birds residing in or migrating through Japan.