A new species of Heterobothrium (Monogenea: Diclidophoridae) from half-smooth golden pufferfish Lagocephalus spadiceus in the Gulf of Tonkin, Vietnam, with an identification key for the genus

Abstract

Heterobothrium phamvanluci n. sp., a polyopisthocotylean monogenean infesting the gills of the half-smooth golden pufferfish Lagocephalus spadiceus, was collected off the coasts of Hai Phong and Nam Dinh provinces in the Gulf of Tonkin, Vietnam. The prevalence of infestation was 29.73 % (11/37), with an intensity range of 1–2 worms per fish. Heterobothrium phamvanluci n. sp. closely resembles H. indicum, H. victorwepeneri, and H. tonkinense, by having a male copulatory organ with 8–9 hooks. However, H. phamvanluci n. sp. can be distinguished from H. tonkinense by having fewer testes (24–40 vs. 50–100) and their position (posterior to the ovary vs. in level with it), a smaller haptor relative to body length, and a forth pair of clamps that is the smallest (vs. similar size across all pairs). Compared to H. indicum, it has a larger body length (4977 μm vs. 3105 μm) and a larger ratio of haptor length to body length (30 % vs. 10 %). Heterobothrium phamvanluci n. sp. differs from H. victorwepeneri by having a body length approximately three times larger (4977 μm vs. 1094 μm) and fewer testes (24–40, mean 28 vs. 40–50, mean 47). The 28S rDNA sequences showed that H. phamvanluci n. sp. is closely related to H. victorwepeneri, H. okamotoi, and H. tetrodonis, clustering as sibling species within the genus Heterobothrium, except H. indicum. We also propose an identification key for all known species within the genus Heterobothrium.