Folia Parasitologica 67:028 (2020) | DOI: 10.14411/fp.2020.028

Five monogenean species (Allodiscocotylidae, Heteromicrocotylidae, Microcotylidae) from the Pacific seabream Acanthopagrus pacificus (Perciformes: Sparidae) in the Gulf of Tonkin off Vietnam, with descriptions of three new species

Ha Van Nguyen¹, Hung Manh Nguyen^1,6*, Ngo Duy Ha¹, Chinh Nguyen Ngoc¹, Thanh Bui Ngoc², Sinh Xuan Le³, Yulia Tatonova⁴, Stephen E. Greiman⁵

¹ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Cau Giay, Hanoi, Vietnam;

² Research Institute for Aquaculture No. 1, Dinh Bang, Tu Son, Bac Ninh province, Vietnam;

³ Institute of Marine Environment and Resources, Ngo Quyen, Hai Phong, Vietnam;

⁴ Federal Scientific Center of the East Asia Terrestrial Biodiversity, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia;

⁵ Georgia Southern University, Statesboro, United States of America

⁶ Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Cau Giay, Hanoi, Vietnam.

A total of 52 specimens of the Pacific seabream Acanthopagrus pacificus Iwatsuki, Kume et Yoshino from the Gulf of Tonkin off Vietnam were examined for monogeneans. Twenty fish were parasitised by 101 individuals of five monogenean species, including two known species Allodiscocotyla diacanthi Unnithan, 1962 and Heterapta chorinemi (Tripathi, 1956), as well as three new species, Polylabroides tienyenensis sp. n., Polylabroides tonkinensis sp. n. and Metacamopia lebedevi sp. n. Polylabroides tienyenensis and P. tonkinensis are morphologically more similar to Polylabroides guangdongensis Zhang et Yang, 2001 in comparison with other species within the genus, based on the absence of small spines on the cirrus. However, P. tonkinensis is distinguished from P. guangdongensis by fewer clamps on the haptor and by the different shapes of the large spines on the cirrus. Similarly, P. tienyenensis differs from P. guangdongensis by vaginal ducts with fewer branches, fewer clamps and smaller egg size. Metacamopia lebedevi is distinguished from Metacamopia chorinemi (Yamaguti, 1953) by the arrangement of testes (one row vs two rows), diverticula absent in the oesophagus, and the number of anchor pairs (one vs two); it differs from Metacamopia oligoplites Takemoto, Amato et Luque, 1996 by the smaller haptor, shape and absence of small sclerotised hooks, the number of ribs in their clamps, and the position of the testes; it can be separated from Metacamopia indica (Unnithan, 1962) by having fewer testes and lacking sclerotised structures in the vagina. The present study also provides the measurements for A. diacanthi, H. chorinemi, and proposes a new key to all species of Polylabroides.

Keywords: Polyopisthocotylea taxonomy, Monogenea, marine parasites, sparids, western Pacific

Received: April 13, 2020; Revised: July 16, 2020; Accepted: July 16, 2020; Published online: October 21, 2020  Show citation