Description of Three New Species of Rhadinorhynchus Lühe, 1911 (Acanthocephala: Rhadinorhynchidae) from Marine Fish off the Pacific Coast of Vietnam.

BACKGROUND: Of the 43 valid species of Rhadinorhynchus Lühe, 1911, 20 species are now known from the Pacific Ocean off Australia, Japan, and Vietnam. We have already described over 50 species and higher taxa from the Pacific Ocean off Vietnam over the last 15 years. PURPOSE: The present research is a continuation of our efforts to taxonomically map new acanthocephalan taxa, especially from Vietnam. Some of our collections in 2016 and 2017 revealed the presence of new species of the genus Rhadinorhynchus from various species of marine fish off the Pacific coast of Vietnam. We provide descriptions of these new species here. METHODS: Standard methods of collection and examination of marine hosts, processing and illustrating of specimens, and taxonomic identification of parasites using the extensive collections of the lead author were used. Type specimens were deposited at the Harold W. Manter Lab. collection, Lincoln, Nebraska. RESULTS: Three species Rhadinorhynchus are described from marine fish off the Vietnamese coast. Rhadinorhynchus circumspinus n. sp. with fusiform trunk, 1 field of anterior trunk spines, and anteriorly globular proboscis with up to 21 dorsoventrally differentiated hooks in 17-18 rows is described from Triacanthus biaculeatus Bloch (Triacanthidae) off Hai Phong. Rhadinorhynchus pacificus n. sp. with cylidrical trunk and proboscis with up to 25 dorso-ventrally similar hooks in 14-18 rows and trunk spines in 2 fields of dorsal, ventral and lateral spines is described from Auxis thazard (Lacepède) and Auxis rochei (Lacepède) (Scombridae) off Nha Trang. Rhadinorhynchus multispinosus n. sp. with cylindrical trunk and proboscis with up to 32 dorso-ventrally differentiated hooks in 12 rows, and many trunk spines in 2 fields of dorsal, ventral and lateral spines is described from Decapterus maruadsi (Temminck and Schlegel) (Carangidae) also off Hai Phong. Rhadinorhynchus polynemi Smales, 2014 of Australia is not the Indian species (with smallest basal hooks) as the basal hooks are largest and is now named Rhadinorhynchus australis nom. nov. (=Rhadinorhynchus polynemi Smales, 2014). Rhadinorhynchus trivandricus George and Nadakal, 1978 with smallest basal hooks and 8 pyriform cement glands is relegated to genus Indorhynchus Golvan, 1969. CONCLUSIONS: With the description of these 3 new species, the numner of valid species of Rhadinorhynchus has now increased to 46. We include a new generic diagnosis to accommodate the increased knowledge of variability within this genus.

Morphological Studies of Developmental Stages of Oculotrema hippopotami (Monogenea: Polystomatidae) Infecting the Eye of Hippopotamus amphibius (Mammalia: Hippopotamidae) Using SEM and EDXA with Notes on Histopathology.

The present study was performed to observe histopathological effects of Oculotrema hippopotami Stunkard, 1924 infection in the eye of Hippopotamus amphibius, as well as to reveal new details of morphology and structural features of this monogenean and its comparison between 2 age stages of the parasite. This was done using both light and scanning electron microscopy, energy dispersive X-ray analysis (EDXA) and histopathology. The presence of a mixture of different generations (adult and sub-adult) in one host individual is common for Oculotrema Stunkard, 1924 in contrast to Polystoma Zeder, 1800. New metrical and graphical information obtained for adults and sub-adults compared with the previous studies. Here we show the presence of genital papillae in adults, metrical data on the distal part of the vas deferens. SEM micrographs of sperm ejaculatory structures and information about the flattened dorsal side of the body provided for the first time. Histopathological changes, such as necrosis and hemorrhage in host tissues as a result of O. hippopotami attachment structures are described. Structural analysis of different body parts of O. hippopotami of both age groups are also included. We show qualitative differences in the presence of hardening ions (S, P, Ca) in attachment structures (oral and haptor suckers) that increase with the age of the worm. The presence of sub-adults and adults on the same host, together with high levels of infection without high pathogenicity may account for Oculotrema being one of the most successful parasites among the Monogenea.

Description and morphometrical variability of a new species of Ligophorus and of Ligophorus chabaudi (Monogenea: Dactylogyridae) on Mugil cephalus (Teleostei) from the Mediterranean basin.

A comparative morphological study of specimens of Ligophorus spp. from Mugil cephalus in western Mediterranean and the Black Sea localities has been carried out, indicating the presence of 2 distinct forms, i.e., Ligophorus chabaudi and Ligophorus cephali n. sp. A detailed description of the latter and an up-to-date redescription of L. chabaudi are provided. The existence of these 2 morphological species was additionally supported by principal component analysis based on 19 metric characters of 87 specimens arranged in samples defined by parasite species and geographical locality. The analysis indicated consistent differences between species but not between localities; this pattern was well supported by jackknife procedures. Linear discriminant analyses showed that the main metric differences between the 2 species were attributable to the lengths of the dorsal and ventral bars and to the uncinulus length; use of the first 2 variables was enough to allocate all specimens studied to either form. The erection of L. cephali n. sp. raises the number of sympatric Mediterranean species of Ligophorus on M. cephalus to 3. The known geographical ranges of these species are compared.