Pseudempleurosoma haywardi

Niyom, Nussaba, Wiroonpan, Pichit & Purivirojkul, Watchariya, 2023, New record of endoparasitic Pseudempleurosoma haywardi (Monogenea: Dactylogyridae) in sillaginid fishes from Thailand, with updates on host range, zoogeography, and morphological variation, Raffles Bulletin of Zoology 71, pp. 317-330 : 323

publication ID	https://doi.org/ 10.26107/RBZ-2023-0024
publication LSID	lsid:zoobank.org:pub:FEDCAC2C-3086-458A-9DA5-2069261103AB
DOI	https://doi.org/10.5281/zenodo.14014869
persistent identifier	https://treatment.plazi.org/id/D1283B51-FFEE-FF93-EB86-FB5F90A79221
treatment provided by	Felipe
scientific name	Pseudempleurosoma haywardi
status

Treatment

Pseudempleurosoma haywardi View in CoL ( Figs. 2–4 View Fig View Fig View Fig )

Host: S. aeolus and S. sihama ( Figs. 5A, B View Fig )

Locality: Samut Sakhon Province, the upper Gulf of Thailand (13°19′23.9″N 100°23′23.2″E) and Surat Thani Province, the middle Gulf of Thailand (9°22′55.2″N 99°42′32.5″E) Site of infection: Stomach

Original records: Oesophagus/proximal stomach of Nibea soldado (type host), Johnius amblycephalus and Otolithes ruber from Cilacap, South Java coast and Kedonganan, South Bali coast, Indonesia ( Theisen et al., 2017; Theisen, 2019). Specimen deposition: No. ZMKU-PM-002001 at Zoological Museum, Kasetsart University: ZMKU, Bangkok, Thailand .

Infection rates of the monogenean in sillaginid fishes.

Of 629 sillaginid fishes examined, 16 individuals (10 of S. aeolus and 6 of S. sihama ) ( Fig. 5 View Fig ) were infected with the monogenean P. haywardi , representing 2.5% and 1.3 monogeneans/infected fish in terms of overall prevalence and mean intensity of the infection, respectively ( Table 1 View Table 1 ). Prevalence and mean intensity of the infection in S. aeolus were 3.4% and 1.0, respectively; in the case of S. sihama they were 3.6% and 1.7 respectively ( Table 1 View Table 1 ). The remaining four fish species were not infected.

Morphological description. The morphological features of the P. haywardi ( Figs. 2 View Fig , 3 View Fig ) observed were considered based on both descriptive and measurement characteristics. All measurement parameters ( Table 3 View Table 3 ; Fig. 1 View Fig ) were represented as minimum and maximum values (range) followed by the mean value within parentheses; most of these parameters were shown as dimensions of length × width. All values are in micrometres (µm). The body shape is slender and unspined ( Figs. 2A View Fig , 3A View Fig ), 1000–2112 (1468) × 221–362 (294). A single pair of head glands extends to the pharyngeal region ( Figs. 2A View Fig , 3A View Fig ) and two pairs of eye spots were observed ( Figs. 2A View Fig , 3A View Fig ). The oral aperture is present ventrally ( Figs. 2A View Fig , 3A View Fig ), and the pharynx is subspherical ( Figs. 2A View Fig , 3A View Fig ), 58–79 (73) × 54–88 (75). Bifurcated intestinal ceca reached the testis posteriorly, coexisting with vitelline follicles and with lateral diverticula lacking hematin pigment ( Fig. 3A View Fig ). The opisthaptor is not distinctly set off from the body ( Figs. 2A–C View Fig , 3A View Fig ), 139–167 (147) × 80–103 (91). Two pairs of dissimilar hamuli and marginal hooks were observed. Dorsal anchors are present, 57–68 (61) in length, connecting with a single dorsal bar ( Figs. 2B, C View Fig , 3E View Fig ). Ventral anchors ( Figs. 1H View Fig , 2B, C View Fig , 3C View Fig ), 15–17 (16) in length, each one with two bars: one with an attached ventral anchor ( Figs. 1H View Fig , 2C View Fig , 3C View Fig ), 14–18 (16) in length, and another one with a detached ventral anchor ( Figs. 2C View Fig – 3G View Fig ) that is a free irregular bar, 20–22 (21) in length ( Fig. 1I View Fig ). Dorsal bar is slightly concave ( Figs. 1G View Fig , 2B, C View Fig , 3H View Fig ), 17–22 (19) × 10–21 (14). Fourteen marginal hooks, 11–18 (14) in length ( Figs. 1J View Fig , 2B, C View Fig , 3D View Fig ). MCO is sclerotized, slender and tubular, 53–57 (55), initial part of MCO resembles a cup and funnel ( Figs. 3B View Fig , 4 View Fig ). Sclerotized accessory piece is irregularly shaped and located in the middle part of MCO ( Figs. 1A View Fig , 3B View Fig , 4 View Fig ), length 20–23 (22). Testis sub-elongated and oval in shape, size 58–100 (73) × 34–57 (40), ovary heart-shaped, size 60–99 (86) × 56–71 (61) ( Figs. 1D View Fig , 3A View Fig ). Vaginal opening simple, surrounded with muscular genital atrium, 34–41 (37) × 30–32 (31) ( Figs. 1C View Fig , 3A View Fig ). Vitelline follicles form numerous transversely elongated lobes and longitudinally arranged along lateral fields of the body ( Figs. 2A View Fig , 3A View Fig ), and vitelline ducts are connected in a position between the MCO and ovary ( Fig. 3A View Fig ). Egg, 57–97 (71) × 51–84 (64), without polar filament ( Figs. 1B View Fig , 2D, E View Fig , 3F View Fig ).

Phylogenetic relationship and molecular identification.

The overall topology of the phylogram ( Fig. 6 View Fig ) based on 28S rRNA revealed a monophyletic group of species members of dactylogyrid lineage, using diplectanids as an outgroup. Two distinct and major clades were resolved (clades A and B in Fig. 6 View Fig ). In clade A, the high support value of the two novel sequences (ON969400 and ON969401) from our study strongly indicated that the monogenean species found in this study was conspecific to P. haywardi (MF115714), with genetic divergences ranging between 0.0–0.2% among these three sequences (Supplementary Table S1 View Table 1 ). A sequence of Paradiplectanotrema klimpeli (MG763101) was arranged as a sister taxon of P. haywardi . All endoparasitic monogenean sequences investigated here formed a monophyletic cluster. Species members of both Ancyrocephalidae and Dactylogyridae (following the NCBI database classification) are present in the two major clades A and B (see Fig. 6 View Fig ; considered as subfamilies Dactylogyrinae and Ancyrocephalinae, respectively, in Kmentová et al., 2022).