Cage-cultured sutchi catfish Pangasius hypophthalmus (Sauvage, 1878), a favourite food fish in Southeast Asia, proved to be infected by 6 myxozoan species. Three species belonged to the genus Hennegoides (H. berlandi, H. malayensis, and H. pangasii), 1 to Henneguya (H. shariffi) and 2 to Myxobolus (M. baskai, and M. pangasii). Five myxozoans infected the gills and 1 was found on the spleen. Myxozoans infecting the gills were characterised by a specific site selection. H. shariffi sp. n. and H. berlandi sp. n. formed plasmodia in the multi-layered epithelium of the gill filaments. Of the 2 vascular species H. pangasii sp. n. developed in the gill arteries, while M. baskai sp. n. infected the capillary network of the gill lamellae. Plasmodia of H. malayensis sp. n. were found inside the cartilaginous gill rays of the filaments. Large plasmodia of M. pangasii sp. n. were located in a groove of the spleen but they affected only the serosa layer covering the spleen.
We describe new myxosporean species from Malaysian fishes cultured in pond farms and net-cages. Myxobolus omari sp. nov. and M. leptobarbi sp. nov. were found in the muscles of Pangasianodon hypophthalmus and Leptobarbus hoevenii, respectively, while plasmodia and spores of Thelohanellus zahrahae sp. nov. and Henneguya daoudi sp. nov. were detected in the gills of Barbonymus gonionotus and Trichogaster trichopterus, respectively. Plasmodia and spores found in these fishes differed from the known myxosporean species in respect of their morphology, tissue tropism and 18S rDNA structure. No major pathological changes were found, but in the future these species might pose a potential threat to more intensified fish culture.
Cage-cultured Asian redtail catfish Hemibagrus nemurus (Valenciennes, 1840), a popular food fish in Southeast Asia, proved to be infected by 3 myxozoan species. All the 3 species belonged to the genus Henneguya: 2 were identified as H. mystusia Sarkar, 1985 and H. hemibagri Tchang et Ma, 1993, while the other was described as H. basifilamentalis sp. n. All plasmodia were found in the gills and were characterised by a specific site selection. H. mystusia formed plasmodia in the multi-layered epithelium between the gill lamellae and in the non-lamellar edge of the gill filaments, while H. hemibagri developed in the capillary network of the lamellae. H. basifilamentalis sp. n. had large oval plasmodia located deep among the filaments just above the gill arch. MATERIALS AND METHODSFishes were obtained from a cage culture of the Terengganu River close to Kuala, Terengganu, Terengganu Province, northeast Malaysia. Eight fish of 15 to 18 cm and 10 fish of 36 to 42 cm in total length were dissected during a 2 wk period in November 2004. The investigations were aimed at studying myxosporean infections only. For a detailed description of the techniques of parasitological dissections and the processing of the collected material see Molnár et al. (2006). RESULTSMyxozoan infection was found both in fishes of the younger age group and in those of the older generation. All examined Hemibagrus specimens harboured myxosporean plasmodia in the gills, but among the dissected specimens there were individuals infected by only a few plasmodia and there were heavily affected specimens, where the gills contained up to several hundred plasmodia. In most cases the gills were infected by 3 different Henneguya spp. No infection was found in other organs. Two species were identified as H. mystusia Sarkar, 1985 and H. hemibagri Tchang et Ma, 1993, Trophozoites: Ellipsoidal small plasmodia between the gill lamellae 100-120 × 80-95 µm in size and round or ellipsoidal plasmodia 220-700 × 180-240 µm in size at the edge of the gill filaments inside the multi-layered epithelium.Spores: The spores (Figs. 1A & 2A-C) are elongated with 2 straight caudal appendages and with elongated polar capsules located side by side. The spore wall is thin and smooth, composed of 2 equal valves. The suture is distinct in lateral view. The oral end of the spore body is blunt, slightly tapering; the caudal end is rounded but continues into the caudal appendages. In a fresh state the spore body is 11-13 (12.17 ± 0.61) µm, its width is 3-3.7 (3.35 ± 0.25) µm and its thickness is 2-2.5 (2.21 ± 0.22) µm. The 2 polar capsules are composed of 2 equal cylindrical rods opening at the anterior end of the spore body. Polar capsules measure 4-5 (4.5 ± 0.46) µm in length and 0.9-1.2 (1.01 ± 0.08) µm in width. The length of the anterior capsule with its elongated tubular part is 2.8-3.2 (3.0 ± 0.179) µm; the length of the posterior capsule is 4.5-5 (4.83 ± 0.25) µm. The polar filaments are coiled in 6 to 7 turns perpendicular to the long axis of the polar capsules....
The survival of the tropical edible oyster (Crassostrea madrasensis) was examined under the condition of ice-storage in a rectangular thermocol-transport box for a period of 48 h. A total of 100 two-year old farmed oysters were used for the experimental transportation. Inside the box, all oysters were arranged in four layers covered with wet-gunny bags and lined on the top and bottom with ice. Surface and bottom temperature of the transport box varied from 9.7 to 25.2˚ C and 9.7 to 28.4˚ C respectively during the 48 h exposure. The patterns of changing temperature at both surface and bottom were found to be different. Recoveries of the oysters at every two hours till 48h were monitored by taking random samples from the box. All the oysters recovered within 1 h of being placed back into seawater and there was close to 100% recovery within 2 hours. Survival was more than 90% after 8 days of the experiment.
The long-tailed sea slug Stylocheilus longicauda was recorded for the first time from southwest coast of India. A single specimen measuring a total length of 70.51mm was collected from a floating bottle, along with bunch of goose-neck barnacles from Arabian sea off Narakkal, Vypeen Island, Kochi. Earlier identifications were made based on the morphology of the animal without resorting to description of radula. This makes it difficult to differentiate the species from Stylocheilus striatus which has similar characters. The present description details the external and radular morphology of Stylocheilus longicauda.
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