Myxozoan pathogens in cultured Malaysian fishes. II. Myxozoan infections of redtail catfish Hemibagrus nemurus in freshwater cage cultures

Abstract

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....

Myxozoan infections in fishes of the Tasik Kenyir Water Reservoir, Terengganu, Malaysia

“…Remarks: In morphology and size the spores found during the present survey correspond to the spores observed by Molnár et al (2006b) from another locality (net-cage farms on Terengganu River).…”

Henneguya (Cnidaria: Myxosporea: Myxobolidae) infections of cultured barramundi, Lates calcarifer (Perciformes: Latidae) in an estuarine wetlands system of Malaysia: description of Henneguya setiuensis n. sp., Henneguya voronini n. sp. and Henneguya calcarifer n. sp.

“…Previous studies have demonstrated that Henneguya spp. are the most common myxosporean parasites in non-cyprinid fishes in Southeast Asia (Molnár et al 2006a(Molnár et al , 2006bSzékely et al 2009aSzékely et al , 2009b. From Malaysia, the few known Henneguya species are from freshwater host species and/or habitats (Shariff 1982;Molnár et al 2006aMolnár et al , 2006bSzékely et al 2009aSzékely et al , 2009b.…”

“…are the most common myxosporean parasites in non-cyprinid fishes in Southeast Asia (Molnár et al 2006a(Molnár et al , 2006bSzékely et al 2009aSzékely et al , 2009b. From Malaysia, the few known Henneguya species are from freshwater host species and/or habitats (Shariff 1982;Molnár et al 2006aMolnár et al , 2006bSzékely et al 2009aSzékely et al , 2009b. Six species are described from noncyprinid fishes in Malaysia: H. shariffi Molnár, Székely, Mohamed and Shaharom-Harrison, 2006, in Pangasianodon hyphopthalmus Sauvage (Pangasidae: Siluriformes); H. mystusia Sarkar, 1985, in Hemibagrus nemurus Valenciennes (Bagridae: Siluriformes); H. basifilamentalis Molnár, Székely, Mohamed and Shaharom-Harrison, 2006, in H. nemurus;H.…”

Taxonomia e interação parasito-hospedeiro na infecção de mixosporídeos em pintado (Pseudoplatystoma corruscans) e cachara (Pseudoplatystoma fasciatum) oriundos de ambiente natural e de sistemas de cultivo

“…The gill is the major respiratory organ, the primary site of nitrogenous waste excretion and plays an important role in ionic balance (Noga, 2000). Species from the genus Henneguya have different manners of interaction with fish gill structures, resulting in different levels of disease Dykova & Lom, 1978;Bowser & Conroy, 1985;Kalavati & Narasimhamurti, 1985;Duhamel et al, 1986;Molnár, 1998;2205b;Molnár et al, 2006a;2006b).…”