Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
Vol. 90, Num. 3, 1995, pp. 349-352

Mem Inst Oswaldo Cruz, Rio de Janefro, Vol. 90(3): 349- 352, may/jun. 1995

Hysterothylacium rhamdiae sp.n., (Ascaridoidea: Anisakidae) from a Neotropical Catfish, Rhamdia sapo (Pisces: Pimelodidae)

Sandra M Brizzola, Ruben D Tanzola

Laboratorio de Parasitolog/a, Departamento de Biologia y Bioquimica, Universidad Nacional del Sur, San Juan

670, (8000) Bahia Blanca, Provincia de Buenos Aires, Argentina

Code Number: OC95070 Size of Files: Text: 10K Graphics: Line Drawings (gif) 93K

A new species of Hysterothylacium is described and figured. The nematodes were collected from the intestine of a neotropical catfish, Rhamdia sapo, collected from its southernmost locality (Naposta stream and Sauce Grande river, Buenos Aires Province). The specimens resemble H. murrayense but differ in having shorter spicules, in the number and distribution of papillae and the relative size of intestinal caecum and ventricular appendix.

Key words: Hysterothylacium rhattgliae sp.n. - Anisakidae - Rhamdia sapo - freshwater parasite - Argentina - nematodes

The genus Hysterothylacium Ward and Magath, 1917 comprises about fifty species, most of them parasites of marine teleosts (Deardorff & Overstreet 1981, Rye & Baker 1984, Moravec et al. 1985, Petter & Radujkovic 1986, Petter & Maillard 1987, Bruce & Cannon 1989, Bruce 1990). Several species, such as H. analarum (Rye & Baker 1984), H. bidentatum (Mozgovoi 1953), H. brachyurum (Rye & Baker 1984), H. dollfusi (Schmidt et al. 1973), H. murrayerase (Johnston & Mawson 1940) and H. macquariae (Johnston & Mawson 1940), were also recorded in freshwater fishes from Holaic and Oriental regions. H. aduncum and H. claraturn (Mozgovoi 1953) were reported from both marine and freshwater hosts.

Torres et al. (1988) recorded Hysterothylacium sp. in Basilichthys australis and Cauque mauleanum from Valdivia river, Chile.

A sample of nematodes belonging to Hysterolhylacium was collected from the gut of a neotropieal catfish, Rhamidia sapo. They belong to a hither to undescribed species and are described and figured herein.


The nematodes were found in the intestinal lumen of R. sapo (Valenciennes 1840)(Pisces, Pimelodidae). The hosts were caught with line and hook in Naposta stream (38 08'S; 61 47'W) and Sauce Grande river (38 43'S; 62 15'W) in Buenos Aires province, Argentina. The worms were removed from hosts and prepared according to several methods. Some specimens were fixed in glacial acetic acid and preserved in 70 ethanol; others were fixed in ethanol-glycerine and a few were cleared in Amann's lactophenol. Histological section were stained with Erlich's haematoxylin and eosin. Some specimens were examined by SEM using routine methods. All measurements are given in pm unless otherwise indicated. Mean and range (in parentheses) are stated for each feature. Figures were drawn with the aid of a drawing tube.


Hysterothylacium rhamdiae sp.n. (Figs 1-12)

Body less than 30 mm long. Maximum width in midportion. Cuticule bearing transverse striae about 1 um apart. Lips similar in shape about as long as wide. Dorsal lip with pair of double lateral papillae. Lateroventral lips with double lateroventral papillae, a simple laterodorsal papilla and amphid between them. Dentigerous bars absent. Interlabia present. Lateral alae extending from cervical region to tail. Muscular esophagus about 13-15% of body length. Ventriculus as long as wide. Ventricular appendix longitudinally septate. Excretory pore slightly posterior to level of nerve ring. Short conical tail ending in thorny apex. Cervical papillae absent.

Male (based on 14 mature specimens). Body 16.98 (12.08-29.07) mm long by 0.33 (0.14-0.46) mm maximum width. Lips similar in size and shape, 58 (40-84) long, 70 (64-76) wide at base. Interlabia approximately 30 in length. Nerve ring 430 (360-600) from anterior end. Excretory pore 530 (390-700) from anterior end. Esophagus 2.44 (1.65-4.10) mm long. Ventricular appendix 2.09 (1.53-3.42) mm long. Intestinal caecum 660 (480-876) long. Length ratios: intestinal caecum -

Hysterothylacium rhamdiae sp.n.

    Fig. 1: anterior portion of adult wonn, male, bar= 1 mm.

    Fig.2: dorsal lips, male, bar= 0.05 ram.

    Fig.3: lateroventral lip, male, bar= 0.05 mm.

    Fig.4: interlabium, male, bar= 0.05 mm.

    Fig.5: anterior end, frontal view, male, bar= 0.05 mm.

    Fig.6: transverse section by the level A-A', bar= 0.05mm

    Fig.7: transverse section by the level B-B', bar=0.05mm

    Figures 1-7 Hysterothylacium rhamdiae sp.n.

    Fig.8: vagina and uteri, bar= 0.05 mm.

    Fig.9: vulva (detail), bar= 0.1 mm.

    Fig.10: egg, bar=0.05mm

    Fig.11:spicules, bar=0.1mm

    Fig.12: posteria end of male, ventral view (schematic).

    Figures 8-12

ventricular appendix 1:2.13 to 1:3.9; intestinal caecum - muscular esophagus 1:2.69 to 1:4.68; and ventricular appendix - muscular esophagus 1:1 to 1:2. Spicules equal, short, sligthly curved with rounded end, 0.130 (0.100-0.200) mm in length. Spicules 0.4-1.34% of body length. Gubemaculum absent. Caudal papillae 33 to 38 pairs; 27-31 preanal, one paranal, 6 postanal and one lateral postanal pairs. MedioventraI papillated preanal organ inconspicuous. Tail 129 (98-152) long including thomy mucronated process.

Female (based on nine mature specimens). Body 16.19 (10.44-22.3) mm long by 0.27 (0.140.51) mm maximum width. Lips 75 (56- 100) long. Nerve ring 420 (370-490) from anterior end. Excretory pore 510 (420-610) from anterior end. Esophagus 2.28 (1.59-3.00) mm long. Ventriculus 96 (68-110) long. Intestinal caecum 543 (372-684) long. Ventricular appendix 2.02 (1.742.38). Length ratio of intestinal caecum - ventricular appendix 1:3.05 to 1:5.85; intestinal caecum - muscular esophagus 1:3.06 to 1:7.35 and ventricular appendix - muscular esophagus 1: 0.76 to 1:1.32. Ovojector muscular, about 100 long. Vulva opening 7.43 (4.61- 9.98) mm from anterior end. Eggs with smooth, thin shell, moru- lated, 30 (25-31) by 24 (22-27) in diameter. Tail 181 (110-288) long, including thorny mucronated process. Cervical papillae absent.

Host type: Rhamidia sapo (Valenciennes, 1840) (Pisces: Pimelodidae)catfish Site of infection: intestine

Locality: Argentina, Buenos Aires Province, Naposta stream (38 08'S, 61 47'W) and Sauce Grande fiver (38 43'S, 62015' W).

Type material: deposited in Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Buenos Aires, Argentina, ParasitologicaI Collection. Holotype male and allotype female No. 373. Paratypes (two males and females No. 001-004) in Laboratorio de Parasitologia, Departamento de Biologia y Bioquimica, Universidad Nacional del Sur, Bahia Blanca, Argentina.

Etymology: Rhamdiae is taken from the genetic name of the host.


The present species is most similar to H. murrayense Johnston and Mawson, 1917, from freshwater Australian percichthyids. In spite of the similar shape of male spicules in both species, the relative size ratio H. rhamdiae sp.n. versus H. murrayense is approximately 1:1.5. The spicules of the catfish worms are the smallest ones in the genus.

The caudal papillae arrangement differs in number and distribution. H. murrayense has 12 pairs of preanal and 5 pairs of postanal papillae against 27-31 preanal, one paranal and 6 postanal pairs in our specimens. Another differencial fea- tures may be the displacement of the excretory pore to the nerve ring level and the relative size of both intestinal caecum and ventricular appendix.

In the description of H. murrayense the dimensions of the eggs were not given.


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