Scientific Research and Essays Vol. 6(7), pp. 1583-1587, 4 April, 2011 Available online at http://www.academicjournals.org/SRE DOI: 10.5897/SRE10.1046 ISSN 1992-2248 ©2011 Academic Journals

Full Length Research Paper

Trichodina fahaka (Ciliophora: Peritrichia) in Tetradon

fahaka from Nile River, Egypt: Seasonality and histopathology

Abdel-Baki A. S.1,2*, Sakran T.2, Fayed H.3 and Zayed E.2

1Zoology Department, College of Science, King Saud University, P. O. Box 12455, Riyadh 11451, Saudi Arabia.

2Zoology Department, Faculty of Science, Beni-Suef University, Egypt.

3Zoology Department, Faculty of Science, Cairo University, Egypt.

Accepted 23 March, 2011

Specimens of Trichodina fahaka parasitizing Tetradon fahaka, collected from the Nile River, were described. Taxonomic and morphometric data for this trichodinid based on wet silver nitrate impregnated specimens were presented. The infection was severe and prevailed almost throughout the year. The overall prevalence was 45% with maximum rate during winter and minimum rate during summer. The most common signs of the gills tissue were hyperplasia of the gill filaments, degeneration and desquamation of most of the superficial cells with different degree of vacuolation. Key words: Trichodina, Nile River, histopathology, seasonality.

INTRODUCTION Trichodina is one of the most common ciliates present on the skin and gills of fish (Van As and Basson, 1992). Trichodina in low numbers (less than five organisms in a low magnification) are not harmful, but when fish are crowded or stressed, and water quality deteriorates, the parasite multiplies causing clinical signs or leading to mortality of infested hosts (Lom and Dykova, 1992; Shwani et al., 2010). More than 250 species of the trichodinid ciliates are recognized as parasite or symbiont on freshwater and marine fish or other organisms (Asmat et al., 2005). Of them, about 200 species of Trichodina have been described from fish by silver impregnation technique (Shwani et al., 2010). Studies on trichodinids in Egypt were limited mainly to their occurrence on fish (Abdel-Maguid, 1995; Abdel-Ghaffar et al., 1996; Al-Rasheid et al., 2000; Al-Bassel et al., 2007). The present study is the first on the histopathology and seasonality of Trichodina fahaka, which infested the gills of Tetradon fahaka in the Nile River with detail description of the parasite. *Corresponding author. E-mail: azema1@yahoo.com.

MATERIALS AND METHODS A total of 120 live or freshly caught fishes were collected from fishermen or from markets were immediately transported to the laboratory of zoology department, Beni-Suef Faculty of Science where they were examined. Smear preparations from the skin and gills were microscopically examined. Positive smears were air-dried, then impregnated with AgNo3 and irradiated with UV according to Klein's method (Klein's, 1958). All measurements and terminology of the adhesive disc components followed Lom (1958), Welborn (1967) and Arthur and Lom (1984). Measurements were based on 30 specimens. The denticle description was carried out according to Van As and Basson (1989, 1991, 1992). For histological studies, infected gills were fixed in 10% phosphate buffered formalin then embedded in paraffin wax. Sections were stained with H & E. RESULTS Description of the results of this study is shown as follows; Body: Medium sized trichodinid with 32.8 ± 1.5 (30-35) µm in diameter; Adhesive disc: Concave with 26.5 ± 1.6 (23.5-28.5) µm in diameter; Border membrane: 3.1 ± 0.4 (2.5-4) µm wide; Denticle ring: 17.2 ± 1.1 (16-19.5) µm in

1584 Sci. Res. Essays

a b

c d

Figures 1. Photomicrographs of silver impregnated adhesive discs of Trichodina fahaka from Tetradon

fahaka showing the details of adhesive disc structure. Scale bar = 10 µm.

diameter; Center of adhesive disc: have no granulation; Number of denticles: 25 (22-27); Number of redial pins per denticle: 6 (6-7); Denticle length: 6.7 ± 0.4 (6-7.1) µm Blade length: 3.6 ± 0.2 (3.2-4) µm; Central part width: 1.1 ± 0.2 (0.9-1.9) µm; Thorn length: 2.6 ± 0.3 (2.1-3.1) µm (Figure 1). Denticle description Body was of a medium-sized and of a disc- to bell-shaped. Blade was broad rectangular filling all the space between Y axes. Distal blade surface was slightly curved, parallel to border membrane. Tangent point to y axis was flat and formed a small line. Anterior blade surface slightly curved sloped gently to form an angle of about 45˚ with Y + 1 axis. Blade apex was present, rounded

and almost touched the Y+1 axis. Blade apophysis was present. Posterior blade surface formed a shallow curve with deepest point at the lower third. Blade connection was thin and posterior projection was not present. Central part was conical with rounded point, fitting loosely into preceding denticle. Sections of central part above and below X axis were similar. Central part extends to half the way of Y-1 axis. Ray connection was not clear and ray apophysis was present but weakly developed. Ray was wedge like, tapering to a pointed end and slightly curved posteriorly in between Y axis. Sections of denticle above and below X axis were nearly equal (Figure 4). Histopathology The infestation was severe and a large number of

2

Figure 2. Histological section of the gills of Tetradon fahaka showing the parasite (T) between the gill filaments (H & E). Scale bar = 100 µm.

3

Figure 3. Histological section of the infected gill filament showing proliferation of epithelial cells (white stars) around the parasite (T) forming nodule and showing vacuolar degeneration (V) and complete degeneration (black stars) (H & E).Scale bar = 40 µm.

Figure 4. Diagrammatic drawing of the denticles of Trichodina fahaka from Tetradon fahaka. Scale bar = 2.5 µm

Abdel-Baki et al. 1585 Trichodina was observed between the gill lamellae (Figure 2). It was observed that the parasite induced intensive proliferative changes on the epithelium of the gill filaments and the proliferation appeared extending a long the whole gill filaments. As a result, the secondary lamellae fused together and appeared as one unit (Figures 2 and 3). In many cases, the proliferated epithelial cells displayed degeneration and desquamation in most of the superficial cells in different degree either vacuolar and/or complete (Figure 3). Prevalence and seasonal variation The overall prevalence was 45% (54/120). This parasite had a high intensity of infestation and it prevailed almost throughout the year. The maximum rate was during winter (53.3 %) followed by spring (40%) and autumn (33.3%) while the minimum rate of infestation was during summer (20%) (Table 1 and Figure 5).

DISCUSSION The present Trichodina has a distinguish shape of denticles, but some components of the adhesive disc could be compared with the following species: Trichodina capiolosae (Dogiel, 1940), T. macomarcum (Raabe and Raabe, 1959), T. acuta (Lom, 1961), T. nigra (Lom, 1961), T. noturi (Welborn, 1967), T. modesta (Lom, 1970) and T. fahaka (Al-Rasheid et al., 2000).

T. capiolosae as described by Lom (1962) has close blade shape but rays are smaller and have uniform thickness with blunt tips. The dimensions of T. capiolosae are smaller than the present species.

T. macomarcum described from mollusks has very close blade shape but differs in its thin rays and the recent of adhesive disc which contains "peculiar light spots in the shape of rods or spindles". Also, dimensions of T. macomarcum are quite larger than the present trichodinid.

T. acuta as compiled in Lom and Dykova (1992) markedly differs in presence of white circle in the center of adhesive disc. Dimensions of T. acuta are almost twice the present species and denticles number has a wide range of 22 to 33 denticles.

Blades of T. nigra as cited in Lom and Dykova (1992) resemble the present material only in general shape. However, in comparing the dimensions, T. nigra has massive denticles, larger overall dimensions and smaller central area of adhesive disc.

T. noturi has similar blades and dissimilar rays. Comparing the central part of the denticle to that of T. fahaka, dimensions of T. noturi are larger.

Rays of T. modesta are delicate and run uniformly with very conspicuous ray apophysis rather than the wedge shape and pointed ends in T. fahaka.

The present species revealed a resemblance in all

1586 Sci. Res. Essays Table 1. The relationship between season and the prevalence of infestation of Trichodina fahaka from Tetradon fahaka collected from the River Nile.

Summer Autumn Spring Winter

Examined

no.

Infected no.

(%) Examined

no. Infected

no. (%)

Examined no.

Infected no.

(%) Examined

no.

Infected no.

(%)

10 3 30 10 2 20 10 5 50 10 6 60

10 2 20 10 3 30 10 4 40 10 5 50

10 1 10 10 5 50 10 3 30 10 5 50

Total 30 6 20 30 10 33.3 30 12 40 30 16 53.3

0

10

20

30

40

50

60

Summer Autumn Spring Winter

Seasons

Pre

vale

nce (

%)

Figure 5. The relationship between season and the prevalence of infestation of Trichodina

fahaka from Tetradon fahaka collected from the River Nile.

dimensions, shape, host and site of infection with T. fahaka therefore the present species identified as T. fahaka. Histopathology The severity of trichodiniasis on the gill filaments was noticed to be highly dependent on the relatively number of parasites infecting gill region. The gill lesions were similar to those previously reported by Ahmed (1976), Mcardle (1984) and Eisa et al. (1985). The lesions were characterized by hypertrophy, vacuolar degeneration and desquamation of the epithelial cells. These lesions were associated with congestion of lamellar blood vessels.

Additionally, the present study had revealed excessive epithelial cells proliferation resulting in adhesion of the secondary lamellae. Seasonal variation The present species showed a high prevalence during

winter and spring followed by autumn and summer. This result is in agreement with other studies where Ahmed et al. (1991) and Hossain et al. (2008) recorded species of Trichodina with the highest infection rate during winter and spring seasons. Similar prevalence rates varying from 17.6 to 52.6% of trichodinids were also observed by Bachamnn et al. (2007) in Pimelodus maculates. In con-trast, Azevedo et al. (2006) and Martins et al. (2010) did not observe trichodinid infestation in winter. The seasonal data revealed that the outbreak of diseases found in the winter season for particular species leads to a conclusion that a biological factor of the host as well as the water quality may play an important role in that period (Hossain et al., 2008). However, Heckmann et al. (1997) found that the highest infestations Trichodina this parasite occurred during the late spring and summer sampling periods. ACKNOWLEDGEMENT The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project number

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