Thaparotrema botswanensis, Rensburg & van As & King, 2013

Rensburg, Candice Jansen van, van As, Jo G. & King, Pieter H., 2013, New records of digenean parasites of Clarias gariepinus (Pisces: Clariidae) from the Okavango Delta, Botswana, with description of Thaparotrema botswanensis sp. n. (Plathelminthes: Trematoda), African Invertebrates 54 (2), pp. 431-431 : 442-444

Thaparotrema botswanensis sp. n.

Figs 1F , 4A–H ; Table 1

Etymology: This species is named after Botswana, where the material was collected.

Description:

Body elongate, narrow with round extremities, maximum width at level of acetabulum ( Figs 1F , 4A ). Tegument spined except for extreme part of post-testicular end of body. Suckers muscular. Oral sucker terminal round to oval in shape. Acetabulum slightly smaller than oral sucker, situated in first quarter of anterior part of body ( Fig. 1F ). Prepharynx absent. Pharynx round, some instances overlaps oral sucker dorsally ( Fig. 4B ). Oesophagus long; caecal bifurcation pre-acetabular closer to oral sucker; caeca narrow, extend to almost end of posterior extremity ( Fig. 1F ). Two testes, slightly oval, tandem to diagonal within inter-caecal space near to posterior extremity of body, separated from each other by excretory bladder ( Fig. 4C ). Posterior testis slightly bigger than anterior. Cirrus sac absent. Seminal vesicle tubular commencing post-acetabular ( Fig. 4D ). Genital pore median, just pre-acetabular ( Fig. 4E ). Ovary smooth, intercaecal ( Figs 1F , 4F ). Mehlis’ gland present. Seminal receptacle situated obliquely anterior to ovary ( Fig. 4F ). Laurer’s canal not observed.Vitelline follicles extending post-acetabular to level of ovary, slightly overlapping caeca ( Figs 1F , 4G ). Uterus extensively coiled, intercaecal, with ascending limb only, sinistral to seminal vesicle ( Fig. 4G ). Eggs yellow-brown, operculate. Excretory bladder saccular, passing between testes ending at posterior level of ovary; pore subterminal ( Figs 1F , 4H ).

Comparison: The new species is similar to Th. piscicola with the body being elongate and spined, having suckers that are almost of equal size and position, the absence of the cirrus sac, as well as the vitellarium beginning post-acetabular and extending to the level of the ovary, but differs in having a prominent seminal receptacle, greater space between the testes, and the testes being also not situated as close to the posterior extremity. The vitelline follicles are also much larger than those in Th. piscicola .

The new species is also similar to Th. pedicellatum (Verma, 1927) from the intestine of Rita rita from India in having suckers of almost equal size and a more prominent seminal receptacle. It differs, however, in that the body is not as wide nearer to the posterior extremity, the distance between the oral sucker and acetabulum is shorter and the vitelline follicles begin a distance post-acetabular and extend to the level of the ovary. Thaparotrema botswanensis sp. n. also differs from Th. vitallani in that the vitelline follicles do not begin anterior to the level of the acetabulum, the vitelline follicles are also more compact and the testes are situated close together. Based on the above remarks and the differences between Th. botswanensis sp. n. and the known species, it can be regarded as a new species. This is the first record of Thaparotrema from Clarias gariepinus , as well as the first report of the genus from the Okavango Delta.

Holotype: BOTSWANA: Okavango Delta , Shakawe mainstream (18°26'05.0''S 21°54'23.0''E), 01/ 10 / 25- 9c ( NMBP 355 ).

Paratype: BOTSWANA: Okavango Delta , Kalatog channel (18°25'08.2''S 21°54'05.0''E), 01/ 10 / 25-9b ( NMBP 356 ) .

Other material examined: same as paratype, 01/ 10/ 25-9e ( BMNH 2013.9.27.1) .

Site of infection: Gall bladder.

Prevalence of infection: 4.7%.

CONCLUDING REMARKS

Among the digeneans collected during the present investigation only Clinostomoides brieni , Neodiplostomum sp. (both metacercariae), Glossidium pedatum , Phyllodistomum vanderwaali , Phyllodistomum bavuri and Thaparotrema botswanensis sp. n. were found infecting C. gariepinus . A certain degree of site specificity was also observed, with T. botswanensis sp. n. being found only in the gall bladder of C. gariepinus , while both Phyllodistomum species were found only in the urinary bladder and thus seem to occupy a certain niche within their host. At any one time a single C. gariepinus may host four species of digeneans, each occupying its own niche within the host. Not only are these fish infected with adult and larval digeneans, but they also host other ecto- and endoparasites, sometimes having a heavy parasite burden ( Jansen van Rensburg et al. 2001).

Clarias gariepinus plays a notably important role in the life cycles of digenean parasites in the Okavango Delta, as it acts as a definitive host for adults of four species, and as a second intermediate host to two metacercarial trematodes.

Figures

Fig.1. Light microscope projection drawings of digeneans from Clarias gariepinus in the Okavango Delta: (A) Clinostomoides brieni Dollfus, 1950; (B) Neodiplostomum Railliet, 1919 type 1 metacercaria; (C) Phyllodistomum bavuri Boomker, 1984; (D) Phyllodistomum vanderwaali Prudhoe & Hussey, 1977; (E) Glossidium pedatum Looss, 1899; (F) Thaparotrema botswanensis sp. n. Scale bars: A, C – 1 mm; D – 0.3 mm; B, E – 0.1 mm; F – 0.2 mm.

Fig. 4. Light micrographs of Thaparotrema botswanensis sp. n. collected from Clarias gariepinus in the Okavango Delta:(A)whole mount;(B) pharynx; (C) anterior and posterior testes; (D) seminal vesicle; (E) genital opening; (F) ovary and seminal receptacle; (G) vitellaria and uterus filled with eggs; (H) excretory bladder. Scale bars:A – 1 mm; B, C, E, F, H – 0.1 mm; D, G – 0.05 mm.