Siphodera ghanensis sp. n. (Cryptogonimidae), a Digenetic Trematode from an Estuarine Fish from Ghana

Abstract

Siphodera ghanensis sp. n., a cryptogonimid trematode from the small intestine of an estuarine fish, Chrysichthys nigrodigitatus (Lacepede) (Bagridae) from Ghana is described. It is differentiated from the type and only species in the genus, S. vinaledwardsii (Linton, 1901) Linton, 1910, in possessing an acetabulum larger than the oral sucker, an unlobed or trilobed ovary, and a greater extent of vitellaria; it differs further in lacking uterine coils anterior to the testes, and a pitlike cavity in which the acetabulum lies. This report is the fourth in a series by the authors on the digenetic trematodes of fishes from Ghana. The worms were killed in hot water, fixed overnight in FAA, and stored in 70% alcohol plus 2% glycerine; they were stained in Mayer's carmalum, and mounted in permount. All measurements are in microns. Siphodera ghanensis sp. n. (Figs. 1, 2) Host: Chrysichthys nigrodigitatus (Lacepede) (Bagridae). Site: Small intestine. Localities: Kakum river estuary at Iture; creek near Ekotsi; Ghana. Dates: 2, 3, 18 November 1965. Specimens: USNM Helm. Coll. No. 71189 (holotype); No. 71190 (paratypes). Diagnosis (based on four mature specimens): Body elongate oval, extremities round, 2,480 to 3,085 long, 930 to 1,035 wide at testicular level; preoral space 22 to 46 long; forebody 560 to 690 long, hindbody 1,560 to 2,100 long. Tegument spined to short distance posterior to testes. Glands scattered primarily in lateral fields of forebody, confluent dorsal to prepharynx. Eyespot pigment granules scattered in forebody. Oral sucker subterminal ventral, round to slightly elongate transversely, 230 to 250 long, 230 to 263 wide. Postoral circular muscle ring present. Acetabulum muscular, not in pitlike cavity, slightly elongate transversely, 280 to 300 long, 295 to 327 wide, center at level of anterior 1/4 to 3/10 of body length. Length ratio of suckers 1:1.17 to 1.25. Prepharynx emerging from posterodorsal part of oral sucker, 92 to 123 long in well extended specimens; pharynx pyriform, with circular muscle band around anterior part, 190 to 216 long, 144 to 177 wide; esophagus shorter than prepharynx, 65 to 85 long in well-extended specimens; small, compact mass of Received for publication 5 April 1968. * This work was supported in part by a State University of New York Faculty Research Fellowship (FRF68-40-003) awarded to the senior author. glands adjacent to prepharynx, pharynx, and esophagus; cecal bifurcation 56 to 65 anterior to acetabulum; ceca cell-lined, thin-walled, extending into posttesticular space but not reaching posterior extremity. Testes nine in number, smooth, lateral to c ca, five sinistral and four dextral in two worms, reverse distribution in other two, round to longitudinally or transversely elongate, 160 to 253 long, 133 to 230 wide; row with four testes extending slightly more anteriorly than one with five, lying 190 to 295 posterior to acetabulum; posttesticular space 445 to 760 long. Cirrus sac absent. Seminal vesicle with some undulations, bipartite, 412 to 585 long, 157 to 172 wide, extending 136 to 300 posterior to acetabulum, usually overlapping ovary dorsally; chambers thin-walled, anterior chamber lined with large cells. Prostatic vesicle cell-lined, much smaller than acetabulum, surrounded by dense mass of prostate cells, lying anterodorsal to acetabulum. Ejaculatory duct very short. Genital atrium short. Genital pore median, anteroventral to acetabulum. Ovary median to submedian (right or left), longitudinally or transversely elongate, unlobed and smooth in two specimens, with three smooth lobes in other two, 270 to 335 long, 270 to 340 wide, lying 90 to 195 posterior to acetabulum. Oviduct emerging from dorsal surface of ovary. Mehlis' gland well developed, anterodorsal to ovary. Seminal receptacle large, almost round to longitudinally elongate, 170 to 198 long, 145 to 165 wide, anterodorsal to ovary. Laurer's canal winding to surface dorsal to ovary. Uterus overlapping ceca and testes ventrally; with coiled descending limb on left in two specimens, on right in other two; with coiled ascending limb to ovarian level on opposite side, sinuous anterior to ovary in median to submedian position, lacking coils anterior to testes. Metraterm muscular, thickwalled, very short, beginning at anterior margin of acetabulum. Vitellaria follicular, extending from level of acetabulum to midlength of testicular fields or to posteriormost testes, filling dorsoventral depth of body between acetabulum and testes, lying dorsal only to testes, confluent dorsally from posterior part of ovary almost to posteriormost extent of follicles; vitelline duct from each side uniting dorsal to ovary to form common duct. Eggs nu-