Pseudocrepidobothrium ludovici, Ruedi & Chambrier & P.O. & Ch-, 2012

Ruedi, Virginie & De Chambrier, Alain, 2012, Pseudocrepidobothrium ludovici sp. n. (Eucestoda: Proteocephalidea), a parasite of Phractocephalus hemioliopterus (Pisces: Pimelodidae) from Brazilian Amazon, Revue suisse de Zoologie 119 (1), pp. 137-147 : 138-141

Pseudocrepidobothrium ludovici sp. n.

Figs 1-16

TYPE MATERIAL: Holotype MHNG INVE 22003 , 1 whole mounted slide, field number Br 334. – 29 paratypes MHNG INVE 22000 , 22108 , 30531-32 , 79281-85 , 79302 , 79306-20 , 79327 , 79335 , 79340-41 . – 2 paratypes IPCAS C-610 , field number Br 785, Br 649 3/5z; 1 paratype NHMUK 2012.1.23. 1, field number Br 785.

OTHER MATERIAL: From Itacoatiara, Amazon River , Amazonas Province, Brazil; collected 15-17.09.1992; MHNG INVE 22001 , 22003 , 22016 , 79281-85 , 79305 . – Same locality as in previous series, collected 01-18.10.1995: MHNG INVE 22000 , 22047 , 22103 , 22108 , 25600 , 25610 , 27437 , 28298 , 30531-32 , 31199 , 35186 , 79302-04 , 79306-20 , 79327 , 79333 , 79335 , 79337-42 , 79345 , 79349-50 , 79354 , 79356 , 79360 , 79363-64 , 79388 ; NHMUK 2012.1.12. 1; IPCAS No C-610 ( Br 695z paratypes, cross section; Br 649 3/5 & Br 804, Br 804a), MACN No. 520/1-3 (Br 649 3/5y).

TYPE LOCALITY: Itacoatiara, Amazon River , Amazonas Province, Brazil, 17.09.1992. 03.1536°S 58.4382°W, Field number Br 334, A. de Chambrier & A. A. Rego leg.

DESCRIPTION (BASED ON 32 ENTIRE SPECIMENS): Proteocephalidae , Proteocephalinae. Small-sized worm, 7-23 mm long, up to 1150 wide, flattened dorsoventrally. Strobila acraspedote, anapolytic, bearing 20-36 proglottides in total, 9- 22 immature, 1-6 mature, 3-19 gravid. Proliferation zone posterior to scolex short, up to 620 long and 283-765 wide. Immature and mature proglottides wider than long; pregravid proglottides wider than long, then longer than wide and gravid proglottides longer than wide. Some abnormal proglottides (e.g. with hypertrophy of vitelline follicles) were not considered in this study.

Scolex massive, round, 515-1020 in diameter (x = 775, n = 23) ( Figs 1-4 , 7 ), clearly separated from strobila. Apical tegumental folds present ( Figs 2, 4 ). Four heartshaped suckers, with notched posterior margin, disposed dorsally and ventrally by pairs, 230-385 (x = 290; n = 12) in diameter ( Fig. 5 ). Apical organ absent. Scolex usually rectangle-shaped in apical view. Surface of scolex uniformly covered with capilliform filitriches ( Fig. 6 ).

Internal longitudinal musculature weakly developed ( Figs 13, 14 ) forming small anastomosed bundles of muscular fibers. Osmoregulatory canals usually situated between vitellaria and testes. Ventral canals about 35 in diameter with a secondary canal situated posteriorly near lateral margin and which seems to end at ventral surface ( Fig. 8 ). Dorsal osmoregulatory canals about 15 in diameter, sometimes anastomosed or double.

Testes medullary, spherical to oval, 50-95 by 25-85 in diameter, numbering 37-79 (x = 55, n = 37, CV = 19%), in one (rarely two) layer, in two lateral fields ( Figs 8-10 , 13 ), usually connected with some testes anteriorly; testes degenerated in last gravid proglottides. Vas deferens coiled, very thin-walled, reaching to midline of proglottis, rarely overlapping it ( Fig. 8 ). Cirrus-sac elongate to piriform, thin-walled, 155-260 long and 65-125 wide, representing 25-35% (x = 30%, n = 30, CV = 9%) of proglottis width. Cirrus occupying 35-57% (n = 26) of cirrus-sac length ( Fig. 11 ).

Genital ducts passing between osmoregulatory canals. Genital atrium present. Genital pores irregularly alternating, situated at 15-29% (x = 22%, n = 28, CV = 14%) of proglottis length.

Vagina posterior (in 53% of proglottides) or anterior (in 47% of proglottides, n = 112) to cirrus-sac, in proximal part lined with chromophil cells. Muscular terminal sphincter present ( Fig. 11 ). Mehlis’ glands 35-100 in diameter, representing 6-14% of proglottis width.

Ovary medullary, bilobed, butterfly-shaped in gravid proglottides, 310-565 wide, occupying 53-67% (x = 59%, n = 30, CV = 6%) of proglottis width ( Figs 8-10 , 14 ).

Vitelline follicles medullary and paramuscular (according to de Chambrier, 1990), oval to elongate, small, in two lateral fields, absent in preporal area, occupying porally 63-78% (x = 69%; n = 16) and aporally 75-95% (x = 84%; n = 17) ( Figs 8-10 , 13, 14 ).

Anlage of uterus medullary, already present in immature proglottides. Uterus with 14-20 very short lateral diverticula on each side ( Fig. 12 ). Formation of uterus of type 1 according to de Chambrier et al. (2004a): uterine stem with tubular concentration of numerous intensely staining cells and with lumen in last immature and first mature proglottides ( Figs 8, 9 , 13, 14 ). In mature proglottides, thin-walled lateral diverticula appear. In pregravid proglottides, eggs filling uterine stem and diverticula. In gravid proglottides, uterus sometimes opening precociously ventrally by one longitudinal aperture and sometimes conserving eggs up to last proglottis. In last proglottides, uterus occupies up to 71% of proglottis width ( Fig. 11 )

Eggs spherical, with thin, hyaline outer envelope, up to 60 in diameter; inner envelope consisting in two-layered embryophore, with external thick layer, 17 in diameter, and nucleate irregular envelope, 12-14 in diameter; oncospheres 8-9 in diameter, with 3 pairs of embryonic hooks, 5-6 long ( Figs 15, 16 ).

TYPE-HOST: Phractocephalus hemioliopterus (Bloch & Schneider, 1801) , ( Siluriformes : Pimelodidae ).

SITE OF INFECTION: From anterior to middle of the intestine.

PREVALENCE: 12/29 (41%) in Brazil, 0/11 (0%) in Peru.

ETYMOLOGY: The new species is named in honour of Ludovic Ruedi, brother of the first author.

DIFFERENTIAL DIAGNOSIS: The present species is placed in Pseudocrepidobothrium Rego and Ivanov, 2001 (Proteocephalinae) because of the medullary position of the genital organs, the medullary and paramuscular position of vitellaria and the heart-shaped structure of suckers ( Freze, 1965; Schmidt, 1986; Rego and Ivanov, 2001).

The present species differs from Pseudocrepidobothrium eirasi , the only other species known in that genus, by the following characters: absence of appendix at the ventral posterior edge of each side of the proglottis, absence of a polar structure on the egg, number of testes (37-79, x = 55 in P. ludovici versus 21-51, x = 32), the disposition of vitelline follicles (more numerous posteriorly in P. eirasi ) the number of segments (20-36 in P. ludovici versus 7-12 for P. eirasi ) and the shape of the scolex (which is usually rectangular in apical view in P. ludovici and square in apical view in P. eirasi , see Fig. 2 in the present paper, and Fig. 9 in Rego and Ivanov, 2001).

In a recent paper ( de Chambrier et al., 2004a, Fig. 1 ), the genus Pseudocrepidobothrium , including by P. eirasi and Pseudocrepidobothrium sp. (= P. ludovici sp. n.) represented a natural taxon, because the 28S sequences data strongly supported a close relationship between both species. In a forthcoming paper dealing with molecular reconstructions, both species also represent a monophyletic group (unpublished data).

Figures

FIGS 1-6. Pseudocrepidobothrium ludovici sp. n. from Phractocephalus hemioliopterus. Scanning electron photomicrographs. MHNG INVE 79302, paratype. (1) Scolex, dorsoventral view, with a anterior part of strobila. (2) Scolex, apical view. (3) Scolex, lateral view. (4) Scolex, dorsoventral view. (5) Detail of a sucker. (6) Capilliform filitriches near the center of the apical region. Scale-bars: 1 = 300 µm; 2 = 130 µm; 3 = 95 µm; 4 = 110 µm; 5 = 60 µm; 6 = 3 µm.

FIGS 7-10. Pseudocrepidobothrium ludovici sp. n. from Phractocephalus hemioliopterus. (7) MHNG INVE 79281, paratype. Scolex, dorsoventral view. (8) MHNG INVE 22003, holotype. Mature proglottis, ventral view. (9) Mature proglottis, dorsal view; note secondary canals of the ventral osmoregulatory canals. (10) Gravid proglottis, ventral view. Abbreviations: do = dorsal osmoregulatory canal; mg = Mehlis gland; ov = ovary; sc = secondary canal; te = testes; ut = uterus; va = vas deferens; vd = vitelloduct; vi = vitellaria; vo = ventral osmoregulatory canal. Scale-bars: 7 = 250 µm; 8-10 = 500 µm.

FIGS 11-16. Pseudocrepidobothrium ludovici sp. n. from Phractocephalus hemioliopterus. (11) MHNG INVE 79283, paratype. Cirrus-sac and vagina, dorsal view; note the presence of a vaginal sphincter. (12) Schematic view of the uterus in gravid proglottis. (13) MHNG INVE 79341, paratype. Pregravid proglottis, transverse section at testes level. (14) MHNG INVE 79341, paratype. Pregravid proglottis, transverse section at ovarian level. (15, 16) Eggs in distilled water, captured with Leica DMLB, showing the bi-layered embryophore. (15) IPCAS C-610, (Field number Br 649 3/5w). (16) MHNG INVE 22103, (field number Br 445). Abbreviations: ci = cirrus; cs = cirrus-sac; do = dorsal osmoregulatory canal; em = embryophore; lm = internal longitudinal musculature; ln = longitudinal lateral nerves; oe = outer envelope; om = oncospheric membrane; on = oncosphere; ov = ovary; te = testes; ut = uterus; va = vas deferens; vc = vaginal canal; vi = vitellaria; vo = ventral osmoregulatory canal; vs = vaginal sphincter. Scale-bars: 12 = 500 µm; 11, 13, 14 = 250 µm; 15, 16 = 20 µm.