Benedeniella posterocolpa ( Hargis, 1955 ) Yamaguti, 1963

Whittington, Ian D., 2010, Revision of Benedeniella Johnston, 1929 (Monogenea: Capsalidae), its assignment to Entobdellinae Bychowsky, 1957 and comments on subfamilial composition, Zootaxa 2519, pp. 1-30 : 15-21

Benedeniella posterocolpa ( Hargis, 1955) Yamaguti, 1963

( Figs. 3 C–D, 5B, 8–11)

Synonym: Benedenia posterocolpa Hargis, 1955 .

Type host: Rhinoptera bonasus (Mitchill) [syn: R. quadriloba (Le Sueur) ; see Lawler 1981] ( Myliobatidae ), the cownose ray ( Hargis 1955).

Type locality: Tampa Bay, Pinellas County, Florida, Gulf of Mexico, USA ( Hargis 1955).

Other published host and locality records: R. bonasus, Chesapeake Bay , Atlantic coast of USA ( McMahon 1963); R. bonasus , ‘northern Gulf of Mexico’, USA ( Overstreet 1978); R. bonasus, Punta Gorda, Gulf of Mexico, Florida, USA and on captive R. bonasus at Sea World, Florida, USA ( Thoney 1990); R. bonasus, Ocean Springs , Mississippi, Gulf of Mexico, USA ( Kearn & Whittington 1992; present study); R. bonasus, Champotón , Campeche, Gulf of Mexico, Mexico ( Pulido-Flores & Monks 2005); R. bonasus, Punta Gorda, Gulf of Mexico, Florida and Sea World, Florida, USA (present study); R. bonasus held captive at the New York Aquarium, New York City, USA (hosts initially collected in ‘Virginia’ [pers. comm., Dr A.D.M. Dove]) ( Perkins et al. 2009; present study).

Site of infection: Ventral skin ( Hargis 1955; McMahon 1963; Pulido-Flores & Monks 2005; present study); skin ( Thoney 1990).

Infection details: Not determined for any new material examined here.

Material deposited: SAMA AHC 29908 (1 specimen, 1 slide), USNPC No. 103019 (1 specimen, 1 slide) ex R. bonasus (site unknown), Ocean Springs, Mississippi, Gulf of Mexico, USA (original source, RMO); SAMA AHC 29909 (1 slide, 2 specimens), USNPC No. 103020 (1 slide, 7 specimens) ex R. bonasus (site unknown) Punta Gorda, Gulf of Mexico, Florida, USA (original source, DAT); BMNH 2010.4.16.12-13 (2 slides, 2 specimens), SAMA AHC 29910 (1 slide, 1 specimen), USNPC No. 103021 (1 slide, 1 specimen) ex ventral skin surface of R. bonasus, Punta Gorda, Gulf of Mexico, Florida, USA (original source, DAT); BMNH 2010.4.16.14-21 (8 specimens, 8 slides), SAMA AHC 29911 (11 specimens, 11 slides), USNPC No. 103022 – 103031 (10 specimens, 10 slides) ex ventral skin surface of R. bonasus held captive at the New York Aquarium, New York City, USA (hosts initially collected in ‘Virginia’ [pers. comm., Dr A.D.M. Dove]).

Redescription: Based on 38 flattened wholemounted adult and 6 flattened wholemounted juvenile specimens from various locations off the east coast of the USA. Measurements from 38 flattened wholemounted specimens (all sexually mature), except hooklets measured in flattened wholemounted, mostly juvenile, specimens. Body broadly oval ( Fig. 8 ). Total length (including haptor) and maximum breadth (at a level just posterior to testes): 3.77–17.12 (7.95, n = 38) x 2.44–11.15 (4.54, n = 38) mm. Haptor 1.14–4.19 (2.07, n = 38) x 1.07–3.88 (1.92, n = 38) mm; mostly wider anteriorly, tapering posteriorly ( Fig. 8 ). Accessory sclerites large, 258–863 (378, n = 76) long, near haptor centre; spear head-shaped with transverse ridges proximally ( Fig. 9 A); proximal end with notch ( Figs 3 C, 8, 9A); distal tips sharply-pointed, anteriorly directed ( Fig. 8 ). Anterior hamuli large, stout, strongly recurved distally, 404–1,270 (613, n = 74) long, with hooked distal tips ( Fig. 9 B). Hooked distal tips of one or both anterior hamuli broken off and missing in 21 of 38 mounted specimens leaving blunt tips. Posterior hamuli relatively small, 46–81 (67, n = 74) long, slender with hooked distal tips ( Fig. 9 C); location at haptor periphery indicated by marginal indentation ( Fig. 8 ). Hooklets 13–15 (13, n = 28) long ( Fig. 9 D); positions on posterior and posterolateral borders of haptor indicated by marginal indentations ( Fig. 8 ). Tendons conspicuous, passing posteriorly from extrinsic muscles associated with haptor on each side of body; passing through notch at proximal ends of accessory sclerites before dividing, with part attaching to proximal ends of anterior hamuli and part attaching to ventral haptor tissue ( Figs 3 C, 9E). Marginal valve running anteriorly from position of hooklets IV on each side of haptor extending to anteriormost extremity of haptor; wider anteriorly; absence at posteriormost part of haptor (e.g. Fig. 8 ) from narrowness and damage. Ventral haptor surface apapillate. Pair of elongate, conical structures dorsal to haptor near peduncle observed in stained wholemounts when viewed with dorsal surface uppermost (e.g. Fig. 5 B).

Anterior attachment organs ventral, almost circular, saucer-like discs, 563–2,307 (1,138, n = 64) x 559–2,264 (1,076, n = 64); ventral anterolateral region bearing conspicuous, complete grooves ( Figs 3 D, 8) of variable number, 13–26 (20, n = 34). Number of grooves in juvenile individuals similar to adults. In addition to complete grooves, 0–7 (3, n = 24) incomplete grooves present, of different lengths, occupying positions between complete grooves ( Fig. 3 D). Pair of tapering, horn-like papillae, one horn dorsal to each anterior attachment organ near junction with body ( Figs 3 D, 8); affinity for histological stains (e.g. carmine) in some stained specimens (e.g. Fig. 3 D). Eyes two pairs, pigment-shielded, dorsal, immediately anterior to pharynx. Pharynx conspicuous, 465–2,012 (914, n = 36) x 551–1,796 (852, n = 36); intrinsic gland cells numerous posteriorly. Intestinal caeca branching extensively in body proper, coextensive with and mostly obscured by vitellarium; unclear whether gut caeca confluent posteriorly. Excretory bladders conspicuous, often with lateral bend anteriorly, orientated obliquely towards body margins, each opening dorsally on distinct excretory papilla at level of cirrus base ( Figs 5 B, 8, 10), with some affinity for histological stains.

Testes ovoid, juxtaposed, 452–2,191 (992, n = 74) x 434–1,777 (812, n = 74); penetrated by numerous dorsoventral muscle bundles ( Fig. 8 ). Glands of Goto absent in juvenile and adult specimens. Vasa efferentia short uniting immediately posterior to germarium ( Fig. 10 ). Vas deferens skirting left of germarium, passing dorsal to transverse vitelline duct and proximal part of vagina before numerous intense convolutions occupying bulk of region immediately posterior and left of ootype chamber ( Figs 8 , 10 ); entering muscular wall of cirrus sac dorsally at level of anterior region of ootype chamber. Within cirrus sac, vas deferens narrowing, following posterior course dorsally to region of median turn of sac, then returning ventrally to enter base of cirrus ( Fig. 10 ). Widening of vas deferens or presence of sperm-filled reservoir inside cirrus sac not observed. Male accessory gland reservoir single, located ventrally in cirrus sac, not occupying posteriormost region ( Fig. 10 ); source of male accessory secretion not identified; no ducts observed penetrating cirrus sac proximally. Cirrus sac with muscular walls (not shown); distal two-thirds lying diagonally in body posterior to pharynx; proximal third curving medianly, immediately anterior to germarium and vitelline reservoir ( Figs 8 , 10 ). Relationship between total length and extent of curvature of cirrus sac with total parasite length observed for B. macrocolpa not apparent for B. posterocolpa . Distal duct from male accessory gland reservoir and distal region of vas deferens uniting near base of cirrus at level of excretory papillae ( Fig. 10 ). Cirrus long, sinuous, sometimes twisted, running anterolaterally inside terminal male genital duct, ventral to separate uterus, opening submarginally, dorsally, on left side of body at level of anterior region of pharynx via common genital pore ( Figs 8 , 10 ); common genital papilla not observed. Cirrus eversible outside animal to length of 0.4–2.9 (2.0, n = 30 measured along curves from wholemounted adult specimens) mm.

Germarium immediately pretesticular with conspicuous, branched, expanded fertilisation chamber ventrally at mid-line ( Figs 8 , 10 ), containing ripe oocytes. Oviduct short, wide, joining short common vitelline duct from vitelline reservoir to form ovo-vitelline duct immediately pregermarial, dorsal to transverse vitelline duct ( Fig. 11 ). Ovo-vitelline duct long, winding, travelling anteriorly to join ootype ( Figs 10 , 11 ). Numerous fine gland ducts entering ovo-vitelline duct at base of proximal region of ootype ( Figs 8 , 10 , 11 ); many small gland cells (not shown) located in curve of cirrus sac, right of ovo-vitelline duct. Ootype with convoluted proximal duct leading to tetrahedral-shaped chamber at level of excretory bladders, joining uterus ( Fig. 10 ). Uterus long, following similar but dorsal course parallel to terminal male genital duct, uniting short distance from common genital pore ( Fig. 10 ; see also Kearn & Whittington 1992). Common genital duct short, opening dorsomarginally at common genital pore at level of anterior part of pharynx ( Figs 8 , 10 ). No common genital papilla observed.

Vitelline reservoir ventral, curving anteromedianly near proximal end of cirrus sac. Vagina 1.2–5.7 (2.6, n = 38, measured along curves) mm long; originating proximally via narrow duct from left dorsal margin of vitelline reservoir. No seminal receptacles or proximal specialisations to vagina. Vagina following posterolateral path dorsal to transverse vitelline ducts to a level posterior to testes, opening posteriorly, dorsomarginally ( Figs 8 , 10 ). Vitellarium follicular, extending from between anterior attachment organs almost to posterior extremity of body proper, coextensive with intestinal caeca ( Fig. 8 ). Free eggs not observed; in some mounted specimens, eggs observed inside ootype, with tetrahedral shape and appendage; no egg measurements made due to distortion during specimen processing.

Remarks: The anatomy of B. posterocolpa presented here is consistent in most respects with the original description by Hargis (1955) and additional details provided by McMahon (1963). The principal differences reported here relate to the arrangement of the terminal female and male genital systems. Hargis (1955) described separate female, male and vaginal pores in B. posterocolpa whereas in the present study, the same arrangement as described for B. macrocolpa (see above) is confirmed and agrees with the opinion of Kearn & Whittington (1992): in B. posterocolpa , the uterus is very long, running dorsal to, and parallel with, the separate long terminal male genital duct, with the female and male systems uniting distally near the dorsal common genital pore. Hargis’s (1955) description of the uterine pore opening dorsal to the left bifurcation of the major gut branches (see his Plate V, figure 38) was clearly an error. Hargis (1955) also referred to ‘prostate glands’ (= male accessory glands) in 2 large fields close to the excretory bladders, but these glands were not observed in the present study and may be associated with differences in specimen preparation.

The route of conspicuous tendons in the haptor and, after dividing, their partial association with the proximal ends of the accessory sclerites and anterior hamuli and the presence of complete and some incomplete grooves on the anterior attachment organs, were also noted in this redescription of B. posterocolpa . Hargis (1955) illustrated the route of tendons in the haptor of B. posterocolpa (see his Plate V, figure 38), but did not describe them. However Hargis did refer to the anterior attachment organs as follows: ‘anterior half curiously striated’. In the present study, 13–26 complete and 0–7 incomplete grooves were observed.

The presence of horn-like dorsal structures identified on the anterior attachment organs by McMahon (1963) is confirmed here. Other dorsal features (papillae associated with the excretory bladders; elongate conical structures associated with the haptor near the peduncle) are reported here for the first time in B. posterocolpa (e.g. Figs 3 D, 5B, 8). These dorsal features are shared with B. macrocolpa (see above).

Figures

FIGURE 3. Differential interference contrast photomicrographs of haptor and anterior attachment organs from stained, mounted specimens of Benedeniella species. A. Accessory sclerite (as) and anterior (= proximal) part of anterior hamulus (ah) on one side of haptor of B. macrocolpa (Lühe, 1906) Yamaguti, 1963 showing route of tendon through proximal notch (pn) of accessory sclerite before attaching to proximal end of anterior hamulus with a branch (b) of the tendon apparently attaching to haptor tissue. AHC 29906 (specimen labeled no. 1). B. The left anterior attachment organ of B. macrocolpa showing complete ventral grooves (gr) and some incomplete grooves (ig) anterolaterally. Note the rounded papillae (rp) at the anterior extremity of the parasite. AHC 29906 (specimen labeled no. 1). C. Accessory sclerite (as) and anterior (= proximal) part of anterior hamulus (ah) on one side of haptor of B. posterocolpa (Hargis, 1955) Yamaguti, 1963 showing route of tendon through proximal notch of accessory sclerite before attaching to proximal end of anterior hamulus with a branch (b) of the tendon apparently attaching to haptor tissue. AHC 29911 (specimen labeled no. 13). D. The left anterior attachment organ of B. posterocolpa showing ventral grooves (gr) and some incomplete grooves (ig) anterolaterally. Note the dorsal horn (dh) where the body and anterior attachment organ join. AHC 29911 (specimen labeled no. 13). Scale bars: 200 µm.

FIGURE 5. Diagrammatic outlines of adult Benedeniella macrocolpa (Lühe, 1906) Yamaguti, 1963 (A) and B. posterocolpa (Hargis, 1955) Yamaguti, 1963 (B) in dorsal view showing relative positions of paired anterior tapering horns (dh), common genital papilla (cgp; absent in B. posterocolpa), paired excretory papillae (ep) and paired conical structures (co). Drawn from several wholemounted specimens viewed dorsally. Scale bar: 4 mm.

FIGURE 8. Benedeniella posterocolpa (Hargis, 1955) Yamaguti, 1963. Whole adult parasite, composite drawing, in ventral view based on AHC 29911 (specimen labeled no. 4) with some additions by hand. For clarity, intestinal diverticula (entirely coextensive with the vitellarium) other than immediately posterior to pharynx and full extent of convolutions of vas deferens are simplified (but are shown in full in Figure 10). Abbreviations as for Figures 1 and 6. Scale bar: 1 mm.

FIGURE 9. Benedeniella posterocolpa (Hargis, 1955) Yamaguti, 1963. Haptoral sclerites of adult parasite. A. Accessory sclerite. Note proximal transverse ridges (tv). B. Anterior hamulus. C. Posterior hamulus. D. Hooklet. E. Proximal ends of anterior hamulus (ah) and accessory sclerite (as) showing main tendon path (stippled) plus branch (solid) to haptor tissue (see also Figure 3 C). Scale bars: A – B, 100 µm; C, 50 µm; D, 10 µm; E, 200 µm.

FIGURE 10. Benedeniella posterocolpa (Hargis, 1955) Yamaguti, 1963. Anterolateral region of body (left side) of adult parasite. Composite drawing in ventral view based on AHC 29911 (specimen labeled no. 3) with some additions by hand. Note that positions of some ducts (e. g. transverse vitelline duct, vas deferens and uterus) are displaced slightly for clarity. Also, common genital pore, excretory papilla and vaginal pore open dorsally and are shown here as seen by transparency. Details of junction of oviduct, common vitelline duct and ovo-vitelline duct (all these structures are dorsal to the transverse vitelline duct) are shown in Figure 11. Abbreviation: ve, vas efferens. Other abbreviations as for Figures 1 and 6. Scale bar: 1 mm.

FIGURE 11. Benedeniella posterocolpa (Hargis, 1955) Yamaguti, 1963. Region of germarium, transverse vitelline duct, vitelline reservoir and ootype in ventral view based on AHC 29911 (specimen labeled no. 3) with some additions by hand. Note that full extent of the transverse vitelline duct (dotted lines) is not shown and cirrus sac is omitted (see Figures 8 and 10 for details) to depict the junction of oviduct (ov) and common vitelline duct (cv) to form the ovovitelline duct (ovo) which is dorsal to the transverse vitelline duct. Abbreviations as for Figures 1 and 6. Scale bar: 1 mm.