Dendromonocotyle colorni Chisholm, Whittington & Kearn, 2001

Vaughan, David, Chisholm, Leslie & Christison, Kevin, 2008, Overview of South African Dendromonocotyle (Monogenea: Monocotylidae), with descriptions of 2 new species from stingrays (Dasyatidae) kept in public aquaria, Zootaxa 1826, pp. 26-44 : 40-41

Dendromonocotyle colorni Chisholm, Whittington & Kearn, 2001 ( Figs. 2 B, 4F, 8–10)

Type-host: Himantura uarnak (Forsskål) .

Additional host: H. gerrardi (Gray) .

Type locality: Eilat Underwater Observatory, Israel.

Additional locality: uShaka Sea World, Durban, South Africa.

Site on host: Dorsal skin surface.

Materials examined: SAMCTA 29450 (7 vouchers), AHC 29171-29177 (6 vouchers), BMNH 2007.2.21.5-10 (6 vouchers).

Redescription. Based on 20 flattened adult specimens. Total body length 3255 ± 532.8 (2080–4300, n = 20). Body-proper 2510 ± 485.1 (1500–3520, n = 20) long, and 2136 ± 486.3 (1150–3200, n = 20) maximum width ( Fig. 8 A). Haptor 2195 ± 376.8 (1330–2800, n = 20) in diameter ( Fig. 7 B), with 8 peripheral, and 1 central loculus. Hamuli present ( Figs 8 B, 8I, 9A), 512 ± 4.6 (46–59, n = 13) long. Fourteen marginal hooklets ( Fig. 8 J) 11 ± 1.4 (10–15, n = 13) long, distributed in marginal valve between every 4 papillae. Haptoral rim with 56 marginal haptoral papillae each armed with 3 or 4 sclerites ( Figs 8 G, 8H, 9B, 9C). Terminal papillary sclerite as illustrated ( Figs 8 H, 9B, 9D). Outer-ring septal sclerites distinct ( Fig. 8 C) and radial septal sclerites ( Fig. 8 D) larger than papillary sclerites ( Fig. 8 G), but smaller than terminal papillary sclerite ( Fig. 8 H). Tripartite sclerites observed at junction of radial septa and inner-ring septum and at junction of radial septa and outer ring septum ( Figs 8 E, 8F, 9C). Anterior and anterolateral loculus pairs each with 6 associated marginal haptoral papillae. Posterolateral and posterior loculus pairs each with 8 associated marginal haptoral papillae ( Figs 2 B, 8B). Mouth ventral, subterminal, subterminal groove anterior to mouth ( Fig. 8 A). Six distinct anterior gland duct openings open laterally on anterior end of worm as illustrated ( Figs 8 A, 9E). One pair of eyespots, situated dorsally to pharynx. Pharynx 286 ± 45.2 (189–368, n = 20) long, and 179 ± 26.7 (129–229, n = 20) wide. Dendritic intestinal caecum anterordorsal to pharynx, extending to both posterior marginal lobes of body proper ( Fig. 8 A). Intestinal caecum highly pigmented. Testis singular with vas deferens originating from the left side of testis, dorsal to the ovary. Testis 231 ± 36 (170–280, n = 8) long, and 454 ± 71.6 (287–620, n = 20) wide. Vas deferens extends anterodorsally to vagina, with 2 small loops, 1 on each side of vagina. Vas deferens crosses ventrally over posterior portion of ejaculatory bulb and swells to form seminal vesicle, which narrows and enters ejaculatory bulb distally. Ejaculatory bulb 179 ± 30 (136–231, n = 20) long, and 194 ± 30.6 (143–235, n = 20) wide. Male copulatory organ sclerotised ( Fig. 10 A), 804 ± 31.9 (751–852, n = 18) long, 9 ± 0.5 (9–10, n = 20) wide. Accessory flange present at distal end of male copulatory organ ( Figs 4 F, 10B). Muscular sheath 57 ± 8.8 (50–75, n = 18) wide, covers entire length of male copulatory organ ( Fig. 10 A). Ovary bi-lobed 360 ± 53.4 (240–430, n = 14) long, and 715 ± 139.6 (420–980, n = 16) wide, immediately anterior to testis with lobes extending to either side of testis ( Figs 8 A, 10C). Single ovarian branch loops right intestinal caecum dorsoventrally. Ootype 314 ± 54.4 (212–387, n = 20) long, ventral to male copulatory organ. Tetrahedral egg ( Fig. 10 C) side length 74 ± 10.3 (55–90, n = 7); filament 158 ± 32.3 (110–210, n = 9) long extending from 1 pole of egg. Mehlis glands not observed. Vaginal pore on left side of body at level of anterior portion of ejaculatory bulb ( Fig. 8 A). Vagina narrows to form distinctly coiled translucent duct, which narrows to enter ovoid seminal receptacle anterior to ovary ( Fig. 10 C). Seminal receptacle 141 ± 24.4 (105– 175, n = 13) long, and 106 ± 15.2 (87–140, n = 13) wide. No spermatophores observed. Vitellaria obscured by pigmented intestinal caecum.

Remarks. All stingrays in the exhibit were collected from immediate local wild population in Durban Bay in 2003. Dendromonocotyle colorni was only observed on the hosts when an outbreak occurred months later in the aquarium exhibit. No local wild populations of H. uarnak or H. gerrardi have been examined for D. colorni . Furthermore, we could not determine whether the infection of D. colorni on H. uarnak and H. gerrardi represents a natural association between closely related hosts, or an artificially created host-parasite interaction between similar host species under lower-than-normal spatial arrangements and increased stress levels in captivity.

The D. colorni collected in South Africa differ slightly from those collected in Israel but we do not deem these minor differences to be enough to warrant erection of a separate species. The marginal haptoral papillae of the South African material are sometimes armed with 4 sclerites (including the terminal papillary sclerite) whereas the specimens from Israel only have 3. Tripartite sclerites were found at the junction of the radial septum and the outer-ring septum as well as inner-ring septum ( Figs 8 E, 8F, 9C) in the South African specimens whereas tripartite sclerites were only seen at the junction of the radial septa and inner ring septum from those specimens from Israel ( Chisholm et al. 2001a).

We only found 1 pair of eyespots the South African specimens, not 2, as indicated by Chisholm et al. (2001a), however, it is likely that the second pair was obscured by the dark pigment in the intestinal caeca. The vas deferens in the South African specimens crosses the posterior end the ejaculatory bulb not the anterior end as illustrated by Chisholm et al. (2001a) for specimens from Israel.

Figures

FIGURE 2. Diagrammatic representation of 2 groups of Dendromonocotyle species with 56 marginal papillae separated by their papillae-to-loculus associations. A. Group 1 (6 - 7 - 7 - 8) represents Dendromonocotyle akajeii, D. bradsmithi, D. centrourae, D. citrosa n. sp., D. cortesi, D. kuhlii, and D. ukuthena n. sp. B. Group 2 (6 - 6 - 8 - 8) represents D. colorni. Note: hamuli are not present for D. bradsmithi, D. centrourae, D. citrosa n. sp., D. cortesi or D. kuhlii. Orientational marginal hooklet (omh) pair remains constant for all species with or without hamuli (ham) in both groups 1 and 2 and can be used to assist correct haptor orientation; other marginal hooklets (mh) distributed as illustrated.

FIGURE 4. Male copulatory organ. A. Dendromonocotyle citrosa n. sp. ex Two Oceans Aquarium, distal portion of male copulatory organ. B. Dendromonocotyle citrosa ex uShaka Sea World Aquarium: sf – spiral filament. C. Dendromonocotyle ukuthena n. sp. male copulatory organ (mco): eb – ejaculatory bulb, mdist – missing distal portion of male copulatory organ, ms – muscular sheath. D. Distal portion of male copulatory organ of D. ukuthena n. sp. showing criss-crossed sperm duct (sd). E. Missing distal portion of male copulatory organ of D. ukuthena n. sp. with area of possible point of breakage (bp). F. Distal portion of male copulatory organ of D. colorni showing the accessory flange (af) and spiral filament (sf). G. Possible area of D. ukuthena n. sp distal portion of male copulatory organ re-growth (r): bp – breakage point, sd – criss-crossed sperm duct. Scale bar =. Scale bars: A, B, D, F = 100 μm; C, E, G = 50 μm.

FIGURE 7. Dendromonocotyle ukuthena n. sp. egg and oncomiracidium. A. Single egg with club-shaped filament. B. Egg with forming oncomiracidium; note eyespot (es) development. C. Egg with fully embryonated oncomiracidium. D. Hatching oncomiracidium. E. Oncomiracidium: F. Refringent droplets in ciliated epithelial cells. Abbreviations: ab, anterior band of ciliated cells; cl, crystalline lens; hb, haptoral band of ciliated cells; mp, median patch of ciliated cells; p, pharynx; pb, pigmented band. Scale bars = 30 μm.

FIGURE 8. Dendromonocotyle colorni. A. Ventral view body-proper, composite. B. Haptor including hamulus (ham). C. Outer ring septal sclerite. D. Septal sclerites. E. Inner-ring tripartite sclerite. F. Outer-ring tripartite sclerite. G. Papillary sclerites. H. Terminal papillary sclerites. I. Hamulus. J. Marginal hooklet. Scale bars: A, B = 500 μm; C – J = 10 μm.

FIGURE 10. Dendromonocotyle colorni. A. Male reproductive system. B. Distal portion of male copulatory organ showing sclerotised accessory flange (af). C. Female reproductive system; note translucent coiled duct (tcd) of vagina. Scale bars = 100 μm.