Cantharus capricornia

Barnett, Leonie J., Smales, Lesley R. & Cribb, Thomas H., 2008, A complex of putative acanthocolpid cercariae (Digenea) from Nassarius olivaceus and N. dorsatus (Gastropoda: Nassariidae) in Central Queensland, Australia, Zootaxa 1705, pp. 21-39 : 27-29

Cercaria capricornia III

( Fig. 3 )

Host: Nassarius olivaceus (Bruguière) (Gastropoda, Nassariidae ). Locality: Ross Creek, Yeppoon, Queensland (23°8' S, 150°45' E). Habitat: Amongst and immediately adjacent to mangroves on intertidal mudflats. Prevalence of emergence: 0.10% (2 of 1908 N. olivaceus ). Material: South Australian Museum, AHC 29312–AHC 29313, AHC 34549–AHC 34553. Dates of collection: February and November 2005. Description:

Redia

Site. Reproductive and digestive glands.

Structure. Body elongate, cylindrical with posterior extremity tapering to point ( Figure 3e ). Mouth opens terminally; pharynx spherical. Cercariae in various stages of development. Dimensions. Based on 10 unflattened rediae.

Length: 620–1000 (801.0)

Width: 100–170 (121.0)

Pharynx: 22–30 (25.5) x 20–30 (26.3)

Naturally emerged cercaria

Body. Flattened, with conspicuous constriction immediately posterior to ventral sucker ( Figure 3a ). Forebody reduced, arched ventrally; body anterior to constriction pyriform, widest at level of anterior margin of ventral sucker. Hindbody posterior to constriction expanded, large, broadly ovate, extremely flattened, extending backwards beyond tail junction on both sides, with deep ventral keel longitudinally between constriction and midpoint of excretory vesicle; keel oblong in profile, deepest at anterior margin of excretory vesicle ( Figure 3b ). In life, body bent dorsally (~90°) at constriction, forebody bent forward ventrally at eyespots; fleshy portion around ventral sucker extremely expanded; hindbody bent ventrally (~120°) at level of anterior margin of excretory vesicle; sides of hindbody anterior from this point to appendage flexed dorsally in a shallow V, sides of posterior hindbody curving ventrally, bowl shaped ( Figures 3c, 3d ).

Appendages: Paired appendages, arising from dorsal surface near lateral edge of hindbody, flat paddle shape variable from short, wide to longer, narrow.

Tegument. Spines anterior to constriction, arranged in regular rows in anterior forebody, longest in anterior two-thirds forebody, decreasing in size towards constriction.

Suckers. Oral sucker opening ventrosubterminally, spinose, lacking stylet. Ventral sucker round, row of approximately 93–94 inward pointing spines at aperture, several rows of spines bordering the cavity.

Eye-spots. Round, dense, lateral on either side of prepharynx.

Pigment. Golden brown shading, throughout hindbody, in fleshy portion anterior to ventral sucker.

Penetration glands. Two pairs of small central glands; ducts run anteriorly either side of pharynx, continue forward medially, diverging laterally anterior to eye-spots and running to dorsal lip of oral sucker; three pairs of large lateral glands present, anterolateral to ventral sucker; ducts run anteriorly on lateral edges of body to dorsal lip of oral sucker; all anterior to constriction.

Digestive system. Mouth opens anteroventrally. Prepharynx long, narrow. Pharynx pyriform, small.

Excretory system. Excretory vesicle I-shaped, cylindrical, turgid, thin-walled, slightly longer than onethird length hindbody. Two lateral ducts open into anterior extremity of vesicle, continue in close association with vesicle towards posterior extremity. Flame cells difficult to discern, formula not determined.

Tail. Simple, long, cylindrical, gradually tapering terminally; lacks spines, setae or fins.

Dimensions. Based on 36 naturally emerged specimens.

Total length body: 485–760 (584.6 ± 81.1)

Length anterior end to tail base: 445–700 (541.4 ± 74.9)

Maximum width hindbody: 215–420 (280.7 ± 57.0)

Maximum width forebody: 115–183 (143.5 ± 18.5)

Width at constriction: 70–133 (95.2 ± 16.3)

Length forebody: 125–175 (149.8 ± 12.4)

Oral sucker: 42–53 (48.1 ± 2.8) x 45 –53 (48.7 ± 2.1)

Ventral sucker: 77–105 (91.0 ± 7.1) x 75 –103 (87.4 ± 7.2)

Prepharynx: 85–120 (104.0 ± 9.1)

Pharynx: 20–25 (22.4 ± 1.7)

Excretory vesicle: 122–220 (157.4 ± 26.9) x 25–35 (27.7 ± 3.0)

Tail: 430–810 (608.2 ± 123.3) x 35 –63 (47.8 ± 8.8)

Appendage (n=70): 35–265 (92.4 ± 54.3) x 15–63 (36.7 ± 11.3)

Cercarial emergence: rhythm and variation. Large numbers seen to emerge on consecutive days, length of time between periods of emergence not determined.

Behavior. Naturally emerged cercariae are free-swimming and swim actively toward light. When swimming, the hindbody is folded ventrally and the forebody is contracted longitudinally, appendages are contracted; the tail lashes from side to side for movement. When resting, the hindbody is held in threedimensional shape ( Figure 3c ); tail extends backwards dorsally from hindbody, curves ventrally. When first emerged, cercariae swim actively towards light and frequently rise to surface, float in water column, slowly settle. After about 24 hours, cercariae become less active, may attach to the substrate at tip of tail, decaudation may occur and they start to die. The cercariae never encyst.

Figures

FIGURE 3. a – e. Cercaria capricornia III, naturally emerged from Nassarius olivaceus: a. Body, heat-killed, in ventral view; b. Entire cercaria, heat-killed, from side view; c. Live cercaria, resting attitude, side view; d. Live cercaria, resting attitude, ventral view; e. Rediae, fixed, containing cercariae at different stages of development. Scale bars a, b = 100 μm; c, d not to scale; e = 200 μm.