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 : 34-36

Cercaria capricornia VI

( Fig. 6 )

Host: Nassarius dorsatus (Röding) (Gastropoda, Nassariidae ).

Locality: Sandy Point, Corio Bay, Queensland (22°58' S, 150°46' E).

Habitat: Intertidal mudflats.

Prevalence of emergence: 0.06% (1 of 1766 N. dorsatus ).

Material: South Australian Museum, AHC 29318, AHC 34567–AHC 34568.

Date of collection: 15 August, 2004.

Description:

Redia

Site. Reproductive and digestive glands.

Structure. Body elongate, cylindrical with posterior extremity tapering to rounded point ( Figure 6c ). Mouth opens terminally; pharynx spherical. Cercariae in various stages of development.

Dimensions. Based on 10 unflattened rediae.

Length: 340–470 (422.0)

Width: 60–80 (72.0)

Pharynx: 20–25 (22.5) x 20–23 (21.5)

Naturally emerged cercaria

Body. Flattened, with conspicuous constriction immediately posterior to ventral sucker ( Figure 6a ). Forebody reduced, expanded immediately anterior to ventral sucker, angled 90° dorsally from posterior hindbody at constriction; 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 shallow, wide ventral keel longitudinally between constriction and posterior hindbody, keel virtually a cylindrical expansion ( Figure 6b ). Conformation of live cercariae not documented.

Appendages: Long tubular filament-like appendages arising from dorsal surface of hindbody at level slightly forward of anterior extremity of excretory vesicle and near margin of body, projecting anterolaterally. 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, aperture surrounded by single row of 66–81 inwardly facing minute spines.

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

Pigment. Live cercariae, white.

Penetration glands. Central and lateral glands present, unable to be determined, lateral glands may extend posteriorly from ventral sucker.

Digestive system. Mouth opens anteroventrally. Prepharynx and pharynx unable to be determined.

Excretory system. Excretory vesicle I-shaped, cylindrical, turgid, with cuboidal cells, about two-fifths length hindbody. Two lateral ducts open into anterior extremity of vesicle. Flame cells difficult to discern, formula not determined.

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

Dimensions. Based on 10 naturally emerged specimens.

Total length body: 400–460 (431.0)

Length anterior end to tail base: 370–430 (398.0)

Maximum width hindbody: 210–265 (238.8)

Maximum width forebody: 110–145 (128.0)

Width at constriction (n=9): 55–88 (74.7)

Length forebody: 102–120 (113.0)

Oral sucker: 35–40 (36.0) x 35 –40 (38.0)

Ventral sucker: 67–73 (69.5) x 67 –75 (71.5)

Excretory vesicle: 115–150 (133.3) x 25–35 (30.5)

Tail: 580–660 (624.5) x 25–38 (31.0)

Appendage (n=20): 30–205 (110.9) x 10–15 (12.8)

Cercarial emergence: rhythm and variation. These cercariae emerged in highly variable numbers, with 1– 3 observed to emerge for up to 4 consecutive days, with breaks of approximately 3–7 days between emergences; two emergences of>100 cercariae were also observed.

Behavior. Naturally emerged cercariae are free-swimming and swim actively toward light.

Figures

FIGURE 6. a – c. Cercaria capricornia VI, naturally emerged from Nassarius dorsatus: a. Body, heat-killed, in ventral view; b. Entire cercaria, heat-killed, from side view; c. Rediae, fixed, containing cercariae at different stages of development. Scale bars a, b = 100 μm; c = 200 μm.