A complex of putative acanthocolpid cercariae (Digenea) from Nassarius olivaceus and N. dorsatus (Gastropoda: Nassariidae) in Central Queensland, Australia Author Barnett, Leonie J. Author Smales, Lesley R. Author Cribb, Thomas H. text Zootaxa 2008 1705 21 39 journal article 10.5281/zenodo.180897 d0034a16-cad2-4058-9569-95a0dd26699c 1175-5326 180897 Cercaria capricornia V ( Fig. 5 ) Host: Nassarius dorsatus (Röding) (Gastropoda, Nassariidae ). Locality: Cawarral Creek, Keppel Sands, Queensland ( 23°19' S , 150°47' E ). Habitat: Intertidal mudflats. Prevalence of emergence: 0.06% (1 of 1766 N. dorsatus ). Material: South Australian Museum, AHC 29317, AHC 34565–AHC 34566. Date of collection: 16 August , 2004. Description: Redia Site . Reproductive and digestive glands. Structure . Body elongate, cylindrical with posterior extremity tapering to point ( Figure 5e ). Mouth opens terminally; pharynx spherical. Cercariae in various stages of development. Dimensions . Based on 10 unflattened rediae. Length: 490–810 (617.0) Width: 45–70 (54.5) Pharynx: 17–23 (20.0) x 17–20 (19.3) Naturally emerged cercaria Body . Flattened, with conspicuous constriction immediately posterior to ventral sucker ( Figure 5a ). 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 very deep ventral keel longitudinally between constriction and midpoint of excretory vesicle; keel oblong in profile, deepest at anterior margin of excretory vesicle ( Figure 5b ). In life, body bent dorsally at constriction (~105°), forebody bent forward ventrally at eyespots; fleshy portion around ventral sucker extremely expanded; hindbody bent ventrally (~130°) at level of anterior margin of excretory vesicle; anterior sides of hindbody from this point to appendage flexed dorsally in a shallow V, posterior hindbody almost in single plane with sides curving slightly ventrally, shallowly bowl shaped ( Figure 5c, 5d ). 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. Extremely extensible, more extended in live cercariae. 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 86–88 inward facing spines at aperture, several rows of spines bordering cavity. Eye-spots . Round, dense, lateral on either side of prepharynx. Pigment . Red brown, dense, conspicuous, on posterior extremity of hindbody either side of tail base, oval in shape; red brown, diffuse, anterior from base of tail by about one-third length excretory vesicle; golden brown, diffuse shading, in fleshy portion anterior to ventral sucker, over keel and anterior and posterior areas of hindbody. In life, body white with bright orange spots on posterior extremity. Penetration glands . Two pairs of small central glands; ducts run anteriorly either side of pharynx, continue forward medially; possibly three pairs of large lateral glands present, difficult to determine, anterolateral to ventral sucker; ducts run anteriorly on lateral edges of body; all anterior to constriction. FIGURE 5. a–E. Cercaria capricornia V, naturally emerged from Nassarius dorsatus : 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. Digestive system . Mouth opens anteroventrally. Prepharynx long, narrow. Pharynx pyriform, small. Excretory system . Excretory vesicle I-shaped, cylindrical, turgid, thin-walled, about half 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 10 naturally emerged specimens. Total length body: 700–870 (770.0) Length anterior end to tail base: 650–800 (720.0) Maximum width hindbody: 320–370 (345.0) Maximum width forebody: 167–183 (177.0) Length forebody: 162–200 (179.8) Oral sucker: 50–58 (53.8) x 52 –58 (54.3) Ventral sucker: 105–115 (112.3) x 100–108 (103.5) Prepharynx: 105–125 (114.3) Pharynx: 20–25 (23.5) Excretory vesicle: 260–315 (289.5) x 25–38 (27.5) Tail: 850–900 (875.5) x 50 –60 (56.5) Appendage: (n=20): 270–770 (451.0) x 15–20 (17.5) Cercarial emergence: rhythm and variation. Large numbers emerge with a few days between emergences. Behavior. Naturally emerged cercariae are free-swimming and swim actively toward light. When resting, the hindbody is flexed ventrally; tail extends backwards dorsally from hindbody, curved ventrally ( Figure 5c ). 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.