Cloacitrema michiganensis McIntosh, 1938

Hechinger, Ryan F., 2019, Guide to the trematodes (Platyhelminthes) that infect the California horn snail (Cerithideopsis californica: Potamididae: Gastropoda) as first intermediate host, Zootaxa 4711 (3), pp. 459-494 : 475-476

Cloacitrema michiganensis McIntosh

(8. Clmi; Figs. 1 , 30–33 )

Diagnosis: Parthenitae. Colony comprised of active rediae, densely concentrated in snail gonad region with dispersion into basal visceral mass. Rediae translucent white to colorless, often with prominent pigmented gut; when filled with cercariae, rediae appear opaque white; ~ 1000–2000 µm long, oblong to elongate (length:width up to ~6:1), often tapers in width gradually toward anterior and posterior ends, with posterior appendages that are often not pronounced.

Cercaria . Body opaque white, usually translucent colorless through ventral sucker; non-oculate; with oral and ventral sucker; with very short esophagus that bifurcates far anterior of ventral sucker (just posterior to pharynx); body ~ 425 µm long, ~equal in length to tail; tail with distal gland (tip appears invaginated).

Cercaria behavior: Fresh, emerged cercariae remain in water column, lengthen body and swim by rapidly ventrally folding body with tail extended (often forming a graceful, undulating S), and will often encyst on dissection dish or in pipette during transfer.

Similar species: Clmi is most readily distinguished from the only other philophthalmid (Pasp [9]) by having almost no esophagus anterior to the gut branching; Clmi also lacks tegumental spines, but these are sometimes difficult to see on Pasp, so be wary of using this as a sole distinguishing trait. Like Pasp, Clmi is easily separated from the himasthlids by having a distal tail gland.

Remarks: LeFlore et al. (1985) document the life cycle (see also Robinson (1952) and Martin [1972]), describing the miracidia, rediae, cercariae, metacercariae, and experimentally obtained adults, which they identified as Cloacitrema michiganensis , which was originally described from eastern North American shorebirds.

Mature, ripe colonies comprise ~24% the soft-tissue weight of an infected snail (summer-time estimate derived from information in [ Hechinger et al. 2009]).

Infection causes (stolen) snail bodies to grow ~ 2x faster than uninfected snails ( Hechinger 2010).

This species has a caste of soldier rediae (noted in Hechinger et al. (2011b) and carefully documented in Garcia- Vedrenne et al. [2016]).

Nadakal (1960b) presents information on the pigments of the rediae and cercariae of this species.

Figures

FIGURE 1. General characteristics of the parthenitae and cercariae of the trematodes infecting Cerithideopsis californica as first intermediate host. Species numbers and codes follow Table 1 and species accounts. Cercariae are all to scale, with additional magnified views of six small species (indicated by dashed lines). Note the oral stylets (presented in right lateral view) for Pruc and Smmi. Parthenitae are not to scale. Scale bars consistently indicate 100 µm.

FIGURES 30–34. Cloacitrema michiganensis (Clmi). 30, Overview of a colony in a freshly deshelled, infected horn snail in sea water. The arrow indicates the colony, which is localized in the gonadal region and part of the basal visceral mass. Scale bar = 1 cm. Base photo credit: Andrew Turner. 31, Reproductive rediae, live, with developing cercariae, under coverslip pressure. Scale bar = 500 µm. 32, Soldier redia, live, under coverslip pressure. Scale bar = 100 µm. 33, Cercariae, live, under coverslip pressure. Scale bar = 100 µm. Base photo credit: Andrew Turner. 34, Developing cercariae, live, under heavy coverslip pressure to make visible the anterior branching of the gut (~ non-existent esophagus). Scale bar = 100 µm.