Renicola buchanani (Martin and Gregory)

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 : 483-485

Renicola buchanani (Martin and Gregory)

(14. Rebu; Figs. 1 , 57–60 )

Diagnosis: Parthenitae. Colony comprised of inactive sporocysts, densely concentrated in snail mantle (in enlarged perirectal sinus). Sporocysts translucent orange, yellow, sometimes white; 1000–2000 µm long, elongate (length: width up to ~6:1), ~sausage-shaped.

Cercaria . Body opaque white; non-oculate; with oral and ventral sucker; with a large Y-shaped excretory blad- der, the arms of which wrap around sides of ventral sucker; body ~ 228 µm long, much shorter than tail (<1/2 length); tail narrow at base, but then with large, sometimes bulbous, proximal portion that narrows distally to a simple tip.

Cercaria behavior: Upon emergence, cercariae either (1) swim solitarily, lashing the distal potion of tail while pressing body adjacent to the greatly inflated, egg-shaped, proximal portion of tail, or (2) form aggregations, where they attach to each other using adhesive proximal-most portions of tail (Martin & Gregory 1951). Cercariae that aggregate together are best referred to as known as “zygocercariae” (see review by Beuret & Pearson 1994). Our unpublished observations clarify that cercariae from the same infection may exhibit these different behaviors (often in different shedding events) (D.C. Metz, unpublished data).

Similar species: The “magnacercous” Rebu is not confusable with any of the other trematodes in this guild.

Remarks: Martin and Gregory (1951) described the sporocysts and cercariae (as Cercaria buchanani ). Based on morphological similarities, Martin (1971) decided that renicolid metacercariae he encountered in estuarine fish livers were the same species, and he assigned the species to Renicola . Hechinger and Miura (2014) provided COI and ITS1 DNA sequence data for this species.

Early Rebu infections can be detected. The sporocysts appear to typically initially form in the basal visceral mass, as generally expected for species that infects the snail with ingested eggs ( Galaktionov & Dobrovolskij 2003) (unpublished observations).

Mature, ripe colonies comprise ~17% the soft-tissue weight of an infected snail (summer-time estimate derived from information in [ Hechinger et al. 2009]).

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

As part of one of the first studies documenting the syncytial nature of trematode integuments, Bils and Martin (1966) examined the fine structure and development of the tegument for the sporocysts and cercariae of this species.

Fingerut et al. (2003a) presents information on the relationship between cercaria emergence and temperature for 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 57–60. Renicola buchanani (Rebu). 57, Overview of a colony in a freshly deshelled, infected horn snail in sea water. Arrow indicates the colony, which is localized in the mantle. Scale bar = 1 cm. 58, Sporocyst, live, with developing cercariae, under coverslip pressure. Scale bar = 1 mm. 59, Cercaria, live, under coverslip pressure. Scale bar = 100 µm. Ocular micrometer hatch mark = 10 µm. 60, Cercariae, live, aggregated clump formed under water at bottom of dissection dish after release from host. Scale bar = 1000 µm.