Polydora rickettsi Woodwick (1961, pp. 78–81, Figs 1–7). — Blake (1983, p. 257). — Radashevsky & Cárdenas (2004, pp. 244–252, Figs 2–6).
? Polydora sp. II: Carrasco (1976, pp. 34–37, Figs 12, 13 L–O, 21 C).
Polydora sp.: Basílio, Cañete & Rozbaczylo (1995, pp. 72–74, Fig. 1 A–H).
Polydora cf. rickettsi: Sato-Okoshi & Takatsuka (2001, pp. 489–490, Fig. 2 A–D).
Adult morphology (based on material from Brazil)
Specimens in poor condition. Up to 15 mm long and 0.6 mm wide at chaetiger 7 for 130 chaetigers. Black pigment diffused on palps along longitudinal ciliated grove, on sides of prostomium and on 1–4 anterior chaetigers; present only on prostomium or absent in some specimens. Largest individual with 130 chaetigers and with black bands on palps. Prostomium blunt to rounded anteriorly. Caruncle extending to middle of chaetiger 3. Occipital antenna absent. One to four eyes present or eyes absent.
Chaetiger 1 with short capillaries in neuropodia and postchaetal lamellae in both rami; notochaetae absent. Posterior notopodia with only capillary chaetae.
Chaetiger 5 greatly modified, with 2–3 dorsal superior capillaries, 4–6 major spines alternating with bilimbate-tipped companion chaetae, and ventral tuft of 4–6 capillaries; postchaetal lamellae absent. Dorsal superior and ventral capillaries shorter and fewer than those on chaetigers 4 and 6. Major spines falcate, with lateral tooth and narrow longitudinal flange located laterally on main fang above accessory tooth.
Branchiae from chaetiger 7 to almost end of body, full-sized from chaetiger 10–11, greatly diminishing on posterior chaetigers.
Hooks in neuropodia from chaetiger 7, bidentate, with constriction on shaft, up to 9 in a series.
Pygidium small, cup-shaped to disc-like with dorsal incision.
Gizzard-like structure in digestive tract not distinguished.
Remarks
Polydora rickettsi was originally described by Woodwick (1961) as associated with calcareous tubes of the serpulid polychaete Spirobranchus incrassatus Mörch from Lower California, Mexico. Sato-Okoshi & Takatsuka (2001) reported P. cf. rickettsi boring into shells of the oysters Crassostrea gigas and Ostrea chilensis (Philippi, 1845) in southern Chile. The worms resided in U-shaped burrows within the shells. More than 50 worms were found in one oyster shell, and 1–2 worms per cm 2 were found on the shell surface (Sato-Okoshi & Takatsuka 2001). Radashevsky & Cárdenas (2004) also described adult and larval morphology of the species from Chile and indicated that identification of the Chilean worms should be verified by further studies on specimens from Mexico.
In Brazil, worms were found in a shell of the scallop Nodipecten nodosus (Linnaeus, 1758). The scallop was collected off the coast of the state of São Paulo and maintained for a long time in an aquarium of the University of São Paulo (USP). The fixed scallop shell with worms was received for examination from João M. de M. Nogueira in 2001. Specimens from Brazil appear similar to P. rickettsi from Chile. Both have an entire prostomium, characteristic falcate spines on chaetiger 5, and a small disc-like pygidium. The only difference is that the largest specimen (with 130 chaetigers) from Brazil has black bands on the palps and black pigment on the sides of the prostomium. Worms from Mexico and Chile (largest with 125 chaetigers) have no such pigmentation on palps. The presence of black bars or bands on palps is a diagnostic feature appearing stable in some species (e.g., Polydora brevipalpa Zachs, 1933) and variable in others (e.g., P. ecuadoriana, P. h a s w e l l i, P. neocaeca). Further studies are needed to verify the identification of worms boring in N. nodosus in Brazil.
Distribution
Pacific Mexico; Chile;? Brazil: São Paulo.