Polydorella stolonifera ( Blake and Kudenov, 1978 )

Williams, Jason, 2004, Reproduction and morphology of Polydorella (Polychaeta: Spionidae), including the description of a new species from the Philippines, Journal of Natural History 38 (11), pp. 1339-1358 : 1352-1354

Polydorella stolonifera ( Blake and Kudenov, 1978)

( figures 6 , 8 )

Polydorella stolonifera ( Blake and Kudenov, 1978) : 269–271, figure 50a–j.

Material examined. Twelve paratypes from Australia, Victoria, Westernport Bay, Crawfish Rock , 5 m, 3 January 1972, from Ancorina cordicata (Carter, 1879) ( NMV F42898 , previously registered as G2898; two prepared for SEM) .

Description

Largest single individual 3.8 mm long and 0.6 mm wide at segment 7; 16 segments, with endoparasitic copepod (see Remarks); single individuals with developing growth zone of stolon 1 and 16 segments 2.5 mm long and 0.4 mm wide at segment 7 ( figure 8A ). Prostomium bifid; caruncle short, terminating at posterior margin of segment 1; occipital tentacle and eyes absent ( figure 8A, B ). Palps extend posteriorly for 8–12 segments. Pigmentation absent.

Segment 1 with small notopodial lobe without notosetae; neuropodial lobe with two or three winged capillary neurosetae ( figure 8A, B ). Unilimbate capillary notosetae of segments 2–4, 6 and subsequent segments in two rows. Unilimbate capillary neurosetae of segments 2–4, 6 and 7 arranged in two rows; up to eight bidentate hooded hooks begin on segment 8, not accompanied by capillaries ( figure 8A, B ); hooks with approximately right angle between main fang and shaft, narrow angle between main fang and apical tooth, with constriction on shaft.

Segment 5 slightly modified, about the same size as segments 4 and 6, with

posteroventral fascicle of bilimbate capillary neurosetae in two rows; notosetae absent. Two types of major spines of segment 5 in approximately horizontal curved row; ventral row of three to six spines with expanded tips covered by fine bristles and a dorsal row of up to five simple acicular spines ( figure 6G ).

Branchiae present on segments 7 and 8 ( figure 8A, B ). Dorsal ciliary bands from segment 2 continuing to terminal segments ( figure 8B ).

Pygidium with small cirri surrounding terminal anus ( figure 8A ).

Asexual reproduction and parasitism

Of 12 individuals examined, 10 exhibited asexual reproduction with two individuals joined in a chain ( figure 8A ). The two single individuals consisted of up to 16 segments; both possessed endoparasitic copepods within segments 8–12. Individuals undergoing asexual reproduction contain a growth zone that developed after segment 10. Formation of new posterior stock segments is apparent in side and ventral views ( figure 8A ). The sequence of stolon body formation appears to be similar to that described for Polydorella kamakamai , although no specimens were composed of more than two individuals.

Distribution South China Sea: south-eastern coast of Vietnam, Philippines; Red Sea.

Remarks

Blake and Kudenov (1978) indicated that brown pigmentation was present on the branchiae, peristomium and sides of anterior segments; this pigmentation has been lost from the specimens stored in alcohol for 29 years. This is the first report of parasitic copepods within Polydorella stolonifera , although Radashevsky (1996) noted such parasites in P. dawydoffi . The copepod parasites apparently interfere with the process of asexual reproduction in Polydorella . These parasites may induce larger numbers of segments and longer length in infected individuals; 16 segments in P. stolonifera that contained parasites versus 15 segments in those lacking parasites and 17–18 segments in parasitized P. dawydoffi versus 15 segments in those lacking parasites. The present findings are in contrast to those of McCurdy (2001), who found earlier fragmentation in asexual reproduction via architomy by Pygospio elegans Claparède, 1863 when parasitized by trematode metacercariae. Such differences are not unexpected because host responses to parasites could be influenced by a variety of factors including mode of asexual reproduction (i.e. paratomy versus architomy) and type of parasite (crustacean versus trematode).

Figures

FIG. 6. Polydorella dawydoffi (AMNH 4348) (A), (USNM 1008717) (B, D, F), (USNM 1008716) (C), (USNM 148722) (E) and P. stolonifera (NMV F42898) (G). (A) Dorsal view of specimen from the Philippines; (B) dorsal view of specimen from the Red Sea; extensive black pigmentation is indicated by grey shading; (C) lateral view showing 10 developing segments of stolon 1; (D) dorsal view of posterior end of stock and anterior end of stolon 1 of an individual containing sand grains (shaded structures) within intestine; (E) dorsolateral view of fifth segment spines; (F) hooded hook; (G) lateral view of dorsal (to left) and ventral (to right) major spines of segment 5. Scale: 100 mm (A–D); 25 mm (E); 12.5 mm (F); 5 mm (G).

FIG. 8. Polydorella stolonifera (NMV F42898). (A) Lateral view of paratomic chain containing a developing stolon 1 (St1) and a newly developed segment 11 (11’); (B) dorsolateral view of anterior end of single specimen containing 16 segments; note branchiae on segments 7 and 8. Scale: 250 mm (A); 100mm (B).