Prosphaerosyllis, San Martin, 1984

Guillermo San Martin, 2005, Exogoninae (Polychaeta: Syllidae) from Australia With the Description of a New Genus and Twenty-two New Species, Records of the Australian Museum 57, pp. 39-152 : 59-60

Genus Prosphaerosyllis San Martín, 1984

Sphaerosyllis (Prosphaerosyllis) San Martín, 1984b: 377.

Diagnosis. Body small, with few segments, provided with dorsal and ventral papillae, also present on cirri and parapodia; usually covered by detritus; sometimes, some dorsal or ventral papillae long. Prostomium with 3 small, short antennae, 4 eyes, and 2 anterior eyespots, usually partially covered dorsally by peristomium, some species with the prostomium completely retracted inside peristomium. Palps fused along their length, short, slightly ventrally folded, provided with small papillae. Single pair of tentacular cirri, located ventrolaterally. Nuchal organs 2 small, ciliated lateral clefts, usually covered by peristomium and difficult to see. Antennae, tentacular and dorsal cirri short, pyriform to bulbous, with sphaerical bases and short tips that are usually retractile inside bases, especially in midbody and posterior parapodia; tips sometimes papilliform and short; dorsal cirri present on all parapodia. Parapodial glands absent. Parapodia with compound, heterogomph chaetae with unidentate, short, falcate blades; dorsal and ventral simple, capillary, unidentate chaetae on some parapodia. Acicula usually solitary, acuminate, sometimes slightly modified. Pharynx long and wide, usually without papillae around opening; pharyngeal tooth rhomboidal to oval, located posteriorly from anterior margin of pharynx, sometimes on middle of pharynx. Proventricle long and wide, similar in size to pharynx, provided with numerous, slender muscle cell rows. Reproduction by epigamy with dorsal incubation by means of capillary notochaetae; mature males provided with long, thin natatory chaetae on mature segments.

Type species. Sphaerosyllis xarifae Hartmann-Schröder, 1960 ; designated by San Martín (1984b).

Remarks. Prosphaerosyllis was erected as a subgenus of Sphaerosyllis Claparède, 1863 for a group of species differing from the type species of the genus, S. hystrix Claparède, 1863 , and other species included in the nominal subgenus Sphaerosyllis , in the shape and position of the pharyngeal tooth, shape of pharynx and proventricle, shape of dorsal cirri and presence of dorsal cirri on chaetiger 2. This differentiation, however, has not been universally accepted, as these taxa are “based on artificial characters more than important phylogenetic characters” (Russell, 1989; Westheide, 1990; Kudenov & Harris, 1995), although these authors do not analyze the characters of the genus and do not explain which characters are of phylogenetic importance, and which are not. Riser (1991) discussed the genus and recognized three groups of species, one of which mostly agrees with Prosphaerosyllis , but he considered this not relevant to the concept of subgenera in Sphaerosyllis . In fact, there is another character not considered by any of the above mentioned authors, the type of reproduction, which is different in Prosphaerosyllis (females carrying eggs by means of capillary notochaeta) to that present in Sphaerosyllis (females without notochaetae, brooding ventrally eggs and juveniles). For the above reasons, I propose here that Prosphaerosyllis be elevated to genus level taxon.

All species of Prosphaerosyllis have similar chaetae; species identification is based principally on the shape of dorsal cirri, position of pharyngeal tooth, and the arrangement of papillae; the papillae, however, can appear different when they are covered in debris, so the specimens must be cleaned before identification. Some species have papillae of three different sizes, short, moderate and long (see Fig. 17A,B) or of two sizes, short and moderate (see Figs. 15A, 16B,C).

Key to species of Prosphaerosyllis recorded from Australia

1 Some papillae on dorsum elongate, digitiform ............................................................................. 2

—— All dorsal papillae similar, rounded ............................................................................................... 4

2 Papillae on dorsum of each segment, at least on midbody, arranged in transverse lines of 4–5 similar, moderately long papillae. Dorsal cirri of midbody similar to those of anterior parapodia but more elongate, similar in length to parapodial lobes ................................................................ P. xarifae

—— Dorsal papillae long. Dorsal cirri from midbody distinctly more elongate than antennae and anterior dorsal cirri ............................................................................ 3

3 Two longitudinal rows of papillae close to midline of dorsum, and 2 longitudinal rows of similar, but distinctly shorter, papillae, between long papillae and dorsal cirri. Dorsal cirri from midbody moderately long, slightly longer than parapodial lobes ....................................... P. longipapillata

—— All long dorsal papillae similar. Dorsal cirri from midbody long and slender, some distinctly longer than parapodial lobes ............................................. P. nathani

4 Papillae small ................................................................................................................................. 5

—— Papillae large, similar to vesicles ................................................................................................... 8

5 Papillae on dorsum forming a V, with 3 small papillae on each side ............................................................................................................................ P. sexpapillata

—— Papillae irregularly distributed ....................................................................................................... 6

6 All antennae on anterior margin of prostomium, close to eyespots ....................... P. opisthoculata

—— Median antenna inserted most posteriorly than lateral antennae .................................................. 7

7 Pharynx long, through about 7 segments. Palps densely papillated and dorsum with few minute papillae. Eyes small ....................................................... P. isabellae

—— Pharynx short, through about 4 segments. Papillae distributed on palps and dorsum. Eyes large ................................................................................. P. magnoculata

8 Papillae few, large, inflated and forming large vesicles ...................................... P. papillosissima

—— Papillae numerous, smaller ............................................................................................................ 9

9 Palps completely fused along their length. Dorsal cirri minute, papilliform. Prostomium and palps usually completely retracted into peristomium ................................................................................................... P. multipapillata

—— Palps fused but with a distinct distal notch. Dorsal cirri distinct, with a bulbous bases. Prostomium and palps not retracted into peristomium ............................................................................................................... P. battiri n.sp.