Paulodora watsoni, Artois, Tom J. & Tessens, Bart S., 2008

Artois, Tom J. & Tessens, Bart S., 2008, Polycystididae (Rhabditophora: Rhabdocoela: Kalyptorhynchia) from the Indian Ocean, with the description of twelve new species, Zootaxa 1849, pp. 1-27 : 17-18

Paulodora watsoni n. sp.

( Fig. 4 D, L)

Localities in the Indian Ocean. Zanzibar Island ( Tanzania), mangrove area near Pete (southern region of Unguja), sea grass from a large exposed sea grass field ( Thalassia ) (16/08/1995) (type locality). English Point, Mombasa ( Kenya), green algae (5m) (October 1987).

Material. Studies on live animals. Four whole mounts (two from each locality), one of them designated holotype ( SMNH, no. 7450), another one paratype (HU, no. 365).

Etymology. Named after Dr. Nikki Watson (Armidale, Australia), for her contributions to flatworm morphology and systematics.

Description. Habitus and the internal organisation as in P. c o n t o r t a (see Schockaert & Karling 1975). In most specimens, the oviducts are swollen and filled with sperm.

The prostate stylet type I is large and heavily built. It is 129–149 µm long (= 138, n = 4). It almost immediately makes a 270° turn, continues more or less straight for some distance and distally turns again 90°. The inner stylet can be followed over almost all of the length of the outer one. Just distally from the funnelshaped proximal end of the stylet, the outer stylet forms an inconspicuous fold that continues as a gutter along whole of the length of the outer stylet. In this fold presumably the sperm is drained.

Diagnosis. Species of Paulodora with a heavily-built prostate stylet type I ca 138 µm long, immediately making a 270° turn, near to the distal tip again turning 90°. Outer stylet proximally forming an inconspicuous fold, continuing as a gutter to the distal tip of the stylet. Bursal stalk very short. Ovaries long-drawn, kidneyshaped. Seminal receptacles absent.

Discussion. The taxon Paulodora consists of a large number of very similar species, which are typically found in tropical areas all over the world, as well as in the Mediterranean. Only P. c o n t o r t a occurs at higher latitudes (Swedish west coast, see Schockaert & Karling 1975).

The presence of the hard “nozzles” (x in Fig. 3 B–C) on the ovaries, the fact that the ejaculatory duct turns about 270° around the prostate vesicle, and the fact that the oviducts and/or the female duct are tightly grown together with the male bursa are unique and diagnostic features of the taxon, and most probably are synapomorphies of all species of Paulodora (see Artois & Schockaert 1998). The species differ from each other mostly in the detailed construction of the stylet, but also some features of the female system may differ from species to species.

Most species have long-drawn, somewhat kidney-shaped ovaries with the oocytes arranged in rows, the smallest ones situated most proximally (see Artois & Schockaert 1998). In P. porcellus , P. hamifer , P. schockaerti and P. subcontorta , however, the ovaries are globular, as is the case in most Polycystididae (and even most Eukalyptorhynchia). The globular shape of the ovaries is therefore probably a synplesiomorphy of the four species mentioned. Three of these four species have seminal receptacles that are placed asymmetrically on the oviducts: P. subcontorta , P. hamifer and P. schockaerti . The appearance of these vesicles can vary from small optically-transparent vacuoles in specimens that are female immature (see Schockaert 1982) to large vesicles with multiple sperm-containing compartments in specimens that had presumably just copulated, as is illustrated in Fig. 4 A. The presence of this type of receptacle is unique within the Polycystididae , and therefore these three species probably form a monophyletic group. Moreover, P. schockaerti , P. hamifer and P. subcontorta all have a more-or-less hook-shaped stylet, with a straight proximal part and a longer, curved distal part. The proximal part is relatively longest in P. schockaerti ; the stylet starting to curve only at about its midpoint. In this species, the semitubular fold of the outer stylet is just as long as the straight part itself. The large plate-like extension formed by the outer stylet is yet another typical feature that distinguishes this species from the other two species. In P. hamifer and P. subcontorta the straight proximal part of the stylet is much shorter. In P. hamifer the semitubular fold of the proximal part of the outer stylet is still obvious, although smaller than in P. schockaerti , whereas in P. subcontorta it is lacking. The stylet of P. subcontorta is also much longer than in the other two species, which gives the stylet a more elegant appearance. The stylet of P. porcellus has the same basic construction as in the other three species, but here the distal part is relatively longer and more slender, and is turned over a 270° angle, thereby losing the typical hook-shaped appearance.

All other species presented in this paper have the long-drawn ovaries typical of the taxon, and additional seminal receptacles are lacking. Of these remaining species, P. drepanophora is the only species with a sickleshaped stylet, somewhat comparable with the hook-shaped stylet of the species discussed above. However, in this species the “grip of the sickle” (probably) consists of the short, slightly curved proximal double-walled stylet proper, while the blade is formed by a flap-like projection that is attached to this stylet. In the four species discussed above, the sickle is formed by the entire prostate stylet. Only P. f e l i s ( Marcus, 1954) Artois & Schockaert, 1998 and P. asymmetrica Artois & Schockaert, 2001 have a similar sickle-shaped stylet. These two species have an identical stylet morphology, and therefore were considered subspecies of P. felis by Artois & Schockaert (2001). They, however, clearly and consistently differ from each other in the construction of the female genital system, and hence are better treated as separate species. Artois & Schockaert (2001) did not designate a holotype for P. felis asymmetrica , but the syntype is present in the collections of the Zoologisches Museum der Universität Göttingen. From this syntype, a serially-sectioned specimen should be designated lectotype (whole mounts are lacking), but repeated requests for the syntype were unsuccessful up to now. For a diagnosis of P. asymmetrica n. sp, we refer to the diagnosis given by Artois & Schockaert (2001) for P. f e l i s asymmetrica .

The stylet of P. drepanophora largely resembles that of P. felis and P. asymmetrica , but is much sturdier and distally ends in a very blunt tip. In P. felis and P. asymmetrica , the distal part of the stylet is slender and appears more fragile, distally ending in a more sharp point. Moreover, it is also much shorter in P. drepanophora than in the other two species, being only 53 µm long [84 µm in P. asymmetrica ; 73–90 µm in P. f e l i s; see Artois & Schockaert (2001)].

The stylet of P. ancora slightly resembles that of P. c o n t o r t a, which also has a stylet that is bent at a right angle in about its middle (see Schockaert & Karling 1975). The flap-like projections of the outer stylet are, however, much larger than in P. c o n t o r t a, and in P. contorta the long spur is lacking.

On the other hand, the stylet of P. contortoides closely resembles that of P. contorta . However, some consistent differences can be found, justifying the appointment of a new species for the specimens from the Indian Ocean. P. contorta has a stylet that also bends at a right angle ( Schockaert & Karling 1975), but it is much larger (51–57 µm) and is bent about in its middle. In this species the outer stylet forms one plate-like extension, which winds around the stylet and follows its course throughout its whole length. Compared to the situation in P. contortoides , the part of the plate that is parallel to the proximal part of the stylet starts much more proximally in P. c o n t o r t a, just beneath the proximal funnel.

Apart from P. watsoni , only two other species of Paulodora have an elongated stylet that makes a large turn: P. matarazzoi Marcus, 1948 and P. dolichocephala (Pereyaslawzewa, 1892) Artois & Schockaert, 1998 . Both, however, have a more slender and much longer stylet. In P. dolichocephala it turns over more than 360° and the outer stylet proximally forms a very large fold. This fold is lacking in P. m a t a r a z z o i, which makes it more reminiscent of P. watsoni . However the exceptional length of the stylet of P. matarazzoi , its slenderness and the fact that it coils much more make it clearly different from that of P. watsoni . In the three species discussed here the bursal stalk is rather long and slender, and at least in P. dolichocephala and P. m a t a r a z z o i (partly) covered by a basement membrane (pseudocuticula) only. In all other species of Paulodora , the bursal stalk is much shorter, and covered by an epithelium that in some cases is degenerating (pseudociliation).

Figures

FIGURE 3. Paulodora ancora n. sp. A, Prostate stylet type I (from the holotype). P. contortoides n. sp. B, Caudal body end (from a live specimen). C, Reconstruction of the atrial organs from the left side. D, Prostate stylet type I (from the holotype). E, Prostate stylet type I (from a specimen from La Réuniuon). P. drepanophora n. sp. F, Prostate stylet type I (from the holotype). P. h a m i f e r n. sp. G, Prostate stylet type I (from the holotype). P. porcellus n. sp. H, Prostate stylet type I (from the holotype).

FIGURE 4. Paulodora schockaerti n. sp. A, Atrial organs (from a live specimen). B, Prostate stylet type I (from the holotype). P. subcontorta Schockaert, 1982 C, Prostate stylet type I (from a specimen from Zanzibar). P. watsoni n. sp. D, Prostate stylet type I (from the holotype). P. a n c o r a n. sp. E, picture of the prostate stylet type I (from the holotype). P. contortoides n. sp. F, idem (from the holotype), P. contortoides n. sp. F, idem (from the holotype), P. drepanophora n. sp. G, idem (from the holotype), P. porcellus n. sp. H, idem (from the holotype), P. hamifer n. sp. I, idem (from the holotype), P. schockaerti n. sp. J, idem (from the holotype), P. subcontorta Schockaert, 1982 K, idem (from the same specimen as C), P. w a t s o n i n. sp. L, idem (from the holotype).