Polypheretima mindanaoensis, Aspe & James, 2015

Aspe, Nonillon M. & James, Samuel W., 2015, New Polypheretima and Pithemera (Oligochaeta: Megascolecidae) species from the Mt. Malindang Range, Mindanao Island, Philippines, Journal of Natural History 49 (37), pp. 2233-2255 : 2238-2243

Polypheretima mindanaoensis sp. nov.

( Figures 2A and 3A )

Diagnosis

Body white; stout, adult length 90–118 mm; paired, sublateral genital markings on each of xix to xxvi; intestinal origin in xv; small spermathecae present in batteries or lacking.

Etymology

The species is named for Mindanao Island.

Material examined

Holotype: adult (NMA 4527), Barangay Lake Duminagat , municipality of Don Victoriano , Misamis Occidental Province, Mt. Malindang Range (8.2986°N, 123.6169°E), 1357 m a.s.l, Mindanao Island, Philippines; coll. Nonillon Aspe, Nolan Aspe and J. Adeva, 9–15 October 2003 . Paratypes: one adult, one juvenile (NMA 4545); two adults ( ZRC.ANN.0013); same collection data as for holotype .

Description

White, clitellum pinkish-grey. Body stout, adult length 90–118 mm; diameter 5.1 mm at x, 7 mm at xx; 140–141 segments (n = four adults); body cylindrical in crosssection, tail narrowing gradually to sharp point. First dorsal pore at 12/13; spermathecal pores lacking or inconspicuous; female pore single in xiv, male pores on paired low papillae on xviii, 0.23 circumference apart, 10 setae between openings. Clitellum annular, from xiv to xvi. Setae pointed posteriorly, unevenly distributed around segmental equators; 41–53 setae on vii, 44–46 setae on xx; dorsal and ventral setal gaps lacking. Genital markings widely paired on xix to xxv and/or xxvi, between the sixth and seventh setal lines.

Septa 4/5/6/7/8 muscular, 8/9 absent, 9/10 present around dorsal vessel and hearts; 10/11 to 13/14 thickly muscular. Dense tufts of nephridia on anterior faces of 5/6 and 6/7; nephridia of intestinal segments located at septum–body wall junction, mainly on body wall near anterior and posterior faces of septa. Oesophageal gizzard large, extending from viii–x; oesophagus with lamellar inner surface extend from xi–xiii; intestinal origin in xv, caeca lacking; typhlosole a simple fold of about one sixth lumen diameter originating in xvi; intestinal wall without longitudinal blood vessels but with two pairs of vertical vessels per segment.

Hearts in x to xii, oesophageal. Commissural vessels in vi, vii and ix, lateral; lacking in viii. Supra-oesophageal vessel extending from x to xii; extra-oesophageal vessels joining ventral oesophageal wall in x, receiving efferent parieto-oesophageal vessels in xiv.

Ovaries and funnels free in xiii, spermathecae lacking in two adults, one adult individual with five spermathecae closely lining up on the left side of vi, another adult individual with three spermathecae closely lining up on the left side and five spermathecae closely lining up on the right in vi and two spermathecae on left and two on right in vii; spermathecae small, ampulla pyriform, spermathecal duct short, slender; diverticulum stalk long and slender, attached ectally to duct, with one kink, terminating in short, sausage-shaped receptacle; no nephridia on spermathecal ducts. Male sexual system holandric, testes and funnels enclosed in paired ventral sacs in x and xi; seminal vesicles in xi and xii; pseudovesicles in xiii; vasa deferentia slender, free from body wall en route to ental end of prostatic ducts; prostates in xvi to xxi, each prostate racemose, trilobed but compact; copulatory bursae lacking.

Remarks

Polypheretima mindanaoensis sp. nov., the first member of Polypheretima reported from Mindanao Island, belongs to the Po. elongata Perrier, 1872 species group of Easton (1979), characterised by having a pair of genital markings in xix, successive segments in line with the male pores, paired batteries of up to 28 spermathecae in vi and/or vii, and shallow copulatory bursae with no stalked glands. Easton (1979) included five species in the group: Po. elongata ; Po. everetti ; Po. kinabaluensis Beddard and Fedarb, 1895 ; Po. phacellotheca Michaelsen, 1899 ; and Po. stelleri Michaelsen, 1892 . Polypheretima mindanaoensis markedly differs from Po. elongata and Po. everetti in size (355 × 4 in Po. elongata ; 300 × 12 in Po. everetti ), in the number of segments covered by the genital markings (extending from xix to xxii in Po. elongata ; xix to xxi in Po. everetti ) and in the number of setae on vii (usually 80–130 in Po. elongata ; 130 in Po. everetti ) ( Table 2). Polypheretima mindanaoensis (white) differs in colour from Po. everetti and Po. kinabaluensis (reddish-purple and red, respectively). Those individuals of Polypheretima mindanaoensis that have spermathecae have fewer spermathecae in each battery than Po. kinabaluensis (6–12 in 5/6/7), Po. phacellotheca (9–12 in 5/6) or Po. stelleri (up to 28 in 5/6/7), and individuals have fewer setae (41–53) on vii than Po. phacellotheca (80) or Po. stelleri (130). Finally, Po. mindanaoensis differs from all congeners in the Po. elongata species group in lacking copulatory bursae. Congeners reported from the Philippines include Po. fruticosa Hong and James, 2008a , Po. perlucidula Hong and James, 2008a , and Po. bannaworensis Hong and James, 2008a , from Banaue, Luzon Island; Po. pagudpudensis Hong and James, 2011a from Kalbaryo, Luzon Island; Po. monticola Beddard, 1912 from Mt. Pulong (Mt. Pulag), Benguet Province, and from Luzon Island; and Po. everetti and Po. elongata , both collected on Balabac Island, Palawan. Polypheretima perlucidula , Po. bannaworensis , Po. pagudpudensis and Po. monticola belong to the Po. bifaria species group of Easton (1979), characterised by having pairs of spermathecae in 5/6–8/9 or only in 6/7 or 7/8, while Po. fruticosa is closely related to Po. voeltzkowi Michaelsen, 1907 , characterised by having a pair of spermathecae in only in 5/6. The new species also differs from the other species in the number of setae between male pores, in the genital marking pattern and in the size and segmental position of the prostate glands ( Table 2).

Spermathecae function to receive and store sperm released by the male pores of the partner during copulation; loss of spermathecae usually means a loss of male function. Loss of spermathecae, reduction of testes and lack of spermatozoal iridescence in the sperm funnels in earthworms are indicative of reproduction by parthenogenesis ( Gates 1972), in which the egg develops into a new individual without being fertilised by sperm. In the case of Po. elongata , which has been introduced into many parts of the world (see Table 4), Easton (1979) observed that athecate individuals are especially numerous in introduced populations, presumably reproducing parthenogenetically.

In one specimen of Po. mindanaoensis sp. nov., the ventral nerve cord has a solid dark core, perhaps related to parasitism. We observed several nematodes near an empty nerve cord swelling in xvii.

Occurrence

Polypheretima mindanaoensis sp. nov. was found at two of five collecting sites. In all, eight individuals were collected in disturbed forests in Barangays Lake Duminagat and Sibucal at elevations of 902–1662 m a.s.l. The soil it inhabited was covered with thick leaf litter and roots, bryophytes and lichens. We did not observe it on rotten logs.

Figures

Figure 2. Schematic drawings of the external anterio-ventral area of (A) Polypheretima mindanaoensis sp. nov., (B) Pithemera malindangensis sp. nov., (C) Pithemera duminagati sp. nov. and (D) Pithemera donvictorianoi sp. nov. Abbreviations: fp, female pore; cl, clitellum; mp, male pore; gm, genital markings. Scale bars: 5 mm.

Figure 3. Schematic drawings of the internal morphology of (A) Polypheretima mindanaoensis sp. nov., (B) Pithemera malindangensis sp. nov., (C) Pithemera duminagati sp. nov. and (D) Pithemera donvictorianoi sp. nov. Abbreviations: s, spermatheca; n, dense tufts of nephridia; h, heart; p, prostate gland; c, caecum. Scale bars: 5 mm.