Pheretima lago, Aspe, Nonillon M. & James, Samuel W., 2014

Aspe, Nonillon M. & James, Samuel W., 2014, New species of Pheretima (Oligochaeta: Megascolecidae) from the Mt. Malindang Range, Mindanao Island, Philippines, Zootaxa 3881 (5), pp. 401-439 : 413-414

Pheretima lago n. sp.

( Fig. 4 A, Table 2)

Material examined. Holotype: adult (NMA 4508), Brgy Lake Duminagat, municipality of Don Victoriano, Misamis Oriental Province, Mt. Malindang Range (8º17'55"N, 123º37'01"E), 1500 m asl., Mindanao Island, Philippines, coll. Nonillon Aspe, Nolan Aspe, and J. Adeva, Oct. 9–15, 2003. Paratypes: one adult (NMA 4533); two adults ( ZRC.ANN.0018), same collection data as for holotype.

Etymology. The species name 'lago' means 'large worm' in the Cebuano dialect of the Philippines.

Diagnosis. Worms large, up to 315 mm long; dorsum dark, gradually fading towards ventral side; one pair of spermathecal pores at 7/8; relatively small spermathecae, diverticula with 2–4 chambered receptacles; intestine originating in xiv; hearts in xi to xiii, lacking in x, prostate glands located mostly anterior to copulatory bursae; 36–38 intestinal vessels.

Description. Living individuals with dark-brown to black dorsum anteriorly, lighter posteriorly, with gradually widening, non-pigmented equators; head setal rings with very thin non-pigmented area. Length 223–315 mm (n= 4 adults); diameter 10–11 mm at x, 10–11 mm at xx; body cylindrical in cross-section, tail narrowing abruptly in last 6 segments; 116–134 segments. First dorsal pore at 12/13; inconspicuous spermathecal pores one pair in 7/8, 0.18–0.24 circumference apart ventrally; female pore single in xiv; openings of copulatory bursae paired in xviii, 0.15 circumference apart ventrally, 0–2 setae between openings. Clitellum annular, extending from xiv to xvi. Setae unevenly distributed; 49 setae on vii, 53 setae on xx, dorsal gap present, ventral gap absent.

Septa 5/6– 7 /8, 10/11–13/14 muscular, 8/9 thin, 9/10 absent. Dense tufts of nephridia on anterior faces of 5/6 and 6/7; nephridia of intestinal segments sparser on segmental equators. Large gizzard extending from ix to x; esophagus with low vertical lamellae within x to xiii; intestinal origin in xiv; slender caeca originating in xxvii, extending forward to xxi, ventral margins slightly incised; typhlosole originates in xxvii, simple fold of 1/5 lumen diameter; intestinal wall with 36–38 longitudinal blood vessels.

Hearts in xi to xiii, esophageal; hearts in x much reduced, hidden under membrane that is perhaps remnant of septum 9/10; commissural vessels vi, vii, and ix lateral; those in viii extend to gizzard; supra-esophageal vessel extends from xi to xiii; extra-esophageal vessel joins ventral esophageal wall in x, receives efferent parietoesophageal vessel in xiii, with upper and lower branches.

Ovaries and funnels free in xiii; spermathecae paired, preseptal in vii, with nephridia on ducts; each spermatheca with large irregular rounded ampulla, stout muscular duct, stalked diverticulum attached to duct near ampulla, terminating in 2–4 chambered receptacle; stalks long, muscular. Spermathecal ducts fluted internally and off center from duct axis, ducts bearing rosette-shaped structure engorged with blood. Numerous ovate to pyriform spermatophores in each ampulla, tails longer than spermatophore body. Male sexual system holandric; testes and funnels enclosed in ventrally paired sacs in x and xi; seminal vesicles in xi and xii, each with long digitate dorsal lobe; vasa deferentia slender, free from body wall en route to ental end of prostatic ducts; each prostate racemose, with 6–7 main lobes in xiv to xviii; short, curved muscular duct enters anterior surface of copulatory bursa; paired elongate copulatory bursae extend from xvii to xx, coelomic surface of copulatory bursae muscular, secretory diverticula lacking; posterior portion of bursae filled with solid glandular tissue; long penis in anterior chamber of bursa; half-circle collar around anterior base of penis; copulatory bursae lack penial sheaths. Three long ridges in bursae, lateral to opening, one each on roof, floor, and lateral face of chamber.

Remarks. Pheretima lago n. sp. belongs to the P. sangirensis group of Sims & Easton (1972) but differs from all subspecies of P. sangirensis in having septa in 8/9, preseptal spermathecae in vii, and the intestine originating in xiv. It is a large worm, similar in size to P. ceramensis and P. s. crassicystis , but P. ceramensis has the intestine originating in xv and has shorter caeca (xxvii–xxiv), and P. s. crassicystis has no dorsal setal gap, the septum in 8/9 is lacking, and the prostates extend from xvii–xix. Pheretima lago is the second largest Pheretima species from Mt. Malindang next to P. immanis n. sp. Pheretima lago n. sp. differs from P. i m m an i s and another large worm, P. t igris n. sp., in pigmentation pattern, in having a dorsal setal gap, in the origin of the gizzard, in having spermathecal diverticula with chambered receptacles, in the number of hearts, in the extent of the caeca, in the number of intestinal vessels, and in having long penes ( Table 2). Pheretima lago is similar to P. c a l l os a James, 2004 in size, but the latter has 3 pairs of spermathecal pores in 6/7–8/9, the intestinal origin in xv, and prostates confined to xviii.

Occurrence. Pheretima lago was found at elevations of 900–2030 m asl. It was common at higher elevations in primary forest in Brgy Lake Duminagat, but uncommon at lower elevations (Table 1).

Figures

FIGURE 4. Schematic drawings of the internal morphology of Philippine Pheretima species, in dorsal view: (A) P. lago n. sp.; (B) P. nunezae n. sp.; (C) P. boniaoi n. sp. Abbreviations: s, spermatheca; h, heart; p, prostate gland; cb, copulatory bursa; c, caecum. Scale bars: 10 mm.