Pheretima immanis, 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 : 412-413

Pheretima immanis n. sp.

( Figs 2 C, 3D, Table 2)

Material examined. Holotype: adult (NMA 4507), Brgy Lake Duminagat, municipality of Don Victoriano, Misamis Occidental 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. Paratype: one adult, tail end missing ( ZRC.ANN.0017), same data as for holotype.

Etymology. The species name is from the Latin 'immanis' (huge, enormous), referring to the large size.

Diagnosis. Adults large, reaching 365 mm in length; thick dark purple to black dorsal stripes at intersegmental furrows, equators unpigmented; one pair of spermathecal pores at 7/8; spermathecae, prostate glands and copulatory bursae small relative to body size; penes lacking; 28–32 intestinal vessels.

Description. Living animals with iridescent, broad, dark blue-purple to black dorsal pigment stripes at intersegmental furrows; stripes narrow ventrally to fine points, non-pigmented equators widest ventrally. Length 365 mm (n= 1 adult), diameter 17 mm at x, 18 mm at xx; body cylindrical in cross-section; 119 segments. First dorsal pore at 12/13; spermathecal pores one pair at 7/8, 0.12 circumference apart ventrally; female pore single in xiv, openings of copulatory bursae paired in xviii, 0.14 mm circumference apart ventrally, 5 setae between openings. Clitellum annular, extending from xiv to xvi. Setae unevenly distributed; 61–69 setae on vii; 63–68 setae on xx; no dorsal or ventral gaps.

Septa 5/6 and 7/8 slightly muscular, 10/11–15/16 muscular, 8/9 thin, 9/10 absent. 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 at anterior and posterior faces of septa. Large gizzard extending from viii to x, esophagus with low vertical lamellae from x to xiii; intestine originates in xvi; caeca originate in xxvii, extend forward to xx; typhlosole originates in xxvii, simple fold ¼ lumen diameter. Intestinal wall with 28–32 longitudinal blood vessels.

Hearts in x to xiii, esophageal; commissural vessels vi, vii and ix lateral; those in viii extend to gizzard; supraesophageal vessel extends from x to xiii; extra-esophageal vessels join ventral esophageal wall in x, receive efferent parieto-esophageal vessels in xiii.

Ovaries and funnels free in xiii; spermathecae paired, postseptal in viii, with nephridia on ducts; each spermatheca with large, rounded rectangular ampulla, stout muscular duct, stalked diverticulum attached to duct near ampulla, terminating in oblong receptacle wider at distal end, attached by its side near narrow ental end; stalks short. Four spermatophores present in each ampulla. Male sexual system holandric; testes and funnels enclosed in paired sacs in x and xi; seminal vesicles xi and xii each with dorsal lobe; vasa deferentia slender, free from body wall en route to ental end of prostatic ducts; each prostate densely racemose, in xvii and xviii, muscular duct attached to surface of hemispheric copulatory bursa, entering posterior dorsal face of copulatory bursa; paired small copulatory bursae extend from xvi to xvii; coelomic surfaces of copulatory bursae muscular, secretory diverticula lacking; floor of bursae with two small pads lateral to opening; penes absent.

Remarks. A member of the P. sangirensis group, P. immanis n. sp. is by far the largest of any earthworm species previously known from the Philippines. Other large-sized worms in the Philippines include P. vi rga t a James, 2004 (length 290 mm) from Mt. Kitanglad; P. barligensis Hong & James, 2011b (length 225–255 mm) from Mt. Province on Luzon Island; P. ca l l os a Gates, 1937 (length 330 mm) from Benguet on Luzon Island; and P. maculodorsalis n. sp. (length 226–235 mm), P. tigris n. sp. (length 230–283 mm), and P. l ago n. sp. (length 223–315 mm) described herein. Pheretima immanis differs from these species in pigmentation pattern; the origins of the intestine; the shape and size of spermathecae, diverticula, prostates and copulatory bursae; and the lengths of the caeca. Pheretima immanis , with one pair of spermathecae in viii, differs from the large worms P. barligensis (4 pairs in 5/6–8/9) and P. c al l o s a (3 pairs in 6/7–8/9). Pheretima immanis is most similar to P. tigris in having dorsal stripes, in the arrangement of septa and the origins of the intestine and typhlosole, and in lacking penes; both also lack setal gaps on the dorsum and ventrum. However, mature individuals of P. immanis reach a larger size, and the dorsal stripes are much thicker than those of P. tigris . Internally, the two species differ in the extent of the caeca, the size and position of prostate glands and copulatory bursae ( Table 2), the number of intestinal vessels, and the shape and size of spermathecae. Other large worms in the P. sangirensis group are P. ce r a m e n s i s (140–440 mm) and P. s. crassicystis (240 mm), but these two species markedly differ from P. immanis in having pigmentation all over the body. Moreover, P. ceramensis has the intestinal origin in xv and has shorter caeca (xxvii–xxiv); P. crassicystis has no septa in 8/9, the prostate is a bit longer (xvii–xix), and the caeca are shorter (xxvii–xxii). The largest Pheretima species in the world, which Blakemore et al. (2007) identified as P. darnleiensis , reaches 700 mm in length; that species differs markedly from P. immanis in having 4 or 5 pairs of spermathecal pores located in 5/6–8/9.

Occurrence. Pheretima immanis was found at elevations of 915–2027 m, but was somewhat more common at elevations above around 1480 m than at lower elevations (Table 1).

Figures

FIGURE 2. Photographs of living Pheretima worms in dorsal view, showing coloration. (A) P. maculodorsalis n. sp.; (B) P. tigris n. sp.; (C) P. immanis n. sp.; (D) P. longigula n. sp.; (E) P. malindangensis n. sp. Scale bars: A – D, 5 cm; E, 3 cm.