Acanthodrilus millei, Csuzdi & Pearlson & Pavlíček, 2017

Csuzdi, Csaba, Pearlson, Oren & Pavlíček, Tomás, 2017, New Acanthodrilus species from New Caledonia (Clitellata, Megadrili, Acanthodrilidae), Journal of Natural History (J. Nat. Hist.) 51 (31 - 32), pp. 1899-1912 : 1904-1905

Acanthodrilus millei sp. nov.

Figure 3

Type material

Holotype. HNHM / AF5681 , clitellate adult, tail missing. New Caledonia, Blue River Provincial Park (22.11° S, 166.69° E), rain forest, 1 February 2014, leg. T. Pavlí Č ek and O. Pearlson . Paratype: HNHM / AF5682 , one clitellate adult ex ., locality same as that of holotype.

Etymology

The new species is named in honour of Christian Mille for his generous help during the collecting trip to New Caledonia.

Diagnosis

L. 30–40 mm. D. 2.5 mm. Average weight 0.15 g. Colour red-violet. First dorsal pore in 12/13. Clitellum ½13–½17, circular. Prostatic pores paired in 17, 19. Penial setae L. 3.5 mm, D. 0.063 mm, ornamentation group of spines. Spermathecal pores 7/8, 8/9 b. Muscular gizzard in 6, calciferous glands lacking. Last pair of hearts in 13. Spermathecae with long narrow duct and a somewhat shorter oval ampoule joining the duct in right angle. The duct entally bears a small diverticulum filled with sperm-chambers. Genital setae lacking.

Description

Holotype. L. 30 mm, D. 2.5 mm, No. segments 63, tail missing.

Paratype. 22 mm in length, 2.5 mm in diameter, No. segments 62, tail missing. Colour red-violet. Prostomium tanylobous, the first dorsal pore occurs in the intersegmental furrow 12/13. Setae closely paired, setal formula after the clitellum aa:ab:bc:cd: dd = 5.6:1.2:6:1:25. The clitellum extends over segments ½13–½17, circular ( Figure 3a ). Prostatic pores paired on 17, 19. Male pores externally clearly visible on segment 18, in the laterally highly convex seminal grooves. Female pores paired on 14, small slits just anterior to setae a–a. Spermathecal pores clearly visible in furrows 7/8, 8/ 9 in setal line b. Nephridiopores aligned in setal line cd. Genital papillae lacking.

Internal characters

All septa membranous. Oesophageal gizzard large in 6. Calciferous glands lacking, intestine gradually widens from segment 17 but reaches full width in 19. Typhlosole lacking. Excretory system holoic, nephridial bladders J-shaped ( Figure 3b ). Paired hearts are present in segments 10–13. Testes are in 10, 11 enclosed in the cavity formed by the fused septa 9/10–11/12. Two pairs of seminal vesicles present in 9, 12. A pair of small ovaries in segment 13. Two pairs of prostates present in 17, 19. The glands are long, reaching up to segment 28. Prostates accompanied by a penial setal sac containing an adult and several replacement setae. The adult seta 3.5 mm in length and the middle 0.063 mm wide, tip slightly bent, spoon-shaped, ornamentation consists of scattered groups of 3–5 spines ( Figure 3c ). Two pairs of spermathecae present in segments 8 and 9. Each consists of a narrow and long duct and a somewhat shorter, oval ampoule. The ampoule joins the ental elbow of the duct almost at a right angle. The ental part of the duct just below the elbow bears a small diverticulum containing several small sperm chambers ( Figure 3d ). Genital setae lacking.

Remarks

The new species is one of the smallest Acanthodrilus . Unfortunately, the tail in both specimens available is truncated, but the real length of the species can be around 35 mm. The closest A. canalanus Michaelsen, 1913 is more than double-sized (70– 80 mm). The new species differs furthermore from A. canalanus in the shape and ornamentation of the penial setae and the form of spermathecae.

Figures

Figure 3. Acanthodrilus millei sp. n. (a) ventral view of the clitellar region; Fp, female pore; Mp, male pore; Prp, prostate pores; scale bar 1 mm. (b) nephridial bladder from the postclitellar segments. (c) penial seta; scale bar, 0.05 mm. (d) spermatheca.