Metaphire songkhramensis Chanabun & Panha, 2023

Chanabun, Ratmanee, Aoonkum, Anuwat, Seesamut, Teerapong, Bantaowong, Ueangfa & Panha, Somsak, 2023, Four new terrestrial earthworm species from the northeast Thailand (Oligochaeta, Megascolecidae), ZooKeys 1176, pp. 195-219 : 195

Metaphire songkhramensis Chanabun & Panha sp. nov.

Figs 1C , 3D , 4

Type material.

Holotype: Adult specimen (CUMZ 3821), Kong Ngong, Akat Amnuai, Sakon Nakhon, northeast of Thailand, 17°45'19.4"N, 104°01'18.8"E, 148 m a.m.s.l., 8 November 2022, coll. R. Chanabun, A. Aoonkum. Paratypes: 45 adults (CUMZ 3822), 2 adults (NHMUK), 2 adults (ZMH), same collection data as for holotype.

Diagnosis.

Large sized; length 229-427 mm, diameter 10-14 mm, 129-240 segments. Male pores paired in segment XVIII, each represented by a large invaginated area, conspicuous, deep holes that resemble eyes, genital markings absent. Spermathecal pores paired in intersegment 6/7-8/9. Spermathecae with large, round, and flat ampulla, with a long and thick duct, diverticulum thin, long, and zigzagged towards the distal end. No nephridia on the spermathecal duct. Holandric. Intestinal caeca simple. First dorsal pore in 12/13. Prostate gland large in XV-XXII, long, slender with U-shape duct, large paired of glandular masses on the copulatory sac, no genital marking glands.

Description of holotype.

Length 333 mm, diameter 12 mm, cylindrical body with 167 segments. Preserved specimens are dark brownish on the dorsal part and pale gray on the ventral part. Setae regularly distributed around segmental equators, numbering 65 at segment VII, 85 at segment XX, and nine between male pores at segment XVIII. Setal formula AA:AB:ZZ:ZY=1:1:2:1 at segment XIII. Single female pore on the ventral side at segment XIV. Prostomium epilobic. First dorsal pore in 12/13. Clitellum annular in XIV-XVI with no dorsal pores or setae.

Male pores in copulatory pouches that have wrinkled and convex margins on ventrolateral sides of segment XVIII; pouches 5 mm apart, which is 0.13 × the body circumference. These pores are large, conspicuous, deep holes that resemble eyes. There is no skin folding, and genital markings absent. Large spermathecal pores arranged in three pairs in ventral region 6/7-8/9, distance between each pair is ~ 0.26 × the body circumference ventrally apart. There are no genital markings in this area.

The septa at 5/6-7/8 thick, absent in 8/9-9/10, slightly thick in 10/11-11/12, thin in 12/13-14/15, and very thin behind 15/16. Intestine begins at segment XV. Gizzard large within IX-X. Long and simple intestinal caeca in XXVII-XIX. Esophageal hearts four pairs in X-XIII. Holandric; testes and funnels in segments X and XI. Seminal vesicles are paired, one at XI-XII, the other at XIII-XIV; the hindmost pair is larger. Prostate glands large, located in segments XV-XXII, and divided into several lobules. Prostate duct long, slender with U-shape, and with large paired glandular masses on the copulatory sac at segments XVII-XVIII and XIX-XX.

The ovaries are located in segment XIII. Three pairs of spermathecae present on VII-IX. Ampulla large, round, and flat-shaped, with long and thick duct that can be clearly seen from the ampulla. Diverticulum is thin, long, and zigzagged towards the distal end.

Variation.

Forty-nine paratypes ranged in size from 229-427 mm (318.75 ± 40.32 mm) body length with 129-240 (159.29 ± 19.77) segments.

Etymology.

This new species was named after its type locality, Songkhram River.

Distribution.

This species is known only from the type locality.

Remarks.

Metaphire songkhramensis is a new species of sexthecal earthworm without postclitellar genital markings. It has three pairs of spermathecal pores in intersegmental furrows 6/7-8/9. This species keys to the Metaphire houlleti species group, which has more than 40 species ( Sims and Easton 1972). Below, comparison of the new species with other species found in different regions in the Metaphire houlleti species group: M. umbraticola (Gates, 1932) and M. quadrigemina (Gates, 1932) from Myanmar, M. amplectens (Michaelsen, 1934), M. dawydovi (Michaelsen, 1934), M. acampanulata Nguyen, 2022 from Vietnam ( Nguyen et al. 2022), M. bindjeyensis (Michaelsen, 1899) from Sumatra, and M. hijauensis Ng & Panha, 2018 from Malysia ( Ng et al. 2018) are stated.

Metaphire songkhramensis sp. nov. differs from M. umbraticola and M. quadrigemina from Myanmar by having smaller size than the new species. Metaphire umbraticola which has a body size that ranges from 115-122 mm, a diameter of 6-7 mm, with 125-135 segments, M. quadrigemina which has a size that ranges from 64-72 mm by 3-4 mm, with 115, while the new species ranges from 229-427 mm, a diameter of 10-14 mm, with 129-240 segments.

Metaphire songkhramensis sp. nov. differs from M. amplectens , M. dawydovi , and M. acampanulata from Vietnam through the body size and spermathecae. Metaphire songkhramensis sp. nov. differs from M. amplectens by M. amplectens has a smaller body size than the new species (body length 44-52 mm, diameter 2½-3½ mm with 90-112 segments). Metaphire songkhramensis sp. nov. differs from M. dawydovi in that M. dawydovi has a smaller size (body length 275 mm, diameter 7 mm, with 160 segments), and flask-shaped ampullae with small diverticulum, whereas the new species has a larger body size with large, round, and flat-shaped ampullae with thin, long, and zigzag diverticulum. Metaphire songkhramensis sp. nov. differs from M. acampanulata from Vietnam in body size and spermathecae; the latter has a smaller size than the new species (body length 77-198 mm, diameter 4.03-6.91 mm with 56-144 segments), and ampulla mushroom-shaped with grooves on the surface while the new species has a larger size and has large, round, and flat-shaped of ampulla.

Metaphire songkhramensis sp. nov. similar to M. bindjeyensis from Sumatra in body size length but M. bindjeyensis obclavate ampullae with zigzag diverticulum, while the new species has a large, round, and flat-shaped ampulla with a thin, long, and zigzagged diverticulum. Metaphire songkhramensis sp. nov. differs from M. hijauensis from Malysia by the latter species has a smaller size than the new species (body size range 66-87 mm, diameter of 2.8-3.1 mm, with 101-120 segments), and the first dorsal pores in 10/11 while the new species has first dorsal pores in 12/13.

In Thailand, five species have been reported, M. houlleti (Perrier, 1872), M. virgo (Beddard, 1900), M. perichaeta (Beddard, 1900), M. khaochamao Bantaowong & Panha, 2016, and M. khaoluangensis Bantaowong & Panha, 2016. Metaphire songkhramensis sp. nov. can be distinguished from this group of five as follows: M. houlleti and M. virgo have first dorsal pores in 11/12 while the new species has first dorsal pores in 12/13, and a large, round, and flat-shaped ampulla with a thin, long, and zigzagged diverticulum (spherical and small sac in M. houlleti and M. virgo , respectively). The new species does not have the contorted diverticulum stalk enveloped in connective tissue as found in M. houlleti , and also lacks the typhlosole present in M. houlleti . Metaphire virgo has a spermathecal diverticulum stalk with multiple folds, while the new species is absent. Metaphire houlleti and M. virgo have genital markings bearing stalked glands in association with spermathecae and copulatory sacs, while the new species lacks them. This new species differs from M. perichaeta in that M. perichaeta has a smaller size, inverted pear-shaped spermathecae with coiled diverticulum, and the last hearts in XII ( Beddard 1900; Stephenson 1932). Metaphire songkhramensis sp. nov. differs from M. khaochamao and M. khaoluangensis , through the male opening, body size, and spermathecae. Metaphire khaochamao has smaller body size (body size range 100-148 mm, with 110-120 segments), the male field including the lateral slits associated with the male pores, the absence of setae between male pores, and an elliptic ampulla with a short duct. Metaphire khaoluangensis has smaller body size (body size range 130-265 mm, with 113-131 segments), a secondary male opening with puckered margin, an elongate ampulla, and a sac-like duct, whereas the new species has a larger size with setae between male pore, a large, round, and flat-shaped ampulla, and a thin, long, and zigzag diverticulum. A comparison of characters between M. songkhramensis sp. nov. and other related species is presented in Table 1 .

Figures

Figure 1. Collecting earthworms in the early morning of the winter season A villagers in Sakon Nakhon collect the migratory earthworms with their bare hands B large numbers of caught earthworms being sold to middlemen C Metaphire songkhramensis sp. nov. from Akat Amnuai, Sakon Nakhon, moving on the soil during the migration season, and D dried earthworms.

Figure 3. Photographs showing the A type locality of Metaphire songkhramensis sp. nov. from Kong Ngong, Akat Amnuai, Sakon Nakhon, Thailand B habitat of the new species covered with small bamboo and small shrubs C casts of the new species, and D coloration of newly collected paratype (CUMZ 3822) after the first preservation step in 30 % (v / v) ethanol.

Figure 4. External and internal morphology of Metaphire songkhramensis sp. nov., holotype (CUMZ 3821) A external ventral view B internal dorsal view, and C spermatheca with location of spermathecal pore arrowed.