Amynthas triatmowidii, Amaliah & Fahri & Nguyen, 2024

Amaliah, Rizki, Fahri, F. & Nguyen, Anh D., 2024, New species and new record of the genus Amynthas Kinberg, 1867 (Oligochaeta: Megascolecidae) from Sulawesi, Indonesia, Raffles Bulletin of Zoology 72, pp. 116-126 : 118-121

Amynthas triatmowidii , new species

( Table 1–2, Fig. 2 )

Material examined. Holotype: Clitellate ( MZB. Oli 0067), primary forest, near Lake Kalimpa’a , Lore Lindu National Park (01°19′35.27″S, 120°18′36.71″E), elevation of 1,674 m asl, South Kulawi, Central Sulawesi Province, Indonesia, leg. Rizki Amaliah et al., 1 November 2016 . Paratype. One mature ( UNTAD. Oli 012), same data as for holotype .

Diagnosis. Small worms, length 67–98 mm, diameter 1.5–2.0 mm, and segments 67–115. Prostomium epilobous. First dorsal pore in 12/13. Setal numbers: 25–37 in v, 28–44 in vii, 35–41 in viii, 31–52 in xxv, and 8–10 between male porophores in xviii. Three pairs of spermathecal pores in lateroventral 6/7/8/9. Male pores simple, paired in xviii. Genital markings absent. Septa 8/9/10 absent. Spermathecal ampulla oval-shaped, duct enlarged, about 1/2 as long as ampulla. Diverticulum cylindrical, stalk coiled, about 3/4 as long as ampulla, attached to duct. Holandric, prostate glands paired in xvi–xx. Intestinal caeca simple and smooth, paired in xxvii.

Description. External characters. Body generally cylindrical, small-sized, length 67–98 mm (n=2), diameter 1.5–2.0 mm, and segments 67–115. For living specimens, colouration dark brown on dorsum and light brown on ventrum. For fixed specimens, colouration yellowish light brown on ventrum.

Prostomium epilobous. First dorsal pore in 12/13. Perichaetine, setal numbers: 25–37 in v, 28–44 in vii, 35–41 in viii, and 31–52 in xxv and 8–10 between male porophores in ventral xviii; setal distance: aa=ab, zz=1–2zy. Clitellum annular, within xiv–xvi, smooth without setae and dorsal pores. Female pore single, mid-ventral in xiv.

Spermathecal pores small, lateroventrally paired in 6/7/8/9, distance between spermathecal pores about 0.35x body circumference ventrally ( Fig. 2A ). Male pores simple on setal ring ( Fig. 2D ), paired in xviii, distance between male pores about 0.25x body circumference ventrally. Genital markings absent in both spermathecal and male pore regions ( Fig. 2A, D ).

Internal characters. Septa 3/4–7/8 thick, 8/9/10 absent, 10/11–12/13 thin. Oesophageal gizzard large in viii–x. Oesophageal hearts paired in xi–xiii. Intestine enlarged from xv; intestinal caeca paired in xxvii, extending anteriorly to xxv ( Fig. 2E ), simple and smooth. Typhlosole simple.

Spermathecae large, paired in vii–ix ( Fig. 2B ). Ampulla oval, duct enlarged, about 1/2 as long as ampulla. Diverticulum cylindrical, stalk coiled, about 3/4 as long as ampulla, attached to duct. No spermathecal accessory glands.

Holandric. Testes sacs yellowish, small, ventrally paired but separated in x–xi. Seminal vesicles well-developed in xi–xii. Ovaries paired in xiii; ovisacs paired in xiii. Prostate glands racemose, paired in xvi–xx ( Fig. 2C ); prostatic duct C-shaped. No prostatic accessory glands.

Etymology. This species is named after Prof. Dr. Tri Atmowidi, Chairman of the Animal Biosciences Study Program in IPB University for his great encouragement to reveal the diversity and ecology of earthworms and insect fauna in Indonesia, including Sulawesi Island. He is supervisor of RA and FF and also a colleague and partner of the Discovery Earthworms Project at Sulawesi in 2017–2023.

Habitat and ecology. Specimens were collected in primary forest near Lake Kalimpa’a, Lore Lindu National Park, South Kulawi, Central Sulawesi at the elevation of 1,674 m asl. This species was found at the depth of 15–20 cm in moist and sandy soils around rocks and decayed wood.

Remarks. This new species belongs to the A. sieboldi group characterised by three pairs of spermathecal pores in intersegments 6/7–8/9 and a holandric male sexual system ( Sims & Easton, 1972; James et al., 2005). Previously, the A. sieboldi group was renamed the A. aelianus group (James, 2005) and the name has been adopted by Bantaowong et al. (2014, 2015, 2023). However, owing to the lack of clarity regarding the defining character of the A. aelianus group and pending resolution of its phylogeny, we follow Aspe et al. (2021) in recognising the A. sieboldi group, along with the majority of earthworm taxonomists, e.g., Zhao et al. (2013, 2018), Shen et al. (2014), Dong et al. (2018), and Hong (2019).

This new species is similar to A. aelianus ( Rosa, 1892) from Bua-Bua, Enggano (Sumatra) in characters such as the absence of genital markings and body length. However, they differ in the number of segments (67–115 vs. 115–120), shape of ampulla (ampulla oval, duct enlarged, about 1/2 as long as ampulla vs. oval sac with slender short ducts), diverticula shape (diverticula cylindrical, about 3/4 as long as ampulla, duct looks like a circular vs. slender diverticula and longer than spermathecae), intestinal caeca (xxv–xxvii vs. xxiii–xxvii), and prostate position (xvi–xx vs. xvii–xix) ( Table 2).

This new species is similar to A. udei ( Rosa, 1896) from Mt. Si-Rambe, Sumatra and A. dammermani ( Michaelsen, 1924) from Mt. Krakatau, Sumatra, in the absence of genital markings, as well as small and simple male pores. However, these three species are different in prostate position (five segments on xvi–xx vs. one segment in A. udei vs. three segments in xvii–xix in A. dammermani ), diverticulum (stalk coiled as a circle, about 3/4 as long as ampulla in A. triatmowidii , new species vs. short, straight stalk with an oval seminal chamber in A. udei vs. long, coiled, spiralshaped stalk and more than twice as long as the ampulla in A. dammermani ) ( Table 2).

When compared with species from Java, this new species is similar to A. buitendijki ( Michaelsen, 1922) from Sukabumi, Java in colour, absence of genital markings, five prostate segments in xvi–xx, and simple male pores on setal ring. However, these two species are different in number of setae (less than 60 in A. triatmowidii , new species vs. more than 60 in A. buitendijki ), ventral distance between spermathecal pores (0.35x vs. 0.3x body circumference) and shape of spermathecae (oval ampulla with an enlarged duct and a diverticulum coiled as a circle in A. triatmowidii , new species vs. elongated, sack-shaped ampulla with a short duct and a long, heavily coiled diverticulum in A. buitendijki ). This new species is also different from A. buitendijki in the development of intestinal caeca (three segments vs. more than four segments) ( Table 2).

The new species is also similar to A. dongyinensis Shen, 2014 from Dongyin, Matsu, Taiwan in spermathecal pores in 6/7/8/9, holandry, absence of genital markings, setal numbers, and distance between male pores (0.25x vs 0.26–0.3x body circumference). However, those two species are different in the spermathecal shape (oval ampulla with an enlarged duct and a diverticulum coiled as a circle in A. triatmowidii , new species vs. round, peach- or elongated oval-shaped ampulla with a stout duct and a diverticulum with a straight stalk and an oval- or rod-shaped seminal chamber in A. dongyinensis ), and the male sexual system (yellowish, small, ventrally paired testes sacs, but separated in x–xi vs. two pairs of large, oval testes in ventrally joined sacs in x and xi) ( Table 2).

This new species also resembles A. magnaprostata Aspe et al., 2021 from Palawan, Philippines by having spermathecal pores in 6/7/8/9, holandry male system, and absence of genital markings. However, those two species are different in size (67–98 mm, diameter 1.5–2.0 mm in A. triatmowidii , new species vs. 105 mm, diameter 4–4.5 mm in A. magnaprostata ), the number of setae in vii (28–44 setae in A. triatmowidii , new species vs. 51–56 setae in A. magnaprostata ), the position of intestinal caeca (originating in xxvii, extending anteriorly to xxv in A. triatmowidii , new species vs. originating in xxvi, extending anteriorly to xxi in A. magnaprostata ), and the spermathecal shape (oval ampulla with an enlarged duct and a diverticulum coiled as a circle in A. triatmowidii , new species vs. ovate ampulla with sausage-shape apex, slender and muscular duct, and single stalked diverticulum in A. magnaprostata ) ( Table 2).

Figures

Fig. 2. Amynthas triatmowidii, new species, holotype, MZB. Oli 0067. A, spermathecal pores (sp) B, spermathecae, right side in vii–ix (amp = ampulla; dv = diverticulum) C, prostate gland D, male pore region (mp = male pore) E, intestinal caecum. Scale bars = 1 mm.