Amynthas magnaprostata, Aspe & Manasan & Manlavi & Patiluna & Sebido & Obusan & Simbahan & James, 2021

Aspe, Nonillon M., Manasan, Rafael Ethan, Manlavi, Albert B., Patiluna, Ma. Lotus E., Sebido, Maria Asela B., Obusan, Marie Christine M., Simbahan, Jessica F. & James, Samuel W., 2021, The earthworm fauna of Palawan, Philippines with description of nineteen new pheretimoid species (Clitellata: Megascolecidae), Journal of Natural History 55 (11 - 12), pp. 733-797 : 777-779

Amynthas magnaprostata sp. nov.

( Figure 17 )

Material examined

Holotype: adult ( MSUN-A014 ), Brgy. Pasadena, municipality of El Nido (11.216°N, 119.450° E), 196 m asl, Palawan Province, Philippines, coll. S. James, 27 September 2005 . Paratype: one adult amputee ( MSUN-A 015), same collection data as for holotype.

Etymology

The word ‘magnaprostata’ is Latin referring to the species’ large prostates relative to its size, covering seven segments, from xiv to xxi.

Diagnosis

Brown worm with adult length 105 mm, diameter 4–4.5 mm; 110 segments; three pairs of spermathecal pores at 6/7–8/9; 51–56 setae on vii, 58–65 setae on xx; no setae between male pores; spermathecal pores 0.28 circumference apart ventrally; male openings 0.23–- 0.25 circumference apart ventrally; genital markings lacking; prostates large in xiv–xxi.

Description

Dark brown, equators pigmented. Length 105 mm (n = 1 adult); diameter 4–4.5 mm at x, 4.5 mm at xx; body circular in cross section, tail tapering; 110 segments. First dorsal pore at 12/13, three pairs of spermathecal pores at 6/7–8/9, spermathecal pores 3.3–4 mm (0.- 26–0.28 circumference apart ventrally). Female pore single in xiv, pair of male openings in xviii, distance between openings 3.2–3.5 mm (0.23–0.25 circumference apart ventrally), no setae between openings. Clitellum annular, from xiv to xvi. Setae unevenly distributed around equators in some segments; 51–56 setae on vii, 58–65 setae on xx, dorsal and ventral setal gaps present. Genital markings lacking.

Septa 4/5–8/9 and 10/11–13/14 thin, 9/10 lacking. Dense tufts of nephridia on anterior faces of 5/6 and 6/7; nephridia in intestinal segments located mainly on body near septum/body wall junction. Large gizzard in ix–x, oesophagus with low vertical lamellae x–xiii, intestinal origin in xiv; caeca simple, originating in xxvi, extending forward to xxi. Hearts in x–xiii, oesophageal; commissural vessels in vi, vii and ix lateral.

Ovaries and funnels free in xiii. Spermathecae paired, postseptal in vii, viii and ix, no nephridia on ducts.Each spermatheca with ovate ampulla with sausage-shaped apex; slender, bulbous, muscular duct; single stalked diverticulum attached to the ectal portion of the spermathecal duct; stalk long, convoluted, terminating in small, round receptacle. Male sexual system holandric; testes and funnels enclosed in paired sacs in x, xi; seminal vesicles in xi–xiii, each with digitate dorsal lobe; vesicles of xi enclosed in testes sac; vasa deferentia slender,free from body wall on way to ental end of prostatic ducts; prostates large, covering xiv–xxi; each prostate a single, dense, racemose mass; U-shaped duct from the lateral surface of prostate directed towards the body wall on xviii. Copulatory bursae lacking.

Remarks

Amynthas magnaprostata sp. nov. belongs to the Am. sieboldi group of Sims and Easton (1972) characterised by having three pairs of spermathecal pores in 6/7–8/9 and a holandric male system. Easton (1981) transferred Am. sieboldi to Metaphire due to the presence of copulatory bursae in the type specimen. James et al. (2005), supporting this move, proposed to rename the species group the aelianus group, after Am. aelianus Rosa, 1892 , that being the first in the species group list in Sims and Easton (1972). There are more than 50 species in this group coming from China and Eastern Asia ( Rosa 1890, 1891, 1896, 1901; Michaelsen 1895, 1896, 1900, 1907, 1922, 1923, 1924, 1928, 1931, 1934; Goto and Hatai 1899; Cognetti 1908; Beddard 1912; Chen 1930, 1931, 1933, 1936, 1946; Gates 1930, 1932, 1933, 1935; Hatai 1930; Kobayashi 1934; Ohfuchi 1951, 1956; Tsai 1964; Qiu 1992; Qiu et al. 1993; Tsai et al. 1999; Hong et al. 2001; Hong and Kim 2002, 2005; Shen et al. 2003, 2014; James et al. 2005; Zhao et al. 2013, 2018; Dong et al. 2018; Hong 2019), including the new species, which is the first record of this group in the Philippines. However, it is not very clear which of the species have copulatory bursae, and James et al. (2005) proposed to review the definition of the character ‘copulatory bursae’. Aspe and James (2014) suggested the relative size of the copulatory bursae be a distinguishing character for Pheretima vs Metaphire , with species in Pheretima tending to have more prominent, dome-shaped, intra-coelomic copulatory bursae than those in Metaphire , while there are none at all in Amynthas . James et al. (2005) also proposed a critical review of the assignments of species to genera based on this character, and this is especially important since Zhao et al. (2015) demonstrated the non-monophyly of both Amythas and Metaphire , showing their scattered positions in the phylogenetic tree. As earthworm taxonomists continue to use the Am. sieboldi species group (e.g. Zhao et al. 2013, 2018; Shen et al. 2014; Dong et al. 2018; Hong 2019; although Bantaowong et al. (2014, 2015) have adopted the Am. aelianus species group), following the majority and the more updated references, here we also use the Am. sieboldi group.

Many members of the Am. sieboldi group have genital markings. Among the members of this group, Amynthas magnaprostata sp. nov. is relatively similar to Am. apapillatus Zhao et al. 2013 , Am. dongyinensis Shen et al. 2014 , Am. udei Rosa, 1896 , Am. kamitai Kobayashi, 1934 and Am. minjae Hong et al. 2001 in size and in having no genital markings. However, Am. apapillatus and Am. dongyinensis have significantly more space between spermathecal pores and between male pores (0.4 and 0.6, respectively, in Am. apapillatus and 0.28–0.31 and 0.31, respectively, in Am. dongyinensis vs 0.26–0.28 and 0.23–0.25, respectively, in Am. magnaprostata sp. nov.) and have smaller prostates (xvii– xviii in Am. apapillatus and xvi–xxi in Am. dongyinensis vs xiv–xxi in Am. magnaprostata sp. nov.); Am. udei has fewer segments (90 vs 110 in Am. magnaprostata sp. nov.) and fewer setae (~40 vs 51–65 in Am. magnaprostata sp. nov.) and has 8 setae between male pores (vs 0 in Am. magnaprostata sp. nov.); and Am. kamitai and Am. minjae have more setae on xx (70–71 vs 58–65 in Am. magnaprostata sp. nov.) and between male pores (13–15 vs 0 in Am. magnaprostata sp. nov.). The latter three species also have smaller prostates compared with the new species (xviii in Am. udei , xvii–xix in Am. kamitai and xvii–xx in Am. minjae vs xiv–xxi in Am. magnaprostata sp. nov.). Amynthas crassitubus Qiu and Dong, 2018 in Zhao et al. 2018 and Am. hupeiensis Michaelsen 1895 are also similar to the new species in size but both of the latter species have genital markings. In addition, Am. crassitubus has significantly more space between spermathecal pores (0.4) and between male pores (0.4), has fewer setae on vii (20–22) and has 12 setae between male pores, while Am. hupeiensis has more segments (119–132) and has 10–16 setae between male pores.

Figures

Figure 17. Amynthas magnaprostata sp. nov. (a) External ventral view. (b) Internal dorsal view. (c) Spermathecae. Abbreviations: c, caecum; fp, female pores; mp, male pores; p, prostate gland; s, spermathecae; sp, spermathecal pores; sv, seminal vesicles.