Amynthas corticis ( Kinberg, 1867 ), 2015

False synonymy between Amynthas corticis ( Kinberg, 1867) View in CoL and Amynthas sheni ( Chen, 1935)

Amynthas sheni ( Chen, 1935) from Hong Kong is an earthworm lacking spermathecae ( Chen 1935). This species is listed as a synonym of A. corticis with a question mark by Blakemore (2003; 2010; 2012; 2013b). Blakemore (2003, p. 16) cites Gates (1972, p. 217) and states that “ Pheretima sheni Chen, 1935 may be athecal morphs of either A. robustus or A. diffringens (= A. corticis ), most likely the latter”. Tsai et al. (2007, p. 365) elaborate differences between A. sheni and Amynthas robustus ( Perrier, 1872) and also those between A. sheni and A. corticis , and conclude that A. sheni is not referable to A. robustus and shows no affinity with A. corticis , either. An earthworm having no spermathecae is not necessarily the athecal morph of some other species. Among the 75 endemic earthworm species reported from Taiwan so far, eleven of them have variable numbers of spermathecae or even no spermathecae, and absence of spermathecae is commonly observed for seven of them. Among the eleven species, eight of them have been genetically proved distinctive including five species generally without spermathecae (Shen 2012; Shen et al. 2016; 2019). According to Semblat et al. (1998), for soil organisms particularly, parthenogenesis is likely to provide a selective advantage allowing conservation of the best adapted genotype for its specific environment. Parthenogenesis might have provided some benefits in propagation and survival for earthworms inhabiting the mountainous island of Taiwan with diverse habitats ( Shen et al. 2012). Tsai et al. (2007, p. 375) also state that “Apparently, parthenogenetic earthworms are highly adapted to various environments, and each species has its own independent evolutionary lineage”.

Furthermore, as indicated in Shen et al. (2024), A. corticis has no postsetal papillae on the ventral side of the preclitellar region except those above spermathecal pores. Nevertheless, A. sheni has postsetal papillae on ventrum of VIII and occasionally also on IX ( Fig. 4A View FIGURE 4 ). Additionally, A. sheni has four pairs of esophageal hearts in X–XIII, well-developed prostate glands in XVI–XXI and long, U-curved prostatic ducts ( Chen 1935), whereas A. corticis has three pairs of esophageal hearts in XI–XIII ( Chen 1931; 1933; Gates 1972; HPS, personal observation) and its prostate glands are often absent with prostatic ducts confined to XVIII ( Shen et al. 2024). In fact, Chen (1935) provides a detailed description of A. sheni which is not easy for readers to confuse with A. corticis . However, inadequate literature review is always a problem in earthworm taxonomy as addressed in Chang et al. (2024) and Shen et al. (2024). Worse still, it is not uncommon for researchers to refer to secondary citations rather than the original description. All these are sources of confusion and problems. HPS examined the type specimen of A. sheni deposited in the National Museum of Natural History, Smithsonian Institution, Washington, D.C., USA. (USNM no. 20181, Fig. 4A, B View FIGURE 4 ) on 7 September 2001. The result of this examination is consistent with the original description by Chen (1935).