Amynthas carnosus ( Goto & Hatai, 1899 )

Carrera-Martínez, Roberto & Snyder, Bruce A., 2016, First report of Amynthas carnosus (Goto & Hatai, 1899) (Oligochaeta: Megascolecidae) in the Western Hemisphere, Zootaxa 4111 (3), pp. 297-300 : 297-299

Amynthas carnosus ( Goto & Hatai, 1899)

Perichaeta carnosa Goto & Hatai, 1899: 15 , 24, Figs. 4, 5. Pheretima carnosa: Michaelsen 1900: 260 –261.

Amynthas carnosus: Sims & Easton 1972: 235 . Blakemore 2012: 36 –40, Fig. 1 .

Description. Length 150–180 mm. Width 7 mm. Live specimens dark brown or purple dorsally, yellowish ventrally. Preserved specimens lost little pigment within the first six months of storage. Prostomium epilobic. Setae perichaetine. 16–19 setae between male pores. Four paired spermathecal pores just anterior to 5/6–8/ 9 in four of the earthworms. The fifth earthworm had three paired spermathecal pores from 6/7–8/9. First dorsal pore on 12/13. Clitellum at xiv–xvi, annular, cream-yellowish coloration in live and brown in preserved specimens. Two pairs of pre-clitellar genital markings pre-setal on viii and ix; pair on ix spaced further apart than the pair on viii (markings on ix more lateral, similar to the neotype as drawn in Blakemore 2012). Up to three pairs of genital markings near male pores on xviii. First pair pre-setal on xviii, slightly median to male pores; second pair post-setal and more medial than the first; third pair pre-setal on xix, slightly more lateral than the second pair, but not as lateral as the first pair ( Figure 1 B). This arrangement is similar to Figure 3, Type V of post-clitellar genital markings in Blakemore (2012), but with the first and third pairs of genital marking slightly lateral to the second pair. All three pairs were present in two octothecal specimens. Two octothecal specimens had only three genital markings comprised of the post-setal xviii pair and a single marking in xix (left side in one specimen, right side in the other). The sexthecal specimen was only lacking the pre-setal xviii genital marking on the left side. Spermathecae in vi–ix, or vii–ix (in the specimen with only three pairs of spermathecal pores). Gizzard viii–ix. Intestinal origin xv. Intestinal caeca simple, beginning in xxvii and extending anteriorly for 3–4 segments. Prostate glands racemose, ducts in xviii, and extending anteriorly 1–2 segments and posteriorly 1–3 segments.

Following the keys by Reynolds (1978) or Gates (1982), specimens of A. carnosus might be misidentified as A. corticis Kinberg, 1867 , A. gracilis Kinberg, 1867 , or as A. hupeiensis Michaelsen, 1895 . Additionally, Blakemore (2012, 2013b) reported that A. carnosus has been misclassified as A. corticis and A. gracilis . Figure 1 compares key external features of A. corticis , A. carnosus , and A. gracilis . Externally, octothecal A. carnosus might be differentiated from A. corticis , which is also octothecal, by the two pairs of genital markings usually median and anterior to the setal line at viii and ix and by the genital markings median to the male pores and sometimes extending to anterior xix ( Blakemore 2012); A. corticis normally has three small paired genital markings on vii–ix adjacent to the spermathecal pores, and rarely median to the male pores (cf. Fig. 1 A and 1B) ( Gates 1972; Borges & Moreno 1990; Blakemore 2013b).

The sexthecal morph of A. carnosus has also been misidentified as A. gracilis in the past, due to similar genital markings median to the male pores and because A. gracilis is sexthecal. The spermathecal pores on A. gracilis are located on 5/6–7/8 ( Gates 1972), while in the sexthecal morph of A. carnosus spermathecal pores are located at 6/7–8/9 ( Blakemore 2012; our specimens). Amynthas gracilis has been reported to also have genital markings near the spermathecal pores, but not commonly paired and usually extending from vi–ix ( Gates 1972, 1982). The genital markings on A. gracilis median to the male pores are arranged as clusters of 1–11 markings posterior to the setae ( Gates 1972), while other authors reported fewer: one to three genital marks at each male pore ( Borges & Moreno 1990). The genital markings in A. gracilis are smaller than those of A. carnosus (cf. Fig. 1 B and 1C). Male pore-associated genital markings on A. carnosus are highly variable ranging from no genital markings up to 6 individual markings, which might not always be paired and might extend to be on the anterior part of xix ( Blakemore 2012). The first dorsal pore on A. gracilis is usually at 10/11 ( Gates 1972, 1982; Borges & Moreno 1990) and at 11/12 on A. corticis ( Gates 1972; Borges & Moreno 1990), while in A. carnosus it is on 12/13 ( Blakemore 2012). Specimens from North America previously classified as A. corticis or A. gracilis should be carefully reexamined to confirm their identity.

Amynthas hupeiensis is sexthecal with spermathecal pores in the same locations as A. carnosus , but is easily differentiated by the color of live specimens. Amynthas hupeiensis is usually green, while A. carnosus is brown-purple colored ( Blakemore 2012). In addition, A. hupeiensis is usually smaller than A. carnosus .

Amynthas carnosus is known to have a wide range in Asia: it has been reported in Korea, Japan, and China ( Blakemore 2003; 2012; 2013a; Blakemore et al. 2006; Blakemore & Lee 2013). Approximately 10–20 species of this genus are known to be peregrine species ( Edwards & Bohlen 1995; Hendrix et al. 2008). As the vector for introduction of this species can only be speculated, it might have been used as fishing bait, as the area of collection is popular among anglers (C. Berry, pers. comm.). It also appears that A. carnosus might be well established in the area, as it was collected in a relatively high number. The potential of A. carnosus as a peregrine species is yet to be determined, and effects of its colonization are unknown. Close attention should be given to the ecological effects after the establishment of this species, due to the known effects of related species (e.g., Snyder et al. 2011; Greiner et al. 2012).

Figures

FIGURE 1. Diagram of pores and genital markings in a ventral view of A) Amynthas corticis, B) A. carnosus, and C) A. gracilis. ♂ = male pores, ♀ = female pores, ⚥ = spermathecal pores.