Amynthas carnosus

## Source: ResearchGate

The earthworm fauna of North America is still greatly unknown, with undescribed native species and new records of

invasive species continually being discovered. The most recent checklists are difficult to reconcile, since they vary in

their geographic coverage and taxonomy. Reynolds & Wetzel (2012) state that North America (including all of Mexico,

some of the Caribbean, and Hawaii) is home for 256 species of earthworms, from which 188 are considered native or

endemic and 68 are peregrine, exotic, and invasive species. Blakemore (2008) listed North America north of Mexico as

having 183 earthworm species, of which 59 species are exotic. One Megascolecidae genus, Amynthas, is mostly located

in the warmer subtropical and tropical regions of the world, with a few species that are able to survive the winter in the

temperate zones of North America (Edwards & Bohlen 1995; Görres et al. 2014). Here we report for the first time the

occurrence of Amynthas carnosus (Goto & Hatai, 1899) in the United States. To our knowledge, this is not only the first

report of A. carnosus in North America, but also its first report in the Western Hemisphere. The description below is

intended to place our specimens in the correct taxon while avoiding future confusion with similar species, without

making changes to the existing classification system.

The material analyzed included five adult earthworms, of over 30 individuals collected by Christopher Berry and

Andrew Wendland near Tuttle Creek Observation Area, north of Manhattan, Riley County, Kansas, USA (39.2728°N,

96.6259°W). Collection was performed on 10 June 2015 by hand. The earthworms were found crawling on the surface of

the soil after several weeks of near-record rainfall, which saturated the soil and caused a large increase in the water level

of adjacent Tuttle Creek reservoir. All individuals were killed with 70% ethanol and fixed with 5% formalin for 4 days.

Fixed individuals were then permanently stored in 70% ethanol and reside in Snyder’s collection. External and internal

characteristics of each individual were described and compared to existing literature. The specimens studied follow the

redescription of A. carnosus by Blakemore (2012) within an acceptable range of variation for this species. Blakemore

(2012) based his redescription on the fixation of a neotype but still allowed, following Kobayashi (1936), considerable

morphological variation especially in the distribution of the genital markings. We also observed variations in the genital

markings, but the general pattern in our specimens is very similar to that of the neotype of A. carnosus (see below).

Subspecies are not considered here because they were erected mainly on differences in the COI barcode gene

(Blakemore 2013a,b), and COI barcode sequences are not available for our specimens.

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

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on xix, slightly more lateral than the second pair, but not as lateral as the first pair (Figure 1B). 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. 1A 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. 1B 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.

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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).

Acknowledgments

The authors are thankful for support by the Research Experiences for Undergraduates program in biology at Kansas State

University, National Science Foundation DBI-1156571. We also thank Chih-Han Chang for aid with initial determination

of the specimens and helpful comments on the manuscript, and Christopher Berry and Andrew Wendland for donating

the specimens examined in this article.