Amynthas minimus ( Horst, 1893 )

Chang, Chih-Han, Snyder, Bruce A. & Szlavecz, Katalin, 2016, Asian pheretimoid earthworms in North America north of Mexico: An illustrated key to the genera Amynthas, Metaphire, Pithemera, and Polypheretima (Clitellata: Megascolecidae), Zootaxa 4179 (3), pp. 495-529 : 511-512

7. Amynthas minimus ( Horst, 1893)

( Figures 1 E, 13)

Perichaeta minima Horst, 1893: 66 .

Pheretima minima — Gates 1982: 57.

Amynthas minimus — Sims & Easton 1972: 236. Reynolds 1978: 127; 2011: 275. Reynolds & Wetzel 2004: 88; 2008: 180.

Data sources. Gates (1972, 1982); Chang et al. (2009a; for color of live specimens).

Diagnosis. Size 20–56 mm by 1.5– 2 mm. Segment numbers 77–115. Color of live specimens light red to reddish white. Male pores paired in XVIII, on a relatively large porophore. Post-clitellar genital markings unpaired, small mid-ventral tubercles, pre-setal on some of XVII, XIX–XXI. Spermathecal pores paired in 5/6 or absent. Preclitellar genital markings paired small pre-setal tubercles on some of V–VIII. Female pore single in XIV. First dorsal pore 11/12 or 12/13. Spermathecae present or absent; when present, one pair or single in VI, large. Prostate glands present or absent; when present, large, extending through some or all of XVI–XXIII. Intestinal caeca simple, extending anteriorly to XXIII.

Remarks. Easily distinguished from most pheretimoid species by its body size, A. minimus is one of the smallest pheretimoid earthworms in the world. It was first recorded in the continental US in 1969 in Louisiana ( Gates 1982). Reproduction of this species is parthenogenetic.

Figures

FIGURE 1. Color photographs of live individuals of (A) Amynthas agrestis, (B) Amynthas corticis, (C) Amynthas gracilis, (D) Amynthas hupeiensis, (E) Amynthas minimus, (F) Amynthas morrisi, (G) Amynthas tokioensis, (H) Metaphire californica, (I) Metaphire hilgendorfi, (J) Metaphire posthuma, (K) Pithemera bicincta, and (L) Polypheretima elongata, showing interspecific variations in colorations and body shapes. Specimens are from US (A, B, D, G, I) and Taiwan (C, E, F, H, J, K, L). Photo credit: Chih-Han Chang (A, B, D, E, G, H, I) and Wen-Jay Chih (C, F, J, K, L). The photographs of A. minimus and M. californica have been previously presented in Chang et al. (2009 a).