Metaphire hilgendorfi ( Michaelsen, 1892 )

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 : 516-517

12. Metaphire hilgendorfi ( Michaelsen, 1892)

( Figures 1 I, 18; Table 1 )

Perichaeta hilgendorfi Michaelsen, 1892: 235 .

Pheretima hilgendorfi — Gates 1954: 230; 1958: 11, 31; 1982: 49.

Amynthas hilgendorfi — Sims & Easton 1972: 235, 237. Reynolds 1978: 122, 127; 2010: 146; 2011: 272. Reynolds & Wetzel 2004: 88; 2008: 179.

Metaphire hilgendorfi — Blakemore 2010a: 416; 2012b: 106, 108; 2013b: 61.

Data sources. Gates (1954, 1982); Blakemore (2010a, 2013b); this study (USNM 125091, 1421430, 1421432).

Diagnosis. Size 109–170 mm by 6–8 mm. Segment numbers 98–118. Color of live specimens red or reddish brown. Male pores usually absent; when present, unilateral in XVIII, in a large, transversely slit-like copulatory pouch. Primary male pore minute, on the center of a genital pad at the bottom of the copulatory pouch, usually not visible from outside unless everted. Other post-clitellar genital markings present or absent; when present, unpaired, mid-ventral, pre-setal clusters of numerous small tubercles on XVII–XVIII, occasionally on XIX–XXII. Spermathecal pores two pairs in 6/7/8. Pre-clitellar genital markings unpaired, mid-ventral, pre-setal clusters of numerous small tubercles on VIII–IX, occasionally on VII, X, XI, similar to those in the post-clitellar region. Female pore single in XIV. First dorsal pore 11/12 or 12/13. Spermathecae two pairs in VII–VIII, large, duct shorter than ampulla, with a diverticulum longer than the main axis; genital marking glands present with long coelomic stalks. Prostate glands present or absent; when present, large in XV–XXI. Intestinal caeca paired in XXVII, manicate, extending anteriorly to XXII, XXIII, or XXIV.

Remarks. Frequently reported in the continental US and one of the two pheretimoid species recorded in Canada, M. hilgendorfi has been known as Amynthas hilgendorfi for a long time in North America . It was first recorded in 1948 in Kingston, New York ( Gates 1954). Reproduction of this species is obligately parthenogenetic. Metaphire hilgendorfi was recently transferred from Amynthas to Metaphire by Blakemore (2010a; 2013b), but this change has not been reflected in North American literature, partially because all US specimens reported so far lack male pores. However, an USNM specimen identified by G.E. Gates ( USNM 125091 , collected from South Carolina in 1969) has a male pore in the form of an everted copulatory pouch on one side ( Figure 16 C). Moreover, two recently collected specimens from Baltimore, MD ( USNM 1421430, 1421432 ) apparently show a male pore on one side inside a transversely slit-like copulatory pouch opening ( Figure 16 A, B), unambiguously supporting transferring the species to Metaphire . Metaphire hilgendorfi is morphologically similar to A. agrestis and A. tokioensis , with the male pores usually lacking in all three species ( Table 1 ). Co-occurrence of two or all three of the species may be quite common. Metaphire hilgendorfi is an epi-endogeic species. At high abundance it transforms the top several centimeters of soil into granular casts. It is common in urban and suburban areas and is also invading deciduous forests in eastern US (C.- H. Chang and K. Szlavecz, personal observation). Its spread is probably facilitated by commercial mulches, as is in A. agrestis ( Belliturk et al. 2015) . It has been shown to be the superior competitor when interacting with Lumbricus rubellus , an epi-endogeic European earthworm common in the US, for leaf litter. It does not appear to affect Eisenoides lonnbergi , a large native lumbricid common in riparian areas, wetlands, and some upland habitats in the eastern US ( Chang et al. 2016a).

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).

FIGURE 16. Amynthas tokioensis. (A) Right male pore and the associated genital marking (arrow). (B) Single spermathecal pore in 7 / 8 on the lower right (arrow), compared to its absence in 6 / 7 on the right and in 6 / 7 / 8 on the left; ventral view. (C) Left spermatheca in VIII. (D) Right prostate gland. (E) Right intestinal caecum. All photos from USNM 125070, three different specimens: A, specimen 1; B, C, specimen 2; D, E, specimen 3.