New species of Pheretima, Amynthas, Polypheretima, and Pithemera (Clitellata: Megascolecidae) from Mindanao and Associated Islands, Philippines.

Abstract

Nonillon M. Aspe and Samuel W. James (2016) Studies over the past decade have shown the Philippine native earthworm fauna to be highly diverse, with apparent high endemism among islands and localities. Here we describe 17 new species of pheretimoid earthworms collected from priority conservation sites on Mindanao and associated islands. Nine species of the subgenus Pheretima (Pheretima), distinguished by the absence of secretory diverticula on the coelomic surface of the copulatory bursae, were detected. Pheretima acia n. sp., P. dinagatensis n. sp., P. enormis n. sp., P. hamiguitanensis n. sp., P. lantapanensis n. sp. belong to the P. urceolata species group, with a pair of spermathecal pores in 5/6; P. timpoongensis n. sp., P. camiguinensis n. sp., P. sibucalensis n. sp., and P. apoensis n. sp. belong to the P. sangirensis group, with a pair of spermathecal pores in 7/8. Pheretima (Parapheretima) pandanensis n. sp. and P. (Parapheretima) boaensis n. sp., members of the subgenus Pheretima (Parapheretima), with secretory diverticula on the coelomic surface of the copulatory bursae, are the first Philippine records of Parapheretima. In the genus Amynthas, A. dinagatensis n. sp. is athecate; A. cagdianaoensis n. sp. belongs to the belongs to the A. supuensis species group, with a pair of spermathecal pores at 8/9; and A. talaandigensis n. sp. belongs to A. rimosus group, with intrasegmental spermathecae in 6, 7, 8, and 9. In the genus Polypheretima, P. bukidnonensis n. sp. belongs to the Po. elongata species group, with paired genital markings on xix and successive segments, and paired spermathecal batteries in vi and/or vii; Po. zamboangensis n. sp., either has spermathecal pores in 5/6/7 or lacks them, and has a metandric male sexual system. Pithemera nolani n. sp. is unique among congeners in having only one pair of spermathecal pores in 5/6 and in having copulatory bursae. The geological history of Mindanao, which is a collision complex between three arc systems, may have contributed to the high diversity of the earthworm fauna on Mindanao. Future molecular studies can help elucidate the evolutionary relationships and geographical distribution of species and populations, and shed light on mechanisms of earthworm diversification in the Philippines.