The conversion of natural forests to different land uses still occurs in various parts of Southeast Asia with poor records of impact on ecosystem services and biodiversity. We quantified such impacts on earthworm diversity in two communes of Quang Nam province, Vietnam. Both communes are situated within buffer zones of a nature reserve where remaining natural forests are under threat of continued conversion. We identified 25 different earthworm species, out of which 21 were found in natural forests, 15 in agroforestry, 14 in planted forests, and seven each in annual croplands and home gardens. Out of the six species that were omnipresent inhabitants of all observed habitats, Pontoscolex corethrurus largely dominated habitats with intensive anthropogenic activities but was rare in natural forests. Natural and regenerated forests had a much denser earthworm population in the top 10 cm of soil rather than in deeper soil layers. We conclude that the conversion of natural forests into different land uses has reduced earthworm diversity which can substantially affect soil health and ecosystem functions in the two communes. Protection of the remaining natural forests is urgent, while the promotion of a tree-based farming system such as agroforestry can reconcile earthworm conservation and local livelihoods.

The megascolecid earthworms of the Phu Quoc island are intensively investigated. Twelve species in three genera (Lampito Kinberg, 1867, Amynthas Kinberg, 1867, and Metaphire Sims & Easton, 1972) are recorded. Of these, Metaphire doiphamon Bantaowong & Panha, 2016 is recorded for the first time in Vietnam, and three species are newly described, namely Amynthas catenatussp. nov., A. phuquocensissp. nov., and A. poropapillatussp. nov. An identification key to 12 megascolecid species is provided as well.

ABSTRACT:Three new earthworm species are described from Dong Nai Province, Vietnam, namely Metaphire malayanoides Nguyen & Lam sp. n., Metaphire grandiverticulata Nguyen & Lam sp. n., and Metaphire xuanlocensis Nguyen & Lam sp. n. Both M. malayanoides sp. n. and M. grandiverticulata sp. n. have four pairs of spermathecal pores in ventrolateral 5/6/7/8/9. However, M. malayanoides is distinguished by having two to eight pairs of genital markings located in intersegmental furrows, starting from 19/20; M. grandiverticulata sp. n. is characterized by having only one pair of genital markings between male porophores in xviii, and very large tube-shaped diverticulum. M. xuanlocensis sp. n. has one pair of spermathecal pores inside the spermathecal chambers in 7/8, accessory glands stalked and attached to the enlarged base of prostatic duct, and the presence of penial setae.

Four new earthworm species of the genus Amynthas Kinberg, 1867 are described from southeastern Vietnam, named A. longiprostaticus sp. nov., A. dorsomorrioides sp. nov., A. minhdam sp. nov., and A. ocularius sp. nov. A. longiprostaticus sp. nov. belongs to the A. minimus group of species, characterized by spermathecal pores in 5/6. It is distinguished by small body size with length 5–7 cm, and by elongate prostate glands, which extend over more than 10 segments. A. dorsomorrioides sp. nov. belongs to the A. morrisi group, characterized by holandry and spermathecal pores in 5/6/7. It is distinguished by a dorsal location of these pores, by one pair of large genital markings presetal in xvii, and by the absence of genital markings in the spermathecal region. A. minhdam sp. nov. also belongs to the A. morrisi group, and is distinguished by a pair of genital markings located medially in xviii and by the spermathecal diverticula, which have a small seminal chamber sub-divided by constrictions into 4 or 5 parts, in chain-form. A. ocularius sp. nov. belongs to the A. gracilis group by virtue of holandry and spermathecal pores in 5/6/7/8. It is distinguished by numerous small genital markings in the male region, postsetal in xviii and presetal in xix, and arranged in a peculiar fashion reminiscent of eyeglasses connected by a bridge. With these descriptions, there are now 119 species of Amynthas known in Vietnam.

The earthworms of southeastern Vietnam are reported based on literature and samples collected during the period of 2012–2019.  A total of 41 earthworm species of 12 genera in six families are recorded in the southeastern part of Vietnam.  Of these, Polypheretima elongata and Dichogaster affinis are recorded for the first time in the region.  The dominant family is Megascolecidae with 35 species of seven genera while each of the other families is represented by only one species, except for Octochaetidae which has one genus and two species.  The comprehensive checklist also provides data of each species including examined specimens, distributions and remarks.  An identification key to species is compiled for southeastern Vietnam.

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Two new earthworm species are described from the Mekong Delta, Southern Vietnam (An Giang and Ben Tre Provinces), namely Amynthas reductus sp. nov. and Metaphire giengensis sp. nov. The former is recognized by having a pair of spermathecal pores in 6/7, numerous genital markings in transverse lines in 17/18, and spermatheca with strongly reduced diverticula. The latter is distinguished by having two pairs of spermathecal pores in 5/6/7, two pairs of genital markings located closely to male pores in xviii, and the presence of septum 8/9. The COI fragments are also provided for Metaphire giengensis sp. nov.