In the current paper we present an updated checklist of all the megadrile earthworms (Crassiclitellata: Annelida) in the world, and notes on the distribution of families worldwide. Biogeographic responses to geological phenomena including plate tectonics, as well as to past and present climate and habitat distributions, are the main factors determining the present distribution of earthworm families. A total of ca. 5,738 species/subspecies (5,406 species and 332 unique subspecies; i.e., not counting the nomino-typical subspecies) belonging to 23 families (including one non-crassiclitellate family: Moniligastridae) are currently recognized worldwide, of which three families (Tritogeniidae and Kazimierzidae from Southern Africa and Arecoidae, a new family from Brazil described herein), 35 genera and close to 1200 new taxa (including subspecies) were described in the 21st century. Nonetheless, the large number of still undescribed species will likely increase this value to well over 8,000 species. Ten families are monospecific and/or monogeneric and have a mostly restricted distribution. On the other hand, more than 87 widespread cosmopolitan species have been catalogued, some of them with important invasive potential, belonging mainly to families Lumbricidae, Acanthodrilidae, Benhamiidae, Megascolecidae, Rhinodrilidae and Ocnerodrilidae. Taxonomic housekeeping was performed for the preoccupied Rhinodrilidae genus Tairona Righi – herein substituted by Taironina nom. nov., and Guarani camaqua Rodríguez & Lima was reinstated and removed from synonymy with Criodrilus lacuum Hoffmeister, 1845, resulting in a wider definition of the Almidae family. Furthermore, Amynthas maximalis nom. nov. is proposed herein as a substitution name for the preoccupied name Amynthas maximus Qiu & Dong, 2019, and Arecoidae is proposed herein as a new monotypic family for the aquamegadrile species Areco reco Righi, Ayres & Bittencourt, 1978.

As soil invertebrates with a unique digestive system, earthworms are regularly used as bioindicators and test organisms. Due to their burrowing activity and casting, earthworms are involved in the structuring of the soil. However, this way of life exposes them to different pollutants, including microplastic particles. Although the use of plastics is economically justified, it has a major impact on living organisms. In this study, the influence of different concentrations (2.5%, 5%, and 7% (w/w)) of commercial glitter as a primary source of microplastics (MPs) on mortality, growth, cocoon production, avoidance behavior, and bioaccumulation ability during a four-week exposure of the earthworm species Eisenia fetida was investigated. The mortality was higher at 5% and 7% MPs in the soil than at 2.5% and in the control (0%) after 28 days, and the number of cocoons and growth rate decreased with an increasing MP concentration. However, the earthworms did not avoid the soil with MPs. Furthermore, the dissection of the digestive system enabled the identification of MP distribution. The sections of the digestive system were additionally examined under a fluorescence microscope. The results indicated that non-selective feeding enabled the input of MPs into the earthworm’s body and, thus, into food webs.

A list of the endemic earthworms of the Balkan Peninsula is presented. Comprehensive information on the ecology, distribution on the Balkan Peninsula and zoogeographical type of all endemics is given. The list comprises 90 species and subspecies, belonging to 11 genera of the family Lumbricidae. The largest number of the Balkan endemic earthworms belongs to a narrow range group (63.3%). Broad range endemic species take part with 36.7%. Our study shows that the degree of endemism on the Balkan Peninsula is extremely high (about 40%) suggesting an important process of autochthonous speciation on the Balkan Peninsula. This appearance is attributable to relative isolation of the mountains compared to the lowlands within the context of paleoenvironmental changes.

Allolobophora (sensu lato) is one of the most controversial genera in the taxonomy of Lumbricidae. Due to its poor definition, this genus is plagued by extensive taxonomic confusion, and its generic composition and internal relationships have remained uncertain, especially in species of the Balkan Peninsula. In this study, we have combined the study of morphological data and molecular phylogenetics based on five genetic markers, regions of the nuclear 28S rRNA and mitochondrial 16S rRNA, 12S rRNA, NADH dehydrogenase (ND1) and cytochrome oxidase C subunit 1 (COI), to delimit the taxonomic status of five controversial Balkanic endemic species, Allolobophora (s.l.) dofleini, Allolobophora (s.l.) serbica, Allolobophora (s.l.) strumicae, Allolobophora (s.l.) paratuleskovi and Allolobophora (s.l.) treskavicensis, sampled in the Kopaonik Mountain. Phylogenetic analyses based on our sampling of these five species recovered a well-supported clade containing the species Allolobophora (s.l.) robusta, Allolobophora (s.l.) mehadiensis mehadiensis, Allolobophora (s.l.) sturanyi dacica, Cernosvitovia rebeli and Cernosvitovia dudichi. Based on these results and previous evidence, the aforementioned Balkanic species are transferred to a redefined Cernosvitovia. We further present a revised list of all species currently included in Cernosvitovia., which includes now 21 species and subspecies taxa, 13 of them newly combined here. Serbiona Mršić & Šapkarev, 1988 is considered a junior synonym of Cernosvitovia Omodeo, 1956.

In this paper, a list of the earthworm fauna of Bosnia & Herzegovina (Oligochaeta: Lumbricidae) is presented, including literature data, unpublished data from our collection and new data from the field. In this list, earthworm diversity, general ecology, their distribution and zoogeographical types are presented as well. The currently known earthworm fauna of Bosnia & Herzegovina is comprised of 49 species belonging to 12 genera, with Dendrobaena being the species-richest genus (11). Our zoogeographic analysis has shown presence of 9 different types of distribution. Аlmost one third of all species represent either peregrines (14 species, 28.57%) or endemic (13 species, 26.53%). A higher fraction of the endemic species belongs to the Allolobophora and Dendrobaena genera. With the 13 endemic and some Balkanic-Alpine (4), Alpine-Dinaric (2), Illyric (Western Balkans) (2) species, it is proven that 42.85% of the total lumbricidae fauna shows an autochthonous character. These results represent another confirmation of particularity of this fauna and prove the need for further research in this area.