Oxynoemacheilus marunensis, new species, is described from the Marun, a tributary of the Jarrahi River, which flows just east of the Tigris River to the Persian Gulf. It belongs to a group of species (O. argyrogramma, O. euphraticus, O. hanae, O. karunensis, and O. kurdistanicus) having two bold, black, round, or comma-shaped black spots on the caudal-fin base. It is most similar to a newly described species from the Persian Gulf basin, O. karunensis, but distinguished from O. karunensis by having a longer distance between pelvic and anal-fin origins [22.3-23.8 vs. 19.5-22.3 (% SL)] and a K2P distance of 6% based on COI barcode region sequences.The species of the chewing louse genus Guimaraesiella Eichler, 1949 parasitic on drongos (Dicruridae) are reviewed and placed in the new subgenus Dicrurobates, which is described herein together with eight new species, including one species from non-dicrurid hosts. The new species are Guimaraesiella (Dicrurobates) carbonivora n. sp. from Dicrurus bracteatus carbonarius Bonaparte, 1850; Guimaraesiella (Dicrurobates) latitemporalis n. sp. from Dicrurus hottentottus brevirostris (Cabanis, 1851) and Dicrurus hottentottus ssp. (Linnaeus, 1766); Guimaraesiella (Dicrurobates) lurida n. sp. from Dicrurus leucophaeus Vieillot, 1817; Guimaraesiella (Dicrurobates) luzonica n. sp. from Dicrurus balicassius (Linnaeus, 1766); Guimaraesiella (Dicrurobates) nana n. Reversan in vitro sp. from Dicrurus hottentottus samarensis Vaurie, 1947; Guimaraesiella (Dicrurobates) regis n. sp. from Dicrurus annectans (Hodgson, 1836), Dicrurus paradiseus paradiseus (Linnaeus, 1766) and Dicrurus paradiseus rangoonensis (Gould, 13836); Guimaraesiella (Dicrurobates) transvaalensis n. sp. from Dicrurus adsimilis apivorus Clancey, 1976; and Guimaraesiella (Dicrurobates) campanula n. sp. from Oriolus larvatus rolleti Salvadori, 1864 and Prionops plumatus poliocephalus (Stanley, 1814). Also, Guimaraesiella (Dicrurobates) sexmaculata (Piaget, 1880) and Guimaraesiella (Dicrurobates) dicruri (Ansari, 1955) are redescribed and illustrated. A key to identify adults of all 10 species included in the subgenus is provided.In this study, a new species of the genus Gymnaetoides Qin, Liu Li, 2017, namely Gymnaetoides polaoensis sp. nov., from a karst cave in Guizhou Province, China is described. This new species is the first cave-dwelling species belonging to the genus Gymnaetoides. The morphological photographs of the males of this new cave species are provided.The monotypic genus Metasiphonella, originally described from Costa Rica, is now formally recorded from South America with a new species from Brazil-M. amorimi sp. nov. The taxonomic revision includes a detailed description of adult external morphology, female and male terminalia, and the egg stage for all species. A lectotype of M. magnifica Duda is designated and new country records are given.The dicroglossid genus Sphaerotheca was erected by Günther in 1859, with its range of distribution in South Asia. Since then, 13 species have been described and 10 species are considered valid. Many of these descriptions were from low to mid-elevation ranges of homestead areas, agroecosystems and degraded landscapes with a few from forested areas. In the present account, a new species of Sphaerotheca, a genetically distinct lineage with a morphological character set distinguishable from its congeners, is described from the surroundings of Bengaluru city, India. Based on evidence for the origin of the original specimen, we also designated a neotype for Rana variegata Gravenhorst, 1829, a junior primary homonym of Rana variegata Linnaeus, 1758, and permanently invalid name, so that it is now a subjective synonym of Rana (Tomopterna) breviceps rolandae Dubois, 1983.The polynoid genus Chaetacanthus Seidler, 1922 currently includes three nominal species provided with parapodial branchiae. Members of this taxon have palps with longitudinal rows of papillae, notochaetae abundant and neurochaetae spinulose. Most Chaetacanthus species were originally described as belonging to Lepidonotus Leach, 1816, and some of them were later regarded as subjective synonyms of Iphione magnifica Grube, 1876, the type species for Chaetacanthus. This species was described from the Caribbean Sea and later recorded for the tropical Eastern Pacific. After the supposed Amphi-American distribution, a revision of all available material was performed in order to clarify the generic delineation, and to improve the understanding of species systematics. Further, some non-type specimens collected in Panama allowed us to have a better understanding of the variation of elytral shape and ornamentation along the body. The type material of Polynoe brasiliensis de Quatrefages, 1866 was examined and despite its poor condition, it shows parapodial branchial filaments which were overlooked in the original description; these branchiae are also present in the holotype of I. magnifica. We identify that there are no relevant difference between both species, and they are regarded as synonyms, and Chaetacanthus brasiliensis (de Quatrefages, 1866) is newly combined and is the senior synonym. On the other hand, Chaetacanthus pilosus (Treadwell, 1937), from the Eastern Pacific, and C. pomareae (Kinberg, 1856) from the South Central Pacific are redescribed, and C. harrisae n. sp., and C. ornatus n. sp. are both newly described from the Eastern Pacific. A key to identify all species of Chaetacanthus of the World, together with an appendix for the reversal of precedence of Lepidonotus Leach, 1816 over Eumolpe Oken, 1807 are also included.New species, Frenopyxis stierlitzi, is described from tree hollows in the urban parks in Moscow (Russia) and Potsdam (Germany). The species belongs to the new genus of the family Centropyxidae and characterized by unique character, i.e. an internal thick organic lip surrounding an aperture and continuing in a bridle, which connects an aperture with the internal side of a shell wall and broaden in the place of connection of a bridle and a shell wall. The systematics of the family Centropyxidae is discussed and the importance of the structures, which divide inner shell volume into compartments, is underlined.