The ubiquitous sea cucumber Holothuria (Thymiosycia) arenicola Semper, 1868, externally characterized by a double row of dark blotches of various sizes on its dorsal body wall and a cryptic behaviour, is generally assumed to have a wide tropical distribution, although it has not been reported from the Eastern tlantic. Careful morphological examination, with emphasis on the ossicle assemblage, of type and non-type H. arenicola specimens sampled in the Indian, Pacific and tlantic Ocean, its subjective synonyms and species with a similar colouration and habit, revealed that H. arenicola is often confused with other species. This paper formally separates the different species in the H. arenicola complex, one of them being a species new to science: Holothuria (Thymiosycia) kerriensis sp. nov. dditionally, we describe two other species that are often confused with H. arenicola: Holothuria (Lessonothuria) gracilis Semper, 1868 and H. (Thymiosycia) strigosa Selenka, 1867. The H. arenicola complex per se is keyed-out, with the ossicle assemblage of the musculature being recognised as an important, previously largely neglected, guide. This contribution highlights the importance of building and curating well-maintaned natural history collections to understand biodiversity through time and space.
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Nyungwe National Park (NP) is a mountainous region situated in the southwestern part of Rwanda on Congo-Nile watershed. In spite of the high biodiversity in pri- mates, birds and plants, no fish were reported to occur in the park, probably because of the cold temperatures of the rivers. An expedition in 2022 examined the fish diver- sity within the Nyungwe NP and its buffer zones. Additional sampling was performed in the main river draining the park into Lake Kivu: the Kamiranzovu. Three hundred and twenty specimens belonging to 13 species were collected. Specimens were col- lected only in the western part of the park, draining towards the Congo basin. The diversity within the park proper was limited to two putative species within the com- plex of Amphilius cf. kivuensis, which were caught on either side of the Kivu–Rusizi watershed. In contrast, a higher fish diversity, including one clariid species and two species of Enteromius, was observed in the rivers at a lower altitude of the buffer zone. However, the highest species diversity was found near the mouth of Kamiran- zovu River, including 11 species, of which 4 were non-native: the guppy Poecilia reti- culata, Astatotilapia burtoni, the blue-spotted tilapia Oreochromis leucosticus and the Egyptian mouth-brooder Pseudocrenilabrus multicolor.
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RBINS Staff Publications 2025
