A small collection of terrestrial snails (Mollusca: Gastropoda) from Unguja Island (Zanzibar, Tanzania) revealed a species unknown for 67 years

: The study presents findings from a survey of terrestrial snails conducted on Unguja Island (Zanzibar). The survey, conducted in March 2024, focused on the eastern coast of the island, specifically around Uroa Village and Kiwengwa Cave. A total of 12 species of terrestrial snails were recorded, including Gulella minutissima (Thiele, 1911), previously unknown for over six decades.


Introduction
Unguja, the main island of the Zanzibar Archipelago, situated approximately 6° south of the equator and 40 km east of the mainland of Africa, boasts an area of approximately 1600 km 2 (Pakenham, 1984).The island's diverse ecosystems, including high and low scrub forests characterised by coral limestone bedrock, provide habitats for a variety of flora and fauna (Siex, 2011).The vegetation cover on Unguja is classified as Eastern African Coastal Scrub Forest, according to Clarke's scheme (Burgess & Clarke, 2000).
Despite its ecological significance, the land mollusc fauna of the East African coastal region, including Zanzibar, remains inadequately explored (Verdcourt, 2006).While the territory of the Zanzibar autonomous region has received attention in terms of species composition of land snails (Rowson, 2007;Rowson et al., 2010: Gittenberger & Bruggen, 2013), many species are reported without precise localities or are challenging to locate due to taxonomic uncertainties (Rowson, 2007).Recent studies have begun to address this gap in knowledge, with the author re-porting 16 species of terrestrial and mangrove snails from Unguja Island in 2021, including the discovery of Thapsia insulsa (Preston, 1910), a new record for the island (Georgiev, 2021a).
Building on previous research, this study aims to contribute further to our understanding of the terrestrial snail fauna of Unguja Island.Specifically, it provides new information on the distribution and habitats of terrestrial snail species on the island.By conducting field surveys and documenting species occurrences, this study sheds light on the biodiversity of Unguja's terrestrial ecosystems and highlights the importance of continued research and conservation efforts in the region.

Material and methods
The survey was conducted concurrently with an entomological study of Psocoptera (Georgiev, 2021b) between 2-8 March 2024, focusing on the eastern coast of Unguja Island, Zanzibar.The primary study area was the vicinity of Uroa Village, with additional sampling conducted at Kiwengwa Cave near the village of Upenja.Terrestrial snails were sampled using a combination of visual observations, shell collection, and active searching.Snail shells were collected from various habitats, including bush vegetation on coral limestone rocks and secondary broadleaf forests mixed with coconut palms (Cocos nucifera).Additionally, live specimens were occasionally observed on bush branches and cave floors (Achatina, Opeas).Detailed field notes, including GPS coordinates and habitat descriptions, were recorded for each specimen.All collected shells were deposited in the National Natural History Museum -Sofia, Bulgaria.

Results and discussion
The current study documented a total of 12 species of terrestrial snails from previously unexplored localities on Unguja Island, Zanzibar.Notably, among these species, Gulella minutissima (Thiele, 1911) was rediscovered after 67 years, with no photographic records of the shell available.To prevent redundancy with previous publications (Rowson, 2007;Georgiev, 2021a), the known distribution of species is not repeated in the following list.
Remarkably, the exact type locality of this species remains uncertain, as it was simply recorded as "Sansibar" by Thiele in 1911 (Thiele 1911), leaving ambiguity as to whether it refers to Unguja Island or the East African coast (Rowson, 2007).Verdcourt (1962) documented a recollection of this species in 1957, adding to its historical significance.This recent discovery, after a lapse of 67 years, provides concrete evidence of the species' presence on Unguja Island, confirming its existence in the region.This species has not been found anywhere else, i.e., it is presumed to be endemic to Unguja.According to personal communication with Dr Ben Rowson (National Museum of Wales, UK), who checked the late Bernard Verdcourt's unpublished notes, he provided the details as "Tumbatu I., Puopo (Ostheimer et al. in ANSP 214859)".This locality, presumably the small island of Popu, is also in the northern half of Unguja and likely shares a similar habitat.

Succineidae
Quickia concisa (Morelet, 1848): 8.03.2024,Uroa Village, bush on coral limestone rocks, S06 05 02.9 E39 25 28.7, 5 m a.s.l., shells.In conclusion, this study presents important findings regarding the terrestrial snail fauna of Unguja Island, Zanzibar, shedding light on previously unexplored localities and contributing to our understanding of regional biodiversity.The rediscovery of Gulella minutissima after 67 years underscores the significance of ongoing research efforts in documenting and conserving biodiversity.Moving forward, continued investigations are warranted to further elucidate the ecological roles and conservation status of terrestrial snails on Unguja Island and to support effective management and conservation strategies.