Rare and/or Endangered Land and Freshwater Molluscs of St. Martin
Rare and/or Endangered Land and Freshwater Mollusks of St. Martin.
In this article, Sint Maarten means the Dutch part and Saint-Martin the French part of the island. When referring to the entire island, St. Martin is used as the name (English name) along with the satellite islands such as Tintamarre.
Should we be concerned about the disappearance of land snail species on St. Maarten and Saint-Martin? After three visits in 2015, 2020 and 2021, during which the land and freshwater mollusks were inventoried, it is becoming increasingly clear that a number of land snail species are doing badly and that their numbers are declining. It is suspected that a number of species will disappear or decimate to untraceable populations.
About 49 species of land snails are known from St. Martin (Coomans, 1967; Hovestadt & Neckheim, 2020; Neckheim & Hovestadt, 2021). Depending on which species you count, whether or not they are known only from literature. 15-16 species of these are endangered. That's about a third of all land snails. Too little intensive research has been done on freshwater molluscs, but it seems that four freshwater species may no longer be found on St. Martin. Namely Apple Snail Pomacea glauca, Marbled Physa Aplexa marmorata, Glabrous Ramshorn Biomphalaria glabatra and Mottled Fingernail Clam Eupera viridans. In any case, these species have never been found again.
Causes of decline include habitat loss, climatic conditions such as hurricanes, and habitat pollution. The main cause is loss of habitat. There is still a lot of construction on Sint Maarten and the loss of vulnerable habitat is not taken into account. Moreover, many construction sites have an illegal character. On Saint-Martin, the advance of housing construction seems to be much slower. St. Martin actually has almost no primary forest left. Due to the construction of plantations in the past and hurricanes, much primary forest has disappeared. Primary forest is the original forest, so primary forest. Secondary forest is restored forest where, in addition to indigenous species of plants and trees, there are also exotic plants and trees, but it does look natural. Depending on the species, land snail populations can recover if primary forest is changed to secondary forest.
A vulnerable habitat is forest on calcareous moist soil. On Sint Maarten this is mainly present at Billy Folly. On Billy Folly there is only a limited piece of original nature present. That part consists of a strip of 150 x 100 meters with moist forest and an equally large part around the westernmost limestone rock. On the eastern side on the highest part is also a limestone rock with some vegetation consisting of an approximately equal area. A safety light for aircraft has been placed at this location. Almost the entire “mountain” has now been built up with houses. During my visit in 2021, a road was built right through primary forest, so that the last remnant of forest on the south side of the mountain disappears. Most likely houses will be built along this road. Building is accompanied by the complete disappearance of the original habitat. As a result, the land snail species that are bound to that habitat also disappear. Not only the land snails disappear but also all other species of invertebrates bound to this habitat. Species specific to this habitat are Chondropoma pupiforme, Helicina fasciata, Bulimulus diaphanus fraterculus, Macroceramus signatus, Pseudopineria viequensis and Obeliscus swiftianus. Bulimulus diaphanus fraterculus, Macroceramus signatus and Obeliscus swiftianus are most likely only found here on all of St. Martin. Chondropoma pupiforme, Pseudopineria viequensis and Helicina fasciata also occur rare elsewhere respectively on Sint Maarten and Saint-Martin.
Another disappearing habitat is moist secondary forest on neutral soil. This habitat is mainly found on the French part around Mont Paradis. Specifically, here come Pleurodonte guadaloupensis martinensis, Lucidella striatula christophori, Helicina fasciata, Succinea nov. spec. and Bulimulus lehmanni for. This habitat is scarce but not threatened because there are no building plans on and around Mont Paradis. On the Dutch part this habitat is around Sint Peter hill, where roads are built in 2015 and Sentry Hill where a funicular is built.
In this article, a distinction is made between native and long-established species (native) versus recently introduced species (immigrant). A number of immigrant species, also called exotics, can be rare to very rare on St. Martin, but because they are not indigenous and are common elsewhere on other islands or mainland, they do not need to obtain protective status.
The following types of land snails are rare, very rare, or have already disappeared from St. Martin. The used English names are mostly taken from Delannoye et al.(2015):
Helicina fasciata - Striped Drop, Striped Helicinid
A species of moist to wet shaded habitats. Not rare on other Caribbean islands. Rare on Sint Maarten and lesser rare on Saint Martin but does not appear to be endangered. On Sint Maarten it only occurs on Billy Folly and Sint Peter hills. That is why this species is called vulnerable.
Lucidella striatula christophori - Christopher Striated Helicinid
Occurs only on and around Mont Paradis. So very rare on the island. Also occurs on other Caribbean islands, but it is still not clear which (sub)species there are. Coomans (1967) does not mention this species, and therefore this species may have been introduced in recent times, or overlooked because of its rarity.
Chondropoma pupiforme - Pupiform Round Mouth Snail
This species lives on moist calcareous soil with light or thick vegetation. In the past, this species has been found in many places on Sint Maarten and in recent times discovered also on Tintamarre (Bochaton, et al., 2020). Live snails are very rarely observed. But finding freshly empty houses is a sign that the species lives there. In Terres Basses, the species has been observed in many places in the past, but that part is almost completely cultivated. During my inventories, the species has hardly been found. Only empty houses are found on Red Rock as well as on the chalky rocks along the airport and above. So it has become a rare species of St. Martin. On Billy Folly where the species was common, its habitat has been reduced to several hectares. This species is also found on Anguilla.
Diplopoma crenulatum - Crenulated Round Mouth Snail
This limestone lover is only found on the French part of the island. But there it is very rare. In the north of St. Martin there is sporadic calcareous soil on the surface (the Point Blanche formation). But on the small island of Tintamarre, which belongs to Saint-Martin, the species looks common. But in general it is a very rare species. Also occurs on other islands such as Martinique.
Diplopoma sulculosum Sulculos – Wrinkled Round Mouth Snail
This species occurs on Anguilla and St. Barts and possibly on Tintamarre. This has not yet been officially established. If so, this is the rarest species of the Annularidae on St. Martin.
Gundlachia radiata - Radiant Limpet
This is a small species of freshwater snail and only found in the mountain stream La Loterie. It is therefore a very rare snail, but this species occurs on various islands in the Caribbean and it is unclear whether it is an autochthonous species. This freshwater snail is not mentioned by Coomans (1967). It only appears in clean freshwater and this is scares on St. Martin, so this species can be used as an indicator.
Succinea spec. nov. - Ambersnail
This species is described as new for science (Neckheim, Margry) but has not yet been published. The species was previously known as Succinea approximans and is widely distributed on St. Martin. This snail lives in moist to wet places with a lot of vegetation and those places become rare on St. Martin. Because it is an endemic species, protection is important.
Bulimulus diaphanus fraterculus - Transparant Bulimulus
This somewhat larger snail is only known from Billy Folly and then as empty shells. During the last visits, fresh shells were always found in the natural part of Billy Folly, but the species is very rare on the island and needs protection. In fact, the habitat needs protection.
Bulimulus lehmanni - Lehman Bulimulus
This species occurs on Anguilla and has been found a number of times on St. Martin and Tintamarre. Alain Bertrand (Bertrand, 2002) found a freshly empty shell on Mont Caréta. Until now, only empty houses have been found on Tintamarre. It is unclear whether this species is native or extinct.
Macroceramus signatus - Ceramic Signed Urocopt
Occurs on Anguilla and a number of other islands and was recently found on Billy Folly (Neckheim & Hovestadt, 2021). It is possible that the species also occurs somewhere in Basses Terres, but it is difficult to search there because of the many private areas. This species is strongly associated with calcareous soil. It is a very rare species on the island. It is unclear whether it is an indigenous species or recently introduced. At Billy Folly it lives under natural conditions. Not mentioned in Coomans (1967), may be also overlooked.
Pseudopineria viequensis – Viequens Urocopt
This species, bound to calcareous moist areas, is not rare on the Caribbean islands, but on St. Martin only known from Billy Folly, limestone crevices at Mullet and on Tintamarre. Because of his need for a special habitat which is urbanized on St. Martin it is a rare species. Needs protection on the Dutch part.
Pleurodonte guadeloupensis martinensis – St. Martin’s Pleurodonte
This somewhat larger species is only found around Mont Paradis and Mont Caréta. It is therefore a very rare species of which alive snail has never been found. Only empty houses have been found and collected, some of which are freshly empty. This endemic species is therefore most likely living on Saint-Martin. Because this is an endemic subspecies for St. Martin it derives extra attention and protection.
Species not observed, which are known only from literature, the following terrestrial species are either very rare or no longer present on St. Martin.
Omalonyx matheroni – Matheron’s Ambersnail
A species of moist to wet primary forests. Not found recently. Could occur on Mont Paradis. Taxonomy is uncertain, it is may be possible there is a confusion with Amphibulimus spec. which lives on Mount Scenery Saba and other Caribbean islands.
Brachypodella antiperversa – Férussac’s Cylindrella
A limestone lover, who was probably introduced from Guadeloupe in the past with building material. Was known from one location near Grand Case and has not been found in the present. .
Melaniella gracillima sanctithomensis -
This small and anyway rare species has not been found in recent times. It is unclear whether this is an indigenous species.
Bertrand, A., 2002. Notes sur les mollusques terrestres de Saint-Martin (Petites Antilles). – Documents Malacologiques 2: 35-37.
Bochaton, C., D. Cochard, M. Gala, J. Chalifour & A. Lenoble, 2020. Initial observations of the subfossil fauna from Tintamarre island (Anguilla Bank, Lesser Antilles). – Quaternaire, 31(4): 327-340.
Coomans, H.E., 1967. The non-marine mollusca of st. Martin. – Studies on the Fauna of Curaçao 24, (94): 118-145.
Delannoye, R., Charles L., Pointier J.-P. & Massimin D. 2015. Mollusques continentaux de La Martinique. Non-marine Molluscs of Martinique, Lesser Antilles. Biotope, Mèze; Muséum national d’Histoire naturelle, Paris [collection Inventaires et biodiversité], 328 p.
Hovestadt, A & C.M. Neckheim, 2020. A critical checklist of the non-marine molluscs of St. Martin, with notes on the terrestrial malacofauna of Anguilla and Saint-Barthélemy, and the description of a new subspecies. – Folia Conchyliologica, 57: 1 – 38.
Neckheim, C.M. & A. Hovestadt, 2021. Nieuwe gegevens over de land- en zoetwatermollusken van Sint Maarten (Nederlandse Antillen). – Spirula 428: 42-49.