Bulinus Barthi

''Bulinus'' is a genus of small tropical freshwater snails, aquatic gastropod mollusks in the family Bulinidae, the ramshorn snails and their allies.MolluscaBase eds. (2020). MolluscaBase. Bulinus O. F. Müller, 1781. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=224352 on 2020-06-27

This genus is medically important because several species of ''Bulinus'' function as intermediate hosts for the schistosomiasis blood fluke.

Description

The shell of species in the genus ''Bulinus'' is sinistral. It has a very large body whorl and a small spire.

Distribution and habitat

Species of the genus are widespread in Africa including Madagascar and the Middle East.

This genus has not yet become established in the USA, but it is considered to represent a potentially serious threat as a pest, an invasive species which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine significance in the USA.

The genus ''Bulinus'' has arguably the greatest and widespread distribution of all pulmonate snail species in the Afromontane regions. This can be attributed to its great ability to adapt and increase its range from freshwater ponds at sea-level to extreme altitudes as experienced on the “sky islands”. A recent study has recently extended the range of ''Bulinus'' by 900 m to around 4,000 m on top of Mt. Elgon. Specifically, some of the places they can be found in include pools and wetlands marshes. They also can be found in standing or slow-moving (lentic) and running (lotic) waterbodies.

It has been predicted that climate change has been the cause to changes in ''Bulinus'' species distribution. This has led to changes in endemism and evolutionary dynamics such as speciation and extinction.

Feeding Strategies

''Bulinus'' species are herbivorous freshwater snails that primarily graze on algae and detritus. They are classified as grazers, and their feeding habits play an important role in nutrient cycling and the overall ecosystem of freshwater habitats. They graze on biofilms that are composed of bacteria, fungi, and protozoans. They have a similar feeding mechanism to other freshwater gastropods, using their radula to scrape surfaces and ingest food. The radula is lined with rows of microscopic teeth.

Dormancy

Seasonal droughts are common in the habitats of the ''Bulinus'' snails and it has long been a topic of discussion to scientists of how the snails are capable of enduring and aestivate through the long-lasting and harsh climates and weather cycles. Aestivation is common in snails, which is when the snail undergoes periodic dormancy due to decreased moisture in the environment. Studies towards snail dormancy have been halted due to the mystery of where ''Bulinus'' snails aestivate, which therefore complicate efforts into schistosomiasis disease prevention.

After up to seven months of dry season yearly, wet season brings the rapid reemergence of whole ''Bulinus'' snail populations who have been aestivating with decreased metabolism and many various physiological adaptations. It was also discovered that ''Bulinus'' snails delay egg-laying for about 2 weeks following aestivation.

Invasive Effects

''Bulinus'' snails have become established as both an invasive species and a intermediate host of smaller invasive parasites that severely impact human health. Blood flukes are the parasite that latches on to these snails, causing them to indirectly transmit urinary schistosomiasis. An example of this is in China, where the ''Bulinus'' species has been linked to numerous outbreaks. The snails spread through irrigation systems and water projects, creating new transmission hotspots. Another example can be seen in Zimbabwe, where ''Bulinus globosus'' is the primary vector for urinary schistosomiasis. Large outbreaks of blood flukes can occur in rural communities with untreated water. Climate change has expanded the snails range, which has worsened the outbreaks.

Schistosomiasis transmission

Much of the importance of the ''Bulinus'' genus of snails comes from its role as an intermediate host for the disease schistosomiasis. It is vital to understand the epidemiology of the organisms that cause this disease (''Schistosoma'' species) in these snails to create effective plans and measures to control the transmission of schistosomiasis. In Africa alone, at least 130 million people are affected by human urogenital schistosomiasis.

In the transmission of ''S. haematobium'', ''Bulinus'' snails are infected through free-swimming miracidia stage of the parasite where the ''Bulinus'' snails facilitate the asexual reproduction of the flatworm. Cercariae are produced whom then seek out humans who are in water in which they infect and produce eggs which will be urinated and hatch into miracidia to continue the cycle of schistosomiasis infection. Learning the life cycle of both ''Bulinus'' and ''Schistosoma'' species is important because, in rural areas where agriculture is common industry, land is altered to increase agricultural water where ponds and networks of rain catchment become snail hotspots that have great potential to transmit schistosomiasis. There may also be an increase of susceptibility to schistosome transmission in snails following aestivation.

Species

Species within the genus ''Bulinus'' have been placed into four species groups: the ''Bulinus africanus'' group, ''Bulinus forskalii'' group, ''Bulinus reticulatus'' group and the ''Bulinus truncatus/tropicus'' complex. For the most part, species have been classified on the basis of their morphology although, in recent decades, the study of ploidy, allozymes and DNA methods have all played an increasing role in species discrimination. Morphological characters, whilst adequate to allocate a specimen to a species group are sometimes unreliable when used to classify at higher resolution especially within the ''Bulinus africanus'' group.

The following species are recognised in the genus ''Bulinus'':

;''Bulinus africanus'' group
* '' Bulinus abyssinicus'' (Martens, 1866)
* '' Bulinus africanus'' (Krauss, 1848)
* '' Bulinus globosus'' (Morelet, 1866)
* '' Bulinus hightoni'' Brown & Wright, 1978
* '' Bulinus jousseaumei'' (Dautzenberg, 1890)
* '' Bulinus nasutus'' (Martens, 1879)
* '' Bulinus obtusispira'' (Smith, 1882)
* '' Bulinus obtusus'' Mandahl-Barth, 1973
* '' Bulinus ugandae'' Mandahl-Barth, 1954
* '' Bulinus umbilicatus'' Mandahl-Barth, 1973

;''Bulinus forskalii'' group
* '' Bulinus barthi'' Jelnes, 1979
* '' Bulinus bavayi'' (Dautzenberg, 1894)
* '' Bulinus beccarii'' (Paladilhe, 1872)
* ''Bulinus browni'' Jelnes, 1979
* '' Bulinus camerunensis'' Mandahl-Barth, 1957
* '' Bulinus canescens'' (Morelet, 1868)
* '' Bulinus crystallinus'' (Morelet, 1868)
* '' Bulinus forskalii'' (Ehrenberg, 1831)
* '' Bulinus scalaris'' (Dunker, 1845)
* ''Bulinus senegalensis'' Müller, 1781 - the type species of the genus

;''Bulinus reticulatus'' group
* '' Bulinus reticulatus'' Mandahl-Barth, 1954
* ''Bulinus wrighti'' Mandahl-Barth, 1965

;''Bulinus truncatus/tropicus'' complex
* ''Bulinus angolensis'' (Morelet, 1866)
* '' Bulinus depressus'' Haas, 1936
* '' Bulinus hexaploidus'' Burch, 1972
* ''Bulinus liratus'' (Tristram, 1863)
* '' Bulinus mutandensis'' Preston, 1913
* '' Bulinus natalensis'' (Küster, 1841)
* '' Bulinus nyassanus'' (E. A. Smith, 1877)
* '' Bulinus octoploidus'' Burch, 1972
* '' Bulinus permembranaceus'' (Preston, 1912)
* '' Bulinus succinoides'' (E. A. Smith, 1877)
* '' Bulinus transversalis'' (Martens, 1897)
* '' Bulinus trigonus'' (Martens, 1892)
*†'' Bulinus trojanus''
* '' Bulinus tropicus'' (Krauss, 1848)
* '' Bulinus truncatus'' (Audouin, 1827)
* '' Bulinus yemenensis'' Paggi et al., 1978

;Other
* †''Bulinus arinus''
* †'' Bulinus banlashanensis''
* †'' Bulinus bouei'' (Pavlović, 1931) - from late Miocene
* †'' Bulinus corici'' Harzhauser & Neubauer, 2012 - from middle Miocene
* '' Bulinus dautzenbergi''
* †'' Bulinus dilatatus''
* †'' Bulinus fuxinensis''
* '' Bulinus indicus''
* †'' Bulinus kormosi''
* † '' Bulinus matejici'' (Pavlović, 1931) - from middle Miocene
* †'' Bulinus ovaformis''
* † '' Bulinus pavlovici'' (Atanacković, 1959) - from late Miocene
* †'' Bulinus pijiagouensis''
* †'' Bulinus stevanovici'' (Atanacković, 1959) - late Miocene
* †'' Bulinus striatus'' (Milošević, 1978) - late Miocene
* †'' Bulinus yushugouensis''

References

This article incorporates CC-BY-2.5 text from the reference

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