> Habitat & Distribution

Melanoides tuberculata was originally described from India, and boasts a vast native range extending from Southeast Asia through the Mideast and much of Africa.  The first New World population seems to have been introduced into Arizona in the mid-1950s (Murray & Wopschall 1965, Dundee 1974), probably through the aquarium trade.  By the mid-1960s several large Melanoides populations had become established in Texas and Florida, and in the 1970s and 1980s populations were reported in California, Nevada, Colorado, and Montana (Clench 1969, Murray 1971, Anderson 2004).  

We are aware of two populations of M. tuberculata in our southern study area at the present writing, one in North Carolina and one in South Carolina, both inhabiting sandy creeks or ditches in the vicinity of coastal real estate developments, plus one unconfirmed report from Kingsland, GA.  We are also aware of a single population in our Great Plains study area, inhabiting a hot springs in western South Dakota.  The species is pseudo-rare in our 17-state study area, FWGNA Incidence rank I-1p.

> Ecology & Life History

Melanoides populations seem better adapted to rich or disturbed environments than is typical for most prosobranchs.  The snails tend to burrow into the substrate by day and emerge to graze by night (Beeston & Morgan 1979a,b; Morgan & Last 1982).  It seems possible that Melanoides may have evolved special adaptations to low levels of dissolved oxygen.  Populations also seem to tolerate, possibly even thrive in, somewhat elevated salinities (Roessler et al. 1977, Carvalho da Silva & Barros 2015).  The population on Hilton Head Island (SC) seems to reach maximum density grazing organic matter on shallow, sandy bottoms at a (strikingly high) salinity around 14.5 ppt, and extends into salinities as extreme as 17.9 ppt.

Melanoides is an ovoviviparous brooder, its pallial oviduct being evolved into a brood pouch that holds eggs until they hatch.  Newborn juveniles are released from the edge of their mother’s mantle at a standard shell length of approximately 2.0 mm.  Males are entirely absent from most populations, reproduction typically taking place by apomictic parthenogenesis (Heller & Farstey 1990).  See the studies of Jacob (1957a, b) for more about the chromosomal basis of parthenogenesis in this interesting organism.

Maturity can be reached in as little as 100 days, or require as long as 6 months, with continuous reproduction in some environments (Berry & Kadri 1974; Liveshits & Fishelson 1983), but seasonal peaks in others (Dudgeon 1986).  Melanoides populations seem to post unusually high intrinsic rates of natural increase, by prosobranch standards (Pointier et al., 1991, Work & Mills 2013).  Although perhaps not rivaling typical pulmonate populations in this regard, the superior survivorship of M. tuberculata populations and the high densities they are apparently able to sustain have recommended Melanoides introduction as a biological control for the medically important planorbid populations in the tropics and subtropics (Pointier & McCullough 1989, Pointier et al. 1989, 1994, but see Mkoji et al. 1992).

Melanoides populations serve as intermediate hosts for a variety of trematode parasites, back home in the Old World (Ismail & Arif 1993, Karamian et al. 2011) and here in the new (Tolley-Jordan and Chadwick 2018).  The resistance of M. tuberculata shells to attack by crushing predators has been measured by West et al (1991), with consequences as elaborated by Hung et al. (2013).

> Taxonomy & Systematics

The Old World literature contains quite a few subspecies and synonyms for Melanoides tuberculata, presumably based on shell morphological differences among clones, which (blessedly) have not been introduced to the New World along with the snails themselves.

Livshits et al. (1984) published a nice old-school population genetics survey comparing four parthenogenetic and five sexually-reproducing Melanoides populations in Israel.  Samadi et al. (1999) have described 16 different morphs of M. tuberculata worldwide, each apparently corresponding to a single clone.  The molecular phylogenetic analysis of Facon et al. (2003) suggested that Old World clones can be divided into several clades – Pacific, Southeast Asia, and MidEast/Africa – and that our New World populations represent multiple introductions from the Old. 

> Supplementary Resources

• Melanoides distribution in Atlantic drainages (2023)
• Melanoides distribution in The Great Plains (2024)

> Essays

• The North Carolina record of Melanoides tuberculata first came to my attention during a review of the USGS Nonindigenous Aquatic Species database I conducted in late 2015.  See my blog post of 16Oct15, To Only Know Invasives.
• I reported the discovery of Melanoides in South Carolina in my post of 16Dec15, The Many Invasions of Hilton Head.  You'll find more about the biology of the snail and an additional figure in that post as well.
• Perhaps unsurprisingly, Melanoides stocks are are widely retailed through the online aquarium trade.  See my post of 9Oct 17 What's Out There and my post of 24Jan18, Snails by Mail.

> References

Anderson, T. K.  2004.   A review of the United States distribution of Melanoides tuberculatus (Muller, 1774), an exotic freshwater snail.  Ellipsaria 6: 15-17.
Beeston, D., and E. Morgan. 1979a. A  crepuscular rhythm of locomotor activity in the freshwater prosobranch Melanoides tuberculata (Muller). Anim. Behav. 27: 284-291.
Beeston, D., and E. Morgan. 1979b. The effect of varying the light: dark ratio within 24-h photoperiod on the phase relationship of the crepuscular activity peaks in Melanoides tuberculata. Anim. Behav. 27: 292-299.
Berry, A., and A. Kadri. 1974. Reproduction in the Malayan freshwater cerithiacean gastropod Melanoides tuberculata. J. Zool. 172: 369-381.
Carvalho da Silva, E., and F. Barros.  2015.  Sensibility of the invasive snail Melanoides tuberculatus (Müller, 1774) to salinity variations.  Malacologia  58(1–2):365–369.
Clench, W. J. 1969.  Melanoides tuberculata (Muller) in Florida.  Nautilus 83:72.
Dudgeon, D. 1986. The life cycle, population dynamics and productivity of Melanoides tuberculata (Muller, 1774) (Gastropoda: Prosobranchia: Thiaridae) in Hong Kong. J. Zool. Lond. 208: 37-53.
Dudgeon, D.  1989.  Ecological strategies of Hong Kong Thiaridae (Gastropoda: Prosobranchia).  Malacological Review 22: 39-53.
Dudgeon, D., and M. Yipp 1985.  The diets of Hong Kong freshwater gastropods.  Pp 491-509 In:  Proceedings of the  Second International Workshop on the Malacofauna of Hong Kong and Southern China. (B. Morton & D. Dudgeon, eds.)  Hong Kong University Press.
Dundee, D. S. 1974.  Catalog of introduced molluscs of eastern North America (north of Mexico).  Sterkiana 55: 1-37.
Facon B, Jarne P, Pointier JP, David P, 2005. Hybridization and invasiveness in the freshwater snail Melanoides tuberculata: hybrid vigour is more important than increase in genetic variance. Journal of Evolutionary Biology, 18:524-535.
Facon B, Machline E, Pointier JP, David P, 2004. Variation in dessication tolerance in freshwater snails and its consequences for invasion ability. Biological Invasions, 6:283-293.
Facon B, Pointier JP, Glaubrecht M, Poux C, Jarne P, David P, 2003. A molecular phylogeography approach to biological invasions of the New World by parthenogenetic Thiarid snails. Molecular Ecology, 12:3027-3039.
Facon B, Pointier JP, Jarne P, Sarda V, David P, 2008. High genetic variance in life-history strategies within invasive populations by way of multiple introductions. Current Biology, 18(5):363-367.
Heller, J., and V. Farstey. 1989.  A field method to separate males and females of the freshwater snail Melanoides tuberculata.   J. Moll. Stud. 55: 427-429.
Heller, J., and V. Farstey. 1990. Sexual and parthenogenetic populations of the freshwater snail Melanoides tuberculata in Israel. Israel J. Zool. 37: 75-87.
Hodgson, A. N. and J. Heller.  1990.  Spermatogenesis and sperm structure of the normally parthenogenetic freshwater snail Melanoides tuberculata.  Israel J. Zool. 37: 31-50.
Hung, N.M., J.R. Stauffer, and H. Madsen.  2013.  Prey species and size choice of the molluscivorous fish, black carp (Mylopharyngodon piceus).  Journal of Freshwater Ecology  28(4):547-560.
Ismail, N., and A. Arif. 1993. Population dynamics of Melanoides tuberculata (Thiaridae) snails in a desert spring, United Arab Emirates, and infection with larval trematodes. Hydrobiologia 257: 57-64.
Jacob, J. 1957a. Cytological studies of Melaniidae (Mollusca) with special reference to parthenogenesis and polyploidy. I. Oogenesis of the parthenogenetic species of Melanoides. Trans. Roy. Soc. Edin. 63: 341-351.
Jacob, J. 1957b. Cytological studies of Melaniidae (Mollusca) with special reference to parthenogenesis and polyploidy. II. A study of meiosis in the rare males of the polyploid race of Melanoides tuberculata and Melanoides lineatus. Trans. Roy. Soc. Edin. 63: 433-443.
Karamian, M., J.A. Aldhoun, S. Maraghi, G. Hatam, B. Farhangmehr, and S.M. Sadjjadi.  2011.  Parasitological and molecular study of the furcocercariae from Melanoides tuberculata as a probable agent of cercarial dermatitis.  Parasitology Research  108(4):955-962.
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Mkoji G.M., D. Koech, B. Hofkin, E. Loker, J. Kihara, and F. Kageni. 1992. Does the snail Melanoides tuberculata have a role in biological control of Biomphalaria pfeifferi and other medically important African pulmonates. Ann. Trop. Med. Parasitol. 86: 201-204.
Morgan, C., and V. Last. 1982. Observations on the feeding and digestive rhythm of the freshwater prosobranch Melanoides tuberculata Muller. Zool. Anz. 209: 301-393.
Murry, H. D. and L. J. Wopschall. 1965.  Ecology of Melanoides tuberculata (Muller) and Tarebia granifera (Lam) in South Texas (abstract).  Annual Reports of the American Malacological Union 1965: 25-26.
Murray, H. D.  1971.  The introduction and spread of thiarids in the United States.  The Biologist 53: 133-135.
Pointier JP, Delay B, Toffart JL, Lefevre M, Romero-Alvarez R, 1992. Life-history traits of three morphs of Melanoides tuberculata (Gastropoda: Thiaridae), an invading snail in the French West Indies. Journal of Molluscan Studies, 58:415-423.
Pointier, J., A. Guyard and A. Mosser.  1989.  Biological control of Biomphalaria glabrata and B. straminea by the competitor snail Thiara tuberculata in a transmission site of schistosomiasis in Martinique, French West Indies.  Ann. Trop. Med. Parasit. 83: 263-269.
Pointier, J., R. Incani, C. Balzan, P. Chrosciechowski, and S. Prypchan. 1994. Invasion of the rivers of the littoral control region of Venezuela by Thiara granifera and Melanoides tuberculata (Mollusca: Prosbranchia: Thiaridae) and the absence of Biomphalaria glabrata, snail host of Schistosoma mansoni. Nautilus 107: 124-128.
Pointier, J., and F. McCullough.  1989.  Biological control of the snail hosts of Schistosoma mansoni in the Caribbean area using Thiara spp.  Acta Tropica 46: 147-155.
Pointier, J., A. Theron, and G. Borel. 1993. Ecology of the introduced snail Melanoides tuberculata (Gastropoda: Thiaridae) in relation to Biomphalaria glabrata in the marshy forest zone of Guadeloupe, French West Indies.  J. Moll. Stud. 59: 421-428.
Pointier, J., J. Toffart, and M. Lefevre. 1991. Life tables of freshwater snails of the genus Biomphalaria (B.glabrata, B.alexandrina, B. straminea) and of one of its competitors Melanoides tuberculata under laboratory conditions. Malacologia 33: 43-54.
Roessler MA, Beardsley GL, Tabb DC, 1977. New records of the introduced snail, Melanoides tuberculata (Mollusca: Thiaridae) in south Florida. Florida Scientist, 40:87-94.
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Tolley-Jordan, L.R., and M.A. Chadwick. 2018. Effects of parasite infection and host body size on habitat association of invasive aquatic snails: Implications for environmental monitoring.  Journal of Aquatic Animal Health DOI 10: 1002/aah.10059
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Work, K., and C. Mills.  2013.  Rapid population growth countered high mortality in a demographic study of the invasive snail, Melanoides tuberculata (Müller, 1774), in Florida.  Aquatic Invasions  8(4):417-425.