A recent mail thread with Gerard van Buurt set me on the track of the food of snails. Particularly, Gerard was wondering what Drymaeus elongatus might be eating, observing it on the stems of Guaiacum officinale in his garden in Willemstad, Cura??ao. Since on these stems no fungi or lichens are visible – known as snail food – we tried to find any literature reference to Orthalicoid snail food based on field observations.
A reference to Tardigrada (see http://bit.ly/ma0dXx; Glime, 2010) in the faeces of Bulimulus guadalupensis made us wondering to what extent these water bears may contribute to the food of snails. The reference appeared to be a description of a new species of Tardigrades, which happened to be found alive in the faeces of this Bulimulus species in San Juan, Puerto Rico (Fox & Garcia-Moll, 1962); only 2.1% of the specimens was reported as infected by this water bear species, and we concluded that this is probably insignificant as food source, although Fox & Garcia-Moll state that “Tardigrades were found in snail feces at will in 1953, 1959, 1960 and 1961, which argues against the idea of occasional fortuitous occurrence”.
Regarding other Drymaeus species, I could only find a summary in Bledsoe (1977), summarising literature research on D. dormani, and reporting that no lichens were eaten but “a possibility that the snails may eat the spore normally found on the tree trunk”.
That leaves us with bewildering little hard data on the food of these animals. And the quest for more field observations.
Bledsoe, M.E., 1977. Biological studies on the citrus tree snail Drymaeus dormani (Binney), and the citrus rust mite Phyllocoptruta oleivora (Ashmead), as well as the effect of different acaricides on the citrus rust mite. Ph.D. thesis, University of Florida. Available at http://bit.ly/m15XOw
Fox, I. & Garcia-Moll, I., 1961. Echiniscus molluscorum, new Tardigrade from the feces of the land snail Bulimulus exilis (Gmelin) in Perto Rico (Tardigrada: Scutechiniscidae) – Journal of Parasitology 48: 177-181.
Glime, J.M., 2010. Bryophyte ecology, vol. 2. Chapter 5-2. Tardigrades reproduction and food. Michigan Technological University, available online at http://bit.ly/jqGvh9 (accessed 14 May 2011).