Lepetodrilus elevatus (McLean 1988)

Background
Phylum: Mollusca
Class: Gastropoda
Family: Lepetodrillidae

Geography and Distribution
Lepetodrilus elevatus is a gastropod mollusc inhabiting hydrothermal vent sites and the most abundant of the Lepetodrilus genus (McLean, 1988). There are actually two subspecies of L. elevatus, L. elevatus galriftensis and L. elevatus elevatus. This speciation has begun as each subspecies cannot interact with the other, and this is because L. elevatus galriftensis is found exclusively at sites along the Galapagos Rift whereas L. elevatus elevatus is exclusively found only at hydrothermal vents that are along the East Pacific Rise boundary (Fig. 1) (McLean, 1988). It only seems to occur within the latitudes of 9oN and 21oN (Craddock et al., 1996).

Figure 1: Adapted from Vrijenhoek (2010),
Figure 1: Adapted from Vrijenhoek (2010), the approximate geographical distribution of both subspecies of L. elevatus is shown by the red. L. elevatus elevatus is broadly found at sites along the East Pacific Rise, which is the left red line, whilst L. elevatus galriftensis is located at sites along the Galapagos Rift – the right red line.

Within the hydrothermal vent site, L. elevatus is most abundant within the vestimentiferan zone, with significantly lower densities in the bivalve and suspension feeding zones (Mills et al., 2007). Despite lower densities in the latter zones, they are still the most abundant species found within the mussel beds in sites of the East Pacific Rise (Dreyer et al., 2005). L. elevatus tend to attach to Riftia pachyptila tubes (as seen in Fig. 2) or in sulphide particle deposits at the foot of vent chimneys (Fretter, 1988) or on the shells of bivalves.

Figure 2: Lepetodrilus elevatus is abundant in the vestimentiferan zone as it grows on the tubes of Riftia pachyptila and the shells of bivalves.
Figure 2: Lepetodrilus elevatus is abundant in the vestimentiferan zone as it grows on the tubes of Riftia pachyptila and the shells of bivalves.

Appearance and Identification
Both subspecies of L. elevatus are much smaller than other Lepetodrilus species – and of the two subspecies, L. elevatus galriftensis is smaller and about 2/3 of the height of L. elevatus elevatus (McLean, 1988). Despite this, they are the same shape as other limpets, and their shells are non-nacreous aragonite, i.e. non-iridescent calcium carbonate (Fretter, 1988). McLean (1988) describes them as a light greenish-brown colour – the result of the top layer of shell (periostracum) being this colour. Their aperture (the opening at bottom of shell) is oval with acute anterior and posterior ends.

Feeding Strategy
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References
Craddock, C., Lutz, R.A. & Vrijenhoek, R.C. (1997) Patterns of dispersal and larval development of archaeogastropod limpets at hydrothermal vents in the eastern pacific. Journal of Experimental Marine Biology and Ecology, 210, 37-51.

Dive and Discover (2013) Lepetodrilus elevatus on Riftia pachyptila tubes (figure 2).  Available: http://www.divediscover.whoi.edu/expedition15/hottopics/ecosystems.html [09/12/2014, 2014]

Dreyer, J.C., Knick, K.E., Flickinger, W.B. & Van Dover, C.L. (2005) Development of macrofaunal community structure in mussel beds on the northern east pacific rise. Marine Ecology Progress Series, 302, 121-134.

Fretter, V. (1988) New archaeogastropod limpets from hydrothermal vents; superfamily lepetodrilacea II. anatomy. Philosophical Transactions of the Royal Society of London.Series B, Biological Sciences, 319, 33-82.

Mclean, J.H. (1988) New archaeogastropod limpets from hydrothermal vents – superfamily lepetodrilacea .1. systematic descriptions. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 319, 1-&.

Mills, S.W., Mullineaux, L.S. & Tyler, P.A. (2007) Habitat associations in gastropod species at east pacific rise hydrothermal vents (9 degrees 50 ‘ N). Biological Bulletin, 212, 185-194.

Vrijenhoek, R.C. (2010) Bythograea thermydron distribution map, from: Genetic diversity and connectivity of deep-sea hydrothermal vent metapopulations. Molecular Ecology, 19, 4391-4411.

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