See also Mullineaux et al. (1996), Fig. 1, for larval SEM's.
| Size under dissecting microscope: 170-180µm Size under compound microscope: 170µm |
| Morphology: These are small protoconchs with fine pitted sculpture. In some individuals the pits appear to form lines, but this is not usually evident under the light microscope. The line of the aperture continues straight to the posterior edge of the shell in the apical view. There is a distinct medium-width aperture rim visible under the compound microscope. Five species of Lepetodrilus - L. cristatus, L. elevatus, L. ovalis, L. pustulosus (all described in McLean, 1988) and L. tevnianus McLean 1993 , are present at 9°N. All these species have protoconchs that are similar in size and shape. Some individuals are nearly transparent (above left), while others are more opaque; it is possible this is a taxonomically useful trait, but the species cannot be distinguished morphologically at this time. |
| Frequency: Pump EPR 1999-2000: Common Pump EPR 2004: Common Trap 2004-2005: Common |
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Unknown 5. Lepetodrilus has a more streamlined appearance, with the aperture length about half the diameter of the protoconch. Unknown 5 is more rounded and the aperture is closer to 2/3 the protoconch diameter. The aperture rim is narrower in Unknown 5 and it flares out at the anterior edge and at the sides. Unknown 5 has reticulate rather than pitted sculpture, but this may not be apparent under the light microscope. In the bottom photo showing both species, Lepetodrilus is on the left. |
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Benthic Unknown A. This protoconch is about 10µm smaller than Lepetodrilus spp. and has reticulate rather than pitted sculpture. It tends to roll to expose the aperture when moved with a probe, while Lepetodrilus is stable with the apex facing up, as shown above. |
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Gorgoleptis emarginatus (left in top photo) , Gorgoleptis spiralis (right) and Gorgoleptis sp. 3 (bottom). Two of the three presumed Gorgoleptis protoconchs we have found are approximately the same size as Lepetodrilus. The sculpture of Gorgoleptis spp. is much coarser and it has a point at the outer edge of the aperture (two of the species have points on the sides as well). In none of the species does the aperture line up with the base as it does in Lepetodrilus. |
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Clypeosectus delectus (right) and pointy apex (left). Both of these species have coarser sculpture than does Lepetodrilus and their apertures do not line up with the base. Pointy apex is also 15-20 µm smaller. |
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Lepetodrilus-like. There is a group of slightly larger protoconchs (~190-195μm) that closely resemble Lepetodrilus. We have termed them Lepetodrilus-like. They have coarser pitted sculpture than Lepetodrilus and the aperture is slightly curved, sometimes appearing to come to a blunt point in the front. They appear to lack an aperture rim. |
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