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| Reproduction | |||||||||
 Research study 1 |
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NOTE lit. “front foot” G. |
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Research study 2 |
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Research study 3 |
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  A veliger larva of Euspira lewisii spends 4-5wk in the plankton (at 20-22OC) feeding on phytoplankton. Towards the end of its pelagic existence the larva’s foot, shell, and tentacles begin to enlarge, and the velum bifurcates into 4 large lobes (photo on Right). The function of the lobes is not known, but may be involved in selection of a settling site or increased feeding surface or, with the increasing mass of adult features being carried at this late stage of pelagic life, may increase locomotion and/or aid in the larva’s buoyancy. |
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Research study 4 |
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Within 3-5d after settling and metamorphosing, the tiny juvenile moon snail Euspira lewisii is busy drilling and eating small clams and ostracods. Note in the inset photo that the juvenile already is drilling a countersunk hole in its ostracod prey. |
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Sexes are separate in moon snails Euspira lewisii and sperm transfer is direct via a penis. Later, the fertilised eggs are enclosed one to a capsule and extruded from the female in a mucousy mixture that is combined with sand (Left drawing below). The unusual shape of the egg collar results from the extruded mixture being moulded between the 
shell before it sets into its final sand/jelly state (middle drawing below). The extrusion and moulding take place under the sand, commence at the start of flood tide, and take 10-14h. 
Moon snails Euspira lewisii on the east side of Vancouver Island, British Columbia have egg collars that are 2-3mm in thickness. The colour of the egg collar depends upon the type of sand and other inclusions contained within it. Each egg/embryo rests in a jelly matrix within an egg capsule. Moon snail veligers range in shell length from 150-200um. 
Studies on moon snails Euspira lewisi collected at Departure Bay, British Columbia indicate that sex ratios of small specimens (<50g live mass) are close to 1:1, but those of large specimens (270-350g) are heavily biased to females (85% female:15% male). The research additionally shows a sexual dimorphism in shell size, with a male of 300g live mass having a shell about 18% heavier than that of an equivalent-sized female (see graph). The explanation for this is not known. 