Rissoa parva
<p><em>Rissoa parva</em> (da Costa, 1778)</p>
Rissoa parva
Distribution and status
Ecology and behaviour
Often abundant at LWST on rocky shores. Extend to MTL and 15m sublittorally. On Corallina and other fine weeds, Laminaria holdfasts and under stones, grazing epiphytic growths and detritus. Breed all year, with summer maximum. Lens shape spawn capsules, less than 1mm diameter, containing 6-50 white eggs, laid on weed. Hatch in three weeks into veliger larvae with orange marks on edges of bilobed velum, right lobe larger than left. Settle on fine weed, and metamorphose, when shell 0.5mm.
Similar species
- Rissoa guerini
- No brown comma across labial varix.
- Always has costae; no smooth shell form.
- Snout brown.
- Yellow longitudinal line on tentacles.
- Southern species to English Channel and south coast of Ireland.
- Rissoa lilacina
- No brown comma across labial varix.
- Lilac rim on aperture.
- On adults, aperture constricted internally by tuberous growths.
- Snout brown.
- Yellow longitudinal line on tentacles.
- Rissoa rufilabrum
- Resembles R. lilacina but with less constricted aperture and proportionally smaller spire.
- Most records from west Scotland
- Rissoa porifera
- Resembles R. lilacina and R. rufilabrum but no costae or aperture restrictions.
- Most records west Ireland and west Scotland.
Key identification features
References and links
Fretter, V. and Graham, A. 1962. British prosobranch molluscs. London, Ray Society.
Graham, A. 1988. Prosobranch and pyramidellid gastropods. London.
Taxon version key
[NBNSYS0000177721]
Sort order
1520
Taxonomic group
Marine snail
Shell