Introduction

The Rocky Intertidal Experiment

Life History

Taxonomy

Morphology

Reproduction

Works Cited

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 Littorina littorea

            Common periwinkles are oviparous meaning the eggs are laid or spawned by the female. Fertilization occurs internally and females lay their eggs directly into the sea.  Littorea larvae are planktonic and egg release generally coincides with the tides (Jackson, 2002).  Female fecundity is known to increase with size and males usually choose to mate with the larger females (Jackson, 2002).  It is possible that the reason why L. littorea are such a successful invasive species is they lay their eggs with the tides, which are carried to new locations immediately.

Littorina obtusata

              Littorina obtusata live directly on the Ascophyllum nodosum that they consume.  This species does not have a planktonic larval stage, the newly hatched crawl directly onto the Ascophyllum where they remain (Chapman, 1992).  It is possible for the female L. obtusata to undergo multiple copulations with males, store the sperm, and use only a small amount to fertilize each batch of eggs she lays.  This is possible, because the females have two internal storage areas for sperm.  The longer the male guards the female after copulation, the more likely his sperm is to enter the storage area called the seminal receptacle, which is protected because sits  further inside the snail’s body (Paterson et al., 2001).  The temporary sperm sac in the female is called the bursa copulatrix and is described as a blind ended sac (Paterson et al, 2001).  Although this is the primary receptacle for sperm, it is only temporary.  L. obtusata females lay benthic egg masses of 50-100 eggs at a time and emerge as crawling juveniles (Paterson et al, 2001).