The occurrence of abnormal embryos in two ovoviviparous barnacle-dwelling littorinids

The occurrence of developmental abnormalities in two of ovoviparous littori nids (Littorina neglecta and a barnacle-dwelling form of L. sasatilis) inha biting the barnacle zone at Peak Steel, Ravenscar on the north-east coast o f England was investigated. In general developmental abnormalities appeared to be a rare occurrence in both taxa. However, L. neglecta was found to ha ve a significantly greater proportion of deformed embryos in their brood po uches than L. saxatilis B (Figure 1). A distinct seasonal variation in the number of developmental abnormalities was observed in L. neglecta, and it i s suggested this is a result of broods developing outside of the main repro ductive season being more prone to deformity.