Biometric variation in Spadella cephaloptera on the Canary Islands (Chaetognatha)

Specimens of Spadella cephaloptera from Tenerife, Gran Canaria and Gomera (Canary Islands) were compared biometrically in regards to morphometric and meristic characters. Variation exists among the populations on the islands as well as between the islands. The populations on Gomera seem more distinct from the populations on Tenerife and Gran Canaria than the two latter are mutually. An apparent decline in the number of adults occurs in July, which is related to a decrease in the number of eggs. A shortage of food can explain the reduced fecundity of the specimens. S. cephaloptera prefers habitats protected from the influence of waves.