Seasonality in some British intertidal Acari

Abstract

The life cycles of halacarid and non-halacarid littoral Acari are examined, and the results compared with those of other workers. All species can carry out one life cycle in approximately 12 months, with the exception of the genus Isobactrus (Halacaridae) which may have two or more generations per annum. Species exposed to heavy wave action have mechanisms to reduce juvenile mortality, including larval retention, and/or larviparity, extended periods of oviposition to optimize losses as a result of wave action, and niche protection of juveniles. However, these adaptations are preadaptations, because similar mechanisms exist among related species in less stressful environments. The sex ratios of some species follow an annual cycle with females dominant before and during oviposition, suggesting that they live longer than males and die after oviposition. Sex ratios among small groups of Hydrogamasus salinus (Laboulbene) (Cyrtolaelapidae: Mesostigmata) are variable, though these are relatively constant in larger aggregations.

Keywords :

• Acari
• Intertidal
• Seasonality