The life history and ecology of the littoral centipede Strigamia maritima (Leach).

Abstract

The investigation, on the littoral centipede Strigamia maritima (Leach), was carried out between 1956 and 1959 largely at Cuckmere Haven, Suesex. The main habitat studied was a shingle bank the structure and environmental conditions of which are described. A description of the eggs and young stages of Strigamia is given and it is shown how five post larval instars may be distinguished by using head width, average number of coxal glands and structure of the receptaculum seminis in females, and head width and the chaetotaxy of the genital sternite in males. An account of the structure of the reproductive organs and the development of the gametes, and of the succession, moulting, growth rates and length of life and fecundity of the post larval instars is given, and the occurrence of a type of neoteny in the species is discussed. It is shown that S. maritima is able to withstand long periods of immersion in sea water by virtue of the faut that it can utilise oxygen in solution. Tho animal is, however, slowly desiccated under these conditions and it is suggested that this is the reason for the observed migration out of submerged areas and the confinement of the majority of Strigamia populations to the top of the 1ittoral zone. It is further suggested that the population at Port Erin, Isle of Man, which occurs at mid-tide level, may be a physiologically different form. The animal is shown to migrate to the top of the beach to breed and moult and it is suggested that it is only because the top of the beach 1s not covered by spring tides during the summer months that the centipede can remain in the littoral zone throughout the year. Another centipede Hydroschendyla submarina was studied at Plymouth and found to be far better adapted to a littoral life than Strigamia since it lays impermeable eggs and breeds and moults well below the high water mark. Field and laboratory experiments on the feeding habits of Strigamia are reported, and the animal is shown to prey on a variety of invertebrates. It is possible that small specimens of the centipede are preyed on by some littoral beetles. The animal almost completely lacks internal parasites but most individuals bear hypopi of a tyroglyphid mite; these, however, are probably harmless.