Four new species of Eisothistos (Anthuridea: Isopoda) from tubes of Spirorbidae (Serpuloidea: Polychaeta)

Most were slim and <2 mm long. Eisothistos macrurus Wagele, with a cluster of large dorsal setae on heads and anterior pereon of post-partum females, broods in Mediterranean spirorbid tubes. It has one pair of hind telson plumose setae, each with a small companion seta arising from the same marginal notch, separated from each other by four, five or six marginal teeth. Anterior to the hind margin (by a distance ca 0.2 of telson width) two small setae may arise dorsally from the telson in adcentral positions (about the same distance apart as plumose setae). Its 'sibling' relatives, Eisothistos adcentralis sp. nov. from North-West Atlantic and Eisothistos adlateralis sp. nov. from New Zealand, have two small dorsal setae (anterior to hind margin) near the mid-line in the former and close to the sides of the telson in latter, with only two marginal teeth between setae of the plumose pair. Other southern forms also have adlateral dorsal setae. Eisothistos poseidon sp. nov. from Australia has each uropodal ramus like a trident. Eisothistos bifidus sp. nov. from Cape Town has hind telson plumose setae separated by a single bifid tooth. The collections included many juveniles and more than 30 gravid or caring females, but only three males, two of E. poseidon and one of E. adcentralis, with a specimen of doubtful sex, probably a senescent female of E. bifidus.