Aspects of the morphology and ecology of two British tubificids (Oligochaeta)



Two poorly known tubificids have recently been identified from rivers and streams in Britain. Examination of new specimens of Haber simsi (=Peloscolex simsi Brinkhurst, 1966) has shown that the original description is essentially correct. This tubificid shows superficial similarities to Tubifex ignotus and a comparison of the chactae is made. H. simsi has very low population densities in Bere Stream (maximum of three individuals in forty cores of 0.002 m2 area), and mature and breeding individuals have been found from June to November. A form of the genus Limnodrilus, superficially similar to Limnodrilus hoff-meisteri, with a scalloped margin on the penis tube hood has been recorded from several sites in Britain. The mean ratio of length of penis tube/base width is 6.8±0.3 (x̄±s.d.) compared with 9.6±0.2 of L. hoffmeisteri. The chaetae of this type closely resemble those of Limnodrilus claparedeianus.