5 Published Articles on Studies on the Notostraca

Abstract

This thesis consists of a series of reprints of publications in which are reported the results of researches on the systematica of the Notostracan Crustacea. Studies were made on the cytology, the biochemistry end the comparative ecology of the group and were utilised in a systematic study of the Notostrace.

This research was initiated after the finding by the candidate of living Notostraca in a rain-pool in southern England, which proved to be the only known locality for the group in the British Isles in recent years, having been found there previously by Professors Hobson and Fox. Success in culturing Triops cancriformis from this pool under laboratory conditions stimulated efforts to obtain cultures of other species, and finally cultures of all four species of Triops and of two species of Lepidurus were maintained at Bedford College. These, together with the collections of preserved material in a number of European, American and Australian museums, formed the basis of the study.

The cultures were utilised for investigations of the development of exoskeletal characters during growth, for the investigation of the variability of these characters in a single line of individuals under differing environmental conditions, for cytological studies resulting in some knowledge of the chromosome numbers within the group, and for an investigation of the specificity of blood pigments in different species and in different races of a single species.

The study was recorded in five publications, which are bound together to form this thesis; a preliminary report of the discovery that the so-called parthenogenetic forms are in fact hermaphroditic is bound in as E in the thesis. The main paper, B, contains a review of Notostracan literature, the analysis of the validity to systeraatics of the exoskeletal characters used in the past, the chromosome counts, the investigation of biochemical specificity, and the basic systematic revision of the group. The conclusion reached in this paper was that the Hotostraca are composed of a small number of very widely dispersed species, all rather close to each other systematically but characterised by considerable individual variation. The number of species previously described was shown to be much too high.

A separate account of the details of the cytology and reproductive qycle which were elucidated incidentally in the investigation of chromosome numbers appears as D and describes in considerably more detail than hitherto the cytology of the gonads during reproduction.

An attempt was made in a separate publication. A, to explain the widespread nature of the distribution of llotostracan species and to relate it to the extreme longevity of the group in palaeontological terms, and an explanatory hypothesis is developed, derived from the ecology of the group.

Finally, under C, there is an account of the existence of what appears to be a most unusually high proportion of abnormal individuals occurring in populations of Notostraca compared with the proportion in other animal groups, and this again is referred to the palaeontological longevity of the Botostraca.

For convenience the constituent papers of the thesis are listed below: A: Evolution in the Notostraca. Evolution.; B: A review of the Notostraca. Bull. Brit. Mus. (N.H.); C: Abnormal variation in the Notostraca. Syst. Zool.; D: Reproduction in the Notostraca. Proc. Zool. Soc. Lond.; E: Reproduction in the Notostraca. Nature, Lond.