5 Published Articles on Studies on the Notostraca A.R. Longhurst Ph.D Bedford College ProQuest Number: 10098541 All rights reserved INF0RMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed a note will indicate the deletion. uest. ProQuest 10098541 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, MI 48106-1346 sramss as Tm HOfosTRACA Being a thesis presented to the University of London fo r the degree of Doctor of Philosophy» by Alan R. Lon^urot (Formerly of Bedford College, now of Federal Fisheries Service, Lagos) This thesis consists of a series of reprints of publications in which are reported the results of researches on the systematics of the Rotostracan Crustacea* Studies were made on the cytology, the biochemistiy and the comparative ecology of the group and were utilised in a systematic study of the Notostraca, 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 Pox, Success in culturing Triops oancrifoirois from this pool under laboratoiy 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, 'JKiese, 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 ezoskeletal 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 thesisj a preliminary report of the discovery that the so-called parthenogenetic forms are in fact heimaphroditic is bound in as E in the thesis. The main paper, B, contains a review of Hotostracan literature, the analysis of the validity to c^stematics of the ezoskeletal 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 Notostraca are composed of a small number of very widely dispersed speoies, all rather close to each other ^stem atically 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 cycle vdiich were elucidated incidentally in the investigation of chromosome numbers appears as D and d escrib es 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 Notostracan 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 h i^ 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 Notostraca* Per convenience the constituent papers of the thesis are l is te d below* A* Evolution in the Notostraca* Evolution. Bt A review of the Notostraca. Bull* Brit. Mus. (II.H.) Ct Abnormal variation in the Notostraca. Syst.Zool. 3)8 Reproduction in the Notostraca. Proc* Zool. See. Bond. Et Reproduction in the Notostraca. Nature » Lond. EVOLUTION ÎN THE NOTOSTRACA A. R. L o n g h u r s t Bedford College, University of London Received August 16, 1954 The Notostraca are phyHoped Crusta­ dispersal—in or upon larger animals, at­ cea in which the carapace is shield-shaped tached to dry pieces of wind-blown vege­ and covers the anterior part of the body ; tation, or airteme singly in wind cur­ together with other phyllopods, they are rents (a desert dust-devil will whirl considered to be relatively unevolved particles much denser than the eggs of Crustacea—there is a high, but irregular, phyllopods high into the air). number of appendages (forty to sixty That these passive means of dispersal pairs are usual) and the segmentation of are effective is quite clearly shown by the the body is anameristic. ubiquitous occurrence of phyllopods in It is characteristic of phyllopods that suitable pools wherever these occur. they occur in temporary rain pools, gen­ Notostraca occur on such isolated oceanic erally in arid or steppe country where islands as the Hawaiian group, and in the such pools are common, and are unable to few suitable pools that the rainy English maintain themselves in the face of com­ climate permits. The phyllopods show petition from higher Crustacea or Insecta another characteristic of passively distrib­ (Ardo, 1947). uted invertebrates—that of very widely The survival of such primitive and spread, sometimes almost cosmopolitan vulnerable animals poses an interesting species; in a recent study of the No­ problem—the key to which may lie in tostraca for a systematic revision I found their main adaptation to a temporary that Triops longicaudatus, which Linder habitat, the drought-resistant egg. The (1952) showed was the only species of possession of such an egg, from which the genus in the Americas, extends from hatching normally occurs only after the West Indies through Central America desiccation, is an obvious prerequisite and right across the Pacific to Japan ly for the exploitation of a temporary fresh­ way of the Galapagoes, Oahu and New water habitat by a group of animals which Caledonia. In all this area there is vir­ do not have the capacities of aerial migra­ tually no morphological change (Long­ tion which the Insects possess. hurst, 1955). These drought-resistant eggs of phyl­ These facts of dispersal and geographi­ lopods are the only possible means of dis- cal distribution seem to me to explain the pc^rsal for the group, for the pools in survival of the phyllopods. The initii^ which the animals occur are isolated from arthropod invasion of temporary pdo||# one another, and are only rarely part of may well have been performed by the a stream system along which dispersal primitive fresh water Crustacean fauna of adults would be possible. and has radiated into the forms of phyllo­ The eggs are small, light in weight be­pods we see today—the carnivorous No­ cause of their dry alveolar shells, and are tostraca, the “pelagic” Anostraca, and sticky when laid in at least one genus the burrowing, detritus-feedii^ Concho?^ (Triops, Notostraca); further, the eggs straca. This early fauna would of some Anostraca are known to retain spread and occupied at least a hq^ viability after passing through the guts portion of the suitable pools, and of Amphibia (Mathias, 1937). These cosmopolitan occupation would ha^ facts suggest several possible means of fectively prevented any geogrmphkaHyiMth Evblutton 9 : 84-86. March, 1955. 84 NOTOSTRACA 85 lated, phyllopod-free, part uf the environ­ era. Triops and Lcpiiiunis, each with a ment from forming a place in which later, small number of very wide-spread spi'cios. more highly evolved forms could have as if the geographical barriers wbich are adapted themselves to-life in temporary essential to spéciation in less passively waters. distributed animals are inefTectiyc in the This is in line with modern theories face of the efficient dispersal of the resting concerning the primary importance of eggs. geographical isolation in, at least, spécia­ Although Notostraca are normally tion and adaptive radiation. The small characteristic of pools in arid regions, one amount of essential adaptation—drought- species— Lcpidftt'ns arcticus—occurs only resistant eggs and a rapid rate of growth in the circumpolar arctic regions, where —would surely have been evolved in. say. it lives in large lakes, stream systems and Amphipods or Isojkk Is if some such pro­ small permanent or teni])orary p(»ols ; pos­ hibitive factor were not operating. Here sibly this is a case where adaptation to the essential adaptation to the unusual one habitat—desert pools—in which there habitat seems to have enabled the pioneer is a premium upon rapid development and arthropods to have retained possession of reproduction may have preadapted the the habitat. animals to another, completely different, The lack of competition and the un­ ■environment where conditions amicable to changing nature of the habitat would have life occur seasonally for similarly short produced no selection forces for further I)eriods. evolution in these phyllopods. and they Some Anostraca exploit the period in have retained a primitive, unevolved form very early spring when the temperature in conse({uence. begins to rise, but before the predatory Fossil Notostraca are. unfortunately, insects are Bronchi pusvernalis sparse, but Guthorl (19.U) illustrates occurs in permanent poo is in North what are certainly carapaces of tlu'se ani­ .America and is active only in this very mals from the Permian deposits, although short period at the end of winter; it then It is not possible to relate these to either lays eggs which lie dormant until the of the modern genera.