• Aspects of the biology of polar pycnogonids

      Richards, Peter Robin (University of BedfordshireUniversity of Bedfordshire, 1976-10)
      The internal morphology of fixed specimens of Antarctic pycnogonids WDS examined. Theories postulated during the course of these histological studies were then tested and modified by observations on live material and specimens fixed specially for histochemistry on visits both to the Arctic and d Antarctic. Live material was also transported back to Britain from these regions and cultured in refrigerated marine aquaria. The digestive system was studied in considerable detail. It is suggested that digestion is intracellular with gut cells changing their morphology during their lifetime. Embryo cells develop into Absorptive cells which at some stage take up a glandular appearance but not a glandular function. There are therefore two gut cell types, 'Embryo' and 'Absorptive/glandular'; this is in disagreement with some previous authors who separate the latter. The rele of the gut cell in the light of present day lysosome theory is discussed and a re-interpretation of work by previous authors suggested. It is found that the digestive process is slow and the prey tastes of the species studied, catholic. Furthermore, it is found that some species can survive for long periods without appearing to feed. Suggestions are made as to the significance and mechanisms of these phenomena. Mass transport in the body cavities is considered flnd compared with that of Hydra, an animal with which previous authors have made comparisons; - their philosophy is questioned. Blood flow, heartbeat and intestine movements are also considered and suggestions for future studies made. The role of blood itself is studied a possible clotting system described. Preliminary experiments on blood electrophoresis and chromatography indicate that such techniques may be useful in clarifying some complexities of pycnogonid classification and might provide a means by which future workers in the field might better link nutritional state, mass transport, digestion and external environment conditions.
    • Nymphon (Pycnogonida) in the Eastern Arctic

      Cranmer, Gary John (University of BedfordshireUniversity of Bedfordshire, 1982-07)
      Nymphon is the largest genus of Pycnogonida reaching its greatest diversity in the Polar regions. A revision of the genus within the Eastern Arctic has proved necessary due to the numerous nomenclatural complexities which have accumulated in the literature since its last major revision by Sars in 1891. This has been achieved using multivariate analyses involving the measurement of over 1500 specimens. Fifteen species are now recognized from the area and each has been redrawn and redescribed. It has not proved necessary to propose any new species. Two distinct sub-groups are found within the genus in this area, differing in leg morphology and reproductive strategy. The first group, exemplified by Nymphon stromi, has a leg morphology suited to walking or striding. A large number of lightly yolked eggs are typically produced and the larvae spend only a short period of their development on the male ovigers before they disperse. The other group, exemplified by Nymphon hirtipes, has a leg morphology more suited to clinging. Fewer eggs are produced but these are richer in yolk and the male overwinters with the larvae which are lost only when metamorphosis is nearly complete. These interspecific differences have been discussed and it is thought that they may enable direct competition to be avoided by the exploitation of different facets of the same environment. In addition, differences in the musculature have been discussed for species within Nymphon and for the Pycnogonida generally. The male ovigers of all species examined show various adaptations which increase the surface area compared with that of the female. These modifications have been discussed and are shown to afford a greater area for attachrnent of the maturing egg masses. A histological examination of the internal structure of the femoral cement glands of Nymphon hirtipes has revealed that the adult males have a broad band of glandular tissue lying under the epidermis whereas specimens in the final larval stage have little or none. The life-cycle of Nymphon hirtipes is postulated, showing the species to take between two and a half and three years to attain maturity. It breeds only once, during its final summer. This is compared with existing knowledge of the life cycles of shallow and tropical water species.