Nephrops norvegicus is a deep water marine decapod crustacean which burrows in fine muddy substrata. It is a commercially important as a fisheries species, but knowledge of its biology, particularly concerning its endocrinology, is limited. This thesis describes the endocrinology of Nephrops norvegicus with particular reference to crustacean hyperglycaemic hormone. Histological investigations of the eyestalk of Nephrops norvegicus enabled the identification d" the X-organ sinus gland complex. The development of a microbioassay allowed the determination of increases of glycaemia following the injection of crude sinus gland extracts into a host animal. The optimal dose for induced haemolymph glycaemia was determined. HPLC separation was used to isolate and purify several neuropeptides from crude sinus gland extracts, which had varying degrees of hyperglycaemic activities. The use of ELISA (enzyme linked immunosorbent assay) showed that the peptides reacted with polyclonal rabbit antiserum raised against the CHH of the crayfish Orconectes limosus and with polyclonal guinea pig antiserum raised against the CHH of the lobster, Homarus americanus. SDS-PAGE of these peptides enabled an estimation of their molecular weights and the purity of one of the active peptides was determined using capillary electrophoresis. The effects of photoperiod and severe hypoxia on the CHH-induced hyperglycaemia of Nephrops norvegicus were also investigated. The responses of N. norvegicus appeared to differ in some respects from other decapods species. Pairs of oligonucleotide primers, based on the sequence of the lobster, Homarus americanus, complimentary to regions of the CHH sequence, were used in the polymerase chain reactions (PCR). Complimentary first strand DNA (cDNA) was synthesised from total Nephrops eyestalk RNA. 35 rounds and 40 rounds of PCR amplification produced a l00bp and 230bp double stranded DNA product respectively, which were resolved by electrophoresis on a tris-borate-EDTA gel. The product size was compared with known standards. Finally, the identification of CHH and GIH synthesis and storage in the eggs of Nephrops norvegicus at various stages of development was investigated. By the use of PCR, it was not possible to determine if synthesis of CHH was occurring in 50% developed eggs. The use of ELISA, however, demonstrated that in 90% developed eggs there was a significant increase of both CHH and GIH immunoactivity.

The defence reactions of the shore crab, Carcinus maenas, to a range of viruses were investigated in vivo and in vitro. In vivo studies with injected bacteriophages showed that C. maenas is capable of discriminating between different bacteriophages and actively removes certain phages from the haemocoele. Rapid initial clearance of the coliphage T2 was followed by slower removal and the phage persisted in the circulation for at least two weeks. The phage was sequestered to the hepatopancreas where it persisted for at least 72 h. Haemocyte counts remained unchanged upon injection of T2. With respect to prophenoloxidase activation, of the viruses tested only the Chlorella phage PBCV-1 was found to activate haemolymph prophenoloxidase at concentrations above 107 particles ml-1This indicates that C. maenas may respond to high concentrations of viruses in vitro. However, neutralization assays failed to reveal inactivation of viruses in HLS, plasma, or extracts of the hepatopancreas, gut, gill or heart, although some activity against an insect baculovirus and parainfluenza vims was detected in digestive juice. At least four antibacterial proteins, of ca. 6.5 kDa, 11.6 kDa, 20 kDa or 25 kDa, are present in C. maenas haemocytes. One, a 6.5 kDa peptide with activity against Gram positive and Gram negative bacteria, was purified. The N-terminal 30 amino acids of this peptide share over 60% sequence identity with bovine Bac 7, a mammalian cathelicidin. This 6.5 kDa peptide in C. maenas is the first antimicrobial peptide described from the Crustacea. Because the sequence of the pre-propeptide is as yet unavailable, it is not known whether or not it can be included among the cathelicidins. It has not been established whether or not the C. maenas 6.5 kDa peptide has antiviral activity.