During taxonomic work on tho three species of Orchestia studied a new morph and a new subspecies were discovered and described. Discriminatory criteria are given by which all the life history stages of these forms could be distinguished, except juvenile C. mediterranea and C. cavimana. The estuarine penetration and shore position of species of Orchestia in the Medway estuary was studied and compared with that in other estuaries. Laboratory investigations suggested that dilute seawater affected both survival and moult length and that these were important factors limiting estuarine penetration. The role of active locomotion in zonal aggregation was investigated and it was thought that visual attract ion was one of the stimulii involved in maintaining up and down shore directional trends. Species of Orchestia were nocturnal and showed definite circadian rhythms of activity which, in O. mediterranea, was related to extrinsic lunar/tidal rhythms.

The Brackish Water Prawn Palaemonetes varians (Leach) is common throughout coastal waters of the UK and Western Europe. Its preferred habitat is within sheltered waters of lagoons, though it is not a major constituent of estuarine tidal flux. Bottle traps were used to assess the seasonal 'activity' and habitat density of P. varians in artificial coastal lagoons on saltmarshes and claimed marshland habitats. Additionally, the potential diet resources available to P. varians were investigated between sites. The data revealed that relict landward lagoons and saltmarsh borrow pits were successful breeding areas for P. varians, the latter acting as a major replenishing resource in the estuary. Differences in breeding period and growth rate, assessed using maturation, zoeal and enclosure data were found to be attributed to environmental temperature rather than habitat food resources. P. varians was found to adapt to varying prey resources showing an ontogenetic shift in prey size with increasing body size, which was correlated with chelal grab width. The chelal morphology of P. varians in relation to feeding behaviour was described using Scanning Electron Microscopy (SEM). Structural and setal variation accounted for 'passive' and 'active' feeding behaviour portrayed by P. varians. Within the sites studied, the Common Goby, Pomatoschistus microps (Kreyer) was also a cohabitant with P. varians. Bottle trap data demonstrated that whilst the seasonal activity of P. microps in claimed marsh lagoons was linked to temperature, within the intertidal borrow pits an autumnal inmigration pattern was identified. The autumnal peak of P. microps was shown to have a profound effect on the abundance of P. varians. Different seasonal and ontogenetic diet trends were established for P. microps, via gut and morphological analyses and they were used to investigate the extent to which P. varians was utilised as a prey resource. Furthermore, comparisons were made between the Grass 'Shrimp', P. pugio (Holthuis) and MUmmichog, Fundulus heteroclitus L. These species occupy a comparative habit and are important species in the ecological structuring of American saltmarsh ecosystems. Digital video and mesocosms were used as further tools to investigate the interrelationships and predation of P. varians by P. microps. It is shown that whilst the predation of P. varians does occur in microcosms, the predation efficiency of P. microps was limited by tail-flip escape swimming (TFES) of P. varians.

Some effects of DDT on the shore crab (Carcinus maenas) were investigated. Parameters examined included the activity of gill ATPases and their effects on ion and ammonia levels of the haemolymph. Histological alterations were observed by light microscopy. In an in vitro study, an homogenate of Carcinus gills was exposed to concentrations of DDT from 10ˉ¹º M to 10-5M. The activity of Na+ , K+ -ATPase was stimulated at all concentrations. The activity of Mg2+ -ATPase was inhibited at all concentrations. Total -ATPase activity represented the combined activity of both. In vivo studies on the effect of DDT on ATPases showed that the activities of both Na+, K+- and Mg2+ -ATPases were inhibited. There was evidence that osmoregulation was affected over the short term, but not over a longer time course. After injection of a solution of ammonium chloride into the haemolymph of Carcinus, there was no consistent pattern to the rate of loss of ammonia from the haemolymph in DDT - exposed and control animals. Histological examination of gill tissue exposed to DDT revealed that the mucopolysaccharides around the gill lamellae were reduced in thickness. Ca2+ -ATPase activity and the R.N.A. content of the tissue were reduced. Estimations of the quantity of DDT and derivatives which had accumulated in some organs after DDT exposure were made. The greatest amounts were found in gills, followed by digestive gland, stomach and gonad.

No description available.

This thesis examined factors influencing the success of the larval cyprid phase, and the distribution of adult Semibalanus balanoides in the Clyde Sea. Experiments were conducted in the Clyde Sea area (2004 – 2007) because it is effectively both a closed system in its whole extent for release of nauplii and cypris settlement, and at a larger scale it is an open system for the actual settlement on individual rock types. The effect of geology, exposure and position on the shore is examined in relation to barnacle fecundity (number of eggs produced) with metamorphic rock, exposed shores and mid shore settlement of Semibalanus balanoides having higher barnacle fecundity than igneous and sedimentary rock types, sheltered shores and upper or lower shore height areas. Frustum volume was found to be a reliable non-destructive way to estimate fecundity, and egg size did not alter significantly from year to year. Supply was most reliably measured using pumps or adhesive panels, and artificial rock panels as an alternative to natural rock; the majority of cypris left after four seconds investigating artificial panels. Cannibalism takes place in the Clyde Sea with 44 % of adults investigated on the shore showing signs of this, frustum size and height didn’t affect propensity to cannibalise. Video recording demonstrated a mean of nine cypris and / or nauplii consumed per adult per hour. Settlement occurred on all major rock types in the Clyde Sea. Cypris preferentially settled on metamorphic and igneous rock types. There was no significant effect of north or south orientation on vertical panels for settlement intensification. Settlement levels were higher on natural rock substratum than artificial panels, but were not significantly different; and showed larger per area settlement on smaller areas as 1 cm2 had a mean settlement of 49.40 cypris, 5 cm² 18.40, 10 cm² 22.42, 50 cm² 13.92, 100 cm² 9.34 and 500 cm2 5.65. On natural rock around the Clyde Sea (as opposed to areas cleared for experiments), areas of < 1 cm² and 1 cm² are more common as potential settlement sites, comprising of 51.99 % and 23.98 %, respectively of available settlement area. The mean number of barnacles in the Clyde Sea area was calculated to be 9.454 x 10¹¹, which could produce a mean number of 1.444 x 10¹⁵ eggs.

The stalked barnacle, Pollicipes pollicipes, is considered a delicacy on the Iberian Peninsula and has a high market value. Despite being a dangerous activity, increased collection efforts and associated stock shortage have raised awareness of the need for effective conservation and stock management policies. Accordingly, aquaculture has received interest as an alternative to supply the market and for re-stocking programmes. However, knowledge on the aquaculture requirement of this species and applicable production cycles is limited. Research challenges span the entire P. pollicipes life cycle, from adult reproduction to larval settlement. Though adults have been kept in culture, the conditions required for broodstock reproduction and larval release remain poorly studied and larvae have been routinely extracted from wild-collected adults and reared to cyprids. Optimization of larval culture is essential for the production of high-quality larvae and avoidance of high mortality. Furthermore, cyprid settlement on artificial substrata presents a bottleneck to production, with settlement occurring mostly on conspecific adults. The conditions that mediate settlement on preferential substrata have yet to be established. Though juvenile behaviour and growth in the wild have been the subject of ecological studies, research on culture conditions is limited and the influence of environmental factors is poorly understood. In the present work, the effect of environmental conditions on the behaviour and development of P. pollicipes was tested throughout the life cycle to identify optimal culture conditions and assess potential for larger-scale culture. Research focused on broodstock reproductive conditioning, larval culture, larval settlement and juvenile culture and behaviour. Broodstock reproductive conditioning was investigated by monitoring larval production and nauplius quality from adults reared under different temperature regimes. P. pollicipes larvae were also cultured under different conditions of temperature, food quality, photoperiod and salinity, and monitored for growth and survival. Larval attachment and metamorphosis on adults were tested for cyprids of different age and batch, and according to environmental factors such as temperature, salinity, hydrodynamics and light conditions. Optimal conditions were then used for investigating settlement on substrata in culture, and natural and artificial structures were ii tested for settlement in the wild. Juvenile feeding behaviour and performance in culture were investigated in relation to hydrodynamics, temperature, food quality and quantity.

No description available.

This study investigated the defensive responses of juvenile signal crayfish (Pacifastacus leniusculus, Dana) to two putative predators, perch (Perca fluviatilis, L.) and eel (Anguilla anguilla, L.), and attempted to determine the Importance of direct and indirect predatory effects on the distribution of newly independent Juvenile crayfish in a Swedish pond. Eels are thought to be more detrimental to crayfish populations than perch. Experiments using juvenile crayfish did not support this assertion. Visual and chemical stimuli elicited crayfish avoidance behaviour. This was most marked when both stimuli were presented together. Both predators elicited similar avoidance behaviour. Crayfish were less active by day, spending more time under shelter. Shelter provided by vegetation and substrata reduced crayfish mortality. Crayfish also avoided small non-predatory fish (Leucaspius delineates, Heckel). It is suggested that these fish indirectly increased crayfish mortality. Adult crayfish increased juvenile crayfish mortality but caused juveniles to be more active by day than at night. These responses illustrate the conflicting demands on crayfish defensive behaviour in multi-predator environments. Mechanical and visual stimuli elicited evasive behaviour. Crayfish evaded predatory strikes by perch and eels. The response to eels was delayed. Perch chased fleeing crayfish, and caught more crayfish than eels, which never chased prey. Initially, perch preyed on juvenile crayfish more rapidly than eels. Despite having distinct foraging behaviours, perch and eels produced similar crayfish mortalities. If eels are more detrimental than perch to crayfish populations, this may be a result of differences in size selective predation. The initial distribution of newly independent crayfish in a Swedish pond was influenced by the distribution of gravid female crayfish. Perch preyed on juvenile crayfish but were not a major factor determining crayfish distribution. Intraspecific competition and Invertebrate predation may have had a greater effect. Crayfish populations may be influenced by perch predation on yearling crayfish.

No description available.

No description available.