The role of the circadian time-keeping system in regulation of locomotor activity and certain aspects of reproduction has been investigated in wild Polynesian rats, Rattus exulans. Locomotor activity is under circadian control and data are consistent with a general model of the pacemaker mechanism as a weakly interacting population of circadian oscillators. Experimental studies and field observations indicate that the action of light in entrainment of this rhythm is primarily non-parametric. Female R. exulans continue to ovulate during prolonged periods in constant conditions and undergo a pattern of change in vaginal cytology through the estrous cycle which closely resembles that of laboratory R. norvegicus. These findings are consistent with the hypothesis that the estrous cycle in R. exulans is regulated by a similar circadian mechanism to that controlling the timing of ovulation, and hence the duration of estrous cycle, in laboratory rats. Female R. exulans do not exhibit regular fluctuations in either the period of the activity rhythm or intensity of the active phase in association with the estrous cycle. Ovariectomy also has no significant effect on the period of the activity rhythm and no discernible effect on the distribution or intensity of activity. It is therefore concluded that there is no feedback action of the ovaries or estradiol on the circadian pacemaker regulating locomotor activity in R. exulans, which thus differs from laboratory rodents. This proposition is further supported by the observation that there are no significant changes in either period or variability of the activity rhythm in association with the degenerative changes that occur in the female reproductive system in old age. The adaptive significance of these findings is considered. Field studies on breeding patterns of R. exulans throughout its distribution provide several lines of indirect evidence in support of the hypothesis that the onset of breeding in this species in temperate latitudes is regulated by seasonal changes in photoperiod. Accelerated attainment of puberty occurs in juvenile females collected during the non-breeding part of the year and housed in LD 16:8. Juvenile females collected at the same times but housed in LD 8:16 for an identical duration remain immature. Groups of mature females collected during the breeding season do not show a differential response to these light regimes. These results are discussed in relation to field data on breeding patterns in the population from which experimental animals were collected. It is concluded that the onset of breeding in this population is controlled primarily by a photoperiodic mechanism regulating the attainment of reproductive maturity in females. Information on the physiological organization of circadian systems in mammals is reviewed, with particular emphasis on the relationships between locomotor activity rhythms, the estrous cycle, and the effects of photoperiod on reproductive function in rodents.

The thesis answers the general question of whether the quality of artificially reared insect species should be based on performance tests for intended use or whether quality should be based on a more holistic biological approach. The empirical research is carried out using the lepidopteran leafroller 'Cnephasia' jactatana (Walker). The thesis defines biological performance and quality in terms of the success of an insect population in survival and reproduction and regards the laboratory environment as an artificial habitat that insects must colonise in order to survive and reproduce. Changes in biological performance that occurred during 12 successive generations of laboratory rearing were due to selection, acclimatisation and domestication and not adaptation. Artificial colonisation is theoretically successful within a limited range of environmental factors. As the inherent genetic variability of the founder population determines the resilience of the population to changes in performance, the ranges of environmental factors during colonisation should be wide to 'capture' much of the variability. Using body size (weight) as an aspect of overall quality, the thesis presents evidence that the final instar larva of C. jactatana has a threshold mechanism (larval critical weight, LCW) that determines pupal and adult size. There is a proportionate decrease in weight from the maximum weight that a larva attains in the final instar (LMW) to pupa ( described as constant DP ) and to adult (DA). There is a direct relation between the latent feeding period (period between attaining an LCW and LMW), LMW, pupal and adult size, and the reproductive performance (fecundity ). Within the experimental conditions diet quality, temperature, photoperiod and artificial selection had no effect on the larval critical weight, DP or DA, the larval threshold mechanism in C. jactatana is probably a mechanical trigger that initiates pupation. Diet quality, temperature and thermophotoperiods affected pupal size, adult size and reproductive performance. Photoperiod had no significant effects on size and reproductive performance. Positive assortative selections for slow development and low pupal weight significantly decreased pupal and adult size, and reproductive performance. Selection for fast development and heavy pupal weight for three generations had no significant effect on size or reproductive performance. Larval critical weight is demonstrated as useful to define quality indices and predict the performance of laboratory reared insects. The general conclusion of the thesis is that insect quality should be defined more in terms of the success in survival and colonising ability rather than solely on the success for 'intended role' or 'fitness for use'.

This thesis describes the behavioural ecology of the tui, Prosthemadera novaeseelandiae, a member of the Meliphagidae (honeyeaters), in the suburban Auckland region of the mainland of New Zealand. Tui are highly nectarivorous but observations show differences in degree of importance between the three food categories; nectar, fruit and insects according to season. when foraging for nectar tui are not responsive to flower colour but use all flowers with nectar concentrations greater than 7% (wt. per wt.) and use fruit when nectar availability falls. Foraging observations are significantly different for male and female tui with males taking more nectar and females taking more insects, in response to greater protein requirement as well as a result of status affecting foraging. There is also a seasonal difference in method of prey capture with the more energetically expensive hawking occurring in times of greater nectar availability or when very few insects in relation to nectar are taken. Colour-banded tui are shown to move in family groups over distances ranging from 5 to 35km in search of nectar for much of the year, but are localised into small foraging areas during breeding when nectar is abundant. Group members remain together and nest near each other, female offspring nesting closer to parents than male offspring. There is differential access to both natural and artificial food resources and the various asymmetries of sex, age and residency determine relative status at food sources but are not absolute. Loud song is the most conspicuous behaviour and is used to mediate avoidance between individuals and between groups. An artificial food source is partitioned temporally and spatially during breeding with the local higher status birds that use the feeders having significantly greater breeding success. Unlike results published for most passerines, both sexes of tui sing throughout the year and songs in their repertoire show sexual, seasonal, behavioural and individual variation. Pairs duet and both sexes will match songs with mates and with neighbours; resulting in apparent dialect areas corresponding with group boundaries. Avian spirochaetosis is identified as one of the causes of death in a population with 13-30% annual loss. Losses are readily compensated for as the nesting cycle is short and the breeding season is long. This, together with an opportunistic foraging strategy, great mobility and prolonged association in family groups explains the continued presence of tui in suburban areas.

Endogeneity of valve movement rhythms was demonstrated for the Pacific oyster Crassostrea gigas under constant conditions of temperature, light, salinity, water level and food availability. Rhythms continued for up to 6 weeks until the experiments were terminated. The rhythms showed a high degree of temperature compensation between 13 - 24˚C, but at 4˚C the free-running period was abnormally long. The length of the “open", or active phase decreased with temperature. Oysters collected from subtidal sites, as opposed to intertidal sites, also exhibited endogenous rhythms when held under constant condition. Oysters that received no food during a starvation trial were also rhythmic. Oysters subjected to artificial tidal cycles (HL 6:6h), show very precise synchronization of valve opening and closing to the cycles. Oysters were also be entrained to water disturbance cycles (6:6h) and light cycles (LD 12:12h), but the synchronization was not as precise. Rhythms were characterized by (1) split rhythms (2) spontaneous changes in the free-running period (3) spontaneous changes in rhythm clarity (4) spontaneous phase changes (5) and a Lot of "noise". These characteristics suggest that the underlying pacemaker controlling the rhythm may consist of more than one oscillator or more than one group of oscillators. No conclusive evidence could be found for semilunar or lunar rhythmicity. Cycles in the rate of algal cell clearance over a 24h period were shown by individual oysters. As a consequence of the variability between individuals combining the data tended to hide the existence of the rhythms. No evidence for rhythms in assimilation efficiency was found. Cell clearance rates were also affected by rising temperature over the range 4 - 25˚C, reaching a peak value at 17˚C. The rate of cell clearance fell sharply after 60 - 90min of feeding in a closed system, indicating that the rate was significantly affected by the decline in food availability. The time taken to open the valves and to start faeces production fell with increasing temperature. The amount of faeces production followed a similar trend. Assimilation efficiency fell with increasing temperature and many negative values were evident, suggesting contamination. However the total weight of faeces produced was less than that of food available implying that the oysters were assimilating inorganic material. The time taken to open the valves and the % oysters that opened their valves was adversely affected by declining salinity over the range 8.5 - 34‰. The time taken to start faeces production and. the % of oysters that produced faeces followed a similar trend. Assimilation efficiency was not significantly different at 25.5 and 34‰. AE% could not be measured at 8.5 and 17‰ due to a lack of normal faeces. Individual oysters showed cycles in the rate of oxygen uptake, but these were not synchronized to the tides or to each other. Pooling the data to calculate means cancelled out the individual rhythmicities. The presence or absence of food did not affect the expression of the cycle. The rate of oxygen uptake was positively correlated to oyster dry weight, temperature and salinity. Though for salinity the rate of oxygen uptake fell sharply below a critical salinity occurring between 10 - 13‰. Oysters held in sealed respirometers maintained a constant rate of oxygen uptake until a critical level of oxygen availability was reached, the rate of oxygen uptake dropped .significantly below this level. The slope of the regression lines (˚b˚), prior to reaching the critical oxygen level, increased with temperature, salinity and food concentration. But the time taken to reach the critical oxygen level, and the level of oxygen availability at which this occurred, was not significantly correlated with temperature, salinity or food concentration. The pattern of valve movement corresponded to the level of oxygen available. Valve movements became very frequent as the critical oxygen level was approached. Activity was reduced to occasional periods of valve movement after it was reached. The level of activity was adversely affected by declining salinity, but was not affected by the level of food availability.

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In her classic review of the echinoderms, Hyman (1955), describes the ophiuroids as "the most successful echinoderm group living today". This success has largely been attributed to both their smaller size and their remarkable agility. Many authors have commented on their great importance in the bionomics of the sea; various species participate in food chains involving demersal fish and many others serve as agents for the disposal and recycling of organic materials on the benthos. Their wide occurrence in the marine environment, coupled with their dense numbers, has led to their inclusion in the nomenclature of benthic communities and sub-comnunities, particularly in European waters. Some 1,900 extant species, being referred to 255 genera, have no been described (Fell, 1960).

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