EFFECTS OF EMBRYONIC EXPOSURE TO PREDATOR CUES ON PRE- AND POST-HATCHING ANTIPREDATOR BEHAVIOUR IN COMMON CUTTLEFISH (SEPIA OFFICINALIS)

Since neonates are often the age-class most susceptible to predation, there should be strong selective pressure on prey for the early development of successful antipredator behaviour. The ability to assess predation risk as early as the embryonic stages may increase an individual’s survival, as it would allow young individuals to be better adapted to current predation risk, since present conditions are often a good short-term indicator of future conditions. I exposed embryonic cuttlefish (Sepia officinalis) to the odour of a predator and tested both the responses of the embryos to this stimulus, and the latent effects of both long (approximately 3 weeks)- and short (a few days)- exposure on the behaviour of newly-hatched juveniles, in particular the efficiency of cryptic behaviour on uniform and sandy substrates. Exposure to novel odours, whether they were predators or non-predators, increased the ventilation rate of embryos. This may be adaptive, because it helps an individual survive first encounters with unknown potential dangers before they have opportunity to collect information about a novel stimulus. Long-term exposure to predator odour increased the camouflage efficiencies of juveniles on uniform substrates. On sandy substrate, the exposure did not affect camouflage, but increased the extent of sand digging behaviour. Juveniles were also larger in size at hatching when exposed to predators compared to those that were not. These results were not seen in individuals with only short-term exposure to predator. Short-term exposure also had no effect on camouflage efficiencies on uniform or sandy substrates, or on sand digging behaviour. The results of my thesis indicate that high predation risk during embryonic development induces behavioural and morphological changes in camouflage expression and body size in cuttlefish hatchlings. The behavioural plasticity may provide survival benefits for newly hatched individuals, but may come at a cost in terms of body size. Such behavioural and morphological plasticity may have an impact on predator-prey dynamics and organization of communities

Improvement of individual camouflage through background choice in ground-nesting birds.

Animal camouflage is a longstanding example of adaptation. Much research has tested how camouflage prevents detection and recognition, largely focusing on changes to an animal's own appearance over evolution. However, animals could also substantially alter their camouflage by behaviourally choosing appropriate substrates. Recent studies suggest that individuals from several animal taxa could select backgrounds or positions to improve concealment. Here, we test whether individual wild animals choose backgrounds in complex environments, and whether this improves camouflage against predator vision. We studied nest site selection by nine species of ground-nesting birds (nightjars, plovers and coursers) in Zambia, and used image analysis and vision modeling to quantify egg and plumage camouflage to predator vision. Individual birds chose backgrounds that enhanced their camouflage, being better matched to their chosen backgrounds than to other potential backgrounds with respect to multiple aspects of camouflage. This occurred at all three spatial scales tested (a few cm and five meters from the nest, and compared to other sites chosen by conspecifics), and was the case for the eggs of all bird groups studied, and for adult nightjar plumage. Thus, individual wild animals improve their camouflage through active background choice, with choices highly refined across multiple spatial scales

The Role of Conspecific Damage-Released Alarm Cue and Plastic Pollution on Caddisfly Larvae Case Construction Behaviour

Organisms interact with their environment using sensory systems to forage, communicate with other organisms, and detect predators. Prey can detect and assess predation risk using predator-related chemical cues, and this can influence their decision-making process. Antipredator responses are essential for the survival of an organism, and these responses can be displayed physiologically, morphologically, and behaviourally. While some prey rely on single antipredator responses, others combine several antipredator responses to increase their chances of survival. For instance, caddisfly larvae are known to display both morphological changes and behavioural responses when exposed to predation risk (i.e., their case construction behaviour). The portable case of an actively foraging caddisfly larva is generally understood to have evolved as a predator defence strategy. Larvae of many caddisfly species construct transportable cases of different sizes and shapes with various surrounding materials present using self-secreted silk to bind them together. This case construction behaviour can be influenced by predation risk and the surrounding sediments. Thus, this thesis examined the effect of these two factors on caddisfly larvae case construction behaviour. In the first experiment, denuded Limnephilus spp. larvae were exposed to conspecific damaged-released alarm cue, a predator-related chemical cue, twice within 48 hours during case reconstruction. Larvae exposed to alarm cue added more sticks to their cases than those exposed to dechlorinated tap water (control) after 24 hours of the first exposure. However, alarm cue had no effect on larval case length and the rate at which they constructed new cases when compared to larvae in the control group after 24 and 48 hours of exposure. In the second experiment, Phryganea spp. larval preference for different case construction materials was examined based on their surrounding materials. The experiment also investigated which case construction material offered more protection when the Phryganea spp. larvae were exposed to predatory crayfish. As an addition to the second experiment, larval recognition by predatory crayfish using empty larval cases was examined. Larvae were removed from their cases and provided with either their native construction materials (leaves), non- native case construction materials (plastics), or a mixture of both materials for case construction. Larvae were exposed to crayfish after 72 hours of case construction to determine which case type offers more protection against predation. Larvae constructed their cases using the materials provided, and these materials did not affect the proportion of larvae that constructed new cases in each group. However, larvae provided with both leaves and plastics preferred their native case construction materials (leaves). Also, larval survival when exposed to crayfish was not affected by their case type, rather, larval survival depends on the predator’s experience with case-building caddisfly larvae. Similarly, only those crayfish that had previously eaten larvae attacked the empty cases. These two studies also show that predation risk and surrounding materials could influence case construction behaviour. Larvae adjusted their behaviour based on the information perceived from their environment. In this study, Limnephilus spp. larvae were able to modify their case building behaviour to match the intensity of the perceived predation risk by adding more sticks to their cases. Although the protective function of Phryganea spp. larval cases based on material type could not be assessed in the second experiment, the result shows that prey recognition needed to be learned to initiate predatory attack. The assessment of larvae case construction behaviour can help understand larval interactions with their environments, such as predation risk and human activities (plastic pollution). Caddisfly larvae offer various ecosystem services in the freshwater habitat, and their case construction behaviour has been linked to their survival. Hence, natural (e.g., predation risk) and anthropogenic activities (e.g., plastic pollution) that can influence this construction behaviour needs to be investigated and monitored to ensure that their role within the ecosystem is not altered

Effects of Environmental Enrichment on the Behavior of Octopus vulgaris in a Recirculating Aquaculture System

Octopus vulgaris is a commercially valuable species. It is overexploited in the natural environment and is considered to be an innovative species for aquaculture. However, large-scale farming is generally designed only based on economic requirements, disregarding any form of enrichment that induces the natural behavior of aquatic species. Although many studies have shown the influence of environmental enrichment on terrestrial vertebrates, fish, and cephalopod mollusks, information on the effect of environmental enrichment on the body patterns of O. vulgaris is limited. Therefore, in this study, we assessed how different environmental conditions (Basic vs. Enriched) affect sub-adults of O. vulgaris kept in recirculation systems, through qualitative–quantitative studies of the main body patterns and their potential application in the commercial production of this species. The results indicated that octopuses kept in the enriched environment showed several body patterns and gained a significantly higher weight than those kept in the basic environment. The body patterns displayed by the individuals kept in the basic environment were similar to those exhibited under situations of hostility and inter/intra-specific conflict. Hence, the environment of octopuses needs to be enriched, especially for the large-scale production of this species

Effects of environmental enrichment on the behavior of Octopus vulgaris in a recirculating aquaculture system

Octopus vulgaris is a commercially valuable species. It is overexploited in the natural envi-24 ronment and is considered to be an innovative species for aquaculture. However, large-scale farm-25 ing is generally designed only based on economic requirements, disregarding any form of enrich-26 ment that to induce the natural behavior of aquatic species. Although many studies have shown the 27 influence of environmental enrichment on terrestrial vertebrates, fish, and cephalopod mollusks, 28 information on the effect of environmental enrichment on the body patterns of O. vulgaris is limited. 29 Therefore, in this study, we assessed how different environmental conditions (Basic vs. Enriched) 30 affect sub-adults of O. vulgaris kept in recirculation systems, through qualitative–quantitative stud-31 ies of the main body patterns and their potential application in the commercial production of this 32 species. The results indicated that octopuses kept in the enriched environment showed several body 33 patterns and gained a significantly higher weight than those kept in the basic environment. The 34 body patterns displayed by the individuals kept in the basic environment were similar to those 35 exhibited under situations of hostility and inter/intra-specific conflict. Hence, the environment of 36 octopuses needs to be enriched, especially for the large-scale production of this species

Light Organ Photosensitivity in Deep-Sea Shrimp May Suggest a Novel Role in Counterillumination

Extraocular photoreception, the ability to detect and respond to light outside of the eye, has not been previously described in deep-sea invertebrates. Here, we investigate photosensitivity in the bioluminescent light organs (photophores) of deep-sea shrimp, an autogenic system in which the organism possesses the substrates and enzymes to produce light. Through the integration of transcriptomics, in situ hybridization and immunohistochemistry we find evidence for the expression of opsins and phototransduction genes known to play a role in light detection in most animals. Subsequent shipboard light exposure experiments showed ultrastructural changes in the photophore similar to those seen in crustacean eyes, providing further evidence that photophores are light sensitive. In many deep-sea species, it has long been documented that photophores emit light to aid in counterillumination – a dynamic form of camouflage that requires adjusting the organ’s light intensity to “hide” their silhouettes from predators below. However, it remains a mystery how animals fine-tune their photophore luminescence to match the intensity of downwelling light. Photophore photosensitivity allows us to reconsider the organ’s role in counterillumination - not only in light emission but also light detection and regulation