Syngnathidae (seahorse, pipefish, pipehorses & seadragons) are highly visual feeders with different species feeding on specific types of prey, a behaviour that has been related to snout length. Worldwide, many species have become threatened by habitat destruction, collection for the aquarium trade and exploitation for traditional medicine, as well as recreational and commercial bycatch. Attempts to establish aquaculture programs have been of limited success. Little is known about their visual capabilities in detail. The visual systems of fishes are known to have evolved specific adaptations that can be related to the colour of water in which they live and specific visual tasks such as predator detection and acquisition of food. This study examined the ocular and retinal morphology, photoreceptor structure and spectral sensitivity of adult individuals of a local pipefish (S. argus), local seahorse (Hippocampus subelongatus) which both inhabit green water seagrass beds, and a tropical species of seahorse (Hippocampus barbouri) from blue water coral reefs. Some juveniles were also investigated. Accordingly, we developed an understanding of the features that are common to all syngnathids and those that have evolved for specific environments. Cryosections of the eyes were taken to determine morphological distinctions of this group. Lens characteristics measured using a spectrophotometer determined 50% cut-off wavelengths below 408nm for all 3 species, hence no transmission of UV light to the retina. Histological examination determined a cone dominated fovea in the ventro-temporal retina and very large rods concentrated in the peripheral retina and adjacent to the optic nerve. Microspectrophotometry measured the absorption characteristics of the visual pigments within the photoreceptors showing the presence and maximum sensitivity (λmax) of rods, SWS single cones, and a broad, complex array of LWS double/twin cones. The results are discussed in relation to the light environment inhabited by each species and their feeding requirements. The implications for the design of suitable light environments for aquarium and aquaculture programs for the Syngnathidae are also discussed. Rearing success of this family of fish, for both the aquarium trade and re-stocking programs, would be advised to take lighting regimes and specifics of the animals’ vision into account

The effects of intraluminal distention (25 cm H₂O, 120 minutes) and subsequent decompression (60 minutes) on the intramural vascular patterns of the equine small intestine was evaluated in 7 anesthetized horses. The vascular system of experimental and control segments were injected with a blue-colored radiopaque medium for microangiography and histology or a diluted methyl methacrylate (MERCOX CL-2B) for scanning electron microscopy. The distended segments had shortened villi that were separated by expanded crypts and mesothelial cell loss, neutrophil infiltration and edema in the seromuscular layer. The number of filled vessels was decreased in the seromuscular layer and to a lesser extent in the mucosal layer in the distended segments compared to controls. Following reperfusion, the morphologic lesions progressed and the number of observed vessels increased in all layers; however the vascular density did not return to the pre distention state. This study identifies altered intramural vascular patterns in the equine jejunum during luminal distention and reperfusion. / Master of Science