Studies on Tursiops truncatus and Stenella coeruleoalba Dolphin Species: from Retinal Cell Morphological Comparisons Towards its Surrounding environment.

Abstract In this current study, the retinal cell morphology of two dolphin species, Tursiops truncatus and Stenella coeruleoalba was compared, and supplemented with a miniature review of how it relates to surrounding environment. Retinal cell morphology involved sectioning and retino-separation of eyes, morphometric analysis of retinal cell layers and its corresponding neurons, followed by stratigraphy of both retina and area/density of ganglion neuron cell bodies. A qualification criteria was developed to describe both thickness and visibility. To relate with surrounding environment of studied species, we searched relevant synthesized literature combining such key words as ‘dolphin’, ‘Tursiops truncatus’, ‘Stenella coeruleoalba’, ‘eye’, ‘vision’, ‘ecology’ and ‘environment’. Retinal cell morphology comparisons showed that the thickness of outer nuclear layer had upper (37.8 – 38.5 μm) whereas outer plexiform layer had lower (7.8 – 8.7 μm) range values, with some differences between individual retinal layers (p<0.05) but specific to some cases. Area of ganglion cell layer of multipolar neurons of retina of both studied species could surpass the 800 μm2 mark, which suggests the presence of ‘giant’ size cell types. Plausibly, the retino-morphological comparisons of studied dolphin species depict the context of micro-view, and able to relate with a macro-view with respect to its surrounding environment.