The specific arrangement and distribution of photoreceptors in the retina can vary among
different fish species, with each species exhibiting adaptations related to its habitat, behavior, and
visual requirements. Poecilia sphenops, a diurnal fish, was the focus of this study. The retinas of a
total of eighteen Molly fish were investigated utilizing light and electron microscopy. The retina
exhibited a square mosaic pattern of the inner segments of cones. This pattern comprised double
cones positioned along the sides of a square, with two types of single cones situated at the center and
corners of the square arrangement across the entire retina. The corner cones were slightly shorter
than the central ones. Additionally, the outer plexiform layer contained both cone pedicles and rod
spherules. The rod spherule consisted of a single synaptic ribbon arranged in a triad or quadrat
junctional arrangement within the invaginating free ends of the horizontal and bipolar cell processes.
On the other hand, cone pedicles have more than one synaptic ribbon in their junctional complex.
The inner nuclear layer consisted of the amacrine, bipolar, Müller, and horizontal cell bodies. Müller
cell processes, expressing GFAP, extended across all retinal layers, segmenting the deeper retina into
alternating fascicles of optic axons and ganglion cells. The outer and inner plexiform layers showed
many astrocyte cell processes expressing GFAP. In conclusion, the current study is the first record of
the retinal structures of Molly fish. This study illustrated the mosaic arrangement of photoreceptors
and GFAP expression patterns of astrocytes and Müller cells. The presence of three cone types,
coupled with a sufficient number of rods, likely facilitates motion awareness for tasks like finding
food and performing elaborate mating ceremonies