We systematically analysed the characteristics of the Cyclopterus lumpus eye and retina during cultured post‐hatch developmental stages using gross observations, histology, immunohistochemistry, microscopy, fundus imaging and spectral domain optical coherence tomography retinal imaging. Post‐hatch developing cultured C. lumpus eye and retinal tissues share a number of features typically conserved in other teleost fish. However, cultured C. lumpus possess some novel ocular and retinal features different from previous descriptions of other teleosts, including a prominent retractor lentis pigmented tissue closely associated with the vascular rete mirabile, peripherally located lobes of separate retinal tissue containing proliferative cells, extensive tapetum material of varying thickness, prominent fundus stripes and an elongated rod‐shaped optic nerve stalk. Post‐hatch developing cultured C. lumpus also developmentally regulate a protein homologous to alpha smooth‐muscle actin in strikingly dense continuous bands in the plexiform layers of the retina. The novel features of the eye and retina of cultured C. lumpus described here could contribute to our understanding of fitness and survival of C. lumpus in a widely ranging habitat.

Lumpfish use their vision to hunt prey or, in the case of aquaculture, to see and eat pelleted diets. A common anterior ocular opacity abnormality designated in the literature as “cataract” described in both farmed and wild lumpfish has not yet been characterized in detail at the pathobiological level. We describe here lens tissue changes associated with cataract in cultured and domesticated lumpfish. Methodology included gross observations, ophthalmoscopy and histology. Young adult cultured animals approaching 400 days post‐hatch presented a range of anterior segment opacities associated with lenticular abnormalities observable at a histological level. Wild aged domesticated animals also displayed cataracts characterized mainly by abnormalities of the lens observed by both ophthalmoscopy and histology. Dysplastic lesions of the lens in one aged domesticated lumpfish were accompanied with both retinal and optic nerve degeneration. These novel naturally occurring anatomical changes in lumpfish present both commonalities and unique features associated with cataract in young adult cultured animals versus aged domesticated broodstock animals.

Lumpfish (Cyclopterus lumpus), a North Atlantic “cleaner“ fish, is utilized to biocontrol salmon louse (Lepeophtheirus salmonis) in Atlantic salmon (Salmo salar) farms. Lumpfish require excellent vision to scan for and eat louse on salmon skin. The lumpfish eye immune response to infectious diseases has not been explored. We examined the ocular response to a natural parasite infection in wild lumpfish and to an experimental bacterial infection in cultured lumpfish. Cysts associated with natural myxozoan infection in the ocular scleral cartilage of wild adult lumpfish harbored cells expressing cluster of differentiation 10 (CD10) and immunoglobulin M (IgM). Experimental Vibrio anguillarum infection, which led to exophthalmos and disorganization of the retinal tissues was associated with disruption of normal CD10 expression, CD10+ cellular infiltration and IgM expression. We further describe the lumpfish CD10 orthologue and characterize the lumpfish scleral skeleton in the context of myxozoan scleral cysts. We propose that lumpfish develop an intraocular response to pathogens, exemplified herein by myxozoan and V. anguillarum infection involving novel CD10+ cells and IgM+ cells to contain and mitigate damage to eye structures. This work is the first demonstration of CD10 and IgM expressing cells in a novel ocular immune system component in response to disease in a teleost.