Comparative Morphology of the Eye (with Particular Attention to the Retina) in Various Species of Cardinal Fish (Apogonidae, Teleostei) Fishelson, L., Ayalon, G., Zverdling, A., Holzman, R Comparative Morphology of the Eye (with Particular Attention to the Retina) in Various Species of Cardinal Fish (Apogonidae, Teleostei). The Anatomical Record 271A:

Background Information: Class: Actinopterygii Class: Actinopterygii –Ray-finned fishes Order: Perciformes Order: Perciformes –Perch-like Family: Apogonidae Family: Apogonidae –Cardinal fish

Apogonidae Apogonidae –Approximately 300 species –Diurnal or Nocturnal –Warm-water seas –Shallow waters –Benthic –Feed on small prey and plankton

Apogon cookii Apogon angustatus Apogon coccineusApogon annularis

In past studies: In past studies: –Diurnal species Retinas contain more cones in the cone/rod ratio Retinas contain more cones in the cone/rod ratio –Nocturnal species Retinas contain more rods in the cone/rod ratio Retinas contain more rods in the cone/rod ratio –Reasoning: Cones enable the eye to adapt to various intensities of UV-light Cones enable the eye to adapt to various intensities of UV-light Rods adjust to enhance vision at low light or during darkness Rods adjust to enhance vision at low light or during darkness

Objectives: To compare the eyes, particularly the retinas, of several species of cardinal fish To compare the eyes, particularly the retinas, of several species of cardinal fish Observe differences in the retinas of diurnal and nocturnal cardinal fish Observe differences in the retinas of diurnal and nocturnal cardinal fish C. quinquelineatus

Methods: Most fish were observed and collected along reefs of the Red Sea and Mombassa, Kenya Most fish were observed and collected along reefs of the Red Sea and Mombassa, Kenya The fish were taken to a laboratory where they were injected with an overdose of MS 222 (anesthetic for aquatic wildlife) The fish were taken to a laboratory where they were injected with an overdose of MS 222 (anesthetic for aquatic wildlife) Body length measurements were taken for comparisons Body length measurements were taken for comparisons Eyes removed, measured, dissected, examined under microscopes Eyes removed, measured, dissected, examined under microscopes Total of 140 eyes from 110 fish representing 15 species Total of 140 eyes from 110 fish representing 15 species

Results and Discussion: Compared to past research, the eyes of the cardinal fish are much larger than other perciforms in comparison to total body length. Compared to past research, the eyes of the cardinal fish are much larger than other perciforms in comparison to total body length. As cardinal fish grow in size, their eyes grow as well As cardinal fish grow in size, their eyes grow as well Nocturnal cardinal fish have higher eye diameter per total length than diurnal cardinal fish Nocturnal cardinal fish have higher eye diameter per total length than diurnal cardinal fish

As cardinal fish grow in size, their %ED/TL decreases As cardinal fish grow in size, their %ED/TL decreases –This decrease occurs less in the small nocturnal fish than the diurnal fish Results and Discussion:

The larger the eye, the larger the retina The larger the eye, the larger the retina More visual cells in the smaller, nocturnal fish than the larger diurnal fish More visual cells in the smaller, nocturnal fish than the larger diurnal fish –ex.) A. fucata, 68mm TL – 562,500 visual cells –ex.) C. lineatus, 180mm TL – 155,560 visual cells

Results and Discussion: The cones of the eyes do not differ significantly between the nocturnal or diurnal cardinal fish with similar retinal size The cones of the eyes do not differ significantly between the nocturnal or diurnal cardinal fish with similar retinal size The rods differ significantly: The rods differ significantly: –ex.) A. annularis 72mm TL, 150mm 2 retina –ex.) Ch. lineatus, 150mm TL, 150mm 2 retina

Conclusions: in comparison Nocturnal cardinal fish: Nocturnal cardinal fish: –Tend to be smaller in total length –Have larger retinas per total length –Retain large retinas as total length increases –Retinas are rich in rods –Therefore, can see better in darkness or in low-lit waters Diurnal cardinal fish: Diurnal cardinal fish: –Grow larger in total length –Retina sizes aren’t as large compared to body length –Retinas are rich in cones –Better adapted to see during the day or afternoon hours