Developmental changes in the opacity of larval herring, Clupea harengus, and their implications for vulnerability to predation

The relative contributions of the eye, pigmentation (melanophores), and gut contents to the lateral body areas of herring larvae, Clupea harengus L., were measured using a combination of photography and computer image analysis. There was a power relationship between body area and body length (exponent 2.62) which was similar to that of the eye area (exponent 2.57) whereas the pigmented area increased at a greater rate (exponent 4.41). The area of the full gut relative to body length increased at an intermediate rate (exponent 3.04). Melanophores dilated under the effects of anaesthetic, increasing the projected pigment area of herring larvae by an average of 94% after 10 minutes of anaesthesia. These results are discussed in relation to the vulnerability of herring larvae to visual predation.

High Oxygen Pressures as a Contributing Factor in Retinal Detachments

Retinal detachment results from a number of causes and has received attention since 1904 when Gonin postulated the entry of vitreous fluid into the pigment area after a hole occurred in the retina. A symposium on retinal detachment held in 1952 summarized the current information and concluded that breaks in the retina are the most essential factor in the production of detachments and listed three main causes for such breaks: l) localized atrophying processes; 2) localized vitreous pull and 3) trauma. Recent work in our laboratory with tissue culture cells and animals exposed to 100% oxygen has suggested another mechanism.Mouse fibroblast L-929 and Don Chinese Hamster tissue culture cells were exposed for 3, 6 and 12 hours to 100% oxygen at one atmosphere while the rats and rabbits were exposed to the same conditions for 12, 24, 36, 48 and 72 hours. The tissue culture cells were fixed in situ to reduce any mechanical damage and the animals were fixed by perfusion to prevent any movement of the retina before fixation. Conventional methods of dehydration, embedding and sectioning were used.