. Bulletin. Science; Natural history; Natural history. 102 BULLETIN SOUTHERN CALIFORNIA ACADEMY OF SCIENCES VOLUME 75 i 11 ? 9. 100 110 LENGTH mm Figure I. Relationship of egg number and total length of Okkelbergia aepyptera from Delaware. nonparasitic lampreys. The maturity index (ovary weight/total weight) of the 23 adults ranged from (mean ). We note that the eggs of nonparasitic lampreys such as O. aepyptera are larger than those of parasitic species. Vladykov (1951) reported a mean egg diameter of and mm, respec- tively, for the nonparasitic L. lamottenii and Ichth
. Bulletin. Science; Natural history; Natural history. 102 BULLETIN SOUTHERN CALIFORNIA ACADEMY OF SCIENCES VOLUME 75 i 11 ? 9. 100 110 LENGTH mm Figure I. Relationship of egg number and total length of Okkelbergia aepyptera from Delaware. nonparasitic lampreys. The maturity index (ovary weight/total weight) of the 23 adults ranged from (mean ). We note that the eggs of nonparasitic lampreys such as O. aepyptera are larger than those of parasitic species. Vladykov (1951) reported a mean egg diameter of and mm, respec- tively, for the nonparasitic L. lamottenii and Ichthyomyzon fossor, and a mean of and mm, respectively, for the parasitic /. unicuspis and Petromyzon marinus. The relatively large mean egg size ( mm) we noted in adult O. aepyptera conforms to this trend. Based on data for a number of species in Vladykov (1951) and Hardisty (1971) and on our data, however, we note that an increase in mean egg size is correlated with a decrease in total number of eggs produced. This relationship appears to be in agreement with Svardson (1949) who suggested that reduced fecundity in fishes might be favored by selection if such a reduction were accompanied by an increase in the size of the eggs, thus enhancing the chance of survival of the fry. Early Life History.—Okkelbergia aepyptera eggs are spherical, adhesive and demersal. Several minutes after they were spawned their mean diameter was mm (range , n = 23). The perivitelline space averaged mm wide (range , n = 23). Egg color ranged from pale yellow to light green. Just prior to hatching, egg diameter averaged mm (range , n= 10). Eggs hatched in 24—26 days at water tem- peratures ranging from 5-16 C under aquarium conditions. At hatching the larvae averaged mm (range n = 8). Seversmith (1953) reported that at water temperatures ranging from 18-22 C, about 265 hours ( days) were required for eggs in aquaria to hatch i
Size: 1274px × 1961px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectnaturalhistory, booksubjectscience
