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Morphology of ruffe (Gymnocephalus cernuus) protolarvae from the St. Louis River, Lake Superior

Journal of Freshwater Ecology

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Abstract

We describe hatching and the morphological and meristic characteristics of 2.5-5.6 mm long ruffe protolarvae (Gymnocephalus cernuus). Eggs and sperm from St. Louis River ruffe were mixed, producing fertilized eggs that were 0.9-1.2 mm in diameter. Newly hatched protolarvae were 2.5-3.2 mm long. They had 14-15 preanal and 23-24 postanal myomeres, a continuous finfold of even width, unpigmented eyes, and a large anterior oil globule in the yolk sac, and the head deflected over the yolk sac. Pectoral fin buds appeared on the dorsal side of the yolk sac 5 hours after hatching. Two-day-old protolarvae had fully pigmented eyes, and the head was free from the yolk sac. Three-day-old protolarvae were 3.9-4.3 mm long and possessed opercula, gills, pectoral fins, and a functional jaw. Feeding and swimming began about one week after hatching when the yolk sac was almost completely absorbed. Protolarvae grew rapidly at 20-22 degrees C and were 4.9-5.6 mm long after 13 days. Newly hatched ruffe protolarvae are distinguished from other Lake Superior percids by having the fewest preanal myomeres (14-15), the head deflected over the yolk sac, continuous finfold of even width, and a total length of less than 4.0 mm.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Morphology of ruffe (Gymnocephalus cernuus) protolarvae from the St. Louis River, Lake Superior
Series title:
Journal of Freshwater Ecology
Volume
7
Issue:
1
Year Published:
1992
Language:
English
Contributing office(s):
Great Lakes Science Center
Description:
p. 59-68
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Freshwater Ecology
First page:
59
Last page:
68
Number of Pages:
9