Development of wolffish eggs at different temperature regimes

Abstract

Embryonic development of common wolffish (Anarhichas lupus L.) was studied at constant temperatures 5.0, 7.0, 9.0, 11.0, 13.0 and 15.0°C. Duration of development from egg activation to several morphological stages including 50% hatching was determined. At 5.0-11.0°C, the survival rate of eggs to hatching ranged from 51 to 88% with a tendency to increase at 5.0 and 7.0°C. Morphological anomalies, bacterial contamination and large mortalities were observed in eggs incubated at 13.0 and 15.0°C. The period of hatching lasted from 10 to 50 d in different egg groups. Embryo length and yolk sac volume at identical morphological stages of development showed only slight relation to temperature. At lower temperatures newly hatched larvae were longer and at more advanced stages of ontogeny. Normal numbers of fin rays in larvae (mean values 74 for dorsal fin and 46 for anal fin) were observed at 5.0 and 7.0°C and in most larvae at 9.0°C. At 11.0 and 13.0°C, many rays were absent, with mean values for dorsal fin 60 and 39 respectively and for anal fin 28 and 4 respectively. The approximate upper limit for normal development of fin rays appeared to be 9.0°C.

Sensitive stages during embryonic development of wolffish,Anarhichas lupusL. determining the final numbers of rays in unpaired fins and skeletal abnormalities

“…The most usual tendency is an increase of vertebral number and median fin ray counts with a decrease in incubation temperature, but sometimes a V-shaped relationship is found with the lowest or highest number of meristic characters at intermediate temperatures. In wolffish, the number of myotomes was lower at 5 C, but did not change between 7 C and 11 C, and numbers of dorsal and anal fin rays increased between 5 C and 7 C (Pavlov and Moksness, 1995;Pavlov and Moksness, in press) showing a general tendency for increasing these meristic counts from north to south as observed by Templeman (1984) in this species.…”

“…0.2) and 11.0 (s.d. 0.4) C, these temperatures being selected on the basis of results of an earlier study (Pavlov and Moksness, 1995). In spite of the similar egg survival, a large difference in numbers of dorsal and anal fin rays between larvae hatched from the eggs incubated at these temperatures was observed.…”

“…However, the period of wolffish egg development is very long in nature, reaching about 7-9.5 months in the north-west Atlantic at temperatures decreasing from 7-8 C to about 2.5 C and lower (Pavlov andNovikov, 1986, 1993). Such a long incubation time is not practicable for fish farming and the objective of a recent study (Pavlov and Moksness, 1995;Pavlov and Moksness, in press) was to accelerate embryonic development using temperatures close to the upper limit. In juveniles obtained from eggs incubated at relatively high temperature, the dorsal and anal fins in the precaudal area were abnormally narrow, due to the absence of many rays, and several terminal rays of unusual shape were formed, in spite of normal survival and growth rate.…”

“…Recent study of development of common wolffish (Anarhichas lupus L.) has shown that numbers of rays in the dorsal and anal fins of the larvae decreased abruptly if temperature for egg incubation was above 9 C (Pavlov and Moksness, 1995;Pavlov and Moksness, in press). Large differences in fin ray counts, reaching more than 10 rays in larvae incubated at different temperatures, represent a good opportunity for exact determination of the developmental period for fixation of final numbers of rays in the fins.…”

The effect of water pH on the incubation and larviculture of curimbatá Prochilodus lineatus (Valenciennes, 1837) (Characiformes: Prochilodontidae)

“…The sampled larvae were fixed in 4% buffered formol for the subsequent measurement of the total length, total weight and volume of the yolk sac, according to Pavlov & Moksness (1995). The final survival rate for this stage was estimated 73 hours after fertilization by counting all the larvae.…”