Penaz, 1975


Penaz, M. (1975) Early development of the grayling Thymallus thymallus (Linnaeus, 1758). Acta Sci. Nat. Acad. Sci. Bohemoslov (Brno), pp. 1-35

Associated characteristics

Species Development state Trait Primary Data Secondary Data
Thymallus thymallus Egg Oocyte diameter The mean size of non-inseminated eggs was 2.49 mm 2.49 mm
Thymallus thymallus Egg Egg size after water-hardening 3.27 [Swollen egg diameter] 3.27 mm
Thymallus thymallus Egg Egg adhesiveness The eggs of the grayling are just very slighlty sticky Adhesive
Thymallus thymallus Egg Incubation time At mean water temperature of 10.2°C, the incubation (till the hatching of 50% of embryos) lasts, in one experiment , 387 hours, in the second one, 409 hours ; at 13.0°C, 242 hours [Others stated: 22-23 days at 8.5-9°C, 22 days at 8-10°C, 14-25 at 8°C] 22.5 days
Thymallus thymallus Egg Temperature for incubation At mean water temperature of 10.2°C and 13.0°C 10.2 °C
Thymallus thymallus Egg Degree-days for incubation At mean water temperature of 10.2°C, the incubation (till the hatching of 50% of embryos) lasts, in one experiment , 165.2 DD); in the second one, 174.8 DD; at 13.0°C, 130.9 DD. [Described by other authors as: 137 DD at 11.42°C (range 9-13.2°C) and 139 DD at 9.92 (range 6.5-12.75°C); start at 150 and peak hatching at 170, ended at 190 with temperature 8-12°C 11.1 °C * day
Thymallus thymallus Larvae Initial larval size The length of newly hatched embryos averages 12.4 mm, also described by others as 11.5-13.5 mm 12.5 mm
Thymallus thymallus Larvae Larvae behaviour The hatched embryos are little mobile and mostly lie on one side of the body. From time to time, the embryo swims up to the water column or even to the water surface, then slowly sinks back to the bottom Demersal
Thymallus thymallus Larvae Reaction to light The embryos show no photophobia nor a tendency towards crowding. Few days after, hatched mebryos, now much more mobile, show positive rheophilia and photophobia as well as marked tendency towards seeking shelter; under the conditions of artificial culture, they also tend to forming crowds in the corners of the hatching vessels and rearing apparatus. Photopositive
Thymallus thymallus Larvae Full yolk-sac resorption On the 17-24 th after hatching, the yolk sac is completely resorbed and the larvae rely on exogeneous food only 20.5 °C * day
Thymallus thymallus Larvae Onset of exogeneous feeding On the 8th day after hatching (at 10°C), the embryos, having attained the length of 15 mm, were observed to ingest exogeneous food for the first time 8.0 °C * day