Early ontogeny of the spotted wolffish (Anarhichas minor
Olafsen)
I.-B. Falk-Petersen, T.K. Hansen-2003
Aquaculture
Research, 34(12):
1059
Abstract:
This
study illustrates the embryo development of the spotted wolffish (Anarhichas
minor Olafsen), an interesting candidate for cold-water aquaculture. The
egg morphology (semitransparent, yellow-white with numerous oil droplets in
the yolk), size (5.4-6.5 mm) and long embryogenesis (c. 800-1000 d°,
depending on temperature) of A. minor are very similar to Anarhichas
lupus. Cleavage is slow, and the first cell divisions take place at 12 h
at 8°C. After 12 days the 2-mm embryo with the first somites is laid down
and the blastopore starts closing. The fat globules in the yolk fuse into
one after 22 days, and after 30 days eye pigmentation is noticeable. After
44 days, eye pigmentation is strong, the digestive tract folded and a green
gall bladder can be noted in the now 11-mm-long embryo. One week later the
blood is brightly red, the intestine is pigmented and the lower jaw is well
developed. Premature hatching may occur from this stage. After 58 days
vascularization of the yolk is complete, capillaries are noted in the fin
fold, the first ray rudiments are established in the tail and pectoral fins,
and the four gill arches are covered by the operculum. The preanal finfold
is reduced after 72 days, stomach and gill filaments are formed, and six
pigmented rows are noted on the 17-mm-long embryo body. After 86 days all
fin rays are seen and the digestive tract is intensely pigmented and folded.
Hatching (normal) starts after 110 days and may last for 2-3 weeks. Late
embryos and early larvae of A. minor have more distinct bands of
pigment along the body compared with the closely related A. lupus. An
increase in both length and weight of the embryos in individual batches
occurs during the hatching period.
(Department of Aquatic Resources and
Environmental Biology, The Norwegian College of Fishery Science, University
of Tromsų, N-9037 Tromsų, Norway. E-mail: ingerf@nfh.uit.no)