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Adult fish also prey on fish eggs and larvae. For example, haddock were observed satiating themselves with herring eggs back in 1922. [14] Another study found cod in a herring spawning area with 20,000 herring eggs in their stomachs, and concluded that they could prey on half of the total egg production. [17] Fish also cannibalise their own eggs.
Marine fish can produce high numbers of eggs which are often released into the open water column. The eggs have an average diameter of 1 millimetre (0.039 in). The eggs are generally surrounded by the extraembryonic membranes but do not develop a shell, hard or soft, around these membranes. Some fish have thick, leathery coats, especially if ...
Fish eggs cannot swim at all, and are unambiguously planktonic. Early stage larvae swim poorly, but later stage larvae swim better and cease to be planktonic as they grow into juveniles. Fish larvae are part of the zooplankton that eat smaller plankton, while fish eggs carry their own food supply. Both eggs and larvae are themselves eaten by ...
Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. Once zygotic gene transcription starts, slow cell division begins and cell movements are observable. [4] During this time three cell populations become distinguished. The first population is the yolk syncytial ...
A pregnant Southern platyfish. Pregnancy has been traditionally defined as the period of time eggs are incubated in the body after the egg-sperm union. [1] Although the term often refers to placental mammals, it has also been used in the titles of many international, peer-reviewed, scientific articles on fish.
Cartilaginous fish produce a small number of large yolky eggs. Some species are ovoviviparous, having the young develop internally, but others are oviparous and the larvae develop externally in egg cases. [4] The bony fish lineage shows more derived anatomical
When mating, the female seahorse deposits up to 1,500 eggs in the male's pouch. The male carries the eggs for 9 to 45 days until the seahorses emerge fully developed, but very small. The young are then released into the water, and the male often mates again within hours or days during the breeding season.
GCSE Bitesize was launched in January 1998, covering seven subjects. For each subject, a one- or two-hour long TV programme would be broadcast overnight in the BBC Learning Zone block, and supporting material was available in books and on the BBC website. At the time, only around 9% of UK households had access to the internet at home.