I know of no studies as of yet,However the use of hormones was orginaly used
for foodfish destined for human consumption.
how fish are farmed
p until recently all polypterids were wild caught.And rarely found in local shops.This has recently changed with large numbers of Polypterus senegalus appearing in the shops and at such small sizes they must be being farmed.The normal senegals were the first to appear followed about a year later by albino versions of the senegals and while albinos occur normaly in nature the sheer volume indictates farming.
How do you captive breed polypterids?
While a few species had bred in captivity it had not been on a commercial basis and until recently.There are three methods of fish farming
Currently farm raised species include
Polypterus delhezi
Polypterus palmas polli
Polypterus ornatipinnis
Polypterus endlicheri endlicheri
Polypterus senegalus normal coloration and albino variation
Polypterus bichir lapraedi
Method#1
Lots of male and female fish and let nature take it course (not real efficient)
Naturaly occuring hormones
Gonadotropic hormones (GtH) have been isolated in varying degrees of purity from the pituitary glands of several teleost fishes including some cultivated species such as common carp,Cyprinus carpio,chinook salmon,Heteropneustes fossilis,
Acipenser stellatus,to name some natural sources.
The piscine gonadotropins are glycoprotein in nature.The amino acid composition of gonadotropins from carp, sturgeon,
rainbow trout and others shows a broad similarity to the mammalian luteinizing hormone. The gonadotropins from carp, sturgeon and trout are each composed of two subunits, the alpha and beta chains; the amino acid and carbohydrate compositions,
Where it comes from and how it works.
Below the brain of a fish is a gland called the pituitary, which controls the spawning of fish. It is removed, crushed in distilled water and injected into the fish muscle to stimulate the fish to spawn.
Synthetic hormones
include
Ovaprim
Wova-FH
Ovatide
Method#2
Lots of males and females add some Gonadotropic hormones and and hope for the best.All injections were either intraperitoneal or intramuscular,Usually at a rate of The doses of such hormonal preparations (Ovaprim/Ovatide/Wova-FH), in general, ranges 0.3 - 0.5 ml/kg body weight of female and 0.2 - 0.3 ml/kg body weight. of the male.And then let them bred naturaly.
Method#3
A technique — called the Linpe method — induces ovulation in female fish by injecting them with a combination of a synthetic gonadotropin-releasing hormone analogue (LHRN-A) and the drug domperidone. The hormone stimulates the sex organs of the fish, while the drug inhibits the action of dopamine, a substance produced by the fish that inhibits ovulation.
When appropriate ripe females and males are available, eggs were stripped and fertilized according to the following spawning procedure:The male and female are anesthetized with MS222 in a 1% salt bath. The vent area on both fish is patted dry prior to stripping (Piper et al., 1982; Rottmann et al., 1991c). The milt isstripped into a 50 ml centrifuge tube containing a small amount of tempered Hank’s Balanced Salt Solution (HBSS); if necessary, additional HBSS is added for an equal volume of HBSS and milt. The females’ eggs are stripped into a Ziploc bag (quart or gallon) containing tempered HBSS, enough to cover the expected amount of eggs. The HBSS is then drained and the milt is added along with water for activation and mixed by gently rocking the bag for 3 minutes. The water is poured off and the fertilized eggs are rinsed several times. A tempered bentonite solution (50 grams/liter water)is added to the eggs for 15 minutes while occasionally gently rocking the bag (Rottmann et al.,1991f). Eggs are rinsed thoroughly, then water is added and water hardening occurs for an additional 45 minutes in tempered water (Piper et al., 1982)..
Outside China, a Canadian company, Syndel International Inc., has developed a single product containing both the hormone and the dopamine antagonist in the same solution. Known commercially as Ovaprim, this product has become an industry standard. With traditional fish spawning methods, carp, for example, are raised and killed to produce a pituitary extract used to induce spawning. Many fish are sacrificed in the process and the extract has a poor shelf life. The technique also requires that fish are injected at two separate intervals to induce ovulation.
The new method reduces the cost of production, increases the supply of seed fish, and is more convenient. Rates of spawning, fertilization, hatching, and survival were significantly higher in research trials than could be achieved with pituitary injections. The hormone and drug can be introduced together, which means that brood fish stock are handled only once, reducing the risk of disease or damage to the fish. This method does not alter the reproductive cycle of the fish, and the fertility and viability of offspring are normal. The solution does not require refrigeration and has a long shelf life. It has been tested on a wide range of fresh, salt, and brackish water species, including carp, bream, salmon, catfish, loach, and others.
In China, the kit consists of a vial of the synthetic hormone, a vial of the drug domperidone, saline solution, and a syringe. Workshops have been held in fish hatcheries and with Chinese farmers to promote acceptance and proper use of the new method.-Anne
I do think selective breeding do alter the evolution process.
