Egg growth and ovarian maturation in Hypancistrus zebra

[bekateen]

Viana, I. K. S., Gonçalves, L. A., Ferreira, M. A. P., Mendes, Y. A., & Rocha, R. M. (2018). Oocyte growth, follicular complex formation and extracellular-matrix remodeling in ovarian maturation of the imperial zebra pleco fish Hypancistrus zebra. Scientific reports, 8(1), 13760.

https://www.nature.com/articles/s41598-018-32117-7

ABSTRACT
This contribution describes the growth of oocytes, addressing the formation of structures that compose the follicular complex, as well as the remodeling of the extracellular matrix, specifically laminin, fibronectin and type IV collagen during gonadal maturation. Thirty-seven females of the Acari zebra fish,

Hypancistrus zebra

were captured and the ovaries were submitted to histological processing for light and electron microscopy and immunohistochemistry techniques. Oogonia and four stages (I – IV) of oocytes were distinguished, and structures such as the postovulatory follicle and atretic oocytes (initial and advanced atresia) were observed. The follicular complex consists of the mature oocyte, zona radiata (Zr1, Zr2 and Zr3), follicular cells, basement membrane and theca. During oocyte growth, proteins of the extracellular matrix showed different intensities of staining. Based on these observations, a model of oocyte growth is proposed to define specific characteristics of the oocyte and the remodeling of the extracellular matrix in the ovary of H. zebra. This model of oocyte growth can be extended to other species of ornamental fishes. This study contributes data for induced fertilization and eventual conservation of this species.

[Fundulopanchax76]

They killed 37 females for that survey ? Of extincting species ? If is that it is not very clever !

[bekateen]

They killed 37 females for that survey ? Of extincting species ? If is that it is not very clever !

Yeah, that was very unsmart.

[jac]

Hypancistrus zebra is no where near extinction anymore. It has been secured by many breeders around the world

[Fundulopanchax76]

Yes Jac , then why their prices are still high to the heaven ?

[Jools]

Yes Jac , then why their prices are still high to the heaven ?

Putting Laws and the Xingu to one side, it is primarily fecundity but also growth rate and available market that mean that captive bred zebras should be more expensive than wild caught.

A high price also means that a greater percentage of people look after them better and look to bred them more often too.

Jools

[TwoTankAmin]

There is another big reason why zebras remain expensive. The cost to have acquired sufficient breeding stock is very high. Buy them small and they have to be gotten to breeding age/size. Or buy them mature and pay a whole lot more. Either way its not cheap. And this does not cover the potential for deaths on any level.

Circling back to the paper in this thread. I have an issue with induced breeding via hormones. It relies on some form of human judgment as to the selection of fish. In nature there is a natural method for species reproduction that appears to work, on one level, to produce the "strongest" possible offspring- whatever that means on a species basis. As far as I can tell, zebras in the wild are more likely to spawn in such a fashion as to produce the greatest likelihood of "strong" offspring than we humans can intentionally select for induced spawning in captivity. I do not think the divers who collect fish test them before they decide which are ideal to catch I wonder how many hormones have other hobby breeders used to get their offspring. I know I have used none to get over 33 new zebras for each adult (of both sexes) in my breeder tank.

Last observation re the idea that the research killed 37 females. This is not quite accurate. If we assume that zebras in the wild are still able to survive after the dam, how many more eggs and offspring might these 37 females have given birth to had they been left in the river? Consider if they each spawned only once in a season laid 10 eggs which were fertile and half turn into females. Over three seasons those 37 gals would have potentially created over 1,100 new zebras. And by the end of the 3rd season there could have been 185 new females getting ready to enter the spawning process. If the species is indeed threatened in the wild......

[Janne]

Unfortunate, H. zebra are popular among researchers and students in Brazil, even if they can use another species of Hypancistrus for this kind of research to reach the same results, their first option are always H. zebra. Using hormones does not work for Hypancistrus since they get easily damaged when trying to rip the eggs by the female, and it is quite difficult to fool their pituitary gland, is not even necessary to even try or develop such technique, they are easily reproduced natural. This kind of studies are made out of curiosity, not really by use... and to remove the oocyte or eggs is not necessary to kill them either even if quite difficult in this species. This is a second article about this species lately published, to study how to create "artificial conservation projects" of this species... when it is just to reproduce them natural.

They do reproduce more than 1 time per year in nature, if not they would already be extinct.

Janne

[TwoTankAmin]

My two top of the pecking order males would spawn every 30 days. They were not synchronized, so I was getting a new spawn every two weeks. My point above was to illustrate how many new zebras would never exist if they spawned just once a year. Multiply that by the potential for females to spawn about every two weeks for some time, and yes the numbers get huge really fast.

But I have now been looking for some time for reliable reports on what sort of damage to the Big Bend fish populations has been done since the Belo Monte dam started to function. Given the CITES Appendix listing of zebras, I believe the flow of illegally removed fish has declined significantly. Without the dam, population growth would have been expected. What is really happening to the populations and health of those fish only found in the Big Bend? Is there any daia on this?

[Janne]

The CITES listing made no difference, the illegal traffic has continue as usual to Peru and Colombia.
Is no real data by research published yet, but the upper locations in Volta Grande (close Pimental) the population has declined so much that even the fishermen no longer put effort to collect the H. zebra there, in the lower part the population are still feasible for fishermen to collect and sell for traffic. The only rest H. zebra receive from fishermen are when the water get to turbid to see and collect them, for example end of January these fishermen moved downstream to collect L333 instead, around 3-4 months the traffic stop by natural conditions, not by efforts made to stop the traffic.

Janne