Oversized eggs??

[_BaDgUy_]

I've got a pair of common kribs (Pelvicachromis pulcher) who have spawned over the weekend.

I've checked the eggs to see if they were good, and they are HUGE!!!
Compared to all the other spawns I've had with other pairs, these eggs are about twice the size! There is about half as much eggs, but twice the size.

What is the meaning of this, and also the reason?

Thanks,
David

 

[Randall]

Egg Size

Dear David,

Wow, what a question! Without writing an Ayn Rand sized novel here, I will try to answer.

It is generally believed that cichlid egg size is directly related to the extent and nature of parental investment. Open substrate spawners, for example, generally lay many more smaller eggs than both concealed (cave) spawners and mouthbrooders. Mouthbrooders especially lay fewer but comparatively larger eggs. Due to their size, mouthbrooder fry tend to be significantly larger than those of open substrate spawners.

The prevailing explanation for the differing fry and egg sizes goes to parental investment exemplified, in part, by brood care and method of reproduction. With mouthbrooders, much more parental resouce or investment is expended on offspring before they hatch. Larger eggs means fewer eggs, but it also means larger fry. The larger fry are able to eat a more varied diet sooner than their open substate spawning heterospecifics, and generally achieve independence faster. Fewer fry also means that the parents have a easier time caring for them after they become free swimming, thereby saving or preserving parental resources.

Open substrate spawners, on the other hand, lay many more but smaller eggs. Their fry are comparatively tiny, but there are many more of them. Tiny fry are, for the most part, restricted to eating infusoria, or the equivalent, for a longer period of time. Consequently, they don't achieve independence until significantly later. More fry also means that the lion's share of parental resource and investment is expended after the fry become free swimming, not before.

It appears that at least some concealed spawners fall in between. The eggs are generally larger than those of open substrate spawners, but smaller than those of mouthbrooders. Although considerable parental investment and resource is expended after they are free swimming, concealed spawners generally have somewhat larger fry, that are fewer in number, and that are able to eat more foods sooner than those of open substrate spawners. As with mouthbrooders, this, too, saves parental resource and energy, freeing the parents up to spawn again.

Extensive work has been done on the subject of egg/fry size vs. parental investment vs. method of reproduction--in and of itself and also as it relates to evolutionary adaptation--by Dr. Ron Coleman, Dr. George Barlow and Dr. Keenleyside (1991) to name a few. It's a fascinating subject, don't you think?

All the best,

Randall Kohn

 

[2la]

Randall, does this apply to egg-size variability within the same species as in this case? Can it account for eggs that are twice the size of those of conspecifics? Assuming the diameter was the parameter being measured, that amounts to a roughly eight-fold increase in mass!

 

[Randall]

Egg Size

Randall, does this apply to egg-size variability within the same species as in this case? Can account for eggs that are twice the size of those of conspecifics? Assuming the diameter was the parameter being measured, that amounts to a roughly eight-fold increase in mass!

Dear 2la,

Unfortunately, I don't have definitive answers to your questions, just a few observations. As far as I know, egg size within a particular species should be uniform, but perhaps not absolutely.

In his post, David indicates that the Pelv. pulcher eggs in the current clutch appear to be twice the size of those from other pairs that he has witnessed before. First, are we definitely talking about the same species here? If not, that could explain it. There are at least eight "krib" types from Nigeria/northwest Cameroon corresponding to at least four different species, and retailers/distributors commonly misidentify them. If so, however, I can't say with certainty if, in fact, factors like parent size, age and/or diet contribute to the size of their eggs. For that one may need to contact Ron Coleman.

Randall Kohn

 

[_BaDgUy_]

Here is more information on the P. pulchers I have.

All the couples I have, 3 in all, are mostly the same.

All 3 couples, the males are relatively the same size, almost full grown.
The females are a different story. 2 of the females are albinos, and one is normal color.

All previous spawns from the female in question, an albino, have been regular sized eggs, in my case, similar in size of eggs and number to the other 2 females. The only difference in this spawn has been a switching of the male for that female. Could this be the reason, or one of the factors for her to produce larger eggs?

 

[2la]

Wow, that's even more amazing than intraspecific variability: individual variability! That certainly suggests a physiologic rather than an anatomic mechanism. What that mechanism is--hormonal differences, nutrition, environment, age--I have no idea...

 

[_BaDgUy_]

Well, the eggs have hatched! Took a day longer than usual, and the wrigglers are at least twice the size as normal, if it's not 3x as big....

Can't wait to see them swiming around, I'll have a better idea how big they are...

 

[_BaDgUy_]

Here is another update...

Fry are now free swimming, and seem to be at least twice the size of my other newly free-swimming kribs.

I wonder if they are going to be "super" kribs, larger than normal...

 

[Neil]

_BaDgUy_,

WELCOME TO THE FORUM

Wow! This is very unusual. I tend to think that there would not be that great a difference in the size of the eggs of an individual species, even between species-forms. This sounds like something that Ron Coleman may be interested in. I might email him and see if he has something to say.
Neil

 

[_BaDgUy_]

Thanks Neil

What I find especially strange, is that another female, which is the same size and from the same brood lays normal sized eggs...

I'll do some experimenting in the future with different males to see if anything changes...