"nuchal humps" an expression of dominance in some

#1
In the spring I got some Peruvian scalares from Larry Waybright and the males had -to varying degrees-a nuchal hump which gave them a facial profile rather the opposite to that found in altums. Later on in the summer I obtained a group of 4 sibling domestic silver pearlscales and reared them in the same tank as the peruvian with the largest hump who was also the dominant angel in the tank. One of the pearlscales quickly outgrew his siblings and began to challenge the Peruvian. Over a period of 6-8wks he supplanted the Peruvian and harasses him from time to time. Coincidently he has grown a magnificent hump (if you like humps in angels-I don't) and the deposed Peruvian has completely lost his. Can anyone corroborate/disconfirm that in scalare lineages where males can develop such a hump that it is an indicator of dominance within the group? Incidently one of tthe other male pearlscales mated with another domestic female & showed no hump at any time-there was no other male present. He was smaller and had a classic "altum notch" so from this group I speculate that tendancy to develop a nuchal hump is genetically variable, sensitive to social status & gender specific.

re: "nuchal humps" an expression of dominance in s

#2
Hi Dennis,
My lower familiarity with domestic Angelfish doesn't allow me to comment much about their peculiarities but I do believe domestic Angelfish mature sooner than wild P. scalare and the male's nunchal hump is a secondary sexual characteristic which is related to the position of dominance.
I have raised aquarium strains of Angelfish in their 1000's so I do have some experience and among all the variations I have raised, the most dominant and oldest males had the most prominent nunchal hump. I have always found this feature distracting from the aesthetic appearance of P. scalare.

In Ancistrus spp of the bushy Nosed Plecos, you see that the dominant male develops the largest beard of barbels. less dominant fish, which may well breed under it's bushy nose, may suppress the growth of the heavier bushy nose to avoid direct competition with the dominant males. They may adapt a "sneaker' male tactic similar to that which has been observed among many Apistogramma species?

This seems to be more noticeable among P. scalare than either P. leopoldi and P. altum. These other two species probably use larger relative sizes between males and behavioral signals more than a noticeable nunchal hump to signify status.
Larry Waybright
Trout fly fisherman.

re: "nuchal humps" an expression of dominance in s

#5
I like P. leopoldi. It is the smallest species in the genus and has a distinctive appearance. Not as extravagantly endowed with as long of anal and dorsal fins as the others but a very likable species.
I have only kept them a few times. My first group was about as outgoing as P. scalare but the second batch contracted a disease which I could not seem to treat. Those all died slowly over several months.

I wish I could cite the reference, but I know have read that P. leopoldi made much use of cracks in river bedrock as hiding places when very frightened. Their morphology seems to support an adaptation to that kind of defensive strategy. I have never heard of this behavior among P. scalare. I think they evolved to use the plants and branches much more like the Discus as their ultimate escape strategy.

I think you would find them an interesting species to keep and compare with the other wild Angels. They may be a little more high strung than P. scalare so it may take a little longer to tame them down. Much may depend on how large and healthy are the specimens you can get.
Larry Waybright
Trout fly fisherman.
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