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| Close up of a cichlid [1] |
If you’ve ever been around a family with a small child, you’ve probably heard the phrase “It takes a village!” at some point. Raising kids is a lot of work, and sometimes parents needs an extra pair of hands or two in order to get the job done. In the case of one species of fish, it turns out to be an extra set of fins.
Cichlids are a large family of fish, and the specific species studied in this paper is the cooperatively breeding Neolamprologus obscurus. Many animals, such as birds and meerkats, follow a cooperative breeding strategy in which offspring are raised by their parents with the aid of other individuals called helpers. The purpose of this strategy is to increase the number of young that survive to adulthood (which seems like a reasonable goal). A similar idea would be families that have nannies to help out with the kids, except in species like N. obscurus it is typical to have more than one “nanny”, or helper.
You may be thinking, “the more help the better, right?” This is not always the case, though, because even though these helpers provide support for the parents and in return often receive shelter and the protection of living in a group versus alone, having more bodies around could cause problems such as competition for resources like food. So the question here is: do these cichlid helpers live up to their names, or should we start calling them worseners?
For this study, the authors observed a total of 189 groups of cichlids in Lake Tanganyika near Mpulungu, Zambia, over the course of three years. Different groups had different territories they lived in, with one mother cichlid in each territory. The authors focused on trying to determine how beneficial helpers were in raising young fish by looking at the number of helpers in comparison to the number of young fish across the groups. They also observed how the body size of the mother fish related to the number of helpers she had. Because fish grow indefinitely as they age, the bigger the mother, the older and more experienced she was assumed to be.
Through these observations, it was found that the larger the mother, the more helpers she was likely to have. This was likely due to the fact that cichlids have a hierarchy correlated to body size. In addition, as the number of helpers increased so did the number of young fish in the group. Having more helpers increased food available to the mother which led to higher reproductive success. Helpers were also able to increase the survival of offspring by defending and cleaning the eggs. In the case of the N. obscurus cichlid, it looks like buying into the notion of extra child care is a pretty good idea if you want to give your kids the best shot at not swimming off into that big lake in the sky.
Cooperative breeding is a strategy well studied in many animals, but this research on cichlids is some of the first to support the strategy in fish. Furthering the understanding of how this specific way of breeding evolved in fish also helps to give more insight into fish in general. Who knows, maybe we’ll even start taking parenting advice from them.
References:
Tanaka, Hirokazu, Masanori Kohda, Joachim G Frommen. 2018. Behavioral Ecology and Sociobiology 72: 152. “Helpers Increase the Reproductive Success of Breeders in the Cooperatively Breeding Cichlid Neolamprologus Obscurus.” https://doi.org/10.1007/s00265-018-2566-7
“It Takes a Village to Determine the Origins of an African Proverb.” 2016. NPR. https://www.npr.org/sections/goatsandsoda/2016/07/30/487925796/it-takes-a-village-to-determinethe-origins-of-an-african-proverb
“Cichlid.” 2018. Wikipedia. https://en.wikipedia.org/wiki/Cichlid
“Cooperative Breeding.” 2018. Wikipedia. https://en.wikipedia.org/wiki/Cooperative_breeding#Birds
Media Credits:
[1]: Photo by Charlene N. Simmons. https://flic.kr/p/dnj7qv
Wow, that was really interesting! This is more of a clarification question but, when there are no children in a group does another fish have children and all the other fish stick around to help take care of them, or does the group disperse and find other fish to live with, with children to take care of?
ReplyDeleteThanks! The authors don't mention what the fish do when there are no children. I believe that as long as the breeding female is able to she will have children and there will be children to help raise, but it is possible one of the helpers would become the breeder if the original female could not continue to have children!
DeleteThanks for posting, Monee! Do the helpers have children of their own? I wonder why it would be beneficial to spend energy on helping raise other cichlids' children rather than on having your own?
ReplyDeleteHelpers do not have children of their own, their main job is to help protect and raise the offspring of the breeding female in the group! That's an interesting thing to think about, and I think that part of the reason why helpers raise other children instead of having their own has to do with the social system of cichlids and who ends up being the breeding female.
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