Abstract
Nuchal humps occur in various fish groups, but their functions are rarely studied. Both sexes of Cyphotilapia gibberosa, a cichlid fish endemic to Lake Tanganyika, possess nuchal humps. This study morphologically analysed the humps of this species to assess the primary factors responsible for hump development. Semi-landmarks showed that the size of male humps positively correlated with body condition, and thicknesses of hypodermises implied that the humps were larger in males than in females. These facts suggest that sexual selection on male humps is intense. Semi-landmarks showed that the humps were less prominent in females than in males, and that the transformation of nuchal humps with growth (becoming more prominent) ceased at medium body size in females. These facts suggest that sex recognition likely plays a role in the evolution of the uniform humps of large females, because, according to this hypothesis, a morphologically moderate hump may be favoured. If male humps also function as a sex recognition trait, the transformation of nuchal humps is expected to cease at a certain body size, as did female humps. However, the male humps became continuously more prominent from the smallest to the largest individuals examined. The body size at which hump transformation stops or at which extreme hump shape interferes with sex recognition may be outside of the size range of the present samples. A prominent nuchal hump may also function as a species recognition trait, because sympatric cichlid species do not develop nuchal humps as prominent as this species. In short, the present morphological analyses do not contradict the hypotheses that C. gibberosa individuals recognise conspecifics and their sex from the shapes of the nuchal humps, and that females prefer males with larger humps.
Similar content being viewed by others
References
Adams SM (1999) Ecological role of lipids in the health and success of fish populations. In: Arts MT, Wainman BC (eds) Lipids in freshwater ecosystems. Springer, New York, pp 132‒160
Arai H, Sato T (2007) Prominent ornaments and rapid color change: use of horns as a social and reproductive signal in unicornfish (Acanthuridae: Naso). Ichthyol Res 54:49‒54
Barlow GW, Siri P (1997) Does sexual selection account for the conspicuous head dimorphism in the Midas cichlid? Anim Behav 53:573‒584
Brönmark C, Miner JG (1992) Predator-induced phenotypical change in body morphology in crucian carp. Science 258:1348‒1350
Chakrabarty P (2005) Testing conjectures about morphological diversity in cichlids of Lakes Malawi and Tanganyika. Copeia 2005:359‒373
Chakrabarty P, Sparks JS (2007) Relationships of the New World cichlid genus Hypsophrys Agassiz 1859 (Teleostei: Cichlidae), with diagnoses for the genus and its species. Zootaxa 1523:59‒64
Faye B, Bengoumi M, Cleradin A, Tabarani A, Chilliard Y (2001) Body condition score in dromedary camel: A tool for management of reproduction. Emir J Food Agric 13:1‒6
Kocher TD, Conroy JA, McKaye KR, Stauffer JR (1993) Similar morphologies of cichlid fish in lakes Tanganyika and Malawi are due to convergence. Mol Phylogenet Evol 2:158‒165
Kuwamura T (1997) The evolution of parental care and mating systems among Tanganyikan cichlids. In: Kawanabe H, Hori M, Nagoshi M (eds) Fish communities in Lake Tanganyika. Kyoto University Press, Kyoto, pp 57‒86
Liu M, de Mitcheson YS (2011) Forehead morphology of the humphead wrasse Cheilinus undulatus (Perciformes: Labridae) in relation to body sizes. Copeia 2011:315‒318
Miller RR (1946) Gila cypha, a remarkable new species of cyprinid fish from the Colorado River in Grand Canyon, Arizona. J Wash Acad Sci 36:409‒415
Muñoz H, van Damme PA, Duponchelle F (2006) Breeding behaviour and distribution of the tucunaré Cichla aff. monoculus in a clear water river of the Bolivian Amazon. J Fish Biol 69:1018‒1030
Poll M (1956) Poissons Cichlidae. Résult Scient Explor Hydrobiol Lac Tanganika Inst R Sci Nat Belg 3:1–619
Portz DE, Tyus HM (2004) Fish humps in two Colorado River fishes: a morphological response to cyprinid predation? Environ Biol Fishes 71:233‒245
Takahashi T, Nakaya K (2003) New species of Cyphotilapia (Perciformes: Cichlidae) from Lake Tanganyika, Africa. Copeia 2003:824‒832
Takahashi T, Sota T (2016) A robust phylogeny among major lineages of the East African Cichlids. Mol Phylogenet Evol 100:234‒242
Takahashi T, Ngatunga B, Snoeks J (2007) Taxonomic status of the six-band morph of Cyphotilapia frontosa (Perciformes: Cichlidae) from Lake Tanganyika, Africa. Ichthyol Res 54:55‒60
Tsuboi M, Gonzalez-Voyer A, Höglund J, Kolm N (2012) Ecology and mating competition influence sexual dimorphism in Tanganyikan cichlids. Evol Ecol 26:171-185
Tsuboi M, Gonzalez-Voyer A, Kolm N (2014) Phenotypic integration of brain size and head morphology in Lake Tanganyika cichlids. BMC Evol Biol 14:39
Tsuboi M, Husby A, Kotrschal A, Hayward A, Buechel SD, Zidar J, Løvlie H, Kolm N (2015) Comparative support for the expensive tissue hypothesis: big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids. Evolution 69:190‒200
Acknowledgements
We thank H. Phiri, M. Mbewe, T. Banda, L. Makasa and the other staff members of the Lake Tanganyika Research Unit in Mpulungu for support in the field. We are also grateful to M. Hori and M. Kohda for providing research equipment for the fieldwork, and to K. Tsuji for advice on the manuscript. This study was partly supported by a Grant-in-Aid for Scientific Research (B) (No. 26291078) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
About this article
Cite this article
Takahashi, T. Function of nuchal humps of a cichlid fish from Lake Tanganyika: inferences from morphological data. Ichthyol Res 65, 316–323 (2018). https://doi.org/10.1007/s10228-018-0614-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10228-018-0614-y