Cookies Policy

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies.

I accept this policy

Find out more here

Is the Parental-Care Behaviour of Aequidens Paraguayensis (Cichlidae) Optimal?

No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
The full text of this article is not currently available.

Brill’s MyBook program is exclusively available on BrillOnline Books and Journals. Students and scholars affiliated with an institution that has purchased a Brill E-Book on the BrillOnline platform automatically have access to the MyBook option for the title(s) acquired by the Library. Brill MyBook is a print-on-demand paperback copy which is sold at a favorably uniform low price.

Access this article

+ Tax (if applicable)
Add to Favorites
You must be logged in to use this functionality

image of Behaviour

Aequidens paraguayensis from South America is a biparental larvophilic mouthbrooder. Adhesive eggs are laid on a substrate and fanned until hatching (substratebrooding). The hatching larvae are taken into the mouth by the female. Subsequently the parents relieve each other in mouthbrooding their offspring (larvophilic mouthbrooding). In comparison with pure substratebrooders-which are thought to represent the ancestral state-the time lag between spawning and hatching is shortened. This is interpreted as due to a general selective advantage of the mouthbrooding technique over the substratebrooding technique. Why then didn't evolution favour the transition from mouthbrooding of larvae to mouthbrooding of eggs (ovophilic mouthbrooding) thus allowing the extension of mouthbrooding up to spawning like in other cichlid species? An hypothetical answer is that this is not due to the lack of the adequate selection pressure but may relate to the nonavailability of appropriate ovophilic variants. This would imply that the parental care behaviour in this species is not optimal. To support this hypothesis experimental evidence on how broodcaring is regulated is given: 1. The uptake of larvae at hatching is induced by stimuli from the hatching wrigglers. Mouthbrooding can be induced at any time of the substratebrooding phase by presenting larvae to the adults. 2. The readiness to take up larvae into the mouth is maintained by the simultaneous presence of larvae within the mouth and of egg-like structures outside of it. 3. Females with induced uptaking readiness are not able to retrieve adhesive eggs from the substrate. 4. Females without uptaking readiness fan adhesive eggs, but eat loose eggs. 5. Females with induced uptaking readiness take up loose eggs in their mouths and mouthbrood them successfully at least until hatching. They behave like ovophilic mouthbrooders. Experimentally created ovophilic variants can be used to test the non-optimality hypothesis in nature or under semi-natural conditions. It is concluded that at least two independent traits must change simultaneously within the same generation to produce an ovophilic variant out of a larvophilic ancestor: on the one hand induction of an egg eating inhibition together with mouthbrooding readiness, on the other hand loss of adhesiveness of eggs. In the neodarwinian view of evolutionary change this is only possible if there is pleiotropy of the traits under consideration. The unlikeliness of pleiotropy may explain why A. paraguayensis has not become an ovophilic mouthbrooder, i.e. is not optimally designed.

Affiliations: 1: Zoologisches Institut der Technischen Universität, D-3300 Braunschweig, Federal Republic of Germany


Full text loading...


Data & Media loading...

Article metrics loading...



Can't access your account?
  • Tools

  • Add to Favorites
  • Printable version
  • Email this page
  • Subscribe to ToC alert
  • Get permissions
  • Recommend to your library

    You must fill out fields marked with: *

    Librarian details
    Your details
    Why are you recommending this title?
    Select reason:
    Behaviour — Recommend this title to your library
  • Export citations
  • Key

  • Full access
  • Open Access
  • Partial/No accessInformation