Research by scientists from Sweden published in a recent issue of the Proceedings of the Royal Society B: Biological Sciences has shown that male pipefishes are not always the doting dads they are made out to be.
Gry Sagebakken and coauthors demonstrate in their study that male broad-nosed pipefish (Syngnathus typhle) absorb nutrients from some of the developing embryos in their brood pouch, in effect sucking the life out of their young.
Members of the family Syngnathidae (which include the seahorses and pipefishes) are well known for their unusual mode of reproduction in which the male incubates the eggs in a brood pouch.
Recent research has suggested that the males are not always loving fathers, as there is evidence that the brood can be substantially reduced in some pipefish species (i.e. there are a fewer young pipefishes hatching from a brood with more eggs at the beginning).
However, opinion is divided as to whether or not the resorbed eggs are utilized as food by the developing emryos or the brooding male.
Sagebakken and coauthors have shown that in the broad-snouted pipefish at least, the nutrients from the resorbed eggs end up in the male.
Filial cannibalism
The authors mated male pipefishes with two sets of females, one of which had radioactively labelled eggs (using 14C-labelled amino acids).
This meant that approximately half the eggs in the brood pouch were labelled. The authors detected the labelled amino acids in the male brood pouch, liver and muscle tissues, but not in any of the siblings (or half siblings) in the brood pouch.
Although filial cannibalism may seem cruel, it is probably a method in which the father ensures that at least some of the brood will survive, the authors hypothesize.
This may happen when the father is facing a food shortage and resorbing nutrients from some of the brood may be a method of obtaining sufficient nutrition to ensure that the rest of the brood is carried to term.
For more information, see the paper: Sagebakken, G, I Ahnesjö, KB Mobley, IB Gonçalves and C Kvarnemo (2010) Brooding fathers, not siblings, take up nutrients from embryos. Proceedings of the Royal Society B: Biological Sciences 277, pp. 971–977.