Journal of Comparative Physiology B

, Volume 181, Issue 5, pp 603–613

Enzymatic digestion in stomachless fishes: how a simple gut accommodates both herbivory and carnivory


    • School of Biological SciencesThe University of Queensland
  • Donovan P. German
    • Department of Ecology and Evolutionary BiologyUniversity of California
  • Jennifer M. Manjakasy
    • School of Biological SciencesThe University of Queensland
  • Ingrid Farr
    • School of Biological SciencesThe University of Queensland
  • Mitchell Jay Hansen
    • School of Biological SciencesThe University of Queensland
  • Ian R. Tibbetts
    • School of Biological SciencesThe University of Queensland
Original Paper

DOI: 10.1007/s00360-010-0546-y

Cite this article as:
Day, R.D., German, D.P., Manjakasy, J.M. et al. J Comp Physiol B (2011) 181: 603. doi:10.1007/s00360-010-0546-y


The lack of a stomach is not uncommon amongst teleost fishes, yet our understanding of this reductive specialisation is lacking. The absence of a stomach does not restrict trophic preference, resulting in fishes with very similar alimentary morphology capable of digesting differing diets. We examined the digestive biochemistry of four beloniform fishes: two herbivorous halfbeaks (Hemiramphidae) and two carnivorous needlefish (Belonidae) to determine how these fishes digest their respective diets with their simple, short gut. We found that although the halfbeaks showed significantly greater α-amylase activity than that of the needlefish (P < 0.01), trypsin, lipase, aminopeptidase and maltase activity were not substantially different between the two families. We also found that habitat (freshwater vs. marine) appears to play a significant role in digestive capability, as the two freshwater taxa and the two marine taxa were significantly different (ANOSIM; dietary Gobal R = 0.544, P = 0.001, habitat Global R = 0.437, P = 0.001), despite their phyletic and dietary similarities. Our findings offer partial support for the adaptive modulation hypothesis, support the Plug-Flow Reactor model of digestion in herbivorous halfbeaks and also support the compartmental model of digestion but suggest that another model is required to describe stomachless carnivorous needlefish.


Hemiramphidae Belonidae Adaptive modulation hypothesis Compartmental model Plug-flow reactor Salinity

Supplementary material

360_2010_546_MOESM1_ESM.doc (50 kb)
Supplementary material 1 (DOC 50 kb)

Copyright information

© Springer-Verlag 2011