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.

Item Type:	Refereed Article
Keywords:	Hemiramphidae, Belonidae, adaptive modulation hypothesis, compartmental model, plug-flow reactor, salinity
Research Division:	Biological Sciences
Research Group:	Zoology
Research Field:	Animal structure and function
Objective Division:	Environmental Management
Objective Group:	Marine systems and management
Objective Field:	Marine biodiversity
UTAS Author:	Day, RD (Dr Ryan Day)
ID Code:	95695
Year Published:	2011
Web of Science® Times Cited:	31
Deposited By:	Sustainable Marine Research Collaboration
Deposited On:	2014-10-07
Last Modified:	2017-10-31
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