Evol Ecol Res 17: 685-698 (2016)     Full PDF if your library subscribes.

Ultimate cause(s) of dwarfism in invertebrates: the case of driftwood talitrids

David J. Wildish and Shawn M.C. Robinson

Fisheries and Oceans Canada, St. Andrews, New Brunswick, Canada

Correspondence: D.J. Wildish, Fisheries and Oceans Canada, Biological Station, 531 Brandy Cove Road, St. Andrews, New Brunswick E5B 2L7, Canada. email: wildishd@dfo-mpo.gc.ca


Question: What are the ultimate cause(s) of dwarfism in talitrids (Crustacea, Amphipoda, Talitridae)?

Hypotheses: Dwarfism evolved: (1) to allow talitrids to negotiate small burrows in driftwood made by the primary colonizers of driftwood; (2) because driftwood was a poor quality food; or (3) to minimize oxygen uptake from seawater in small burrows.

Experimental organisms: Platorchestia platensis – driftwood acclimated; Platorchestia platensis – wrack acclimated; and Orchestia gammarellus – wrack acclimated.

Methods: (1) Behavioural, using maze experiments to test the ability of talitrids of a wide range of body sizes to exit from a circular hole of known diameter. (2, 3) Measurements of oxygen uptake rate from seawater by driftwood- and wrack-acclimated P. platensis.

Results: (1) Maze escapes by talitrids were size sorted, such that adults of O. gammarellus were too large, whereas adults of the smaller P. platensis could complete most of their life cycle within small burrows made by primary colonizers of driftwood. (2) Oxygen uptake rate was significantly lower in driftwood-acclimated than in wrack-acclimated P. platensis, consistent with driftwood being a poor quality food. (3) Model predictions of the dissolved oxygen in seawater in burrows showed that both small and large talitrids would be asphyxiated in all available driftwood burrow sizes if they were closed systems.

Conclusions: Results support both hypotheses (1) and (2), but not (3), as possible causes of dwarfism in talitrids.

Keywords: behavioural experiments, invertebrate dwarfism, Orchestia gammarellus, oxygen uptake, Platorchestia platensis.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2016 David J. Wildish. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.