Wednesday, January 26, 2011

Beef or Salmon? Prawns please!!!

A guest post by Ken.

The common prawn (Palaemon serratus) is found on rocky shores around Ireland. They are often trapped in rock pools at low tide but can be difficult to spot due to the transparent body but become visible when moving. A closer look reveals purplish-brown dots and lines on its body. Their antennae are very long and a toothed rostrum extends forward between the eyes. It uses its fan like tail to swim backwards if alarmed. Has a diet mainly of scavenging. (1)

Common Prawn (Palaemon serratus)
Lovell et al. performed a study on P. serratus using a combination of anatomical, electron microscopic and electrophysiological approaches involving the statocyst. In crustaceans, the statocyst is found either at the anterior end of the animal in the basal segment of each antennule, or posteriorly within the uropods, abdomen or telson. It has been known that the statocyst is used as an equilibrium organ to orientate the animal within the water column. This study used an ABR (Auditory Brainstem Response) type investigation to determine the prawns hearing abilities. To acquire an ABR waveform conglomerate responses of peak potentials are averaged, which arise from nuclei in the auditory pathway during acoustic stimulation. This work provided conclusive evidence of low-frequency sound detection of frequencies ranging from 100 to 3000 Hz (a hearing acuity similar to that of a generalist fish) by a member of the sub-phylum crustacea. For hearing ability to be attributed to an organism, the physiological response sound should be initiated by a specialised receptor mechanism and here it was shown to be generated in the statocyst. In addition, recorded neural waveforms were shown to be similar in both amplitude and shape to those from fish and higher vertebrates, when stimulated with low-frequency sound, and complete ablation of the electrophysiological response was achieved by removal of the statocyst. (2)

References:

1. Sterry 1997, Collins Complete Guide to British Wildlife p. 216
2. Lovell et al. 2005, Comparative Biochemistry and Physiology, Part A 140 pp.89-100

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