TY - JOUR
T1 - Extraocular vision in the sea urchin Diadema setosum
AU - Al-Wahaibi, Mohamed K.
AU - Claereboudt, Michel R.
N1 - Funding Information:
This work was supported by Sultan Qaboos University IG program under [grant number IG/AGR/FISH/12/01]. We wish to express all our appreciation to the staff of the ‘Al-Hail Aquaculture Center’ where the experiment took place.
Publisher Copyright:
© 2016 Informa UK Limited, trading as Taylor & Francis Group.
PY - 2017/1/2
Y1 - 2017/1/2
N2 - In most organisms, specific structures are responsible for detecting light patterns and vision. Several species of sea urchins appear to have a diffuse photoreceptor system that enables them to detect light and in some cases objects. The presence of extraocular vision was investigated on a sea urchin common in northern Oman, Diadema setosum. Urchins from 8- to 10-m deep coral communities were used in controlled experiments that quantified the orientation response of the urchins to various visual cues: size, contrast and colour of circular targets simulating urchins’ outlines. Urchins responded to black discs down to 11° initial visual angle but not to smaller discs. The minimum grey-scale value triggering a response was between 50 and 37% black. Urchins responded to red targets but not to green or blue ones. An average angular distance between spines of 5.3° suggested a visual acuity of about 10.6°. D. setosum thus showed extraocular vision allowing them to detect objects of different sizes, contrasts and to some extent colour, supporting the hypothesis that the whole sea urchin’s body acts as a single large compound eye.
AB - In most organisms, specific structures are responsible for detecting light patterns and vision. Several species of sea urchins appear to have a diffuse photoreceptor system that enables them to detect light and in some cases objects. The presence of extraocular vision was investigated on a sea urchin common in northern Oman, Diadema setosum. Urchins from 8- to 10-m deep coral communities were used in controlled experiments that quantified the orientation response of the urchins to various visual cues: size, contrast and colour of circular targets simulating urchins’ outlines. Urchins responded to black discs down to 11° initial visual angle but not to smaller discs. The minimum grey-scale value triggering a response was between 50 and 37% black. Urchins responded to red targets but not to green or blue ones. An average angular distance between spines of 5.3° suggested a visual acuity of about 10.6°. D. setosum thus showed extraocular vision allowing them to detect objects of different sizes, contrasts and to some extent colour, supporting the hypothesis that the whole sea urchin’s body acts as a single large compound eye.
KW - Diadema setosum
KW - Echinoidea
KW - Extraocular vision
KW - behaviour
KW - sea urchin
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U2 - 10.1080/10236244.2016.1265206
DO - 10.1080/10236244.2016.1265206
M3 - Article
AN - SCOPUS:85010635712
SN - 1023-6244
VL - 50
SP - 31
EP - 40
JO - Marine and Freshwater Behaviour and Physiology
JF - Marine and Freshwater Behaviour and Physiology
IS - 1
ER -