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The ' trailing ' behaviour is found in all species of Risbecia , where pairs of animals are often found following each other in single file , the second animal in the line usually touching the ' tail ' of the one in front ( Sea Slug Forum ).
Hypselodoris pulchella is a long slender species with a body size up to 80 mm or even 110 mm . The mantle edges are well extended along the body , with a thin bluish border . The mantle and the foot are creamy white , covered with numerous small rounded yellowish-orange spots of different sizes . There is always a diffuse pattern of pale violet-brown on the back ; this is absent in the similar species Hypselodoris ghardaqana . The sensory tentacles ( the antennae like rhinophores ) are bluish . The main respiratory organs ( gills ) vary from bluish to orange . These sea slugs usually raise and lower rhythmically their head , vibrating their gills . They often show a characteristic ' trailing ' behaviour , with two individuals following closely each other . This species feeds on sponges ( Wikipedia ).
Habitat This benthic species can be found at a depth of 3 – 30 meters ( Wikipedia ).
The Yellowish-Orange Spotted Chromodorid Nudibranch ( Risbecia pulchella [ Hypselodoris pulchella ] Rüppell & Leuckart , 1830 ) from the Sea of Fujairah , Gulf of Oman , Arab Sea , Indian Ocean . Photo by Divemaster Ola Mostafa Khalaf . 31.12.2016 . http :// marine-life-uae . webs . com /
Gazelle : The Palestinian Biological Bulletin - Number 154 – October 2017