Abstract
The detection of chemical signals is involved in a variety of crustacean behaviors, such as social interactions, search and evaluation of food and navigation in the environment. At hydrothermal vents, endemic shrimp may use the chemical signature of vent fluids to locate active edifices, however little is known on their sensory perception in these remote deep-sea habitats. Here, we present the first comparative description of the sensilla on the antennules and antennae of 4 hydrothermal vent shrimp (Rimicaris exoculata, Mirocaris fortunata, Chorocaris chacei, and Alvinocaris markensis) and of a closely related coastal shrimp (Palaemon elegans). These observations revealed no specific adaptation regarding the size or number of aesthetascs (specialized unimodal olfactory sensilla) between hydrothermal and coastal species. We also identified partial sequences of the ionotropic receptor IR25a, a co-receptor putatively involved in olfaction, in 3 coastal and 4 hydrothermal shrimp species, and showed that it is mainly expressed in the lateral flagella of the antennules that bear the unimodal chemosensilla aesthetascs.
Highlights
Chemical senses are crucial in mediating important behavioural patterns for most animals
In the five shrimp species studied for morphology (Palaemon elegans, Mirocaris fortunata, Rimicaris exoculata, Chorocaris chacei and Alvinocaris markensis), antennae and antennules both consist of a peduncle and segmented flagella
In order to identify the regions of antennules and antennae putatively involved in olfaction, we studied the expression pattern of the ionotropic receptor IR25a, which belongs to a conserved family of olfactory receptors amongst Protostomia, involved in olfaction, taste, thermosensation and hygrosensation
Summary
Chemical senses are crucial in mediating important behavioural patterns for most animals. Chemoreception in decapod crustaceans is mediated by chemosensory sensilla that are mainly localized on the first antennae (antennules), pereiopod dactyls and mouthparts (Ache 1982; Derby et al 2016). While the molecular mechanisms of olfaction have been well studied in insects, they remain largely unknown in crustaceans, and the existing knowledge is restricted to a few number of model organisms (lobsters, crayfish and the water flea Daphnia pulex; review in Derby et al 2016). A new family of receptors involved in odorant detection, named the Ionotropic Receptors (IRs), was recently described in Drosophila melanogaster, and was subsequently shown to be conserved in Protostomia, including the crustacean Daphnia pulex (Benton et al 2009; review in Croset et al 2010). Several IRs were identified in other crustaceans, the spiny lobster
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