Role of maxilla 2 and its setae during feeding in the shrimp Palaemon adspersus (Crustacea: Decapoda).
The movements of the basis of maxilla 2 in Palaemon adspersus were examined using macro-video recordings, and the morphology of its setae was examined using both scanning and transmission electron microscopy. The basis of maxilla 2 performs stereotypical movements in the latero-medial plane and gently touches the food with a frequency of 3-5 Hz. The medial rim of the basis of maxilla 2 carries three types of seta. Type 1 is serrate, type 2 and 3 are serrulate, and type 2 has a prominent terminal pore. Type 2 is innervated by 18-25 sensory cells whose cilia protrude through the terminal pore and are in direct contact with the external environment. The structure of type 2 setae indicates that they are mainly gustatory, although still bimodal due to their innervation by presumed chemosensory and mechanosensory neurons. Distally, the three types of setae have a complex arrangement of the cuticle involving water-filled canals, which may serve to improve flexibility. Type 1 and 3 setae have fewer sensory cells (4-9) but probably also have a bimodal sensory function. The function of type 1 setae is probably to protect type 2 setae, while type 3 setae might serve to groom the ventral side of the basis of maxilla 1.
Garm
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Department of Zoomorphology, Zoological Institute, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark. Algarm@zi.ku.dk
Hallberg
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E
Høeg
J T
JT
D000825:Animal Structures / Q000294:innervation / Q000648:ultrastructure*; D000818:Animals; D001696:Biomechanical Phenomena; D005247:Feeding Behavior / Q000502:physiology*; D008854:Microscopy, Electron; D033541:Palaemonidae / Q000033:anatomy & histology* / Q000502:physiology*; D014741:Video Recording