Mucus production and its role in the feeding behaviour of Diarthrodes nobilis (Copepoda: Harpacticoida)

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Abstract
Using light microscope histology and scanning electron microscopy, the secretion, storage and discharge of copious quantities of mucus has been demonstrated in the algadwelling harpacticoid copepod Diarthrodes nobilis (Baird). The mucus is secreted by cells closely associated with large haemocoelomic reservoirs, located in the cephalothorax and urosome, which store the mucus prior to its discharge through large integumental vents (up to 38 μm in greatest dimension). A denned behavioural sequence is recognized whereby the animal utilizes discharged mucus to construct an enmeshing capsule. Late stage nauplii are also capable of capsule fabrication.The mucus bag presumably, acts as a rich and rapidly degradable substrate to marine prokaryotes and is therefore rapidly colonized; suspended organic and inorganic materials are also trapped by the mucus. Observations on gut contents and browsing activity of capsule inhabitants indicate a direct trophic dependence of D. nobilis on the bacteria and organic agglutinations that adhere to the mucus. Utilization of such nutritive materials supports a ‘mucus-trap’ hypothesis recently proposed as a feeding strategy in meiobenthic nematodes.