https://decapoda.nhm.org/pdfs/12763/12763.pdf

Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods

Chemosensory neurons and mechanosensory neurons innervate all the cephalothoracic appendages of the lobster Homarus americanus, including the antennules, antennae, six pairs of mouthparts, and five pairs of pereiopods. The structure and sensory function of sensilla on these appendages are described. Sensilla on the pereiopods and maxillipeds can be classified morphologically and physiologically. Smooth setae and squamous setae are the primary setal types in the rows and tufts of hairs on the walking legs; they also are found on the maxillipeds and, less abundantly, on the crusher and seizer claws. Serrate setae are common on the maxillipeds and the third and fourth walking legs. Hedgehog hairs are located on the cutting edges of the claws of the first two pairs of walking legs and on apposable cuticular surfaces on the last two segments of the fourth pair of walking legs. All four of these types of sensilla are both mechano- and chemosensitive. Sensilla sensitive to mechanical but not to chemical stimuli include peg sensilla, which are small sensilla situated in articulated sockets within cuticular depressions and are distributed over the surface of the carapace, pereiopods, and maxillipeds. Other mechanoreceptive sensilla include cuticular articulated peg organs (=CAP organs), located on the pereiopods and on the third maxillipeds, and campaniform sensilla, found on the antennae and antennules. Exclusively chemosensory sensilla were not found.

Structure and function of cuticular sensilla of the lobster homarus americanus

Penaeid taxonomy, biology ans zoogeography

Consumption and digestion of suspended microbes by juvenile Pacific white shrimp Litopenaeus vannamei

SUMMARY In the spiny lobster Panulirus argus the antennules carrying
olfactory sensilla called aesthetascs and several types of other non-olfactory
sensilla accompanying them are frequently groomed by the third maxillipeds in
a stereotyped behavioral pattern. This behavior can be elicited by chemical
stimulation with l-glutamate. Using selective sensillar ablations,
we tested whether this behavior is driven by the numerous aesthetascs, which
have been implicated as mediating this chemically elicited antennular grooming
behavior in a previous investigation, or other, less numerous sensilla called
asymmetric setae, which are tightly associated with aesthetascs. The selective
sensilla ablations showed that the asymmetric setae are necessary and
sufficient for driving chemically elicited antennular grooming. Bilateral
elimination of the ca. 160 asymmetric setae almost completely abolished the
behavior, whereas bilateral elimination of the ca. 2600 aesthetascs or of
another type of sensilla associated with them (guard setae) did not cause a
reduction in chemically elicited antennular grooming. Microscopical analysis
of the morphological properties of the asymmetric setae revealed the presence
of a terminal pore at the tip of the seta and a phalloidin-positive scolopale
below its base. Since these structures have been identified in decapod
crustaceans as modality-specific structures of bimodal chemo- and
mechanosensory sensilla, we conclude that the asymmetric setae belong to this
type of sensilla and thus have the appropriate features to function as
chemoreceptors in the elicitation of antennular grooming. The identification
of asymmetric setae and not aesthetascs as the drivers of chemically elicited
antennular grooming suggests that it is not the olfactory pathway in the brain
but a parallel pathway, constituted mainly by the lateral antennular
neuropils, that is the neuronal substrate of this behavior. The lateral
antennular neuropils receive non-olfactory sensory input from the antennule
and contain the major arborizations of antennular motoneurons, allowing that
direct sensory-motor coupling is involved in mediating the chemical
elicitation of antennular grooming behavior.

/pdf/non-olfactory-chemoreceptors-in-asymmetric-setae-activate-46ngh43be7.pdf

Non-olfactory chemoreceptors in asymmetric setae activate antennular grooming behavior in the Caribbean spiny lobster Panulirus argus.

The functions of the third maxilliped of Penaeus merguiensis de Man are described. It has a 6-segmented endopodite which is used in feeding, grooming and possible pheromone reception. In feeding, large pieces of food are gripped by the stout spines on inner borders of the ischia which hold them to the mouth so that particles can be torn off and ingested. All the distal segments have long setae used in grooming chelate pereiopods and the antennules. In mature males there is a tuft of about 300 slender setae at the end of the propus, but its function remains obscure.

S. G. Jones

Papers

Structure and function of the third maxillipeds of the banana prawn Penaeus merguiensis