Setal morphology of grooming appendages in the spider crab, Libinia dubia

Abstract

In crustaceans, grooming behaviors decrease fouling by removing debris from the exoskeleton and body structures; these grooming behaviors improve respiration, sensory reception, movement, and reproduction. Setal morphologies of the following grooming appendages in the decapod crustacean spider crab Libinia dubia are examined including the first pereiopod (cheliped), first, second, and third maxillipeds (mouthparts), and first, second, and third epipods (internal extensions of the maxillipeds). The objective of this study was to describe setal morphologies of these grooming appendages and to elucidate possible functions and efficiencies of setal structures. Spider crabs are hypothesized to have elaborate setal morphologies, mainly for cleaning specialized decorating setae as well as for cleaning inside the gill chamber, which has a higher likelihood of becoming fouled compared to other decapods such as shrimps. Fourteen setal types are documented and included several varieties of serrate and pappose setae as well as simple setae, cuspidate setae, papposerrate setae, and canoe setae. Maxillipodal epipods in the gill chamber are free of fouling, suggesting the setation on the third maxilliped protopod has an efficient functional morphology in removing debris before water enters the gill chamber. Serrate setae may function for detangling and separating structures whereas pappose setae may function for fine detailed grooming. The cheliped is the only grooming appendage that can reach decorating setae and it contains only pappose setae; thus decorating setae is not likely groomed in a manner that would greatly decrease fouling. J. Morphol. 277:1045-1061, 2016. © 2016 Wiley Periodicals, Inc.

Grooming behaviors and fouling of the spider crab Libinia dubia (Decapoda: Epialtidae)

“…Libinia dubia H. Milne-Edwards, 1834 (Family Epialtidae), the longnose spider crab, was used in this study; this crab, known as benthic, slow-moving, and nocturnal, has been collected along the Atlantic coast and in the Gulf of Mexico, often in close proximity to other conspecifics (Gray, 1957;Williams, 1984;Wilber and Wilber, 1991;Wicksten, 1993). No known study has documented the detailed grooming behaviors in spider crabs; the grooming setal morphology has been reported (Wortham and LaVelle, 2016). Because of the crab-like body with an enclosed gill chamber, mostly non-chelate walking legs, and a life history in the photic zone, spider crabs may be under higher environmental pressures, leading to increased fouling Wortham and Jedlicka: Grooming behaviors in spider crabs Nauplius, 27: e2019009 levels and the subsequent requirement for increased grooming behaviors, compared with other decapod crustaceans.…”

“…The objectives of this research were to determine for spider crabs the grooming behaviors, time budget for grooming, how grooming behaviors changed with the presence of a conspecific, and if areas with hooked setae were groomed more frequently or for longer durations compared to body regions not associated with decorating. Spider crabs were predicted to use the first pereiopods (cheliped; P1) and third maxillipeds (3M) as their main grooming appendages (see Wortham and LaVelle, 2016 for images of structures) and groom body regions associated respiration and sensory input, not hooked setae. Due to reaching their terminal molt stage and not having an "anti-fouling" event such as molting, large crabs were expected to groom their bodies more than small individuals.…”

“…Following procedures in Wortham and Pascual (2017), crabs had one grooming appendage removed; the 3M epipod has been documented to clean the ventral side of the gills in L. dubia (cf. Wortham and LaVelle, 2016) and was removed. Using forceps, the Wortham and Jedlicka: Grooming behaviors in spider crabs Nauplius, 27: e2019009 epipod was dissected by reaching internally past the protopod and pulling the epipod out of the branchial chamber; the protopod was not damaged.…”

“…The gill selected was based on its presence in the gill chamber, lying medially, and being the one of the largest (similar size to the fifth arthrobranch). Gills were viewed dorsally (with a central axis) and ventrally, to account for the long setae on epipods used to clean the gills (Wortham and LaVelle, 2016). The ventral side of the gills was the side mostly in contact with the 3M epipod (epipod setae can reach dorsally), which was the grooming appendage that was ablated.…”

Genetic analysis of ciliates living on the groundwater amphipod Crangonyx islandicus (Amphipoda: Crangonyctidae)

“…The species composition and community structure of the epibionts can give information on the ecology of the host (Fernandez-Leborans, 2010) and about their interaction with the host, whether it represents symbiosis, commensalism or parasitism (Fernandez-Leborans, 2013). Crustaceans are known to be unstable basibionts as their regular moulting results in frequent renewal of their epibiont community (Threkeld & Willey, 1993) and they often conduct a grooming activity in order to reduce fouling from their body and appendages (e.g., Wortham & LaVelle, 2016).…”