Ultrastructure, histochemistry, and mineralization patterns in the ecdysial suture of the blue crab, Callinectes sapidus

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Carolina Priester (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Niel Hadley

Abstract: The ecdysial suture is the region on an arthropod exoskeleton that splits to allow the animal to escape from its old carapace. To understand why this region preferentially splits, I examined the morphology and composition of the intermolt and premolt suture of the blue crab, Callinectes sapidus, using light and scanning electron microscopy (SEM). No differences were detected between the suture and the adjacent cuticle with the general dyes acridine orange, hematoxylin and eosin, toluidine blue, periodic acid Schiff or paraldehyde fuchsin. Only three of 22 FITC-labeled lectins differentiated the suture. Lens culinaris agglutinin, Vicia faba agglutinin, and Pisum sativum agglutinin, which have an affinity for fucosylated a-N-acetylglucosamine with mannose dendrimers, bound more intensely to the exocuticle of the suture and less intensely to the endocuticle of the suture. The suture had no setae, and was paralleled by a knobbed ridge. The suture was thinner than the surrounding cuticle, especially in the posterior region where it was also wider. Back-scattered electron (BSE) and secondary electron (SE) observations of the fracture surface of intermolt cuticle showed that in the exocuticle of the suture the prisms were not in-filled with calcium, whereas the prisms of the surrounding cuticle were fully mineralized. BSE analysis of premolt and intermolt, resin-embedded cuticle indicated that the suture was less mineralized than the surrounding cuticle. EDAX non-dispersive X-ray microanalysis further demonstrated that the suture was less calcified than the adjacent calcified cuticle and had significantly lower magnesium and phosphorus concentrations, making the calcite in the suture more soluble. While the suture is very similar to non-suture calcified cuticle in terms of anatomy and histology, it differs in several aspects: (1) the presence or absence of a type of glycoprotein in the organic matrix, (2) the extent and composition of the mineral deposited and (3) the thickness of the cuticle. These characteristics make the suture mechanically weaker, more soluble and thus more susceptible to the molting fluid produced by the crab. This renders the suture predetermined to fail when stressed by the internal pressure exerted by the swelling of the underlying new exoskeleton, and ensures successful ecdysis.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Arthropoda--Anatomy, Blue crab--Morphology, Blue crab--Physiology, Blue crab--Research, Callinectes--Physiology, Molting
Blue crab -- Morphology
Blue crab -- Research
Arthropoda -- Anatomy
Callinectes -- Physiology
Blue crab -- Physiology

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