Immunocytochemical localization of actin and tubulin in the integument of land crab (Gecarcinus lateralis) and lobster (Homarus americanus)

Abstract

The crustacean integument consists of the exoskeleton and underlying epithelium and associated tissues. The epithelium, which is composed of a single layer of cells, is responsible for the cyclical breakdown and synthesis of the exoskeleton associated with molting (ecdysis). During premolt (proecdysis) the epithelial cells lengthen and secrete the two outermost layers (epicuticle and exocuticle) of the new exoskeleton while partially degrading the two innermost layers (endocuticle and membranous layer) of the overlying old exoskeleton. This increased cellular activity is associated with increased protein synthesis and a change in cell shape from cuboidal to columnar. The cytoskeleton, composed of microfilaments (actin) and microtubules (tubulin), plays important roles in the intracellular organization and motility of eukaryotic cells. Immunoblot analysis shows that the land crab exoskeleton contains actin, tubulin, and actin‐related proteins (Varadaraj et al. 1996. Gene 171:177–184). In the present study, immunocytochemistry of land crab and lobster integument showed that both proteins were localized in various cell types, including epithelia, connective tissue, tendinal cells, and blood vessels. Muscle immunostained for actin and myosin, but not for tubulin. The membranous layer of land crab (the other layers of the exoskeleton were not examined) and membranous layer and endocuticle of lobster also reacted specifically with anti‐β‐actin and anti‐α‐tubulin monoclonal antibodies, but not with an anti‐myosin heavy chain antibody. During proecdysis immunolabeling of the membranous layer decreased probably due to protein degradation. The staining intensity for actin and tubulin in the proecdysial epithelium was similar to that in the intermolt (anecdysial) epithelium, suggesting that there was a net accumulation of both proteins proportional to the increase in cellular volume. These results support the previous biochemical analyses and, more specifically, localize actin and tubulin in exoskeletal structures, suggesting that they may serve both intracellular and extracellular functions in crustaceans. J. Exp. Zool. 286:329–342, 2000. © 2000 Wiley‐Liss, Inc.

Molecular Characterisation of Colour Formation in the Prawn Fenneropenaeus merguiensis

“…As in this study, Mykles et al [51] detected actin in the epithelium, and membranous and endocuticular layer of crab and lobster exoskeletons. The authors suggested that the epithelium of these crustaceans secreted actin, together with tubulin to enable the incorporation of these proteins into the extracellular matrix, where the proteins could function as stabilizers or organizers of the matrix.…”

Identification of an Alpha-Tubulin Gene from the Chinese Mitten Crab Eriocheir sinensis: Expression Profiles under Immune Challenge and during Larval Development

“…Studies on rice and Arabidopsis indicated hyperosmotic stress induced α-tubulin phosphorylation [44]. Studies on land crab and lobster confirmed that tubulin localized in exoskeletal structures, it may serve both intracellular and extracellular functions in crustaceans [45]. In this study, we found that the EsTUBA mRNA expression fluctuated with the morphological changes in the brachyurization metamorphosis process of E. sinensis.…”

Effects of dietary cholesterol levels on moulting performance, lipid accumulation, ecdysteroid concentration and immune enzymes activities of juvenile Chinese mitten crabEriocheir sinensis

“…As we known, the moulting of juvenile E. sinensis principally required enough preparations of energy storage (Catacutan ), hormone concentration (Chang & Mykles ) and immune system protection (Mykles et al . ). Energy storage in juvenile E. sinensis is mainly dependent on lipid content in the midgut gland and muscles.…”

“…Based on the new cuticle formation and calcification (Sakamoto et al 2009) in the lateral spine, the postmoult phase (Freeman et al 1987) was subdivided into soft, leathery and paper shell stages. As we known, the moulting of juvenile E. sinensis principally required enough preparations of energy storage (Catacutan 2002), hormone concentration (Chang & Mykles 2011) and immune system protection (Mykles et al 2000). Energy storage in juvenile…”