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Robert D. Roer, Shai Abehsera, Amir Sagi | Integrative and Comparative Biology | (2015)
Key Takeaways
Plain English Takeaway
Crustaceans and insects have tough outer shells that work in similar ways, but crustaceans can make theirs hard with minerals. The study explains how their shells are built and what genes are involved.
Study Aim
The paper aims to compare the exoskeletons (outer shells) of pancrustaceans, which include crustaceans like crabs and insects. It investigates how their exoskeletons are built, how they function, and what makes them different, especially focusing on the ability of crustaceans to add minerals to their shells. The study also explores the genes and proteins involved in these processes by analyzing genetic data from the crayfish Cherax quadricarinatus.
Simply put: The study wants to find out how the shells of insects and crustaceans are similar and different, and what genes help build them.
Study Design
The authors conduct a comparative review of the structure, function, and genetic makeup of exoskeletons in insects and crustaceans. They analyze the layers and proteins in the shells, focusing on differences in mineralization (adding minerals like calcium carbonate). The study uses genetic information from the crayfish Cherax quadricarinatus to identify and compare genes related to shell formation. This approach combines information from previous research with new genetic data to provide a broad overview.
Simply put: The researchers compared the shells of insects and crustaceans by looking at their structure, chemistry, and genes, using crayfish as a key example.
Findings
The research demonstrates that both insects and crustaceans have exoskeletons made of similar layers and proteins, which act as barriers to water and ion loss. However, crustaceans have special proteins and genes that allow them to add minerals, making their shells much harder. The study reveals that these differences are linked to unique genes found in crustaceans, as shown by genetic analysis of crayfish. The findings suggest that understanding these genes could help explain how crustaceans evolved their tough, mineralized shells and may guide future research on shell formation and adaptation.
Simply put: The study found that crustaceans can make their shells harder than insects because they have special genes and proteins for adding minerals.
Abstract
The exoskeletons of pancrustaceans, as typified by decapod crustaceans and insects, demonstrate a high degree of similarity with respect to histology, ultrastructure, function, and composition. The cuticular envelope in insects and the outer epicuticle in crustaceans both serve as the primary barrier to permeability of the exoskeleton, preventing loss of water and ions to the external medium. Prior to and following ecdysis, there is a sequence of expression and synthesis of different proteins by the cuticular epithelium for incorporation into the pre-exuvial and post-exuvial procuticle of insects and the exocuticle and endocuticle of crustaceans. Both exhibit regional differences in cuticular composition, e.g., the articular (intersegmental) membranes of insects and the arthrodial (joint) membranes of crustaceans. The primary difference between these cuticles is the ability to mineralize. Crustaceans' cuticles express a unique suite of proteins that provide for the nucleation and deposition of calcium carbonate. Orthologs of genes discussed in the present review were mined from a recently completed cuticular transcriptome of the crayfish, Cherax quadricarinatus, providing new insights into the nature of these proteins.
(2) Another article explains how the exoskeletons of insects and crustaceans are very similar "with respect to histology, ultrastructure, function, and composition" (see the Credo paper summary to get this in "plain English").
The Credo summary also notes this difference: "However, crustaceans have special proteins and genes that allow them to add minerals, making their shells much harder."
You don't actually eat Lobster shell of course, but just another instance showing similarities between the two. And a fun fact in general.