Granules of immune cells are the source of organelles in the regenerated nerves of crayfish antennae

A comparative study on the antennae morphology and ultrastructure of three mud crab species of the genus Scylla from Setiu Wetlands, Terengganu, Malaysia

Crustaceans possess a range of sensory organs crucial in sensory perception, communication, and various ecological functions. Understanding morphological and functional differences in antennae among species could validate taxonomic differentiation and ecological adaptations. The antennae morphology and ultrastructure of mud crab species within the Scylla genus are poorly understood, and their role in ecological adaptation and species differentiation remains unexplored. This study aimed to describe and compare the morphology and ultrastructure of antennae in Scylla olivacea, Scylla tranquebarica, and Scylla paramamosain. Antennae were carefully excised from each crab and subjected to morphological, morphometric, and ultrastructural analysis. The study revealed that the antennae of Scylla species exhibit similar overall morphology, with a series of segments that tapered toward the upper end. All species possess non-branched single setae on the upper end of each segment. The number of antennae segments varied between species, with S. paramamosain having significantly more segments than S. olivacea. Additionally, the length and width of antenna segments differed among the species, with S. tranquebarica having a rougher antenna surface compared to S. olivacea and S. paramamosain. Our findings suggest that Scylla's antennae are distinct between species, especially in the number of segments and setae size. Such difference might be related to ecological adaptation. The role of antennae in sensory perception and social behavioral cues in mud crabs warrants further investigation. This study serves as a foundational reference for future research on the taxonomy, ecological adaptation, and sensory behaviors in the Scylla genus. RESEARCH HIGHLIGHTS: Variations and similarities in morphology and ultrastructure of three Scylla species can be found in the antennae. Scylla paramamosain had significantly higher number of segments than Scylla olivacea in morphology feature. The antennae surface of Scylla tranquebarica was rougher than that of S. olivacea and S. paramamosain. Antennae of three Scylla species possess non-branched single setae.

Identification of key genes and molecular pathways associated with claw regeneration in mud crab (Scylla paramamosain)

The mud crab (Scylla paramamosain) possesses extensive regenerative abilities, enabling it to replace missing body parts, including claws, legs, and even eyes. Studying the genetic and molecular mechanisms underlying regenerative ability in diverse animal phyla has the potential to provide new insights into regenerative medicine in humans. In the present study, we performed mRNA sequencing to reveal the genetic mechanisms underlying the claw regeneration in mud crab. Several differentially expressed genes (DEGs) were expressed in biological pathways associated with cuticle synthase, collagen synthase, tissue regeneration, blastema formation, wound healing, cell cycle, cell division, and cell migration. The top GO enrichment terms were microtubule-based process, collagen trimer, cell cycle process, and extracellular matrix structural constituent. The most enriched KEGG pathways were ECM-receptor interaction and focal adhesion. The genes encoding key functional proteins, such as collagen alpha, cuticle protein, early cuticle protein, arthrodial cuticle protein, dentin sialophosphoprotein (DSPP), epidermal growth factor receptor (EGFR), kinesin family member C1 (KIFC1), and DNA replication licensing factor mcm2-like (MCM2) were the most significant and important DEGs suspected to participate in claw regeneration. The findings of this research offer a comprehensive and insightful understanding of the genetic and molecular mechanisms underlying claw regeneration in S. paramamosain. By elucidating the specific genes and molecular pathways implicated in this process, our study contributes significantly to the broader field of regenerative biology and offers potential avenues for further exploration in crustacean limb regeneration.