The hemocytes of a millipede, Thyropygus poseidon

Area of Science:

• * Arthropod biology
• * Comparative immunology
• * Cell biology

Background:

• * Hemocytes are crucial for immune responses in invertebrates.
• * Limited understanding of hemocyte diversity and function in millipedes (Arthropoda: Diplopoda).
• * Jone's classification system for insect hemocytes provides a framework for comparison.

Purpose of the Study:

• * To characterize the cytological and histochemical properties of hemocytes in the millipede Thyropygus poseidon.
• * To extend Jone's hemocyte classification to millipedes.
• * To investigate the functional similarities and differences between millipede and insect hemocytes.

Main Methods:

• * Cytological examination of hemocyte morphology.
• * Histochemical staining for proteins and catechol oxidation products.
• * Comparative analysis with hemocyte classifications and functions in insects and crustaceans.

Main Results:

• * Seven hemocyte classes identified: prohemocytes, plasmatocytes, granular hemocytes, cytocytes, oenocytoids, spherule cells, and adipohemocytes.
• * Most hemocytes sequester catechol oxidation products and plasma proteins.
• * Granular hemocytes possess phenol-oxidase, similar to crustaceans but distinct from insects; cytocytes do not induce coagulation.

Conclusions:

• * Millipede hemocytes exhibit unique characteristics, particularly granular hemocytes with phenol-oxidase activity.
• * The identified hemocyte types likely represent distinct cell lines rather than inter-transformable forms.
• * These findings highlight significant differences between millipede and insect hemocyte systems, suggesting divergent evolutionary trajectories.