Morphological Evidence for a Chitin-Like Glycoprotein in Penaeid Hatching Envelopes

When chitin hydrolytic enzymes (chitinase and N-acetylglucosaminidase) were used as treatment during formation of the hatching envelope (HE) of the penaeid shrimp Sicyonia ingentis, results indicated the presence of carbohydrate moieties in the envelope. Eggs exposed to these enzymes had abnormal HEs that might elevate and often collapsed. The finding that chitin synthase inhibitors (tunicamycin, nikkomycin Z, and polyoxin D) also interfered with normal HE formation is further evidence for a carbohydrate component. The application of these synthase inhibitors resulted in more fragile envelopes that elevated and collapsed or were easily lost during processing. Similar results were seen in the absence of divalent ions (magnesium and calcium) considered critical for normal chitin formation. This morphological evidence is indicative of a chitin-like, linked carbohydrate in the HE of Sicyonia ingentis.