Hi Alexey – Here are a couple. Cheers – Gustav
Stricker, Stephen A. "The ultrastructure and formation of the calcareous ossicles in the body wall of the sea cucumber Leptosynapta clarki (Echinodermata, Holothuroida)." Zoomorphology 105, no. 4 (1985): 209-222.
Stricker, Stephen A. "The fine structure and development of calcified skeletal elements in the body wall of holothurian echinoderms." Journal of morphology188, no. 3 (1986): 273-288.
I would be very grateful for bibliographic references about holothurian spicules formation and development.
Thanks in advance,