Zoomorphology

, Volume 106, Issue 4, pp 232–243

Ultrastructural investigation of matrix-mediated biomineralization in echinoids (Echinodermata, Echinoida)

Authors

  • Konrad Märkel
    • Lehrstuhl für Spezielle Zoologie und Parasitologie (Arbeitsgruppe Funktionelle Morphologie)Ruhr-Universität Bochum
  • Ursula Röser
    • Lehrstuhl für Spezielle Zoologie und Parasitologie (Arbeitsgruppe Funktionelle Morphologie)Ruhr-Universität Bochum
  • Ute Mackenstedt
    • Lehrstuhl für Spezielle Zoologie und Parasitologie (Arbeitsgruppe Funktionelle Morphologie)Ruhr-Universität Bochum
  • Melanie Klostermann
    • Lehrstuhl für Spezielle Zoologie und Parasitologie (Arbeitsgruppe Funktionelle Morphologie)Ruhr-Universität Bochum
Article

DOI: 10.1007/BF00312044

Cite this article as:
Märkel, K., Röser, U., Mackenstedt, U. et al. Zoomorphology (1986) 106: 232. doi:10.1007/BF00312044

Summary

The formation of echinoderm endoskeletons is studied using echinoid teeth as an example. Echinoid teeth grow rapidly. They consist of many calcareous elements each produced by syncytial odontoblasts. The calcification process in echinoderms needs (1) syncytial sclerocytes or odontoblasts, (2) a spacious vacuolar cavity within this syncytium, (3) an organic matrix coat in the cavity. As long as calcite is deposited, the matrix does not touch the interior face of the syncytium. The cooperation between syncytium, interior cavity and matrix coat during the mineralization process is discussed. The proposed hypothesis applies to the formation of larval skeletons, echinoderm ossicles and echinoid teeth.

When calcite deposition ceases the syncytium largely splits up into filiform processes, and the skeleton is partly exposed to the extracellular space. However, the syncytium is able to reform a continuous sheath and an equivalent of the cavity and may renew calcite deposition.

The tooth odontoblasts come from an apical cluster of proliferative cells, each possessing a cilium. The cilium is lost when the cell becomes a true odontoblast. This suggests that cilia are primitive features of echinoderm cells. The second step in calcification involves the odontoblasts giving rise to calcareous discs which unite the hitherto single tooth elements. During this process the odontoblasts immure themselves. The structures necessary for calcification are maintained until the end of the process.

The mineralizing matrix is EDTA-soluble. The applied method preserves the matrix coating the calcite but more is probably incorporated into the mineral phase and dissolved with the calcite.

Abbreviations

A

adhesive point (LNC)

B

adaxial bag

bb

basal body (ci)

CA

calcareous deposits

cb

cytoplasmic bladder (cp)

ce

centriole

ci

cilium

cp

cable-like cell process

cv

condensing vacuole

dp

distal processes (sh)

E

epithelium of the tooth

ex

extracellular space

f

extracellular fibrils

ga

gasket (sh)

ic

interior cavity

L

lamellae (LNC)

LNC

lamellae needle complex

m

mitochondrium

mc

matrix coat

MF

main fold (P)

MI

mitosis

mt

microtubules

N

nucleus

O

odontoblast

P

primary plate

Ph

phagocyte

PR

proliferative cell

pr

prism

rb

reserve body

RER

rough endopl. reticulum

rl

rootlet (ci)

RY

relatively youngest plate

s

satellite (bb, ce)

sh

synplasmic sheath (O)

SP

secondary plate

sv

smooth-walled vesicle

TF

transversal fold (P)

U

umbo (P)

v

Golgi vesicle

Y

youngest tooth element

Copyright information

© Springer-Verlag 1986