Цирконы и титаномагнетиты морского ежа Scaphechinus griseus (Mortengen, 1927)

Abstract

Sea urchins (Echinoidea), representatives of the suborder Scutellina, have diverticula and accumulate mineral particles of sandy substrate in them. Juvenile Scaphechinus mirabilis (Agassiz, 1863) (Scutellina) select and accumulate only relatively rare minerals - zircon and ilmenite. In this work, minerals were identified for the first time in the diverticula of the related species  Scaphechinus griseus, which lives together with S. mirabilis, on a sandy substrate off the southern coast of the Russky Island (Sea of ​​Japan). The fact that these two species coexist is attributed to a single nutritional structure, which includes both diatoms and minerals. As a result, no fundamental differences in the mineral composition of the diverticula of S. griseus and S. mirabilis were found. The highly selective selection and accumulation of zircon and two ferrotitanium minerals was found to be similar for both Scaphechinus species. At the same time, the content of these minerals of the consumed size in the surrounding sediments was 4 orders of magnitude less. However, mineral compositions of diverticula showed a quantitative preference for zircon selection by the sea urchin S. mirabilis. It was established that the main organic food of the studied urchins from the bottom marine substrate is diatoms, represented by 15 species from the classes Coscinodiscophyceae (4 species), Mediophyceae (2) and Bacillariophyceae (9). Among them, both solitary marine benthic (Navicula dumontiae – 128·10³ кл·см³) and planktonic (Asterionellopsis glacialis – 106·10³ кл·см³) forms that settled to the bottom predominated quantitatively. A significant amount of diatoms in bottom sediments (245·10³ кл·см³) in sea urchin habitats may serve as a decisive factor for the colonization of the Sea of ​​Japan by these two endemic species.

Keywords: sea urchin, diverticulum, minerals, zircon, ferrotitanium oxides, diatoms