A Study on the Growth of the Unstalked Crinoid Heliometra glacialis (Owen 1833 ex Leach MS) (Echinodermata, Crinoidea) Based on Ring-Shaped Bands Formed in the Brachials

The growth of the unstalked crinoid Heliometra glacialis was studied based on material from the northwestern part of the Barents Sea near the Svalbard Archipelago. The calculation of the crinoid age was conducted using ring-shaped markings in the structure of their brachials. The growth rings visible on the surface of the crinoid brachials were considered as annual. The most suitable mathematical model describing the growth of H. glacialis was the Gompertz equation. The averaged theoretically limiting radius of the brachials (R∞), according to this equation, was 1694 ± 119 µm. The exponential deceleration constant of the specific growth rate (g) amounted to 0.41 ± 0.04, and the maximum lifespan was 12–18 years.