Albinism in Callista chione from Grado, Italy

The late Giovanni Grigolon, an Italian shell collector from Grado, was able to collect some interesting and rare albino shells over the decades from local fishermen. The shells referred to were all caught by fisherboats in moderately deep water off Grado between 1980 and 2000. All are fully adult (between 51 and 76 mm) and live taken, so both valves are conserved.
In the collection of the author are several full albinos (Fig. a), one unique “semi-albino” (Fig. b), one unique “partial albino” (Fig. c) as well as typical specimens of Callista chione (Linnaeus, 1758) (Fig. d).
The full albino does not show any pigmentation at any place on both valves. The “semi-albino” has an almost complete albinotic left valve except the entire lunule area, which is regularly coloured. The “partial albino” displays about 50% of its right valve albinotic. It is noteworthy that also this specimen shows the marginal part of the lunule and the posterior part of the right valve regularly pigmented. The transition between albinotic areas and regularly coloured sectors in these two cases are sharply demarcated.
The commonness of partial albinotic specimens is estimated by the author to be about 1 : 10 000 000 (see publication of the author for details) .
last update: 2020-08-12