Ontogeny of an arlequin: morphological and colour pattern changes from juvenile to adult in Gnathophyllum elegans (Risso, 1816) (Decapoda: Palaemonidae), traced through citizen science and social media data mining.

Abstract

The spotted bumblebee shrimp Gnathophyllum elegans (Risso, 1816) is a caridean species of the family Palaemonidae Rafinesque, 1815 widely distributed in the eastern Atlantic and the entire Mediterranean Sea (Zariquiey Alvarez 1968; d'Udekem d'Acoz 1999; De Grave et al. 2015). It is a solitary sciaphilous taxon that grows up to 40 mm of total length, and at daytime hides under stones, in crevices or amidst Posidonia oceanica (Linnaeus) Delile rhizomes from the intertidal to about 30 m depth, with some authors even considering it as preferring coralligenous environments (Pérès Picard 1964; Ledoyer 1968; d'Udekem d'Acoz 1999). Such a cryptic behavior makes the detection of G. elegans often difficult in the field, although the species is easily distinguishable by the other eastern Atlantic-Mediterranean shrimp species due to its colourful appearance and mostly due to its dark purple-brown body entirely covered by yellow-orange dots (Zariquiey Alvarez 1968; Falciai Minervini 1992).