The first report of y-larvae (Crustacea: Facetotecta) from the Caribbean coast of Panama, with an overview of their occurrence in the Americas and surprising parallels to the Okinawan fauna

Abstract Facetotectans, or “y-larvae,” are microscopic planktonic crustaceans whose adults are still unknown. Recent investigations have confirmed a large diversity of both y-nauplii and y-cyprids in shallow coastal waters in East Asia, especially off mainland Japan, Okinawa, and Taiwan. Although y-larvae are widely, if sparsely, distributed in other parts of the world, efforts to evaluate their true abundance and diversity outside East Asia have been few. There have been especially few records in the Americas outside the maritime provinces of Canada. We present the first record of Facetotecta on the Caribbean coast of Panama, and just the third in the Caribbean Sea, based on about ten days of sampling in the Bocas del Toro Archipelago off Panama’s northeastern coast. Sampling six localities yielded seven y-nauplii and naupliar exuviae, all from the same locality, Isla Zapatilla #2. This is a much lower take than would be expected based on previous experience in similar habitats in East Asia. The seven specimens likely represent five different species, all of which could be matched, usually with high confidence, to some of the 40 or so y-naupliar morpho-species that have recently been designated and diagnosed from Okinawa. The true species-level diversity of Facetotecta in the Caribbean region is likely to be appreciably greater than this, but it can only be assessed by a much more intensive sampling program combined with molecular analyses.