Revision of Hyalopale (Chrysopetalidae; Phyllodocida; Annelida): an amphi-Atlantic Hyalopale bispinosa species complex and five new species from reefs of the Caribbean Sea and Indo-Pacific Oceans

Abstract

The formerly monotypic taxon, Hyalopale bispinosa Perkins 1985 (Chrysopetalinae), is comprised of a cryptic species complex from predominantly tropical embayments and island reefs of the Western Atlantic and Indo-Pacific Oceans. Hyalopale species are of meiofaunal size (length: 1−2.8mm), but considered non-interstitial, with the majority of species inhabiting a singular habitat of shallow littoral zones among algae and epifauna overlying sediments in rubble. Hyalopale adults exhibit notochaetal fans characterized by the presence of lateral and midline notochaetal spines. Species of Hyalopale can be distinguished by the shape of glass-like notochaetal paleae and the number of densely stacked ribs. Hyalopale bispinosa forms a western and eastern Atlantic species complex, comprising the type species, Hyalopale bispinosa s.s., a comparatively larger form with the highest number of notochaetal paleael ribs from Florida, and Hyalopale cf. bispinosa, from the western and eastern Mediterranean, a smaller form with a similar notochaetal morphology to the latter. Unfortunately, no molecular sequence data is available for Hyalopale bispinosa s.s. Five new species are described, with molecular sequence data provided for three: Hyalopale leslieae sp. nov., a small form with a comparatively low number of paleal ribs, found from the Florida Keys to Belize, Caribbean Sea, H. zerofskii sp. nov. from southern California and Mexico, eastern Pacific and H. sapphiriglancyorum sp. nov., a distinctive species with the lowest number of paleael ribs, from Raja Ampat, Indonesia and the Great Barrier Reef, Queensland, western Pacific. Two other species are described from morphology alone: H. angeliensis sp. nov. from Dampier, Western Australia and Seychelle Islands, eastern Indian Ocean and H. furfuricula sp. nov. from the Red Sea and Mozambique, western Indian Ocean, possessing a unique paleal brow shape. While well supported as a clade, support for relationships within Hyalopale is low. Hyalopale cf. bispinosa (Mediterranean) was recovered as sister group to the remaining Hyalopale, with H. leslieae sp. nov. as sister to the Hyalopale Pacific clade, comprising H. zerofskii sp. nov. (eastern Pacific) and H. sapphiriglancyorum sp. nov. (western Pacific). Within Chrysopetalinae, Hyalopale and Paleanotus formed a clade that was the sister group to the other paleate chrysopetalids under maximum likelihood, though Paleanotus grouped with the other paleate forms under maximum parsimony. The adult morphology of Hyalopale species is compared with that exhibited in the larvae of Paleanotus species; based on these results, including possession of a shared notochaetal character, Hyalopale is considered to contain paedomorphic taxa.

A Mitogenome-Based Phylogeny of Pilargidae (Phyllodocida, Polychaeta, Annelida) and Evaluation of the Position of Antonbruunia

“…Up until the last few decades, morphology was the only way of assessing species diversity and inferring phylogenetic relationships. Now that molecular phylogenetic methods are well established and readily available, our understanding of the placement of many annelid taxa has been revised at both low [3,4] and high [5,6] taxonomic levels. This is an ongoing process, partially because it is difficult to obtain samples of many taxa due to their rarity or the inaccessibility of their habitat.…”