The First Deep-Sea Stylasterid (Hydrozoa, Stylasteridae) of the Red Sea

Abstract

The Stylasteridae, commonly known as lace corals, is a family of colonial calcifying hydrozoans mostly inhabiting deep waters. Stylasterids show a cosmopolitan distribution but, in some areas, they are characterized by low species diversity, such as in the Red Sea, where only a shallow-water species has been reported so far. With this work, we provide the first evidence of a deep-sea stylasterid inhabiting the NEOM region in the northern Saudi Arabian Red Sea, at depths ranging between 166 and 492 m. Morphological examinations revealed that this species was previously unknown and belonging to the genus Stylaster. We, therefore, describe Stylaster tritoni sp. nov., representing the first record of the genus in the Red Sea. Lastly, the phylogenetic position of the species within the Stylasteridae was evaluated, revealing a close relationship with shallow-water Indo-Pacific and Western Atlantic Stylaster species and confirming the polyphyletic nature of the genus Stylaster.

Bathymetric evolution of black corals through deep time

“…Our time-calibrated phylogeny indicates that black corals diversified at slope depths ∼437 Mya, and radiated bidirectionally, first onto the shelf and much later into the abyss, rather than in a unidirectional onshore-offshore pattern. Bidirectional radiation of lineages has also been found in other marine lineages [25,56,75,76]; however, for most cnidarians this has yet to be formally investigated. Ancestral state reconstruction suggests that morphological adaptations have influenced the invasion and persistence of black corals in different habitats through deep time, a finding consistent with other marine lineages [77][78][79][80].…”

The deepest record of the octocoral Acanthogorgia from the Red Sea

“…Taxa known to form MAFs in other ocean basins, such as black corals and hydrozoans, have previously been described from the deep Red Sea (Chimienti et al, 2022;Maggioni et al, 2022). However, these habitats have been understudied in the deep Red Sea, and only the occurrence of deep-water coral frameworks has been reported (Qurban et al, 2020).…”

“…Often referred to as a young ocean basin (Purkis et al, 2012;Augustin et al, 2021), its isolation and geological history make the Red Sea an interesting setting to study patterns of marine biodiversity (Berumen et al, 2019a), especially considering that it is characterized by high water temperatures and salinities all along the depth gradient (Roder et al, 2013;Manasrah et al, 2019). Recent opportunities for Red Sea deep-water explorations along the depth and latitudinal gradients, and resulting collections of benthic organisms, have significantly enhanced our knowledge of the occurrence, composition and diversity of cnidarian-dominated animal forests (Chimienti et al, 2022;Maggioni et al, 2022;Anker et al, 2023). Octocoral diversity research from the photic to the mesophotic zone has been carried out in the north of the Gulf of Aqaba (Benayahu et al, 2017a;Benayahu et al, 2017b), but a comparable sampling effort at depth in the Saudi Arabian Red Sea is still missing and octocoral diversity remains largely overlooked at the basin scale.…”

Unveiling the Faunal Diversity in the Water Column Adjacent to Two Seamounts in the Deep Arabian Sea Using Environmental DNA Metabarcoding

“…Many organisms with a calcified exoskeleton, except foraminiferans [67] and mussel Amygdalum sp., Ref. [68] avoid oxygenminimum waters, while nematodes [69][70][71][72]; polychaetes [68] and crustaceans, such as ostracods [73,74], copepods [52] and malacostracans [75,76], are adapted to live in the hypoxic conditions.…”

“…Hydrozoans are the dominant group of invertebrates found on the flanks of many seamounts [70]. They follow a life cycle that includes a benthic polyp (hydroid) stage and a pelagic medusan (jellyfish-like) stage [69][70][71][72]. However, the molecular phylogeny of these organisms remains poorly explored [80], which hinders our ability to make complete taxonomic assignments for these groups in seamounts.…”