Bert W Hoeksema

Abstract: The recent rise in ocean temperatures, accompanied by other environmental changes, has notably
increased the occurrence and spread of diseases in Octocorallia, of which many species are integral to shallow
tropical and subtropical coral reef ecosystems. This study focuses on the understanding of these diseases, which
has been largely limited to symptomatic descriptions, with clear etiological factors identified in only a fraction
of cases. A key example is the multifocal purple spots syndrome (MPSS) affecting the common Caribbean
octocoral sea fan Gorgonia ventalina, linked to the gall-forming copepods of the genus Sphaerippe, a member of
the widespread family Lamippidae. The specialized nature of these copepods as endoparasites in octocorals
suggests the potential for the discovery of similar diseases across this host spectrum. Our investigation
employed four molecular markers to study disease hotspots in Saint Eustatius, Curaçao, northwest and
southwest Cuba, and Bonaire. This led to the discovery of a group of copepod species in these varied Caribbean
locations. Importantly, these species are morphologically indistinguishable through traditional methods,
challenging established taxonomic approaches. The observed diversity of symbionts, despite the host species'
genetic uniformity, is likely due to variations in larval dispersal mechanisms. Our phylogenetic analyses
confirmed that the Lamippidae copepods belong to the order Poecilostomatoida (Copepoda) and revealed their
sister group relationship with the Anchimolgidae, Rhynchomolgidae, and Xarifiidae clades, known for their
symbiotic relationships with scleractinian corals. These results add to our understanding of the evolutionary
and ecological interactions of copepods and their hosts, and the diseases they cause, important data in a
changing climate.

Christmas tree worms are polychaetes of the genus, Spirobranchus (Serpulidae). These reef- dwelling species live inside tubes that are usually embedded inside the skeletons of corals belonging to either the order Scleractinia (Anthozoa) or to the family Milleporidae (Hydrozoa) (Hoeksema and Ten Hove 2017, Perry et al. 2017). Extended Spirobranchus worms are visible because of their large, bright-colored branchiae, shaped as twin spirals, and a peduncle (stalk) with a calcified spiny operculum on top. Their colormorph variation and the presence of long spines on the tube may serve as protection against predators (Grassle 1973). When in danger, the worms are able to retract quickly inside their tube, while using their operculum as a shield (Hoeksema et al. 2016, Pezner et al. 2017).

Although little is known about predators of Spirobranchus spp. and no actual attacks have been documented (Kupriyanova et al. 2001), predation has been inferred from damaged and/or missing opercula in about 10% of the examined specimens [Nishi and Kikuchi 1996 for Spirobranchus corniculatus (Grube, 1862)]. 

Abstract

Snails of the genus Coralliophila (Muricidae: Coralliophilinae) are common corallivores in the Caribbean, feeding on a wide range of host species. In the present study, the morphological and genetic variation in C. galea and C. caribaea were studied in relation to their association with host coral species at Curaçao. Differences in shell shape among snails living on different hosts were quantified using geometric morphometric and phylogenet-ic relationships were studied using two mitochondrial markers (12S and COI). Based on these analyses, a new species, C. cura-caoensis sp. nov., was found in association with the scleractinian coral Madracis auretenra. Both C. galea and C. caribaea showed host-specific differences in shell shape, size, and shell allometry (i.e. changes in morphological development during growth). Shell spire variability contributed foremost to the overall variation in shell shape. In C. caribaea minor genetic differences existed between snails associated with scleractinian and alcyonacean cor-als, whereas in C. galea such intraspecific variation was not found. These results shed more light on morphological and genetic differences among coral-associated fauna living on different host species.

Hexactinellid sponges are important members of deep-sea benthic ecosystems because they provide available hard substrate habitats for filter-feeding invertebrates. However, symbioses between hexactinellid sponges and their symbionts are poorly known. Zoantharians associated with hexactinellid sponges have been reported widely from deep-sea marine ecosystems, either on the bodies or stalks of hexactinellid sponges. Despite these records, there has been a lack of research on their diversity and phylogenetic relationships. In this study, 20 specimens associated with amphidiscophoran and hexasterophoran sponges were collected from the waters of Australia and Japan in the Pacific, and from Curaçao in the southern Caribbean, and these were examined in addition to museum specimens. Based on molecular phylogenetic analyses and morphological observations, we formally describe two new genera and three new species of Zoantharia and report several previously described species. The results suggest at least two independent origins for the symbioses between hexactinellid sponges and zoantharians. Our results demonstrate that the diversity of hexactinellid sponge-associated zoantharians is much higher than has been previously thought. The new taxa described in this work further reconfirm that the deep-sea harbours high levels of undescribed zoantharian diversity.

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