Hoeksema, B.W.

Interspecific relationships of invasive species hosting a native associated species are noteworthy, particularly if the invasive does not have a similar relationship in its native range. The azooxanthellate Indo-Pacific coral Tubastraea coccinea (Dendrophylliidae) has become a widespread invasive in the tropical western Atlantic, where it was probably introduced as a fouling organism in the 1930s. During recent coral reef surveys this invader has been observed as host for a native tube worm, Spirobranchus giganteus (Serpulidae), at Curaçao, where this association was most commonly found on a shipwreck. Although Spirobranchus species are known to live in association with various shallow-water corals in the Atlantic and the Indo-Pacific, none of them has been recorded as an associate of a dendrophylliid or of an azooxanthellate coral before. This new association may be possible because of the generalist host selection of S. giganteus, which could have been facilitated by the availability of shipwrecks and other man-made substrates.

Scleractinian reef corals have been acknowledged as the most numerous host group for associated hydroids belonging to the genus Zanclea. To date, their geographical distribution is known to include several Indo-Pacific regions. During the Statia Marine Biodiversity Expedition to St. Eustatius (Lesser Antilles, Dutch Caribbean), the Zanclea-coral association was observed for the first time for the Caribbean Sea as well as for the Atlantic Ocean. Our findings confirm that the biodiversity associated with coral reefs remains insufficiently explored worldwide.

Symbiotic Copepoda comprise a widespread, diverse, and abundant ecological group of small crustaceans associat- ed with various invertebrates, including octocorals. Some copepods, such as Lamippidae, are morphologically high- ly modified endoparasites found in galls or other cavities of various species of octocorals (Buhl-Mortensen and Mortensen 2004). Despite previous investigations of sym- biotic copepods inside Caribbean octocorals (Stock 1973), lamippid copepods associated with the common shallow-water sea fan Gorgonia ventalina Linnaeus, 1758, have not been reported so far. 

The distribution, abundance, and habitat preferences of the spinyhead blenny, Acanthemblemaria spinosa (Perciformes, Blennioidei, Chaenopsidae), were studied on coral reefs along the leeward side of Curaçao, southern Caribbean. The blennies inhabited small holes inside coral, which predominantly consisted of calcareous tubes constructed by coral-associated serpulid worms of the species Spirobranchus giganteus. About 50 % of the fish inhabited holes in dead coral, and the rest had their holes in live corals of eight species. The fishes showed a clustered distribution pattern and their abundance was higher at shallow depths (5 and 10 m) than at 15 m. Although males generally had a larger body size than females and needed larger holes for shelter and guarding eggs, no sexual dominance in hole selection was found. The position of the holes varied in elevation height above the reef floor, which showed a positive correlation with fish size.

Symbiotic relationships on coral reefs involving benthic hosts other than scleractinian corals have been poorly investigated. The hydroid Pteroclava krempfi is a widespread species known to be mainly associated with alcyonacean octocorals in the Indo-Pacific. In the present study, P. krempfi was discovered in association with octocorals of the genus Antillogorgia (Gorgoniidae) at two localities in the Caribbean Sea (St. Eustatius in the eastern Caribbean and Bocas del Toro in the western part), updating its host range with an additional genus and family. The Caribbean specimens showed no morphological differences and the shape of their polyps was consistent with the original P. krempfi description. A multi-locus phylogeny reconstruction of the P. krempfi species complex based on both mitochondrial and nuclear loci revealed three separate molecular clades. Two of them were composed of P. krempfi associated with the families Plexauridae and Alcyoniidae from the Maldives, whereas a new highly supported molecular lineage included all Caribbean specimens of P. krempfi associated with the family Gorgoniidae. These three divergent molecular clades represent distinct cryptic taxa within the P. krempfi species complex, in which the main interspecific difference consists of their host families.

Christmas tree worms, Spirobranchus spp. (Serpulidae), are known for their wide range of stony host corals, being either scleractinians or milleporids. Apparently, octocorals overgrowing scleractinians act as secondary hosts for Spirobranchus worms.

Crabs of the genus Platypodiella (Brachyura: Xanthidae) are known for their association with zoantharians (Hexacorallia: Zoantharia), predom- inantly of the genus Palythoa (Den Hartog and Holthuis 1984; Den Hartog and Tu ̈rkay 1991). They make cavities inside their zoantharian hosts, which they use as shelter.

During the Statia Marine Biodiversity Expedition to St. Eustatius (Lesser Antilles, Dutch Caribbean) in June 2015, small crabs (~5–10 mm wide) of Platypodiella spectabilis (Herbst, 1794) were most commonly observed either inside or in close proximity to encrusting Palythoa caribaeorum (Duchassaing and Michelotti, 1860) (Fig. 1a, b). A larger crab of the same species (~30 mm wide) was found hiding in between sponges and coral (M.A. Faasse and G.W.N.M. van Moorsel, pers. comm.), whereas crevices in dead coral may also be a common habitat (Martin and Zimmerman 2007). All crabs were characteristically colored in variable patterns of orange, yellow, black and white (Fig. 1; Martin and Zimmer- man 2007).
Unexpectedly, two small P. spectabilis individuals were found in cavities inside Niphates digitalis (Lamarck, 1814) sponges associated with the parazoanthid Umimayanthus parasiticus (Duchassaing and Michelotti, 1860). These crab dwellings were similar to burrows ob- served in Palythoa (Fig. 1c). Although N. digitalis was one of the most commonly observed sponges of St. Eustatius, no P. spectabilis was found in sponges without a zoantharian associate. 

Curaçao, Dutch Caribbean, is home to three species of gall crabs belonging to Cryptochiridae, a family obligatorily associated with a wide range of scleractinian host species. Gall crabs are reliant on their host coral; females are sedentary and never leave their dwelling (van der Meij 2014a). One of the three Atlantic gall crab species is Opecarcinus hypostegus (Shaw and Hopkins, 1977), which inhabits corals of the genus Agaricia. Corals of this genus are abundant in the photic zone (<30 m), but also in the mesophotic zone (30–150 m), where they predominantly belong to Agaricia grahamae Wells, 1973 and Agaricia lamarcki Milne- Edwards and Haime, 1851. The latter was found to be most abundant at depths of 25–60 m (Bongaerts et al. 2013). 

During a survey on 31 March, 2014, with the manned CuraSub submersible launched from Substation Curaçao (12°05 ́04.14 ̋N, 68°53 ́53.16 ̋W), a colony of A. lamarcki was observed at approximately 60 m depth (Panel B) exhibiting the characteristic tunnel formed by O. hypostegus. The shape of this tunnel is virtually identical to those found with O. hypostegus crabs in A. lamarcki at shallower depths (Panel A: Slangenbaai, Curaçao). Hence, we contend that this is strong evidence of O. hypostegus at mesophotic depth. 

The present finding is relevant in the light of the “deep reef refugia” hypothesis, which states that mesophotic reefs may act as a refuge in the face of global reef decline (Bongaerts et al. 2010), as it furthers our knowledge on the communities that presently thrive on these deep reefs. 

Many publications on the Caribbean Flora and Fauna are accessible online.

During the last decades, biologists of Naturalis Biodiversity Center and other scientific institutes have been participating in biodiversity research in the Caribbean. Many of their publications concern overviews of particular groups of plants and animals, either marine or terrestrial. Most of these studies were hardly accessible because they were only available in printed form. These papers could not easily be found because they were published in scientific journals that were kept in libraries of scientific institutions. Only dedicated naturalists knew of their existence. This is a pity because such old publications include many detailed species descriptions, including those that were new to science at the time of their discovery.

Contrary to popular belief, new species are usually not discovered during field expeditions but in museums and herbaria that house extensive collections and a special library dedicated to biodiversity studies. Without such reference material and the expertise of taxonomic specialists it is hard to conclude whether an unknown species is new to science or not. A good example consists of new sponge species recently sampled from Bonaire with the help of the Curasub, which is based at Substation Curaçao. These species were published in a recent issue of Zootaxa. The publication (Van Soest et al., 2014) was directly available online. A recent overview of the gall crab fauna of Curaçao (Van der Meij, 2014) is also available via internet.

Many old species descriptions in printed journals cannot be found on the internet. A short survey of this old literature revealed that many Caribbean species were originally described from Curaçao. Most type specimens that served as basis for the descriptions are presently housed in the collections of Naturalis because they were published by Naturalis scientists. The collections are part the cultural heritage of the Netherlands. The species descriptions were published in journals like “Beaufortia”, “Bijdragen tot de Dierkunde”, “Zoölogische Mededelingen”, “Zoölogische Verhandelingen”, “Studies on the Fauna of Curaçao and other Caribbean Islands”, “Studies on the Flora of Curaçao and other Caribbean Islands”, and “Studies on the Natural History of the Caribbean Region”. These journals can now be browsed via the repository of Naturalis Biodiversity Center (http://www.repository.naturalis.nl/)

Hopefully, this access to old literature will help conservationist, naturalists, students and scientists to find and use information on the Caribbean fauna and flora, which is about much more than just the discovery of new species.

Abstract:

Ovulid gastropods and their octocoral hosts were collected along the leeward coast of Curaçao, Netherlands Antilles. New molecular data of Caribbean and a single Atlantic species were combined with comparable data of Indo-Pacific Ovulidae and a single East-Pacific species from GenBank. Based on two DNA markers, viz. CO-I and 16S, the phylogenetic relationships among all ovulid species of which these data are available are reconstructed. The provisional results suggest a dichotomy be- tween the Atlantic and the Indo-Pacific taxa. Fully grown Simnia- lena uniplicata closely resembles juvenile Cyphoma gibbosum conchologically. Cymbovula acicularis and C. bahamaensis might be synonyms. The assignments of Caribbean host species for Cyphoma gibbosum, C. signatum, Cymbovula acicularis and Simnialena uniplicata are revised.