Abstract: A biodiversity survey on three corallivorous snails (Mollusca: Gastropoda) was performed at 28 sites around the island of Bonaire to assess their distribution patterns and associated host corals. The snails and their hosts were identified and counted in three depth zones: 5–10, 10–20, and 20–30 m. The snails were Coralliophila galea and C. salebrosa (Muricidae: Coralliophilinae), and Cyphoma gibbosum (Ovulidae: Simniinae). All three species were widespread around the island without apparent interspecific geographical variation. Coralliophila galea was found exclusively on scleractinian corals, Coralliophila salebrosa almost exclusively on octocorals, and Cyphoma gibbosum only on octocorals. Coralliophila salebrosa showed more dietary overlap with Cyphoma gibbosum than with Coralliophila galea. Coralliophila galea was the most commonly encountered species with the largest number of host species. Owing to its hosts distribution, this species also showed a greater maximum depth and a wider bathymetrical range than the other two snails. The other two snails were shallower and their depth ranges did not differ significantly. Host-coral size did not seem to have influence on the number of snails per host. Coral damage caused by the snails was visible but appeared to be low, causing no mortality in Bonaire, which suggests that the relation with their hosts is more parasitic than predatory. Because these three corallivores have occasionally been reported to occur as outbreaks in other Caribbean localities and may act as vectors in the dispersal of coral diseases, it is recommended that future studies should focus on their population dynamics.
The monotypic soft coral genus Stragulum van Ofwegen and Haddad, 2011 (Octocorallia: Malacalcyonacea: Tubiporidae) was originally described from Brazil, southwest Atlantic Ocean. Here, we report the first records of the genus from the eastern Caribbean and the Persian Gulf in the northwest Indian Ocean. We compare the morphological features of specimens, together with molecular data from three commonly used barcoding markers (COI, mtMutS, 28S rDNA) and 308 ultraconserved elements (UCE) and exon loci sequenced using a target-enrichment approach. The molecular and morphological data together suggest that specimens from all three localities are the same species, i.e., Stragulum bicolor van Ofwegen and Haddad, 2011. It is still not possible to establish the native range of the species or determine whether it may be an introduced species due to the limited number of specimens included in this study. However, the lack of historical records, its fouling abilities on artificial substrates, and a growing number of observations support the invasive nature of the species in Brazilian and Caribbean waters and therefore suggest that it may have been introduced into the Atlantic from elsewhere. Interestingly, the species has not shown any invasive behaviour in the Persian Gulf, where it has been found only on natural, rocky substrates. The aim of the present report is to create awareness of this taxon with the hope that this will lead to new records from other localities and help to establish its native range
Coral reefs are known to be among the most biodiverse marine ecosystems and one of the richest in terms of associations and species interactions, especially those involving invertebrates such as corals and sponges. Despite that, our knowledge about cryptic fauna and their ecological role remains remarkably scarce. This study aimed to address this gap by defining for the first time the spatial ecology of the association between the epibiont hydrozoan Nemalecium lighti and the Porifera community of shallow coral reef systems at Bonaire. In particular, the host range, prevalence, and distribution of the association were examined in relation to different sites, depths, and dimensions of the sponge hosts. We report Nemalecium lighti to be in association with 9 out of 16 genera of sponges encountered and 15 out of 16 of the dive sites examined. The prevalence of the hydroid–sponge association in Bonaire reef was 6.55%, with a maximum value of over 30%. This hydrozoan has been found to be a generalist symbiont, displaying a strong preference for sponges of the genus Aplysina, with no significant preference in relation to depth. On the contrary, the size of the host appeared to influence the prevalence of association, with large tubular sponges found to be the preferred host. Although further studies are needed to better understand the biological and ecological reason for these results, this study improved our knowledge of Bonaire’s coral reef cryptofauna diversity and its interspecific associations. View Full-Text
Abstract: Bioerosion caused by boring mussels (Mytilidae: Lithophaginae) can negatively impact coral reef health. During biodiversity surveys of coral-associated fauna in Curaçao (southern Caribbean), morphological variation in mussel boreholes was studied. Borings were found in 22 coral species, 12 of which represented new host records. Dead corals usually showed twin siphon openings, for each mussel shaped like a figure of eight, which were lined with a calcareous sheath and protruded as tubes from the substrate surface. Most openings surrounded by live coral tissue were deeper and funnel-shaped, with outlines resembling dumbbells, keyholes, ovals or irregular ink blotches. The boreholes appeared to contain black siphon and mantle tissue of the mussel. Because of the black color and the hidden borehole opening in live host corals, the mantle tissue appeared to mimic dark, empty holes, while they were actually cloaking live coral tissue around the hole, which is a new discovery. By illustrating the morphological range of borehole orifices, we aim to facilitate the easy detection of boring mussels for future research.
Abstract: Coral reefs in the Caribbean are known to be affected by many coral diseases, yet the ecology and etiology of most diseases remain understudied. The Caribbean ciliate infection (CCI) caused by ciliates belonging to the genus Halofolliculina is a common disease on Caribbean reefs, with direct contact considered the most likely way through which the ciliates can be transmitted between infected and healthy colonies. Here we report an observation regarding a Coralliophila sp. snail feeding in proximity to a cluster of ciliates forming the typical disease band of CCI. The result of this observation is twofold. The feeding behavior of the snail may allow the passive attachment of ciliates on the body or shell of the snail resulting in indirect transport of the ciliates among colonies, which makes it eligible as a possible disease vector. Alternatively, the lesions created from snail feeding may enhance the progression of the ciliates already present on the coral as well as promoting additional infections allowing pathogens to enter through the feeding scar
Appendix S1.Photographic host records of Petaloconchus sp.
Figure S1. Agaricia agaricitesat Bonaire (2019).
Figure S2. Agaricia humilisat Curaçao (2021).
Figure S3. Agaricia lamarcki at Curaçao (2021).
Figure S4. Cladopsammia manuelensis at Curaçao (2017).
Figure S5. Colpophyllia natansat Curaçao (2021).
Figure S6. Diploria labyrinthiformisat Curaçao (2021).
Figure S7. Eusmilia fastigiataat Curaçao (2014).
Figure S8. Madracis auretenraat Curaçao (2021).
Figure S9. Madracis decactisat Bonaire (2019)
Figure S10. Madracis senariaat Curaçao (2021).
Figure S11. Madracis senariaat Bonaire (2019).
Figure S12. Meandrina meandritesat Curaçao (2021).
Figure S13. Millepora alcicornis at Curaçao (2021).
Figure S14. Millepora complanata at Curaçao (2015).
Figure S15. Montastraea cavernosaat Bonaire (2019).
Figure S16. Orbicella annularisat Bonaire (2019).
Figure S17. Orbicella faveolataat Curaçao (2021).
Figure S18. Orbicella franksiat Bonaire (2019).
Figure S19. Porites astreoidesat Curaçao (2021).
Figure S20. Pseudodiploria strigosaat Curaçao (2021).
Figure S21. Siderastrea siderea at Curaçao (2021).
Figure S22. Stephanocoenia intersepta at Curaçao(2021).
Figure S23. Unidentified dead coralat Curaçao (2021).
The presence of associated endofauna can have an impact on the health of corals. Duringfieldwork on the southern Caribbean island of Curaçao in 2021, the presence of an unknown coral-dwelling worm snail was discovered, which appeared to cause damage to its hosts. A study of photoarchives revealed that the species was already present during earlier surveys at Curaçao since 2014and also in the southern Caribbean island of Bonaire in 2019. It was not found in St. Eustatius, anisland in the eastern Caribbean, during an expedition in 2015. The vermetid snail was preliminarilyidentified asPetaloconchussp. Its habitat choice resembles that ofP. keenae, a West Pacific coralsymbiont. The Caribbean species was observed in 21 host coral species, more than reported for anyother vermetid. BecausePetaloconchussp. is a habitat generalist, it is possible that it was introducedfrom an area with another host-coral fauna. The unknown vermetid is considered to be cryptogenicuntil future studies reveal its actual identity and its native range.
There is much documentation about seahorses (Hippocampus spp.) being threatened by habitat degradation and overfishing, but relatively few published studies mention their natural predators. The present study documents three cases in which seahorses are being caught by octopuses. In one case, the seahorse was partly consumed. These observations made at Bonaire (Caribbean Netherlands) and New South Wales (Australia) suggest that predation on seahorses by octopuses may be more widespread and common than previously thought.
Abstract: A salp swarm was observed in Director’s Bay, Curaçao in July 2021, where salps were caught and consumed by three scleractinian colonial reef corals: Madracis auretenra, Locke, Weil & Coates, 2017; Meandrina meandrites (Linnaeus, 1758), and Montastraea cavernosa (Linnaeus, 1767). The first two scleractinians are newly recorded salpivores. Since the coral polyps were collaborating, predation was not restricted by polyp size. This is the first detailed report on salpivorous corals in the Caribbean
Christmas tree worms (Serpulidae: Spirobranchus) occur in shallow parts of coral reefs, where they
live as associates of a large number of stony coral species [1,2]. They dwell inside a calcareous tube,
which is usually overgrown by the host coral and partly embedded deep inside the coral skeleton,
except for the tube’s opening and the worm’s operculum . Even if host corals and worm tubes
become overgrown by other invertebrates, the worms continue to grow and are able to keep their tube
openings free [4,5].
Despite their wide distribution, high densities, and the damage these tube-dwelling worms
may cause to corals [6,7], little is known about their natural enemies. They appear well protected
by the tube, which is armed by a long spine on the opening margin. Although they may live up
to 40 years , mortality of Spirobranchus worms in dense populations is not uncommon, and most
obvious when their vacated tubes are inhabited by small fish and crustaceans [6,8]. There are a few
reports on attempted feeding of Christmas tree worms by fish and on Spirobranchus remnants found in
fish stomachs (, references therein), but no information is available on other predators.
Therefore, it is surprising that a West Atlantic batwing coral crab, Carpilius corallinus Herbst, 1783,
was observed preying on two individuals of Spirobranchus giganteus (Pallas, 1766) during a night dive at
Playa Pabou (1209041.8” N, 06817001.0” W), Kralendijk, Bonaire on 18 October 2020; time 18:45–21:15
(Electronic Supplementary Material). The worms were living in a colony of the scleractinian coral
Porites astreoides Lamarck, 1801, at a depth of 7 m. The crab was using its slender left claw to break away
the thick calcareous tubes of the worms, which resulted in a deposit of limestone debris aside the coral
(Figure 1a). The crab seemed to extract soft parts of the worm from the tube and manipulate them by
using its second pair of pereiopods, which are the first pair of walking legs (Electronic Supplementary
Material). The use of walking legs during feeding is not uncommon in other brachyuran lineages.
Some spider crabs (Majidae) use walking legs to pry and wedge open gastropod and bivalve shells 
and box crabs (Calappidae) can be seen to use the first two pairs of walking legs to rotate prey shells
to find an opening for easier access and grip for their specialized right claw (W.d.G. pers. obs.).
During another night dive, two days later, the crab was no longer present but the extent of damage
to the worm tubes and the coral was evident (Figure 1b). The worm in the longest of the two tubes
was gone, while the other worm had survived in a part of the tube that was inside the host coral.
Its operculum appeared lost (Figure 1b).
This observation is interesting because little is known about species predating on Christmas tree
worms (see above), while also hardly anything has been published on the diet of the Batwing coral
crab. Carpilius corallinus is well known for its nocturnal activities  and it is the onlyWest Atlantic
member of Carpiliidae, a family of three congeneric species . All three species possess an enlarged
right cheliped (claw-bearing leg), with a blunt molariform tooth found proximally on the cutting edge
of the pollex, which is the fixed ‘finger’ of the claw.
In laboratory conditions in Guam, the Indo-West Pacific species C. convexus (Forskål, 1775) and
C. maculatus (Linnaeus, 1758) have been observed to use their major claw to crush shells of various
species of gastropods . The latter crab species has also been reported as predator of a commercially
important abalone, Haliotis asinina Linnaeus, 1758, in the Philippines , and was found in the field
between the remains of freshly-killed gastropods on two separate occasions in Guam .
Individuals of the West Atlantic C. corallinus were also found to be feeding on gastropods in
captivity, while they were also fed with sardines . In another case, a female individual in an
aquarium was observed to break apart shells inhabited by hermit crabs in an attempt to remove
them from their homes . Only one published record was found on the diet of C. corallinus in its
natural environment, consisting of Diadema sea urchins . There is also unpublished data concerning
C. corallinus feeding on sea urchins, as well as on a topshell, Calliostoma javanicum (Lamarck, 1822),
all from Bonaire (E.M., pers. obs.).
It seems that information on the diet of Carpilius species is rare, but considering the armor of
previously reported prey species, the crushing of serpulid worm tubes seems to be within their capacity
when they use their right claw. The crab at Bonaire was, however, using its slender left claw to feed
from the worm tube. We do not know if the crab had initially crushed the tube using its specialized
right claw and continued feeding using its left claw, or if the crab initially used its left claw to break
The extent of damage on worm tubes is striking (Figure 1). In spite of many dives on Bonaire,
this kind of harm was not reported before. Because Spirobranchus tubes may easily become covered
by coral tissue and algae [3,6,7], it is possible that damaged worm tubes may get unnoticed due
to similar overgrowth. All in all, we do not expect Spirobranchus to be a regular part of the diet
of Carpilius corallinus. The present observation and previously published information suggest that
Carpilius species are not prey specific. More research on the diet and foraging behavior of these
commercially important crab species will teach us more about their role in the food chains of coral reefs.