Non-native molluscan colonizers on deliberately placed shipwrecks in the Florida Keys, with description of a new species of potentially invasive worm-snail (Gastropoda: Vermetidae)

Dead non-native corals (Tubastraea coccinea) and their associated fauna trawled from the North Sea provide evidence for long-distance transport by hull fouling

Four large skeletons of the non-native Indo-Pacific coral Tubastraea coccinea Lesson, 1830 were trawled by a fishing boat in the Dutch part of the North Sea in October 2024. They had empty shells of a non-indigenous worm snail, probably Eualetes tulipa (Rousseau, 1843), attached to them. The corals had remnants of black ship-hull coating on their flat attachment base and resembled biofouling specimens found on semisubmersible platforms in the oil and gas industry. They were compared to museum specimens of T. coccinea from Aruba (Southern Caribbean), collected in 1955 from a metal substrate in a ship wharf, which were smaller but similar in shape and hosting a different worm snail species, Petalaconchus sp. Based on our present knowledge of Tubastraea corals and their associated fauna, it is most likely that the found North Sea corals were transported on a semi-submersible platform from Brazil, crossing at least 8000 km across the Atlantic before detaching and sinking. This finding demonstrates that hull-fouling Tubastraea can survive travel over large distances until reaching the minimum boundary of their temperature range. It also underlines the urgent need for effective defouling management of semisubmersible platforms.

Replacing mechanical protection with colorful faces-twice: parallel evolution of the non-operculate marine worm-snail genera Thylacodes (Guettard, 1770) and Cayo n. gen. (Gastropoda: Vermetidae)

Vermetid worm-snails are sessile and irregularly coiled marine mollusks common in warmer nearshore and coral reef environments that are subject to high predation pressures by fish. Often cryptic, some have evolved sturdy shells or long columellar muscles allowing quick withdrawal into better protected parts of the shell tube, and most have variously developed opercula that protect and seal the shell aperture trapdoor-like. Members of Thylacodes (previously: Serpulorbis) lack such opercular protection. Its species often show polychromatic head-foot coloration, and some have aposematic coloration likely directed at fish predators. A new polychromatic species, Thylacodes bermudensis n. sp., is described from Bermuda and compared morphologically and by DNA barcode markers to the likewise polychromatic western Atlantic species T. decussatus (Gmelin, 1791). Operculum loss, previously assumed to be an autapomorphy of Thylacodes, is shown to have occurred convergently in a second clade of the family, for which a new genus Cayo n. gen. and four new western Atlantic species are introduced: C. margarita n. sp. (type species; with type locality in the Florida Keys), C. galbinus n. sp., C. refulgens n. sp., and C. brunneimaculatus n. sp. (the last three with type locality in the Belizean reef) (all new taxa authored by Bieler, Collins, Golding & Rawlings). Cayo n. gen. differs from Thylacodes in morphology (e.g., a protoconch that is wider than tall), behavior (including deep shell entrenchment into the substratum), reproductive biology (fewer egg capsules and eggs per female; an obliquely attached egg capsule stalk), and in some species, a luminous, "neon-like", head-foot coloration. Comparative investigation of the eusperm and parasperm ultrastructure also revealed differences, with a laterally flattened eusperm acrosome observed in two species of Cayo n. gen. and a spiral keel on the eusperm nucleus in one, the latter feature currently unique within the family. A molecular phylogenetic analysis based on mitochondrial and nuclear rRNA gene sequences (12SrRNA, trnV, 16SrRNA, 28SrRNA) strongly supports the independent evolution of the two non-operculate lineages of vermetids. Thylacodes forms a sister grouping to a clade comprising Petaloconchus, Eualetes, and Cupolaconcha, whereas Cayo n. gen is strongly allied with the small-operculate species Vermetus triquetrus and V. bieleri. COI barcode markers provide support for the species-level status of the new taxa. Aspects of predator avoidance/deterrence are discussed for these non-operculate vermetids, which appear to involve warning coloration, aggressive behavior when approached by fish, and deployment of mucous feeding nets that have been shown, for one vermetid in a prior study, to contain bioactive metabolites avoided by fish. As such, non-operculate vermetids show characteristics similar to nudibranch slugs for which the evolution of warning coloration and chemical defenses has been explored previously.

Non-native coral species dominate the fouling community on a semi-submersible platform in the southern Caribbean

A coral community was examined on a semi-submersible platform that was moored at the leeward side of Curaçao, in the southern Caribbean, from August 2016 until August 2017. This community included several non-native or cryptogenic species. Among them were two scleractinian corals (Tubastraea coccinea and T. tagusensis) and two octocorals (Chromonephthea sp. and an unidentified Nephtheidae sp.). This is the first reported presence of T. tagusensis in the southern Caribbean, and the genus Chromonephthea in the Caribbean region. An ascidian, Perophora cf. regina, is also reported from the southern Caribbean for the first time, as well as a coral-associated vermetid gastropod, Petaloconchus sp., first recorded in the Caribbean in 2014. Lack of biofouling management could potentially harm indigenous marine fauna through the introduction of non-native species. Therefore monitoring communities associated with semi-submersible platforms is essential to track the presence and dispersal of non-native, potentially invasive species.

In the aftermath of Hurricane Irma: Colonization of a 4-year-old shipwreck by native and non-native corals, including a new cryptogenic species for the Caribbean

Little is known about early coral settlement on shipwrecks with regard to their species and size compositions. Hurricanes in the Caribbean have a long history of sinking ships but a link with new coral settlement is understudied. In 2017, Hurricane Irma caused the sinking of over 300 vessels in the coastal waters of Saint Martin, eastern Caribbean. In 2021, coral settlement was studied on one of them, which included two native, one non-native, and two cryptogenic species. The corals were smaller than 8 cm in diameter. The invasive Tubastraea coccinea was the most abundant scleractinian and was predominantly represented by juveniles. A cryptogenic species, Stragulum bicolor, new for the Caribbean, was the most common octocoral. Because they can be harmful to the environment, shipwrecks should be monitored frequently for the occurrence of non-native species, especially when they are only a few years old.

When size matters: the first comprehensive anatomical study of a species of "Condylocardiidae", an extremely miniaturized bivalve

'Miniaturization' is a widespread phenomenon among the Metazoa. In the molluscan class Bivalvia, records of miniaturization are numerous. Among the Archiheterodonta, Warrana besnardi (Klappenbach, 1963) has attracted attention for its tiny size, which does not exceed 1.5 mm in shell length, and because it belongs to a group with limited anatomical information and often-debated status, the "Condylocardiidae" (which recent molecular studies place deeply nested within the family Carditidae). All species of Warrana Laseron, 1953 are small-bodied, and so miniaturization presumably occurred from a large-bodied ancestor within the Carditidae sensu lato. South American W. besnardi is here studied in detail. Its small size and the enlargement of the anterodorsal region during growth, reflects (and likely led) to infaunal habit, living as a burrowing bivalve that passively feeds on deposit particles entering the pallial cavity anteriorly. Mantle glands, previously reported as a common feature of other archiheterodonts, are missing in W. besnardi, but spongiform tissue in the antero-ventral portion of the mantle lobes presumably represents a blood sinus that might compensate for the great reduction of the ctenidia. Lecithotrophy is reported, with yolky oocytes bearing a thick non-cellular capsule layer; brooding was not observed, and it is here hypothesized that the extreme miniaturization, with the great reduction of ctenidia, is responsible for a shift in the reproductive mode of condylocardiids, contrasting with the commonly reported ovoviviparity of the carditids.

Assessment of littoral algal diversity from the northern Gulf of Mexico using environmental DNA metabarcoding

Traditional methods for algal biodiversity monitoring are costly and time inefficient because they rely on high-level taxonomic expertise to address species identity problems involving phenotypic plasticity and morphological convergence. These problems are exacerbated in regions such as the Gulf of Mexico, that has a limited history of phycological exploration, but that are economically important or threatened by numerous anthropogenic stressors. Given the high pace of disturbance to natural systems, there is a critical need for expedient and cost-effective tools for the study of benthic algal communities. Here we document the use of environmental DNA metabarcoding, using the partial LSU rDNA and 23S rDNA plastid molecular markers, to elucidate littoral algal diversity in the Northern Gulf of Mexico. We assigned 73.7% of algal OTUs to genus and 59.6% to species ranks. Our current study detected molecular signals for 35 algal/protist species with no previous reports in the Gulf of Mexico, thus providing an important, molecular-validated, baseline of species richness for this region. We also make several bioinformatic recommendations for the efficient use of high-throughput sequence data to assess biological communities.

Marine hitchhikers: a preliminary study on invertebrates unintentionally transported via the international pet trade

The pet trade in aquatic organisms is a significant source of non-indigenous species introductions. In comparison with ornamental animals, unintentionally transported invertebrate assemblages are easily overlooked by traders and keepers. Moreover, hitchhiking species detection and identification is difficult even for experts. The densities of “hitchhikers” in aquaria may be relatively higher than those in the wild. These phenomena are known in freshwater aquaria but poorly studied in marine ones. We found 17 species of non-ornamental marine invertebrates in one of the leading importers of aquarium species in the Czech Republic in November 2017. The set comprised six gastropods, two bivalves, three cnidarians, two echinoderms, two crustaceans, and two polychaete worms. In one case, a symbiont was also detected, associated with the host “hitchhiker”. No “live rocks” are traded by the surveyed wholesaler. Thus, the found animals were not imported together with this item as larvae or eggs. Contrary to the transport of targeted ornamental species, it is clear that transport of “hitchhikers” is occurring despite standard legislative regulations and should be brought to the attention of conservationists, wildlife managers, policymakers and other stakeholders.

Distribution of Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini in the Mediterranean Sea

The Non-Indigenous Species (NIS) Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini has been reported for the first time in the Mediterranean Sea along the coast of South Turkey. This NIS is actively expanding into the Eastern and Western Mediterranean Sea. In this paper, we present an overview of the current distribution of this alga in the Mediterranean Sea, based on relevant scientific publications, grey literature and personal observations. New records from the Sicilian coast (Italy) are also reported. Caulerpa taxifolia var. distichophylla was found over a wide range of environmental conditions (depth, light and substratum), suggesting a broad ecological plasticity of this alga which makes it a potential threat for the Mediterranean benthic communities. In this respect, artificial structures, often linked to harbours and maritime traffic, seem to provide suitable habitats for this NIS. Since maritime traffic is intense in the Mediterranean Sea, further expansion of C. taxifolia var. distichophylla in this region is to be expected. For this reason, it is very important to build up an overview on the current distribution of the species and its possible pattern of colonisation in relation to environmental conditions, as well as in view of future climate change scenarios.