The zooxanthellate scleractinian coral Oulastrea crispata (Lamarck, 1816), an overlooked newcomer in the Mediterranean Sea?

Abstract

The zooxanthellate scleractinian coral Oulastrea crispata, a widely distributed species across central Indo-Pacific nearshore marine habitats, has been first reported from the Mediterranean Sea (Corsica) in 2014. Here we report on two new sites for this species in the NW Mediterranean Sea and provide a general description of external morphological characters of the colonies and a detailed account of the cnidom to help future identifications. Living specimens may appear virtually identical to small colonies (~5 cm) of the Mediterranean zooxanthellate scleractinian Cladocora caespitosa. While this species shows long, ramified, independent corallites, with cylindrical calices, O. crispata has enlarged, cup-like calices, which can be joined by the coenosteum. It also shows clear differences among several groups of nematocysts, principally the presence in the filaments of large penicilli (p-mastigophore) of one type, which are absent in C. caespitosa. Identifications based on underwater observations or even the analysis of photographs may easily lead to misleading identifications. We hypothesize that O. crispata may have gone unnoticed because of misidentifications as C. caespitosa. More detailed research is needed to get reliable maps of the actual distribution of this apparently non-indigenous species in the Mediterranean Sea.

The Reef Check Mediterranean Underwater Coastal Environment Monitoring Protocol

“…In addition to the different lists of considered species, the major difference between the two protocols lies in the less explicit and not always precise location of the sites (based on hierarchical area codes and not geographic coordinates), the lack of information on the bathymetric distribution of species, and the reduced findability, accessibility, and interoperability of the REEF data. Sea Watchers, launched in Spain in 2009 as "Observadores del Mar, " includes several thematic sub-projects (e.g., massive mortalities of corals, death of pen shells, alien fishes, invasive algae, decapod crustaceans, sharks and rays, and zooxanthellate scleractinian; see Mariani et al, 2018); they are based on visual observations supplemented by photographs that are sent to experts for identification and analysis. Involved experts assess and archive the observations, possibly integrating with additional information interactively requested to the participants.…”

Mediterranean non indigenous species at the start of the 2020s: recent changes

“…Another species most likely spreading via hull fouling is the colonial scleractinian coral Oulastrea crispata (Lamarck, 1816). The species, which was only recorded once in Corsica in 2012 (Hoeksema and Ocaña 2014), has now been found in two additional locations in Spain (Mariani et al 2018) and is considered established in the western Mediterranean.…”

Fouling of a boat hull by the invasive zooxanthellate coral Oculina patagonica - could shipping be enhancing its unique large-scale spread?

“…In this sense, the capacity of the invasive coral O. patagonica populations to foul mobile floating structures and their high abundance on artificial reefs indicates that rafting on mobile floating structures at regional and transoceanic scales could play a significant role in the dispersal potential of the species. At present, only another alien zooxanthellate coral species has already been recorded in the Mediterranean (i.e., Oulastraea crispata), and shipping has been considered a plausible vector for the introduction of this species because although it is native to the Indo-Pacific, its native distribution range does not include the Red Sea (i.e., natural dispersion via the Suez Canal is not a plausible explanation; Mariani et al, 2018).…”