Selective consumption of sacoglossan sea slugs (Mollusca: Gastropoda) by scleractinian corals (Cnidaria: Anthozoa)

Abstract

Recent studies revealed that reef corals can eat large-sized pelagic and benthic animals in addition to small planktonic prey. As follow-up, we document natural ingestion of sea slugs by corals and investigate the role of sacoglossan sea slugs as possible prey items of scleractinian corals. Feeding trials were carried out using six sacoglossan species as prey, two each from the genera Costasiella , Elysia and Plakobranchus , and four free-living solitary corals ( Danafungia scruposa , Fungia fungites , Pleuractis paumotensis and Heteropsammia cochlea ) as predators. Trials were carried out under both in-situ and ex-situ conditions with the aim to observe ingestion and assess signs of prey consumption based on tissue loss of prey individuals over time. Significant differences were observed in both ingestion time and consumption state of prey between prey species, with three of them being ingested more rapidly and preferentially consumed over the others. Additionally, prey size was found to be a significant factor with larger prey (>12 mm) being ingested more slowly and rarely than smaller ones (<6 mm and 6–12 mm). Comparisons of consumption capability among predators showed no significant difference with all coral species showing similar preferences for prey species. While no specific mechanism of prey capture is proposed, we also document instances of kleptoparisitism and resuspension of prey items by wrasses. This study highlights the important distinction between opportunistic prey capture and true predation events.

On the Plakobranchidae (Gastropoda, Sacoglossa) from soft sediment habitats of Koh Tao, Gulf of Thailand, with descriptions of two new species

“…Later, during trials on the ingestive capabilities of scleractinian corals, the same species was referred to as Elysia cf. japonica ( Mehrotra et al 2019 ), due to the resemblance with the species described by Eliot (1913) from Japan. Since the original description of Elysia japonica Eliot, 1913, numerous authors have described other morphologically similar species, based on a variety of characters which were missing in the description of E. japonica , whose type appears to be lost ( Trowbridge et al 2011 ).…”

“…Uncommon, but present in dense coral reef habitats; rare in deeper soft sediment habitats outside the coral reef. Has been observed being ingested naturally by the scleractinian coral Pleuractis paumotensis but is mostly considered unpalatable by such corals ( Mehrotra et al 2015 , 2019 ).…”

“…and Plakobranchus cf. papua by Mehrotra et al (2015Mehrotra et al ( , 2019 in observations of predation. Although Plakobranchus ianthobaptus has long been considered a synonym of Plakobranchus ocellatus van Hasselt, 1824 (see Jensen 1992;Evertsen et al 2007 and others).…”

“… ocellatus and Plakobranchus cf. papua respectively ( Mehrotra et al 2019 ). Molecular evidence has shown that the species historically identified as P. ocellatus represents a complex of multiple species ( Krug et al 2013 ) and thus at present the recently described Plakobranchus papua Meyers-Muñoz et al, 2016 is the only species that is considered taxonomically stable (see discussion).…”

Phestilla subodiosus sp. nov. (Nudibranchia, Trinchesiidae), a corallivorous pest species in the aquarium trade

“…However, this seems to be characteristic of Phestilla species: their fecundity allows them to decimate entire coral colonies in several days in vitro ( Fig. 1; Harris 1975;Rudman 1979Rudman , 1981Rudman , 1982Haramaty 1991), but their populations are heavily suppressed by predators in situ (Gochfeld and Aeby 1997;Mehrotra et al 2019). It is likely that Phestilla subodiosus sp.…”