Zoological Studies 59:62 (2020) doi:10.6620/ZS.2020.59-62 Open Access A New Species of Predatory Nudibranch (Gastropoda: Trinchesiidae) of the Scleractinian Coral Goniopora Juntong Hu1, Yanjie Zhang1,2, Sam King Fung Yiu1, James Yang Xie3, and Jian-Wen Qiu1,2,* 1Department of Biology and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong Baptist University, Hong Kong, China. *Correspondence: E-mail: [email protected] (Qiu). Phone: +852-34117055. E-mail: [email protected] (Hu); [email protected] (Zhang); [email protected] (Yiu) 2HKBU Institute of Research and Continuing Education, Virtual University Park, Shenzhen, China 3Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government, China. E-mail: [email protected] (Xie) Received 18 July 2020 / Accepted 22 October 2020 / Published 23 November 2020 Communicated by Benny K.K. Chan Members of the nudibranch genus Phestilla are common predators of scleractinian corals, but currently this genus has 10 described species only. Here we describe Phestilla goniophaga sp. nov., the first formally named predatory nudibranch species of the stony corals from the genus Goniopora. The new species can be distinguished from its congeneric species by the large number of long cerata (up to 16 rows and 23 cerata per row), and white rounded hump on the notum. The hump resembles the mouth of the coral poly, while the cerata resemble the coral tentacles. The egg masses of P. goniophaga sp. nov. are unique among Phestilla spp. egg masses in being bright orange in color, and forming a coiled ribbon. Analysis of the COI, 16S rRNA and H3 genes of P. goniophaga sp. nov. also showed that this species is distinct from other congeneric species. Key words: Coral, Coral-eating, Corallivory, Mollusca, Phestilla. BACKGROUND and several other related genera (Trinchesia, Catriona and Cuthona) as junior synonyms of Tenellia. Ekimova The genus Phestilla Bergh, 1874 is a small et al. (2017) and Fritts-Penniman et al. (2020) supported group of tergipedid nudibranchs with reduced cephalic this classification scheme, and in the latter publication tentacles and without ceratal cnidocacs (MolluscaBase the authors pointed out that otherwise Cuthona had to 2020). With the exception that P. chaetopterana be divided into many genera. But Korshunova et al. (originally Tenellia chaetopterana) lives inside the tube (2017) reverted the classification of these families and of the polychaete Chaetopterus sp. (Ekimova et al. 2017), genera because they thought Cella et al. (2016) did all Phestilla spp. are obligate predators of scleractinian not fully consider the morphological and ontological corals. There has been some controversy in the characteristics when making the decision. Three recent systematics of nudibranchs of the superfamily Fionoidea studies (Wang et al. 2019; Hu et al. 2020; Mehrotra et Nordsieck, 1972 with a total of 317 species including al. 2020) all considered it more appropriate to retain those classified in Phestilla Bergh, 1874 (Tergipedidae) Phestilla because this genus is monophyletic (except P. (MolluscaBase 2020). Cella et al. (2016) merged sibogae), and all the species except P. chaetopterana the families Calmidae, Eubranchidae, Fionidae and are obligate corallivores. Due to the inclusion of P. Tergipedidae into a single family Fionidae based on the chaetopterana and P. viei in Phestilla, Mehrotra et al. molecular phylogenetic result that this would make the (2020) provided an updated diagnosis of the genus with family monophyletic. In addition, they treated Phestilla respect to the morphology of the oral tentacles, oral Citation: Hu J, Zhang Y, Yiu SKF, Xie JY, Qiu JW. 2020. A new species of predatory nudibranch (Gastropoda: Trinchesiidae) of the scleractinian coral Goniopora. Zool Stud 59:62. doi:10.6620/ZS.2020.59-62. © 2020 Academia Sinica, Taiwan 1 Zoological Studies 59:62 (2020) page 2 of 9 veil, presence of a swollen hump on notum, shape and description of these nudibranchs is available. Ritson- arrangement of cerata, masticatory processes, radular Williams et al. (2003 2007 2009) reported Phestilla teeth and penile stylet. sp. 2 as a specialist predator of the scleractinian Previous studies have found that corallivorous genus Goniopora (Poritidae) and studied its dietary Phestilla spp. are associated with only few genera/ breadth and larval development in Guam. They found species of scleractinican corals. Specifically, P. that, when Porities cylindrica, Goniopora fruticosa, lugubris, P. minor, P. panamica, and P. poritophages are G. minor, G. lobata and G. eclipsensis were offered predators of Porties (Harris 1975; Rudman 1979 1981 to the nudribranch, it showed higher preference for 1982; Gosliner et al. 2018). Phestilla melanobrachia G. fruticosa, followed by G. minor and G. lobata is a predator of dendrophylliid corals Tubastraea spp. (Ritson-Williams et al. 2003). Its larval development and Dendrophyllia spp., and the its color changes took 5 days after which the larvae would undergo according the color of the prey (Harris 1968 1975; metamorphosis in response to the cues from its favorite Salvini-Plawen 1972). Phestilla subodiosa feeds on coral G. fruticosa (Ritson-Williams et al. 2007). Montipora spp., common corals in the aquarium trade Moreover, water-soluble cues from G. fruticosa caused (Wang et al. 2020). Phestilla viei (Mehrotra et al. 2020) a higher percentage of competent larvae of Phestilla and P. fuscostriata (Hu et al. 2020) feeds on Pavona sp. 2 to undergo metamorphosis than those cues from explanulata and Pavona decussata, respectively. As Porites annae, P. Cylindrica, Psammocora contigua, for P. sibogae, it was treated as a junior synonym G. fruticosa, G. tenuidens, G. eclipsensis, G. minor, of Phestilla lugubris by Rudman (1981). However, and G. lobata (Ritson-Williams et al. 2009). This series Gosliner et al. (2018) consider that they are different of experiments show that, although Phestilla sp. 2 can species and P. sibogae feeds on hydroids of the genus feed on multiple species of Goniopora, G. fruticosa is Sertularella. its most favorite species in terms of diet and settlement There have been several records of nudibranchs substrate. feeding on Goniopora corals in Indo-Pacific locations During surveys of coral communities in Hong (Gosliner et al. 2018) including Singapore (Robertson Kong in 2019, we discovered a species of Phestilla 1970), Papua New Guinea (Gosliner 1992; Gosliner feeding on Goniopora spp. and laying eggs on the et al. 1996), and Guam and Palau (Ritson-Williams et skeleton of this genus of corals (Fig. 1A). In this paper, al. 2003; Faucci et al. 2007). Nevertheless, no formal we provide morphological description of this species, Fig. 1. Phestilla goniophaga sp. nov. A, A colony of Goniopora sp. with two adults of P. goniophaga sp. nov. and their coiled egg ribbons. B, Holotype (BU-Mol-20-001). C, Paratype (BU-Mol-20-002). Scale bars: A–C = 10 mm. All photographs were taken when the nudibranchs were alive. © 2020 Academia Sinica, Taiwan Zoological Studies 59:62 (2020) page 3 of 9 and report a molecular phylogenetic analysis of its Serb 2008), H3AF and H3AR (Colgan et al. 1998). relationship with other congeneric species. PCR programs were identical to those in Wang et al. (2019) and Hu et al. (2020). PCR products were sent to BGI Hong Kong for sequencing on an ABI 310 MATERIALS AND METHODS Genetic Analyzer. All new sequences were deposited in GenBank (Table S1). Sample collection To understand the phylogenetic relationship between the new species and other related species, Samples of the Phestilla goniophaga sp. nov. fragments of COI, 16S rRNA and H3 genes from were collected by SCUBA diving from Sharp Island 28 nudibranch species belonging to 11 genera (22°21'32.9"N 114°17'47.8"E, water depth ~2 m) and (MolluscaBase 2020) were downloaded from GenBank Chek Chau (22°30'04"N 114°21'32"E, water depth (Table S1). The species names used in this paper ~ 2 m) in June 2019 and June 2020, respectively. The conformed to those adopted in WORMS (MolluscaBase specimens were preserved either in 95% ethanol for 2020). In some cases, informal names used in previous molecular analysis or in 4% formaldehyde in seawater studies such as Phestilla sp. 2 (Faucci et al. 2007) were for morphological analysis. All specimens examined also used in this study. The COI, 16S rRNA and H3 in this study are deposited in Hong Kong Baptist sequences were aligned separately using MUSCLE University (BU-Mol-20-001 to BU-Mol-20-006). v.3.8.31 (Edgar 2004) under default settings. For each species, the sequences of the three genes were Morphological analysis concatenated using SequenceMatrix v.1.7.8 (Vaidya et al. 2011). Phylogenetic analyses were conducted The external morphological characteristics were using the Maximum Likelihood (ML) method and examined under a Motic SMZ-171 stereomicroscope, the Bayesian inference (BI) method based on the and photos were taken using a Canon Mark IV camera. concatenated dataset. The ML analysis was conducted The veligers were examined under a Motic BA210 using raxmlGUI v.1.3.1 (Silvestro and Michalak 2012) compound microscope. To extract the radula and the with bootstrap supports estimated from analyses of 1000 jaws, the buccal masses from two specimens were pseudoreplicates. The GTR+I+G nucleotide-substitution soaked in 10% bleach solution for 10 min at room model was selected using jModelTest v. 2.1.1 (Darriba temperature (~22°C) to dissolve soft tissues, and then et al. 2012) as the best model for the phylogenetic rinsed in deionized water four times to remove the analysis, based on Akaike information criteria (AIC). bleach. The radula and jaws were dried in an oven, gold- The BI analysis was conducted using MrBayes v plated, mounted on a stub, and examined under a LEO 3.2 (Ronquist and Huelsenbeck 2003) with random 1530 FESEM scanning electron microscope (SEM).