Yu-Rong Cheng

A new copepod with transformed body plan and unique phylogenetic position parasitic in the acorn worm Ptychodera flava.

Symbiotic copepods compose one-third of the known copepod species and are associated with a wide range of animal groups. Two parasitic copepods endoparasitic in acorn worms (Hemichordata), Ive balanoglossi and Ubius hilli, collected in the Mediterranean Sea and Australian waters, respectively, were described a century ago. Here we report a new parasitic copepod species, Ive ptychoderae sp. nov., found in Ptychodera flava, a widespread acorn worm in the Indo-Pacific Ocean and an emerging organism for developmental and evolutionary studies. The female of I. ptychoderae is characterized by having a reduced maxilliped and five pairs of annular swellings along the body that are morphologically similar but distinguishable from those in the two previously described parasitic copepods in acorn worms. Phylogenetic analysis based on the 18S rDNA sequence shows that I. ptychoderae may belong to Poecilostomatoida but represent a new family, which we name Iveidae fam. nov. Ive ptychoderae is commonly found in the acorn worm population with an average prevalence of 42% during the collecting period. The infection of the parasite induces the formation of cysts and causes localized lesions of the host tissues, suggesting that it may have negative effects on its host. Interestingly, most cysts contain a single female with one or multiple male copepods, suggesting that their sex determination may be controlled by environmental conditions. The relationships between the parasitic copepods and acorn worms thus provide a platform for understanding physiological and ecological influences and coevolution between parasites and hosts.

Orstomella yaliuensis n. sp., a xarifiid copepod (Crustacea) parasitic in the polyps of hump coral Porites lutea Milne Edwards & Haime off Taiwan

A new species of xarifiid copepod, Orstomella yaliuensis n. sp., is described. It was found living in the polyps of a scleractinian coral, Porites lutea Milne Edwards & Haime, collected off Yaliu in the northern part of Taiwan. The new species can be distinguished from its two congeners, O. faviae Humes & Ho, 1968 and O. lobophylliae Humes & Ho, 1968, by the presence of five (rather than six) segments on the antennule, a spine only (rather than a seta and a spine) at the tip of the antenna, a uniramous leg 2, and a relatively long (rather than short) spine at the tip of the caudal ramus.

The infection process of the reef coral Stylophora pistillata by the parasitic copepod, Xarifia obesa

Copepods are common parasites of scleractinians and octocorals (Humes 1985a). Among them, the family Xarifiidae which comprises 86 species in 4 genera is a group of coral-specific endoparasites widely distributed in Indo-Pacific coral reefs (Humes 1985b). How the Xarifiids establish intimate associations with their host corals without being killed by nematocysts is still unknown. When studying the parasitic copepods on corals from Taiwan, we observed (n 1⁄4 4) the behavior of Xarifia obesa Humes and Ho, 1968 (Fig. 1a) by reintroducing it to a pocilloporid coral, Stylophora pistillata (Esper, 1797). When X. obesa was reintroduced to the surface of the coral colony, it started to search for polyps (Fig. 1b). When X. obesa approached a coral polyp, tentacles of the polyp began expanding gradually (Fig. 1b, c). The tentacle-expanding behavior is similar to the initial feeding behavior of coral polyps when detecting a prey (Lin et al. 2002). However, unlike the retraction of tentacles, which occurs when prey is captured, no tentacle retraction was observed when in contact with the xarifiid. The xarifiid then entered the polyp quickly (Fig. 1d). These phenomena suggest that the xarifiids may release chemicals to induce the relaxation of coral polyps and are likely immune to the nematocysts of corals. These characteristics enable the xarifiids and possibly other parasitic copepods to establish close associations with their host corals. The mechanism and evolutionary significance of coral-parasite associations invite further studies.

Four new xarifiid copepods (Poecilostomatoida) associated with the scleractinian coral Pavona explanulata (Lamarck) from off Taiwan

Four new xarifiid copepods are described. They were found in association with the scleractinian coral Pavona explanulata (Lamarck) occurring in shallow water reefs off Yenliao in northern Taiwan. The four species are: Xarifia capillata n. sp., X. parva n. sp., X. pavonae n. sp. and X. taiwanensis n. sp. They were found together in a single washing of the host coral. Previously, 13 species of copepods have been found in association with nine species of Pavona Lamarck. More than half (7/13) of these symbionts are members of Xarifia Humes, 1960.

Four anchimolgid copepods (Poecilostomatoida: Anchimolgidae) associated with the scleractinian coral Pavona explanulata (Lamarck, 1816) in Taiwan

Several species of copepods are known to live in association with the coral genus Pavona Lamarck, 1801. In this paper, four poecilostomatoid copepods, including one new genus, two new species, and one species new to Taiwan, are described, i.e. Alienigena triangula gen. et sp. nov., Odontomolgus cognatus sp. nov., O. mucosus Kim, 2006 and Sociellus subgeminus sp. nov. All species were found together in a single washing of the scleractinian coral Pavona explanulata (Lamarck, 1816), collected from shallow water reefs in northern Taiwan. All of them appear closely related to the genera of the Odontomolgus-group in the family Anchimolgidae due to the possession of a large process on the convex margin of the mandible. The present report brings the number of copepod species that live in symbiosis with members of the coral genus Pavona to 17.

Two Rare Species of Xarifia (Copepoda, Xarifiidae) New to Taiwan Parasitic on the Scleractinian Corals

Xarifiid copepods are one of the most common endo-parasites of scleractinian corals in the tropical Indo-Pacific. In this study, two rare species of xarifiid copepods, Xarifia jugalis Humes, 1985 and X. quinaria Humes, 1985, were discovered from 500 colonies of Pocillopora damicornis (Linnaeus, 1758). Both of them are not only new to Taiwan but also new to the waters of North Pacific. A full description of these 2 species is provided to show the possible geographical variations of their morphology.

Caligus lini n.sp., a new caligid (Copepoda, Siphonostomatoida) parasitic on the brilliant pomfret Eumegistus illustris Jordan & Jordan (Perciformes, Bramidae) of Taiwan.

Caligus lini n.sp., a new species of caligid copepod parasitic on the gill rakers and caudal fin of the brilliant pomfret, Eumegistus illustris Jordan & Jordan (Perciformes, Bramidae), is described from fish caught off Tai-Dong, Taiwan. The new species differs from its congeners by its possession of the following, unique combination of features: (1) middle two elements at the tip of leg 1 simple (without accessory process), (2) innermost element shortest and smallest of the four terminal elements on leg 1, (3) leg 4 exopod with an armature formula of I,III, and (4) complex leg 5 represented by 2 seta-bearing processes, a simple anterior process tipped with 1 plumose seta and quadripartite posterior process carrying 3 setae (1 simple and 2 plumose). The new species differs from its closest congener, Caligus tylosuri (Rangnekar, 1956), in the structure of the middle two elements (simple without carrying accessory process) at the tip of leg 1 and a quadripartite (instead of tripartite) posterior process on leg 5.

A new family of poecilostomatoid copepods (Strepidae fam. nov.) associated with the sun coral, Tubastraea coccinea Lesson, 1829 in Taiwan

Both sexes of Strepus elongatus gen. et sp. nov. are described based on specimens obtained from the coral host, Tubastraea coccinea Lesson, 1829, collected from shallow water reefs in Taiwan. The new species belongs to a new family of the copepod order Poecilostomatoida and displays the following morphological characteristics: (1) poecilostome type of well developed piercing mandibles, (2) absence of an oral cone, (3) highly transformed body, (4) 4-segmented antennules, (5) 2-segmented maxilliped, (6) caudal rami with only two setae, and (7) complete loss of legs 1-5 in the female, but legs 1-2 being represented by a free segment bearing two terminal setae in the male. In addition, the phylogenetic analysis based on 18S ribosomal RNA sequence data showed that S. elongatus clustered with a Sabelliphilus-Anchimolgus clade (Sabelliphilidae + Xarifiidae + Rhynchomolgidae + Anchimolgidae), and that the average genetic distance between S. elongatus gen. et sp. nov. and representatives of the six most closely related families (0.064) was higher than the average distances among those families (0.028). Therefore, based on both morphological and molecular data, a new family Strepidae fam. nov. is proposed to accommodate its only known species, S. elongatus gen. et sp. nov.

A bioeroding foraminifer, Hyrrokkin sarcophaga, on deepwater corals from the South China Sea

Foraminifera are widely distributed in the world’s oceans. Approximately 23 species have been reported to bore into the hard substrate of hosts mainly from shallow-water coral reefs, but only few species from cold-water coral ecosystems are known to date (Beuck et al. 2008). Hyrrokkin sarcophaga is a commensal/parasitic foraminifer with large body size (tests up to 7 mm in diameter) that infests hexacorals (Lophelia pertusa, Madrepora oculata, Caryophyllia sarsiae) and an octocoral (Primnoa resedaeformis) in aphotic environments (Cedhagen 1994). Its biogeographic distribution has previously been reported as within the 200to 500-m-depth interval along the North Atlantic continental margin from polar to subtropical where water temperature is from 5 to 11 C (Freiwald and Schönfeld 1996; Beuck et al. 2008). From December 2013 to August 2015, 15 individuals of H. sarcophaga were discovered on three deepwater coral species collected with beam trawl at 339–552 m depth in the South China Sea (Electronic Supplementary Material). The host corals includedMadrepora oculata (1 of 3 specimens examined; Fig. 1a), Flabellum japonicum (13 of 210 specimens examined; Fig. 1b), and Caryophyllia diomedeae (1 of 1 specimen collected; Fig. 1c). The test of H. sarcophaga attached to the host coral skeleton was marginally surrounded by brown organic residue that induced a depression on the skeleton of host coral. The borings produced by this large foraminifer are characterized by a shallow groove of 0.55 ± 0.04 mm (mean ± SD, n = 11) in diameter (Fig. 1d), from which several whip-shaped extensions protrude vertically into the substrate of hosts and act as an anchor to enhance the attachment (Beuck et al. 2008; Cedhagen 1994). This is the first report of the occurrence ofH. sarcophaga in the Pacific. It extends our knowledge of the global distribution ofH. sarcophaga as well as its ecological affinity and host preference.

Description of Indoclausia helioporae sp. nov. (Copepoda, Clausiidae) from blue coral, associated with a number of polychaetes

This is the first study of Helioporacea Bock, 1938 for symbiotic copepods. A new species of copepod, Indoclausia helioporae sp. nov., was obtained by washing segments of blue coral, Heliopora coerulea (Pallas, 1766), collected from shallow water reefs in southern Taiwan. A full description of the new species is provided. The new species can be easily distinguished from its only congener, Indoclausia bacescui Sebastian & Pillai, 1974, by having (1) a small body of 1.32 × 0.20 mm; (2) a small caudal ramus, 33 × 15 μm; (3) a short antennule with formula: 4, 10, 11, 4, 2 + 1 aesthetasc and 7 + 1 aesthetasc (very short); (4) a 2-segmented maxilliped; (5) the exopod of leg 1 with formula: I-0; III-0; (6) the exopod of leg 2 with formula: I-0; I, III; (7) no seta on the endopod of legs 1 and 2; (8) a uniseriate egg-sac with 6 eggs.