Symbiotic Copepods Research Articles

Diving into Diversity: Copepod Crustaceans in Octocoral Associations

This research provides an extensive analysis of the biodiversity and distribution patterns of copepod crustaceans associated with octocoral species. A comprehensive dataset comprising 966 records pertaining to 233 copepod species, encompassing 54 genera, 18 families, and 3 orders, was compiled from 92 scientific papers published between 1858 and 2023, and updated as open data to GBIF. These copepods were found to be closely associated with 183 octocoral species, representing 72 genera and 28 families. The analysis revealed a total of 393 distinct interspecific associations between copepods, classified under the orders Cyclopoida, Harpacticoida, and Siphonostomatoida, and diverse octocorals. Approximately 60% of these associations were reported only once in the literature, which poses challenges to assessing the level of host specificity among the majority of copepod species linked with octocorals. Notably, over 91% of the recorded copepod species were found at depths not exceeding 30 m, with only four copepod species reported at greater depths surpassing 500 m. The presence of these symbiotic copepods was documented across 215 sampling sites situated within 8 of the 12 defined marine ecoregions, with particular attention to the Western Indo-Pacific, Central Indo-Pacific, and Temperate Northern regions. Despite the comprehensive examination of available data, this study highlights substantial gaps in our comprehension of copepod crustacean diversity and distribution in association with octocorals. Moreover, crucial information concerning symbiotic copepods is conspicuously absent for approximately 94% of potential octocoral host species. These disparities emphasize the imperative need for further scientific inquiry to unveil the intricacies of symbiotic relationships and to contribute to a more holistic understanding of copepod–octocoral associations.

Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea.

Thirty-nine species of symbiotic copepods, comprising 24 species of poecilostome Cyclopoida and 15 species of Siphonostomatoida, are reported from Korean waters, which were collected using underwater light traps at 33 collection sites around the South Korean coast. Ten new species are described: Hemicyclopsrapax sp. nov. in the family Clausidiidae; Pontoclausiacochleata sp. nov. and P.pristina sp. nov. in the family Clausiidae; Heteranthessiusunisetatus sp. nov. in the family Lichomolgidae; Pusanomyicolasensitivus gen. nov., sp. nov. in the family Myicolidae; Polyankylisbogilensis sp. nov. in the family Polyankyliidae; Pseudanthessiuslinguifer sp. nov. in the Pseudanthessiidae; Eupolymniphilusfoliatus sp. nov. in the family Sabelliphilidae; and Acontiophorusestivalis sp. nov. and Thermocherespacificus sp. nov. in the family Asterocheridae. Supplementary descriptions or notes for other species are provided as appropriate.

A new Asterocheres (Copepoda, Siphonostomatoida) symbiont of the sea star Nidorellia armata (Gray, 1840) (Echinodermata, Asteroidea) in the Eastern Tropical Pacific

Abstract A new species of the diverse and widely distributed symbiotic copepod genus Asterocheres is described from the sea star Nidorellia armata (Gray, 1840) in Mexican waters of the Eastern Tropical Pacific. The new species resembles various other congeners by sharing several characters including: (1) a siphon extending to the intersection of the maxilliped, (2) a 21-segmented antennule, and (3) a 2-segmented mandible palp. It can be distinguished by the unique structure and ornamentation of the maxilla, the armature and proportions of the fifth leg, and its body shape. This is the first documented record of Asterocheres from the Mexican Pacific and the first finding of a symbiotic copepod on this sea star host. Males, ovigerous females and copepodites were recorded from the host, thus suggesting a well-established symbiotic association. It is likely that copepods feed on the host’s tegument. Further studies will be needed to assess the reproductive traits and seasonality of this copepod as a symbiont.

Xarifiid copepods (Copepoda: Cyclopoidea: Xarifiidae) parasitic in the coral Psammocora digitata Milne Edwards & Haime 1851 from Taiwan

Abstract Four species of xarifiid copepods, including three new species and one new distribution and host record, are discussed based on specimens obtained from a widely distributed scleractinian coral, Psammocora digitata Milne Edwards & Haime, 1851, collected from Taiwan: Xarifia conreptasp. nov., X. gracilissp. nov., X. lata sp. nov., and X. diminutaHumes & Ho, 1967. Xarifia conreptasp. nov. is distinguished from its congeners by the morphology of the endopods and exopods of legs, the genital segment, maxilliped, and maxillule; X. gracilissp. nov. is diagnosed by the morphology of the leg endopods and the region dorsal to the fifth legs; and X. latasp. nov. by its shorter body length, the terminal armature of endopods and exopods, and the morphology of the maxilliped. The specimens of X. diminuta are similar to those in the original description, except for the undeveloped endopods of legs 3 and 4. Including the three new species, five species of xarifiids are now known to use P. digitata as host, raising to 18 the number of species symbiotic copepod recorded from Psammocora.

Three-way symbiotic relationships in whale sharks

Symbiotic relationships between fishes and other organisms are not always easily defined, and three-way symbiotic relationships are rarely reported. Here we examine the relationship between the endangered whale shark, echeneids (remoras and sharksuckers) and a symbiotic copepod. Through their symbiosis with whale sharks, sharksuckers gain one food source from the host’s parasites and energetically-free transportation to foraging areas, where they are also able to feed on the prey targeted by their hosts. The relationship between whale sharks and sharksuckers is complex, and most accurately described as mutualism. Likewise, the whale shark and copepod relationship is also complex, and could be described as a parasitic relationship with commensal or even mutualistic characteristics. Although echeneids are not considered to form host-specific relationships and can be free-ranging, the whale shark copepod occurs only on whale sharks; its survival inextricably linked to that of its host.

<p class="ZootaxaTitle">Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata)

Detailed study of the Monniot collection of copepods belonging to the family Notodelphyidae has revealed an extraordinary diversity of novel taxa. With rare exceptions notodelphyids live in association with ascidians and the Monniot collection was built up over several decades of field collecting and taxonomic research on the ascidian hosts by Drs Claude & Françoise Monniot (MNHN, Paris). This paper describes a total of 178 new species of notodelphyids from ascidian hosts and 37 new genera are established: Bathynotodelphys gen.nov., Pronotodelphys gen. nov., Ooishillgia gen. nov., Nobinerilla gen. nov., Notopygus gen. nov., Chelipygus gen. nov., Sympygus gen. nov., Vaoda gen. nov., Gosbia gen. nov., Pentachaetus gen. nov., Diceratus gen. nov., Prodoroixys gen. nov., Notoixys gen. nov., Borixys gen. nov., Cystixys gen. nov., Ammonixys gen. nov., Ctenixys gen. nov., Ademoixys gen. nov., Gallincola gen. nov., Scoliosoma gen. nov., Contoura gen. nov., Unimeria gen. nov., Mecodelphys gen. nov., Tubipedia gen. nov., Procampodelphys gen. nov., Janius gen. nov., Campodelphys gen. nov., Hamaticoxa gen. nov., Adrodelphys gen. nov., Phyllodelphys gen. nov., Lissodelphys gen. nov., Nodoscarus gen. nov., Diblastus gen. nov., Chilodelphys gen. nov., Scaridelphys gen. nov., Socotradelphys gen. nov., and Aplodelphys gen. nov. Prior to this study the Notodelphyidae comprised exactly 200 valid species classified in 46 genera, a mean species richness of 4.3 species per genus. After the addition of the new taxa described here, the family now comprises 378 species in 83 genera, a mean species richness of 4.6 species per genus. Generic diagnoses are provided for all genera represented in the collection and the availability of a wider range of taxa has allowed certain generic boundaries to be better defined, resulting in transfers of species between genera and the recognition of 16 new combinations. A further 51 existing species are also reported, and brief supplementary notes or full redescriptions are provided as appropriate.

わが国近海に産する軟体動物門に共生するカイアシ亜綱(甲殻亜門)の目録

わが国近海に産する軟体動物門に共生するカイアシ亜綱(甲殻亜門)の目録

Host specificity and microhabitat preference of symbiotic copepods (Cyclopoida: Clausiididae) associated with ghost shrimps (Decapoda: Callichiridae, Callianideidae).

We examined the host specificity of two ectosymbiotic Clausidium Kossman, 1874 copepods (Cyclopoida: Clausiididae) on two co‐occurrence species of host ghost shrimps. Our results revealed that both species of symbiotic copepod demonstrated extremely high host specificity. Moreover, within a single host shrimp species, each symbiont species displayed strong spatial patterns in microhabitat selection on their hosts’ bodies. Clausidium persiaensis Sepahvand & Kihara, 2017, was only found on the host Callianidea typa Milne Edwards, 1837 and almost exclusively within the host shrimp gill chamber, while C. iranensis Sepahvand, Kihara, & Boxshall, 2019 was only found on the host Neocallichirus jousseaumei (Nobili, 1904) and showed extremely strong preferences for the chelae and anterior walking legs. We also found that while the number of symbionts tends to increase with the host size, the two host species differed in the degree of symbiont infestation, with large C. typa hosting approximately 7× as many symbionts as the similarly sized N. jousseaumeia. The mechanisms resulting in the observed differences in infestation levels and microhabitat preferences of clausidium copepods among their hosts, including differences in physiology, burrowing pattern, and host grooming behavior should be further investigated.

A review of Caribbean Copepoda associated with reef-dwelling cnidarians, echinoderms and sponges

This review of copepod crustaceans associated with reef-dwelling cnidarians, sponges and echinoderms of the Greater Caribbean is based on published records, systematically arranged by the classification of symbiotic copepods and their hosts, sampling sites, coordinates, depth and date of sampling, literature sources, and three recent surveys (Cuba, St. Eustatius in the Eastern Caribbean and Curaçao in the Southern Caribbean). This resulted in totals of 532 records of 115 species of symbiotic copepods (47 genera, 17 families, three orders) hosted by 80 species of invertebrates, representing scleractinians (47%), octocorals (9%), echinoderms (3%), and sponges (1%). Among ten Caribbean ecoregions, the Greater Antilles (with 64 species of symbiotic copepods) as well as the Southern and Eastern Caribbean (with 46 and 17 species of copepods, respectively) are the most studied and best represented, whereas only six species of copepods are known from Bermuda, one from Southwestern Caribbean and none from the Gulf of Mexico. The absence of poecilostomatoid copepods (Anchimolgidae, Rhynchomolgidae and Xarifidae) on Caribbean stony corals as noted by Stock (1988) is confirmed. The results indicate that the diversity and ecology of Caribbean symbiotic copepods are still poorly investigated.

Planktonic Phases in Symbiotic Copepods: a Review

In symbiotic copepods, most naupliar stages are typically planktonic, playing a primary role in dispersal, while the first copepodid usually represents the infective stage. Later copepodid stages, including adults, are associated with host organisms. Many symbiotic copepods have abbreviated life cycles, with a reduced number of naupliar stages and two different feeding habits. These patterns are presumably related to distinct life cycles strategies. Exceptional cases are exemplified by members of the Monstrillidae and Thaumatopsyllidae, both of which are protelean parasites, with infective nauplii and non-feeding planktonic adults. In the Caligidae, the life cycle follows a generalized pattern, but adults of many species like Caligus undulatus seem to exhibit a dual mode of life involving host switching. Adults leaving the first host become temporarily planktonic before attaching to the final host. This dual mode of life is also found in adults of the Ergasilidae. Abbreviation of the planktonic phase is characteristic for some symbiotic taxa, thus suggesting that they have evolved to become highly efficient in locating and infecting new hosts without needing long-distance larval dispersal. The life cycle of copepods associated with zooplankters is also briefly reviewed. Zooplankters are clearly less used as hosts by copepods than benthic invertebrates. It is likely that symbiotic copepods dynamically utilize planktonic phases in their life cycle, thus maintaining the balance between dispersal, host location, reproduction, and predator-avoidance strategies.

Lack of host specificity of copepod crustaceans associated with mushroom corals in the Red Sea

The radiation of symbiotic copepods (Crustacea: Copepoda) living in association with stony corals (Cnidaria: Scleractinia) is considered host-specific and linked to the phylogenetic diversification of their hosts. However, symbiotic copepods are poorly investigated, occurrence records are mostly anecdotal, and no explicit analysis exists regarding their relationship with the hosts. Here, we analysed the occurrence of symbiotic copepods on different co-occurring and phylogenetically closely related scleractinian corals. We used an innovative approach of DNA extraction from single microscopic specimens that preserves the shape of the organisms for integrative morphological studies. The rationale of the study involved: (i) sampling of mushroom corals (Fungiidae) belonging to 13 species and eight genera on different reefs along the Saudi coastline in the Red Sea, (ii) extraction of all the associated copepods, (iii) morphological screening and identification of copepod species, (iv) use of DNA taxonomy on mitochondrial and nuclear markers to determine species boundaries for morphologically unknown copepod species, (v) reconstruction of phylogenies to understand their evolutionary relationships, and (vi) analysis of the ecological drivers of the occurrence, diversity and host specificity of the copepods. The seven species of coral-associated copepods, all new to science, did not show any statistically significant evidence of host-specificity or other pattern of ecological association. We thus suggest that, contrary to most assumptions and previous anecdotal evidence on this coral-copepod host-symbiont system, the association between copepods and their host corals is rather labile, not strict, and not phylogenetically constrained, changing our perception on evolutionary patterns and processes in symbiotic copepods.

Copepods associated with scleractinian corals: a worldwide checklist and a case study of their impact on the reef-building coral Pocillopora damicornis (Linnaeus, 1758) (Pocilloporidae).

The Cnidaria have more symbiotic copepods than any other group of invertebrates, and the greatest numbers of these associates occur on hard corals. A review of the scattered literature on the diversity and taxonomic composition of scleractinian-associated copepods and their hosts revealed a total of 148 coral species, representing 66 genera and 15 families that serve as hosts to copepods. At present, 363 copepod species, representing 99 genera, 19 families and three orders, have been recorded as associates of scleractinian corals. The total included 288 cyclopoids, 68 siphonostomatoids and seven harpacticoids. Within the Cyclopoida the representation of species varied greatly among the 13 families, with a disproportionate number of species belonging to the Anchimolgidae (141 species) and Xarifiidae (92 species). Data on host utilization and geographical distribution of all copepods living symbiotically with hard corals is synthesized and host specificity patterns are highlighted.The prevalence, intensity, density, and biodiversity of copepod infection of 480 colonies of the reef-building coral Pocillopora damicornis (Linnaeus, 1758) from Nanwan Bay, southern Taiwan were documented between July 2007 and November 2008. It was hypothesized that certain environmental factors and physiological coral traits, such as the density of Symbiodinium, could influence these infection parameters. Analysis revealed that ectoparasitic copepods were the most likely to infect P. damicornis, and that Asteropontius minutus Kim, 2003 accounted for more than 50% of total copepod density in July-September 2007 when temperatures were high and bleaching occurred in ~75% of the sampled colonies. The data further showed that copepod virulence may be related to their life history strategies, as well as to Symbiodinium density, surface area of the host coral colonies, and concentration of nitrate and chlorophyll-a in the surrounding seawater. By tracking the abundance, diversity, and performance of infectious copepods prior, throughout, and after a natural bleaching event, the potential to use these parasites as bioindicators for predicting the future physiological performance of P. damicornis in response to environmental change, particularly bleaching events, may ultimately be further explored, developed and maximized.Humesimyzon Kim, 2010, previously placed in the Asterocheridae, is tentatively transferred to the recently resurrected family Coralliomyzontidae. The authorship and spelling of Pseudanthessius thorellii (Brady, 1880) are corrected.

Preface: Recent Developments in Taxonomy and Biodiversity of Symbiotic Copepoda (Crustacea)-A Volume in Celebration of the Career ofProf. Il-Hoi Kim.

Symbiosis is one of the most successful modes of life displayed by aquatic organisms, as measured by the number of times it evolved and how many symbiotic species are presently in existence. Among the Crustacea copepods utilize an extraordinary range of hosts, occurring on virtually every phylum of marine macroinvertebrates and, jointly with the monogeneans, are the most speciose group of metazoan ectoparasites of marine fishes (Rhode 2005). Several species have a major impact on global finfish and shellfish aquaculture, causing significant effects on farm production, economic viability and sustainability (Shinn et al. 2015). Parasitism by copepods on other metazoans has evolved independently numerous times in the evolutionary history of animal life on Earth and has led to an exceptional diversity in morphologies, physiologies, life-strategies and habitat preferences of its members. Reflecting the diversity of hosts, copepods show an amazing variety of adaptations which secure infection of and survival on the hosts. Since the first descriptions of parasitic copepods occurring on fish by Linnaeus (1758) and the first report of a copepod utilizing an invertebrate host by Say (1818) (Clausidium caudatum (Say, 1818)) the number of described symbiotic copepods has seen a steady increase over a 200-yr period, culminating in a total of 5,306 valid species recognized today. About 38% of all described copepod species utilize either vertebrate (2,450 spp.) or invertebrate hosts (2,856 spp.), however, many host groups have not been thoroughly examined, and for this reason even approximate estimates of true species numbers are futile. Plotting the proposal of new species by decade (Fig. 1) shows a sharp rise since 1950 with 67% of the species having been described in the preceding 65 years. This period of exceptionally rapid progress can be attributed to a number of highly prolific investigators such as Arthur Humes, Il-Hoi Kim, Ju-shey Ho and Jan Stock who, single-handedly or in collaboration with other authors, described 698, 356, 290 and 246 species, respectively. Historically, the number of described copepod species parasitizing fish typically outnumbered those known to be associated with invertebrates. Only during the mid-1970s the species curves of both categories converged and during the last 30 years the discovery of new species associated with invertebrate hosts appears to progress more rapidly. Despite a significant drop in the number of specialists working on symbiotic copepods the steady addition of new taxa shows that the dynamism of their taxonomy is clearly set to continue.

High diversity of Caligus species (Copepoda: Siphonostomatoida: Caligidae)in Taiwanese waters.

Caligidae, commonly known as sea lice, is the most speciose family of symbiotic copepods comprising over 490 species classified in 31 genera. Caligus Müller, 1785 is the largest genus of this family comprising 255 species. Fifty-three species of Caligus have been reported from Taiwan so far, representing 20.78 % of Caligus currently known in the world. Nevertheless, we believe many more species of Caligus are yet to be discovered from the waters of Taiwan, because only 17.71 % (553/3,121 species) of the potential fish hosts occurring in Taiwanese waters have been examined for parasitic copepods so far. Among the countries in the Far East, Taiwan exhibits the shortest coastline yet displays the highest diversity of Caligus species. This seemingly contradictory phenomenon may be explained by the fact that the Island of Taiwan is straddling over the border of two ecological realms in the western North Pacific, viz. the Temperate Northern Pacific Realm and the Central Indo-Pacific Realm. Pseudocaligus longipes Moon & Kim, 2012 is formally transferred to the genus Caligus as C. longipes (Moon & Kim, 2012) comb. nov.

Poecilostomatoid copepods associated with two species of widely distributed corals, Galaxea astreata (Lamarck, 1816) and Galaxea fascicularis (Linnaeus 1767), in the South China Sea

Seven species of copepods (Copepoda, poecilostomatoida) including two new species and five new records are described as associates of two widely distributed scleractinian corals, Galaxea astreata (Lamarck 1816) and Galaxea fascicularis (Linnaeus 1767), from Dongsha atoll (Pratas Island) in the South China Sea (SCS). They are: Anchimolgus amplius nov. sp., Anchimolgus contractus Humes 1979, Anchimolgus nasutus Humes 1996, Anchimolgus tanaus Humes 1991, Clamocus spinifer Humes 1979, Karanges hypsorophus Humes 1979, and Xarifia dongshensis nov. sp. Anchimolgus amplius nov. sp. can be readily distinguished from its congeners by the following features: (1) the larger body size (1.95 mm), (2) the three digitiform processes on the convex side of the mandible, (3) the third segment of leg 4 exopod arming with four spines, (4) the slender genital double-somite, (5) the caudal ramus with ratio less than 3:1, and (6) the second segment of abdominal somites distinctly shorter than others. Xarifia dongshensis nov. sp. can be readily distinguished from its congeners by the possession of (1) the bulge on the second segment of antenna, (2) the body without lateral processes or knobs, (3) the second segment of exopod of leg 1 bearing with one spine, (4) the armature of antennule being 3, 16, 4, 2 + 1 aesthetasc, and 4 + 1 aesthetasc, (5) the caudal ramus with three terminal setae, and (6) the tip of mandible with unilateral spinules. The three records of Anchimolgus species seem to have larger body size/appendages and more digitiform lobes on the convex side of the mandible than those from the Great Barrier Reef, New Caledonia, and Moluccas. Until now, 18 species of symbiotic copepods have been known to be associated with Galaxea corals.

First record of association of copepods with highly venomous box jellyfish Chironex, with description of new species of Paramacrochiron (Cyclopoida: Macrochironidae).

Paramacrochiron chironecicola n. sp. (Copepoda: Cyclopoida: Macrochironidae) is described from the highly venomous box jellyfish Chironex sp. collected from Malampaya Sound, Palawan Island, The Philippines. This is the first record of copepods associated with cubozoan medusae, although other cnidarian groups such scyphozoans, hydrozoans, and anthozoans are common hosts for symbiotic copepods. The infection sites were on the subumbrella, pedalium, and rhopalium, but also rarely on the adradial furrow. The new species is distinguished from other congeners by a combination of the following features: (1) the fifth pedigerous somite dorsally covering the anterior part of the female genital double-somite; (2) the fine structures of the antenna (relative lengths of segments) and maxilliped (positions of terminal elements) of the female; (3) the relatively long outer spines on the exopodal segments of legs 1-4; (4) the relatively long and thick female leg 5 bearing a long protopodal seta which reaches to the distal margin of the exopod; (5) the relatively short caudal ramus in the female; and (6) the plump prosome and short urosome in the male. Since members of the genus typically parasitize scyphozoans, especially rhizostomes, the association of this parasitic copepod on cubozoans may reflect the relatively close phylogenetic relationship between cubozoans and scyphozoans.

산란기 지중해담치 Mytilus galloprovincialis의 조직병리학적 변화 관찰

Sessile marine bivalves including mussels, oysters and clams are often used as a sentinel species in coastal environmental monitoring since changes in the environmental quality are often well preserved in their tissues and shells. In this study, we investigated overall health condition of the Mediterranean Mussel, Mytilus galloprovincialis on the south coast using histology. Reproductive condition as gonad index (GI), condition index (CI) as a ratio of the tissue weight to the shell weight, digestive gland atrophy (DGA), types of parasites, and pathologic conditions including erosion, necrosis, hemocyte infiltration, and neoplasia were examined from each histological preparation. GI decreased from March to July then increased from July to September and spawning mussel could be observed as early as in April and the activity continued until September. CI also followed the monthly changes in GI, indicating that decrease in CI was associated with the weight loss due to spawning. DGA increased from March to June, decreased in July and increased from July to September. High DGA values observed in June and September were coincided with spawning and high water temperature. Histology also showed high prevalence of erosion in the digestive gland in June (36.0%) and September (56.4%), suggesting that high water temperature and spawning acted as environmental stressors. No parasitic organism was identified during the survey, although some symbiotic copepods were observed. Histology was found to be useful and affordable technique in monitoring the overall health of mussel, providing useful pathologic information of the cells and tissues.

First report of tubular corallites on Stylophora caused by a symbiotic copepod crustacean

Amongthemorethan340speciesofsymbioticcopepodsassociatedwithnumerous scleractinian species, four have been reported from galls orcysts in three species of corals (Dojiri 1988; Kim and Yamashiro 2007).The relationship between these copepods and their scleractinian hostsremains poorly studied. Here, we provide the first report of a tubularcorallite shape caused by copepods.The copepods were found to create short tubular outgrowths (2 mmdiameter) on Stylophora pistillata branches in the Saudi Arabian RedSea, off Thuwal (22 03¢48.5†N, 38 45¢51.2†E) on April 29, 2013(Fig. 1a). Each outgrowth is a modified thick-walled corallite with aterminal opening and a polyp inside (Fig. 1b, c). The inner chamber ofthe modified corallite has longitudinal folds atypical for Stylophora aswell as a reduced columella (Fig. 1c, d). Outgrowths found on S. pi-stillataintheRedSeadifferfromthosepreviouslyreported(Dojiri1988;Kim and Yamashiro 2007) due to the presence of a terminal openingframed by well-developed tentacles of the polyp (Fig. 1b).Single female individuals of the crustacean copepod, representing anew species of the genus Spaniomolgus Humes and Stock 1972 (Poe-cilostomatoida:Rhynchomolgidae),werefoundwithinthegastriccavityof the affected polyps (Fig. 1e). The genus Spaniomolgus was previ-ously known only from Madagascar. Nonscleractinian invertebrates areparticularly understudied in the Red Sea, and further work is needed tofully characterize their diversity and function in this region.

Invasive crayfish and their symbionts in the Greater London area: new data and the fate of Astacus leptodactylus in the Serpentine and Long Water Lakes

The branchial cavities of four non-indigenous crayfish species resident in the Greater London area were examined for crustacean symbionts. Pacifastacus leniusculus from Cripsey Brook, Chipping Ongar, Essex, and the Serpentine Lake, Central London, both carried the symbiotic ostracod Uncinocythere occidentalis, which is indigenous to the western USA. Analysis of covariance showed that crayfish carapace length did have an effect on the abundance of entocytherid associates, whereas intensity did not seem to be dependent on whether the host was female or male. Another invasive entocytherid, Ankylocythere sinuosa, was found on the gills of Procambarus clarkii in Hampstead Heath, representing the first record of the species for northwestern Europe. Contrary to recent model-based predictions, A. sinuosa appears to survive British winters. Examination of the gills of Astacus leptodactylus from the Serpentine revealed the presence of two symbiotic copepods, Nitocra hibernica and Acanthocyclops sp., and a common but accidental association with the cladoceran Bosmina longirostris. The observation of N. hibernica on all three P. leniusculus specimens collected in 2010 suggests that the copepod switched crayfish hosts in the Serpentine following the decimation of the Turkish crayfish population after 2008. This is the first record of an indigenous copepod becoming associated with a non-indigenous crayfish, a case of unusual host switching having previously been reported only for branchiobdellidans. The deliberate introduction of signal crayfish in the Serpentine can probably be attributed to aquarists, ‘well intentioned’ individuals and/or people who have animal release as part of their religious practice. Serpentine signal crayfish that were tested for Aphanomyces astaci (crayfish plague) produced inconclusive results. The sudden collapse of the Turkish crayfish population in the Serpentine between 2008 and 2010 remains unexplained although a number of potentially causative factors are discussed. No crustacean symbionts were obtained from Orconectes virilis in the River Lee at Enfield, Middlesex.

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.