A new parasitic copepod (Copepoda; Cyclopoida; Chondracanthidae) from two pomacentrid fishes caught on the Great Barrier Reef, Queensland, Australia

A new species of the copepod genus Pseudacanthocanthopsis Yamaguti & Yamasu, 1959 (family Chondracanthidae) is described based on material of both sexes collected from two pomacentrid host fishes caught off Lizard Island, Queensland. The type host is Neopomacentrus azysron (Bleeker) and the additional host is N. cyanomos (Bleeker). The new species is distinguishable from all congeners by the form of the antennule of the female, which is dorso-ventrally flattened and extends out anteriorly to the front of the cephalothorax margin.

Copepods associated with Ascidian hosts (Tunicata): Intramolgidae and Lichomolgidae, with descriptions of four new genera and 13 new species

Two new species of the hitherto monotypic family Intramolgidae are described, both are placed in the type genus Intramolgus Marchenkov Boxshall, 1995. Intramolgus heardensis sp. nov. was found in association with Polyzoa opuntia Lesson, 1830, and the host of I. atlantis sp. nov. was Styela chaini Monniot C. Monniot F., 1970. Eleven new species belonging to the family Lichomolgidae are reported. These include four new monotypic genera: Antarctomolgus gen. nov. accommodates A. molgulae gen. et sp. nov. from Molgula pedunculata (Herdman, 1881), Didemnomolgus gen. nov. accommodates D. crenulatus gen. et sp. nov. from Didemnum molle (Herdmann, 1886), Spheromolgus gen. nov. accommodates S. rarus gen. et sp. nov. from Diplosoma simile (Sluiter, 1909), and Alupa gen. nov. accommodates A. geminata gen. et sp. nov. from Leptoclinides madara Tokioka, 1953. The remaining new species are: Debruma deplanata sp. nov. from Ascidia ornata Monniot F. Monniot C., 2001, Lichomolgidium bipartitum sp. nov. from Pyura stolonifera (Heller, 1878), Lichomolgus papuensis sp. nov. from Rhopalaea circula Monniot F. Monniot C., 2001, L. brevicaudatus sp. nov. from an unidentified species of Polycarpa Heller, 1877, L. alatus sp. nov. from Synoicum castellatum Kott, 1992, L. lepidotus sp. nov. from Aplidium altarium (Sluiter, 1909), and Lobomolgus foveolatus sp. nov. from Didemnum molle (Herdmann, 1886). In addition, redescriptions are provided for Henicoxiphium redactum Illg Humes, 1971, Lichomolgidium sardum Kossmann, 1877, Lichomolgus canui Sars, 1917, L. forficula Thorell, 1860, and Zygomolgus dentatus Kim I.H., 2006.

Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species

The Monniot collection of copepods associated with ascidian hosts was built up over several decades of field collecting and taxonomic research on ascidians by Drs Claude Françoise Monniot (MNHN, Paris). This paper describes a total of 84 new species of copepods collected from ascidian hosts and five new genera are established. Prior to this study the family Ascidicolidae comprised two genera accommodating five valid species; here we add two new genera, Hamistyelicola gen. nov. and Bathycopola gen. nov., and eight new species in total. The family Buproridae comprised a single genus consisting of three species; here we add a new monotypic genus, Buprorides gen. nov. The family Botryllophilidae comprised 68 valid species in seven genera and here we add 45 new species; 13 of Botryllophilus Hesse, 1864, nine of Schizoproctus Aurivillius, 1885, three of Haplostomides Chatton Harant, 1924, 12 of Haplostoma Chatton Harant, 1924, seven of Haplostomella Chatton Harant, 1924 and a single new species of Haplosaccus Chatton Harant, 1924. The Enteropsidae comprised 42 species in five genera and here we add two new genera, Monnioticopa gen. nov. and Periboia gen. nov., plus a total of 30 new species; 15 of Enterocola van Beneden, 1860, two of Enterocolides Chatton Harant, 1922, five of Enteropsis C.W.S. Aurivillius, 1885, five of Monnioticopa gen. nov., two of Mychophilus Hesse, 1865, plus the type species of Periboia gen. nov. Generic diagnoses are provided for all genera represented in the collection. A further 13 known species are also reported and brief supplementary descriptive notes or full redescriptions are provided, as appropriate.

New arietellid copepods (Calanoida, Arietellidae) from anchialine caves in the Eastern Adriatic Sea

Two new species of calanoid copepods are described; Metacalanus adriaticus sp. nov. from an anchialine cave on Vis Island, and Paramisophria tvrtkovici sp. nov. from Orljak Cave, located in the lower part of River Krka estuary, near the town of Šibenik (Croatia). This is the first report of arietellid copepods found in any anchialine cave along the coast of the Adriatic Sea. In M. adriaticus sp. nov. the antennules are asymmetrical in both sexes (the female left antennule is 18-segmented, right 20-segmented; male left 16-segmented and right 20-segmented); the uniramous fifth legs of the female are 2-segmented; the terminal segment of the fifth leg in both sexes is the longest; and in the male the fifth leg exopod is 2-segmented. In P. tvrtkovici sp. nov. the antennules of both sexes are asymmetrical with the left antennule longer than the right, the female antennule is 21-segmented on both sides; the male left antennule is 19-segmented, the right 21-segmented; the armature of the terminal exopod segment of leg 1 is II, 2 ,2; the male fifth legs have a rudimentary endopod on the left leg, the third exopodal segment is smallest and bears three unequal processes on its outer margin, and the terminal spine is completely separated from the segment. On the right leg the third segment carries two short, unequal processes on its outer distal margin, as well as a long sigmoidal spine which is fused to the segment. It is inferred that, after the last glaciation, these new Arietellids moved out from their southern Adriatic refuge, colonizing first the anchialine habitats of the outer eastern Adriatic islands and then spreading along the coast.

Parasitic copepods of the family Lernanthropidae Kabata, 1979 (Copepoda: Siphonostomatoida) from Australian fishes, with descriptions of seven new species

The total number of species of Lernanthropidae previously recorded from Australian waters is 15 (i.e., one species each of Aethon Krøyer, 1837, Lernanthropodes Bere, 1936, and Lernanthropsis Do, in Ho Do, 1985; 10 species of Lernanthropus de Blainville, 1822; and two species of Sagum Wilson, 1913), and all of these records are reviewed. We report here the presence of three species of Aethon. One species, A. garricki Hewitt, 1968, is reported from Australian waters for the first time and a new species, A. bicamera sp. nov., is described from the latrid, Latris lineatus (Forster, 1801) caught off South Australia. The genus Lernanthropodes is represented by a single species, L. trachinoti Pillai, 1962. We recognize Chauvanium Kazachenko, Kovaleva, Nguyen Ngo, 2017 as a subjective synonym of Lernanthropodes and transfer its type and only species C. chauvani Kazachenko, Kovaleva, Nguyen Ngo, 2017 which becomes Lernanthropodes chauvani (Kazachenko, Kovaleva, Nguyen Ngo, 2017) n. comb. Lernanthropsis mugilii (Shishido, 1898) is reported here from Mugil cephalus Linnaeus, 1758 sampled in Queensland and in New South Wales. The genus Lernanthropus is the most species rich and we report the presence of 20 nominal species on Australian marine fishes. This total includes six new species: L. alepicolus sp. nov. from Alepes apercna Grant, 1987, L. elegans sp. nov. from Atractoscion aequidens (Cuvier, 1830), L. gnathanodontus sp. nov. from Gnathanodon speciosus (Forsskål, 1775), L. paracruciatus sp. nov. from Protonibea diacanthus (Lacepède, 1802), L. pemphericola sp. nov. from Pempheris compressa (White, 1790), and L. selenotoca sp. nov. from Selenotoca multifasciata (Richardson, 1846). In addition, we report the presence of another four species in Australian waters for the first time: L. abitocephalus Tripathi, 1962, L. cadenati Delamare Deboutteville Nuñes-Ruivo, 1954, L. microlamini Hewitt, 1968, and L. pomadasysis Rangnekar Murti, 1961. After reexamination of the types of L. paenulatus Wilson, 1922 held in the USNM, we relegate this species to subjective synonymy with L. seriolii Shishido, 1898. Previous records of L. paenulatus from Australian Seriola species should be reassigned to L. seriolii. Lernanthropus ecclesi Kensley Grindley, 1973 is recognized as a junior subjective synonym of L. micropterygis Richiardi, 1884, and L. delamarei Marques, 1960, which is based on the male only, is tentatively considered to be a junior subjective synonym of L. micropterygis. Males are described for the first time for three species; L. breviculus Kabata, 1979, L. microlamini and L. mollis Kabata, 1979. A member of the genus Mitrapus Song Chen, 1976, M. oblongus (Pillai, 1964), is reported from Australia for the first time, on Herklotsichthys castelnaui (Ogilby, 1897) caught off Queensland and New South Wales. Finally, two species of Sagum were previously known from Australia and here we add three more. Two of the newly reported species were originally described as species of Lernanthropus but we formally transfer them here to Sagum as S. lativentris (Heller, 1865) n. comb. and S. sanguineus (Song, in Song Chen, 1976) n. comb. The males of S. lativentris and S. vespertilio Kabata, 1979 are described for the first time. A key to the females of the 31 species of lernanthropids found in Australian waters is provided.

Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas

A large collection of mesoparasitic copepods from polychaete hosts collected in northern European waters was examined. The term mesoparasitic refers to highly transformed copepods where the adult female attaches by embedding part of its body in the host. Representatives of five known familes were found and a new family is established. A single new species, Bradophila minuta sp. nov., was described in the family Bradophilidae. It occurred exclusively on the flabelligerid Diplocirus glaucus (Malmgren, 1867). Two genera of the family Herpyllobiidae were represented: Herpyllobius Steenstrup Lütken, 1861 and Eurysilenium M. Sars, 1870. Herpyllobius arcticus Steenstrup Lütken, 1861 was found on at least five different polynoid hosts, two of which, Harmothoe fragilis Moore, 1910 and Antinoe sp., were new host records. A new species, H. cluthensis sp. nov. was described from Malmgrenia species in Scottish waters. The large species, Herpyllobius cordiformis Lützen, 1964, was collected in Arctic waters from Eunoe cf. oerstedi. It is the first report of this parasite in Europe. The common parasite H. polynoes (Krøyer, 1864) was found on six different polynoid hosts, three of which, Harmothoe bifera, Malmgreniella mcintoshi Tebble Chambers, 1982 and Eunoe ?barbata are new host records. Eurysilenium truncatum M. Sars, 1870 was collected from Eucranta villosa Malmgren, 1866, Eunone sp., and Gattyana cirrhosa (Pallas, 1766). The material from Eucranta villosa caught at 72.6ºN comprises both a new host record and is the most northerly report of this parasite. Specimens of Eurysilenium which differed from E. truncatum in a number of features were found on Harmothoe fragilis and H. impar (Johnston, 1839). A new family, the Pholoicolidae, is established to accommodate Pholicola chambersae gen. et sp. nov., parasitic on Pholoe pallida Chambers, 1985. The family Phyllodicolidae was represented by all three of its known species: Phyllodicola petiti (Delamare Deboutteville Laubier, 1960), Cyclorhiza eteonicola Heegaard, 1942 and C. megalova Gotto Leahy, 1988. The former was found on Eumida ockelmanni Eibye-Jacobsen, 1987, a new host record. A single ovigerous female of C. eteonicola was collected from a new host, Eteone spetsbergensis Malmgren, 1865. Cyclorhiza megalova was common on Eteone longa (Fabricius, 1780) and E. longa/flava complex. A rich diversity of members of the family Saccopsidae was found, including three known species of Melinnacheres M. Sars, 1870 plus nine new species placed in four new genera. Melinnacheres was represented by M. ergasiloides M. Sars, 1870, M. steenstrupi Bresciani Lützen, 1961 and M. terebellidis Levinsen, 1878. Melinnacheres ergasiloides was found on Melinna elizabethae McIntosh, 1914, M. steenstrupi on members of the Terebellides stroemi-complex and T. atlantis Williams, 1984, while M. terebellidis was found on the T. stroemi-complex and on T. shetlandica Parapar, Moreira O'Reilly, 2016. A new genus, Trichobranchicola gen. nov., was established to accommodate T. antennatus gen. et sp. nov., a parasite of Trichobranchus sikorskii Leontovich Jirkov in Jirkov, 2001, T. glacialis Malmgren, 1866 and Trichobranchus sp. The second new genus, Lanassicola gen. nov., was established to accommodate the type species, Lanassicola arcticus gen. et sp. nov. parasitic on Lanassa venusta (Malm, 1874), plus two additional species, L. bilobatus gen. et sp. nov. on Lanassa nordenskjoeldi Malmgren, 1866, and L. dorsilobatus gen. et sp. nov. on Proclea graffii (Langerhans, 1884). A new subfamily, Euchonicolinae, was established within the Saccopsidae to accommodate two new genera, Euchonicola gen. nov. and Euchonicoloides gen. nov. The type species of Euchonicola gen. nov. is E. caudatus gen. et sp. nov., a parasite of Euchone sp., and it includes two other species, E. linearis gen. et sp. nov. on Chone sp., and E. parvus gen. et sp. nov. on Euchone sp. The type species of Euchonicoloides gen. nov. is E. elongatus gen. et sp. nov. found on a host belonging to the genus Euchone, and it also includes Euchonicoloides halli gen. et sp. nov. from Jasmineira caudata Langerhans, 1880. Four species of the family Xenocoelomidae were found: Xenocoeloma alleni (Brumpt, 1897), X. brumpti Caullery Mesnil, 1915, X. orbicularis sp. nov. and Aphanodomus terebellae (Levinsen, 1878). Xenocoeloma alleni was found on four different species of Polycirrus and on Amaeana trilobata (M. Sars, 1863) and X. brumpti was found on Polycirrus norvegicus Wollebaek, 1912. Xenocoeloma orbicularis sp. nov. occurred only on Paramphitrite birulai (Ssolowiew, 1899). Aphanodomus terebellae was found on three hosts, only one of which, Leaena abranchiata was new.

A new genus and family of copepods (Crustacea: Copepoda) parasitic on polychaetes of the genus Jasmineira Langerhans, 1880 (family Sabellidae) in the northeastern Atlantic

A new genus and species of copepod, Jasmineiricola mackiei n. gen. et n. sp., parasitic on at least three species of the sabellid polychaete genus Jasmineira Langerhans, 1880 is described. The adult female is mesoparasitic, living with part of its body (the endosoma) embedded within the host and part (the ectosoma) protruding through the host's body wall. The endosoma consists of a well defined head region carried anteriorly on the trunk which has paired lateral lobes housing the ovaries. The head bears a rosette-like array of eight slender lobes, which are probably derived from the mouthparts. The only limbs present on the trunk are the subchelate maxillipeds positioned immediately posterior to the head. The ectosoma consists of a posterior genito-abdominal lobe bearing paired genital apertures. The male is unknown. The new genus cannot be placed in any of the five existing families of mesoparasitic copepods on polychaete hosts and is treated as the type of a new monotypic family, the Jasmineiricolidae. The new species occurs over a depth range from 19 to 279 m, and is widely distributed from UK coastal waters to Norwegian waters inside the Arctic Circle.

Fossil Crustaceans as Parasites and Hosts

Numerous crustacean lineages have independently moved into parasitism as a mode of life. In modern marine ecosystems, parasitic crustaceans use representatives from many metazoan phyla as hosts. Crustaceans also serve as hosts to a rich diversity of parasites, including other crustaceans. Here, we show that the fossil record of such parasitic interactions is sparse, with only 11 examples, one dating back to the Cambrian. This may be due to the limited preservation potential and small size of parasites, as well as to problems with ascribing traces to parasitism with certainty, and to a lack of targeted research. Although the confirmed stratigraphic ranges are limited for nearly every example, evidence of parasitism related to crustaceans has become increasingly more complete for isopod-induced swellings in decapods so that quantitative analyses can be carried out. Little attention has yet been paid to the origin of parasitism in deep time, but insight can be generated by integrating data on fossils with molecular studies on modern parasites. In addition, there are other traces left by parasites that could fossilize, but have not yet been recognized in the fossil record.

A new genus of speleophriid copepod (Copepoda: Misophrioida) from a cenote in the Yucatan, Mexico with a phylogenetic analysis at the species level

A new genus and species of speleophriid copepod, Mexicophria cenoticola gen. et sp. nov., is described based on material collected from a cenote in the Yucatan Peninsula of Mexico. It is characterised by relatively reduced fifth legs that are located adjacent to the ventral midline in both sexes, by the possession of a bulbous swelling on the first antennulary segment in both sexes, and by the reduced setation of the swimming legs. The presence of just one inner margin seta on the second endopodal segment of legs 2 to 4 is a unique feature for the family. A phylogenetic analysis places the new genus on a basal lineage of the family together with its sister taxon, Boxshallia Huys, 1988, from Lanzarote in the Canary Islands, and recovers the existing genera as monophyletic units. The zoogeography is discussed at local, regional, ocean basin  and global scales.

Copepods associated with polychaete worms in European seas

Descriptions are given of 18 species of copepods that live in symbiotic association with polychaete worms in European Seas. Three new genera and six new species of the family Clausiidae Giesbrecht, 1895 are described: Boreoclausia rectan. gen. et n. sp. is described from Galathowenia fragilis (Nilson & Holthe, 1985), Boreoclausia holmesi n. gen. et n. sp.is described from Myriochele danielsseni Hansen, 1879, Sheaderia bifida n. gen. et n. sp. from Euclymene oerstedii (Claparède, 1863), Vivgottoia garwoodi n. gen. et n. sp., was found inside the tail fragment of a terebellid host (probably Phisidia aurea Southward, 1956), Rhodinicola tenuis n. sp. from an unknown host, and R. similis n. sp., from Rhodine gracilor (Tauber, 1879). In addition, four other clausiid species, Clausia lubbockii Claparède, 1863, Mesnilia cluthae (T. and A.Scott, 1896), Rhodinicola gibbosus Bresciani, 1964 and R. rugosum (Giesbrecht, 1895), are redescribed in detail on the basis of newly collected material. The previously-unknown hosts of C. lubbockii were found to be species of the spionid polychaete genus Dipolydora Verrill, 1881. Clausia uniseta Bocquet & Stock, 1960 were recognized as a junior subjective synonym of C. lubbockii, and Mesnilia martinensis Canu, 1898 was recognized as a junior subjective synonym of M. cluthae. The sole species of the monotypic family Anomoclausiidae Gotto, 1964, Anomoclausia indrehusae Gotto, 1964, is redescribed based on new material. The host of A. indrehusae, reported here for the first time, is the spionid Pseudopolydora paucibranchiata (Okuda, 1937). Four new species of the family Nereicolidae Claus, 1875 are described, three belonging to the genus Anomopsyllus Sars, 1921: Anomopsyllus bifurcus n. sp. from Notomastus latericeus M. Sars, 1851, A. geminus n. sp. from Ampharete lindstroemi Malmgren, 1867, and A. hamiltonae n. sp., from Mugga wahrbergi Eliasson, 1955. The fourth new species is Vectoriella gabesensis n. sp., both sexes of which are described from the paraonid Aricidea catherinae Laubier, 1967 collected in the Mediterranean Sea off the coast of Tunisia. Another nereicolid, Sigecheres brittae Bresciani, 1964 is redescribed based on new material collected from the type host Sige fusigera Malmgren, 1865. It is recognized as a junior subjective synonym of Nereicola concinna T. Scott, 1902 and the valid name of this taxon becomes Sigecheres concinna (T. Scott, 1902) new combination. A new species of the family Spiophanicolidae Ho, 1984, Spiophanicola atlanticus n. sp., is described based on European material. Previously European material of Spiophanicola Ho, 1984 has been reported as S. spinulosus Ho, 1984, but based on consistent differences between the Californian S. spinulosus and material from Norway and the British Isles, there is sufficient justification to establish a new species for the European material. Finally one new genus and species is described which cannot be placed, with confidence, in any existing family. This new parasite, Notomasticola frondosus n. gen. et n. sp., is based on material from two hosts, a spionid (Pseudopolydora paucibranchiata) and a capitellid (Notomastus latericeus). It is highly derived and may represent a terminal branch within an existing family. The cluster of families using polychaetes as hosts is in need of revision based on a comprehensive phylogenetic analysis.

The lunule of caligid copepods: an evolutionarily novel structure

Nearly half of the genera of the family Caligidae possess an evolutionarily novel structure called the "lunule" on the ventral surface of the frontal plate. Lunules are paired cup-like suckers that assist in securing attachment of the copepod parasite to its host. Although present in genera such as Caligus and Pseudocaligus, lunules are absent in other caligid genera such as Lepeophtheirus as well as in more primitive caligiforms such as members of the families Trebiidae and Dissonidae. We compared the morphology and development of the anterior margin of the frontal plates between two caligids, Pseudocaligus fugu and Lepeophtheirus sekii, and a more basal caligiform, Dissonus heronensis (a dissonid), using scanning electron, transmission electron, and laser confocal microscopes. Our observations suggest that the lunules originated as a modification of the marginal membranes of the ancestral frontal plates. We also demonstrated the presence of an anlagen cell population for the lunule and marginal membrane in the developing frontal plate. These primordial cells can be detected as early as the first stage of the chalimus phase. Based on these observations, an evolutionary scenario for the lunule is proposed based on cytological evidence. This case study enhances our understanding of "evolutionary novelty," which is a main focus of contemporary evolutionary developmental biology.

Two new species of parasitic copepods (Crustacea) on two immigrant rabbitfishes (Family Siganidae) from the Red Sea

Two new species of parasitic copepods, one from each of the families Hatschekiidae and Bomolochidae, are reported from two immigrant species of rabbitfishes (Family Siganidae), both of which originated from the Red Sea but are now established in the Mediterranean. The descriptions of Hatschekia siganicola n. sp. and Nothobomolochus neomediterraneus n. sp. are based on material of both sexes obtained from the gills of Siganus luridus Rüppell and S. rivulatus Forsskål, respectively, caught in Egyptian Mediterranean waters off the Alexandrian coast.

The discovery of Caligus temnodontis Brian, 1924 (Copepoda: Caligidae) from the bluefish Pomatomus saltatrix (Linnaeus) in the eastern Mediterranean Sea

The temnodontis variety of Caligus mauritanicus Brian, 1924 described by Brian (1924) is a valid species known only from a single host species, Pomatomus saltatrix (Linnaeus). New material of this species has been examined from the same host fish caught from Abuqir Bay, Alexandria (Egypt), from Iskenderun Bay (Turkey) and from off the coast of South Africa. Using this material, C. temnodontis Brian, 1924 is redescribed and compared with related species. It is most closely related to the Indo-Pacific species C. pagrosomi Yamaguti, 1939.

Cladistic analysis of the calanoid Copepoda

Calanoid copepods are extremely successful inhabitants of marine, brackish and freshwater plankton. Morphological data are used to arrive at a first, parsimony-based phylogeny for the calanoid copepods. Each family is represented by at least one exemplar, typically a recognised plesiomorphic species. The Epacteriscidae are sister to all other calanoid copepods – an observation that brings into question the concept of an Epacteriscoidea that includes the Ridgewayiidae. The monophyly of the Augaptiloidea, Centropagoidea, Clausocalanoidea and Pseudocyclopoidea is corroborated. The current analysis suggests there may be two major clades, one containing the Augaptiloidea, Centropagoidea and possibly the Pseudocyclopoidea and Ridgewayiidae and the other including the Megacalanidae, Calanidae/Paracalanidae, Bathypontioidea, Eucalanoidea, Ryocalanoidea, Spinocalanoidea and Clausocalanoidea. The relationships of the Pseudocyclopidae, Boholinidae, and Ridgewayiidae to the Centropagoidea/Augaptiloidea clade received low nodal support. Monophyly of an enlarged Bathypontioidea (including the Fosshageniidae) is proposed. A monophyletic Megacalanoidea is not retrieved. The nature of the inferred ancestral Calanoida is discussed. New evolutionary series are proposed for the female genitalia (including several losses and regaining of seminal receptacles, and independent losses of the genital operculum – once lost it is never regained) and leg 1 endopod. Paedomorphosis appears to be a dominant process in the evolution of the Calanoida.

A revision of the family Dissonidae Kurtz, 1924 (Copepoda: Siphonostomatoida)

Two new species of the parasitic copepod genus Dissonus Wilson, 1906 are described: D. excavatus n. sp. from the gills of a labrid, Bodianus perditio, and a lutjanid, Macolor niger, collected off New Caledonia and Taiwan, and D. inaequalis n. sp. from a hemiscylliid elasmobranch, Chiloscyllium punctatum, collected off Sarawak (Malaysia) and the Philippines. Material of D. heronensis Kabata, 1966 is described from a balistid host, Pseudobalistes fuscus, off New Caledonia, and this constitutes a new host record for this parasite. D. manteri Kabata, 1966 was collected from four serranid host species off New Caledonia and from one of the same hosts off Taiwan. Two of the hosts from New Caledonia, Plectropomus laevis and Epinephelus cyanopodus, represent new host records. D. pastinum Deets & Dojiri, 1990 was recognised as a new synonym of D. nudiventris Kabata, 1966, so the total number of valid species is now twelve. Material from museum collections of D. nudiventris, D. similis Kabata, 1966 and D. spinifer Wilson, 1906 was re-examined and provided new information which is utilised in a key to all valid species of Dissonus.

The evolution of arthropod limbs

Limb morphology across the arthropods is reviewed using external morphological and internal anatomical data from both recent and fossil arthropods. Evolutionary trends in limb structure are identified primarily by reference to the more rigorous of the many existing phylogenetic schemes, but no major new phylogenetic inferences are presented. Tagmosis patterns are not considered, although the origins and patterns of heteronomy within the postantennulary limb series are analysed. The phenomenon of annulation is examined and two basic types of annuli are recognised: terminal and intercalary. The annulation of the apical segment of a limb results in the formation of terminal flagella, and is typical of primarily sensory appendages such as insect and malacostracan antennules and maxillary palps of some hexapods. Intercalary annulation, arising by subdivision of existing subterminal segments, is common, particularly in the tarsal region of arthropodan walking limbs. Differentiating between segments and annuli is discussed and is recognised as a limiting factor in the interpretation of fossils, which usually lack information on intrinsic musculature, and in the construction of groundplans. Rare examples of secondary segmentation, where the criteria for distinguishing between segments and annuli fail, are also highlighted. The basic crown-group arthropodan limb is identified as tripartite, comprising protopodite, telopodite and exopodite, and the basic segmentation patterns of each of these parts are hypothesised. Possible criteria are discussed that can be used for establishing the boundary between protopodite and telopodite in limbs that are uniramous through loss of the exopodite. The subdivision of the protopodite, which is typical of the postantennulary limbs of mandibulates, is examined. The difficulties resulting from the partial or complete failure of expression of articulations within the mandibulate protopodite and subsequent incorporation of partial protopodal segments into the body wall, are also discussed. The development and homology between the various exites, including gills, on the postantennulary limbs of arthropods are considered in some detail, and the question of the possible homology between crustacean gills and insect wings is critically addressed. The hypothesis that there are only two basic limb types in arthropods, antennules and postantennulary limbs, is proposed and its apparent contradiction by the transformation of antennules into walking limbs by homeotic mutation is discussed with respect to the appropriate level of serial homology between these limbs.

Three new species of Enterocola van Beneden, 1860 (Crustacea: Copepoda: Cyclopoida) from ascidian hosts

Three new species of Enterocola are described: E. dicaudatus n. sp., from the ascidian host Polysyncraton rostrum Monniot & Monniot collected in Tanzania, E. monnioti n. sp., from the ascidian host Polyclinum constellatum Savigny collected in Bahrain, and E. parapterophorus n. sp., from the ascidian host Didemnum granulatum Tokioka taken in Djibouti. In all three species, the mandibles are interpreted as being represented by a pair of setulose seta-like elements that are largely concealed beneath similar paired setulose structures, the labral palps, carried on the labrum. The paired elements interpreted as mandibles are transversely orientated and lie in a groove, the anterior margin of which forms a defined ridge ornamented with spinules.

The notodelphyid Genus Doroixys Kerschner, 1879 (Crustacea: Copepoda: Cyclopoida), with the Description of a New Species from the Russian Far East

Doroixys simplex n. sp. is described from material collected from a tunicate of the genus Ciona, collected on the North Pacific coast of Russia. This is the fourth species of the genus and the first for which the male has been found. The new species differs from congeners most noticeably in the absence of posterolateral processes from the rear margin of the dorsal cephalic shield. A key to species is provided.

A new notodelphyid copepod, Paranotodelphys illgi n. sp. (Copepoda: Cyclopoida), parasitic in the ascidian Corynascidia herdmani Ritter in the North Pacific

A new species of the Notodelphyidae belonging to Paranotodelphys Schellenberg, 1922 is described from both sexes. The new species, Paranotodelphys illgi, can be distinguished from its congeners by the combination of its 10-segmented female antennule, the bisetose fifth legs and the extreme elongation of the caudal rami of the female, which are more than 10 times longer than wide and 4.4 times longer than the anal somite. The male has non-geniculate antennules. The new species was collected at a depth of 508m in the North Pacific Ocean, from the ascidian Corynascidia herdmani Ritter.

The Buproridae Thorell, 1859, a family of ascidicolous copepods (Copepoda: Cyclopoida)

The adult female of Buprorus loveni Thorell, 1859, a cyclopoid copepod inhabiting the branchial cavities of solitary ascidians, is redescribed in detail from new material collected in Scandinavian waters and from the southern part of the North Atlantic off Mauritania. The antennal segmentation pattern exhibited by all seven subfamilies of the family Ascidicolidae Thorell, 1860 is compared. The segmentation of the Buprorinae is different from that of all other subfamilies within the ascidicolid series. It is concluded that the antenna of Buprorus is not an appropriate model for interpreting the segmentation of other ascidicolids because the Buprorinae is the only subfamily in which the first and second endopodal segments are primitively fused and the third is distinct. The Buproridae Thorell, 1859 is here treated as a separate family within the Cyclopoida.

New species and new records of Ergasilus Nordmann (Copepoda: Ergasilidae) from the gills of grey mullet (Mugilidae)

Four new Ergasilus species are described from five host species of grey mullet, family Mugilidae, held in the fish collections of The Natural History Museum, London. Ergasilus extensus n. sp. was found on Myxus petardi (Castelnau) from Australia, E. sittangenesis n. sp. on Sicamugil hamiltoni (Day) from Burma, E. piriformis n. sp. on Sicamugil cascasia (Hamilton Buchanan) from India, and E. ecuadorensis n. sp. on Mugil curema Valenciennes and M. hospes Jordan & Culver from Ecuador. New records of E. cyanopictus Caravalho, E. magnicornis Yin, E. orientalis Yamaguti and E. rostralis Ho, Jayarajian & Radhakrishnan on grey mullet are also given.

Gauchergasilus, a new genus for Ergasilus euripedesi Montú, 1980, an abundant parasitic copepod from the Patos Lagoon in southern Brazil

Ergasilus euripedesi is redescribed from newly collected material of both sexes. A new genus, Gauchergasilus, is proposed, with Gauchergasilus euripedesi n. comb., formerly Ergasilus euripedsi Montú, 1980, as its type and only species. The new genus is characterised principally by the five-segmented antennule, the presence of a conspicuous barb on the concave margin of the claw of the antenna, the two-segmented endopod of leg 1 and the reduced fifth leg comprising two setae, one papillate. The male lacks the barb on the antennal claw but its other appendages are similar to those of the female, except for the maxilliped which is absent in females. The affinities of the new genus lie with the Acusicola group of genera.

The mesoparasitic genera of the Ergasilidae (Copepoda): with descriptions of new species of Paeonodes Wilson and Therodamas Krøyer

One species of each of the three mesoparasitic ergasilid genera, Therodamas Krøyer, Mugilicola Tripathi and Paeonodes Wilson, is described in detail. The descriptions of P. subviridis n. sp. and Mugilicola bulbosus Tripathi are based on new material collected from Liza subviridis (Valenciennes) from Guam and India, respectively. The description of Therodamas frontalis n. sp. is based on material from Mugil cephalus L. in Brazil and the redescription of Therodamas serrani Krøyer is based on examination of syntype material. The geographical distributions of all three genera are summarised. Analysis of the phylogenetic relationships between species of these three genera indicates that Paeonodes and Mugilicola form a single clade and that Paeonodes, as currently constituted, is paraphyletic.

Biogeography and phylogeny of Dermoergasilus Ho & Do, 1982 (Copepoda: Ergasilidae), with descriptions of three new species

Three new species of Dermoergasilus are described from six species of grey mullet hosts. Dermoergasilus longiabdominalis n. sp. was found on Valamugil engeli (Bleeker) from the Philippines and Madagascar and on V. cunnesius (Valenciennes) from the Philippines and Mangalore, India. D. semiamplectens n. sp. occurred on Sicamugil hamiltoni (Day) from the Sittang River, Burma, on Liza subviridis (Valenciennes) and L. parsia (Hamilton Buchanan) from Calcutta, India, and on V. cunnesius (Valenciennes) from China. D. curtus n. sp. parasitised Rhinomugil squamipinnis (Swainson) from Alahabad, India. A key to the ten currently accepted species of Dermoergasilus is given. The biogeographical distribution of Dermoergasilus species is analysed and levels of host-specificity are surveyed within the genus. The phylogenetic relationships between the species of Dermoergasilus are also analysed.

A new species of Acusicola Cressey (Copepoda: Ergasilidae) from northeastern Brazil

A new species of Acusicola is described based on adults of both sexes taken from plankton samples collected in the upper reaches of the Piauí River estuary, in the northeast of Brazil. Ovigerous females were present in the plankton. The new species, Acusicola minuta n. sp., can be distinguished from its congeners by its small body size, female antennal morphology and leg setation. The male described here as A. minuta n. sp. is the first known male attributed to the genus.

Parasitic copepods (Copepoda: Siphonostomatoida) from deep-sea and mid-water fishes

The stages in the metamorphosis of the pennellid Cardiodectes medusaeus (Wilson) are described from mid-water fishes in the Indo-Pacific. The earliest metamorphic stage was found within the body cavity of the second host and indicates a double origin for the frontal processes of the cephalic holdfast in this species. A new species of Lophoura (family Sphyriidae) is described from a single female taken from a deep-water synaphobranchid eel caught in the North Atlantic. The new species, L. simplex, is characterised by the lack of any neck processes. Another sphyriid, Periplexis lobodes Wilson, is reported for the second time. It was found on a deep-sea alepocephalid belonging to the genus Rouleina in Fijian waters.

Ergasilid copepods (Poecilostomatoida) from the gills of primitive Mugilidae (grey mullets)

All representatives of the subfamily Agonostominae of grey mullets in the collections of The Natural History Museum in London were examined for parasitic copepods. Agonostomus monticola, Joturus pichardi, Aldrichetta forsteri and Cestraeus goldiei were all infected by copepods. Three new species of Acusicola and two new species of Ergasilus were found: E. parabahiensis n. sp. on A. monticola from Guyana and E. acusicestraeus n. sp. on C. goldiei from Papua New Guinea. Acusicola spinuloderma n. sp. was found on A. monticola and J. pichardi collected from different localities in Central America, A. mazatlanesis n. sp. on the same host from west Mexico (Mazatlan) and A. joturicola n. sp. on J. pichardi from Panama. Descriptions of the five new species and a redescription of E. australiensis Roubal, from Aldrichetta forsteri, are presented. The host-parasite relationships and geographical distributions of hosts and their parasitic copepods are analysed.

The population dynamics of Lepeophtheirus pectoralis (Müller): seasonal variation in abundance and age structure

The ectoparasitic copepod Lepeophtheirus pectoralis exhibited a regular annual cycle of abundance on its hosts. Both the incidence and intensity of infection were greatest in August or September and both declined over winter to their minimum values in April. Very similar cycles were observed in both 1972 and 1973. Analysis of the age structure of the parasite population showed that the increase in abundance coincided with the onset of the breeding season. Although females always outnumbered males the sex ratio approached unity during the breeding season, which extended from May to October. Copulating pairs were most commonly observed during this period.

There was a marked bimodal peak of egg production each year, with the first mode occurring around May and the second mode around August or September. This pattern was produced by a system of alternation of generations operating within the parasite population, with a summer type generation (distinguishable by its rapid maturation rate and reduced longevity) alternating with an overwintering type of generation.

The population dynamics of Lepeophtheirus pectoralis (Müller): dispersion pattern

The numerical relationships between a population of Lepeophtheirus pectoralis and its host population (plaice) have been described. There was no significant difference between infection levels in male and female plaice. In most of the monthly samples (75%) there was no significant relationship between host length and either the incidence or intensity of infection. The samples in which significant positive correlations occurred were usually taken within the period November to April. It is probable that the immigration of smaller fish, with lower levels of infection, from shallower water produces this effect.

The parasite population was found to have an overdispersed distribution (variance > mean) within its habitat, the host population. The frequency distributions of numbers of parasites per fish were calculated and the negative binomial distribution was fitted to these. The fit was good in 22 of the 24 samples and the value of k, the exponent, was found to be directly related to the mean density of the parasite population. Iwao's (1970) method of dispersion analysis indicated that the observed negative binomial was generated by a model of randomly distributed clumps or colonies of individuals. A possible mechanism of producing this pattern was proposed based on evidence from studies of mortality in the parasite population (which indicated that all-or-none type mortality operates on the clumps at certain periods during the year), the infection process (which demonstrated that a single wave of infection produces an overdispersed spatial distribution) and the examination of parasites from individual fish (which displayed a clumping of parasites at certain stages rather than an even spread over the range of possible stages). The mechanism proposed is that the adaptations for host location of the infective copepodid stage tend to produce aggregations of these larvae in favourable areas of a heterogeneous habitat. Fish moving randomly into these areas will tend to be infected by more than one larva (a clump of larvae) at any one time when available for infection. The fish can be regarded as equivalent to random samples of the free larval population and the aggregated distribution of the parasite population on its hosts is therefore directly related to the aggregated distribution of the free-swimming infective larvae.