Exploring evolutionary trends within the Pennellidae (Copepoda: Siphonostomatoida) using molecular data.

The family Pennellidae comprises ecto- and mesoparasitic copepods on marine fishes. Although a preliminary scheme of phylogenetic relationships of pennellids based on morphological characters exists, it is difficult to objectively define character states because of their highly modified bodies and reduced appendages. This molecule-based study analysed phylogenetic relationships among seven genera and 12 species of pennellids, using 18S and 28S ribosomal DNA sequences in order to infer evolutionary trends within the family. Our molecular analysis recovered three clades (Clade-I, Peniculus; Clade-II, Haemobaphes-Lernaeocera-Phrixocephalus-Exopenna-Lernaeenicus radiatus; and Clade-III, Pennella-Lernaeenicus spp.). This result was congruent with some of the morphology-based phylogenetic relationships previously proposed but did not support a sister group comprising Exopenna, Phrixocephalus and Pennella. The second and third offshoots after the divergence of Clade-I species are characterized by reduced body tagmosis and changes in lifestyle from ectoparasites to mesoparasites. In some gill parasites of Clade-II, their sigmoid-shaped bodies and coiled egg strings have likely evolved in adaptation to the limited available space within the gill cavities of the hosts. Phrixocephalus is an eye parasite in Clade-II, which also has coiled egg strings, may have descended from an ancestral gill parasite. All species of Clade-III are characterized by the possession of a head region with processes deeply embedded into the host tissues and functioning as an anchor.

Sea lice (Copepoda: Caligidae) from South Africa, with descriptions of two new species of Caligus.

Thirteen species of sea lice (family Caligidae) are reported from a range of elasmobranch and actinopterygian fishes caught off South Africa or obtained from public aquaria in South Africa. Two new species of Caligus Müller, 1785 are described: C. linearis n. sp. from Pomatomus saltatrix (Linnaeus) and C. tumulus n. sp. from Chrysoblephus cristiceps (Valenciennes). A supplementary description is provided for both sexes of Caligus tetrodontis Barnard, 1948 taken from Amblyrhynchotes honckenii (Bloch) and previous records of this parasite from South African fishes are critically reviewed. It is concluded that Caligus material from Arothron hispidus Linnaeus was previously misidentified as C. tetrodontis and is in urgent need of re-examination. Morphological and molecular observations on Caligus furcisetifer Redkar, Rangnekar & Murti, 1949 indicate that this copepod is phenotypically and genetically identical to Lepeophtheirus natalensis Kensley & Grindley, 1973, and the latter becomes a junior subjective synonym of C. furcisetifer. We include new geographical distribution records for Caligus longipedis Bassett-Smith, 1898, C. rufimaculatus Wilson, 1905 and Lepeophtheirus spinifer Kirtisinghe, 1937, extending into South African waters, as well as both new distribution and host records for Alebion gracilis Wilson, 1905, Caligus dakari van Beneden, 1892 and Lepeophtheirus acutus Heegaard, 1943. The molecular analysis confirmed the monophyly of the genus Caligus. The South African species of Caligus did not cluster together, but the two included South African species of Lepeophtheirus were recovered as sister taxa.

A new species of Pseudopandarus Kirtisinghe, 1950 (Copepoda: Siphonostomatoida: Pandaridae) from sharks of the genus Squalus L. in New Caledonian waters.

Both sexes of a new species of pandarid copepod are described from sharks of the genus Squalus L. (Squaliformes: Squalidae). Specimens of Pseudopandarus cairae n. sp. were collected from Squalus bucephalus Last, Séret & Pogonoski and S. melanurus Fourmanoir & Rivaton in New Caledonian waters, the first parasitic copepod to be described from either host species. This is the eighth nominal species of Pseudopandarus Kirtisinghe, 1950 and the first to be described from a shark of the order Squaliformes. Pseudopandarus cairae n. sp. is easily distinguished from P. australis Cressey & Simpfendorfer, 1988, P. longus (Gnanamuthu, 1951) Cressey, 1967, and P. pelagicus Rangnekar, 1977 in having the female genital complex concealed beneath an elongate dorsal genital shield with a trilobed posterior margin. It can be distinguished from P. gracilis Kirtisinghe, 1950 and P. scyllii Yamaguti & Yamasu, 1959 by the armature of the leg 4 endopod and by the proportions of the dorsal genital shield. The new species is unique among known species of Pseudopandarus in its possession of only 1 setal element on the distal endopod segment of leg 4. In addition to describing the new species, the host associations of all species of Pseudopandarus are reviewed and observations are made regarding sexual dimorphism and mode of attachment. A key to the species considered valid is provided.

Redescription of Tripaphylus musteli (van Beneden, 1851) (Copepoda: Sphyriidae) and the relegation of Paeon Wilson, 1919 to synonymy with Tripaphylus Richiardi in Anonymous, 1878.

Tripaphylus musteli (van Beneden, 1851) (Copepoda, Siphonostomatoida, Sphyriidae) is redescribed from an adult female collected from the branchial chamber of a starry smooth-hound, Mustelus asterias Cloquet (Carcharhiniformes, Triakidae), captured in the English Channel off Portland, UK. The new account of T. musteli is the first based on a complete adult female and highlighted the lack of a robust distinction separating Tripaphylus Richiardi, in Anonymous, 1878 and Paeon Wilson, 1919 prompting us to relegate Paeon to a junior subjective synonym of Tripaphylus. In the light of this synonymy the eight former species of Paeon are transferred to Tripaphylus as follows: T. ferox (Wilson, 1919) new combination, T. elongatus (Wilson, 1932) new combination, T. vassierei (Delamare Deboutteville & Nuñes-Ruivo, 1954) new combination, T. lobatus (Kirtisinghe, 1964) new combination, T. asymboli (Turner, Kyne & Bennett, 2003) new combination, T. versicolor (Wilson, 1919) new combination, T. australis (Kabata, 1993) new combination, and T. triakis (Castro Romero, 2001) new combination. Comparisons between terminology used in this report and that in the literature indicate that all transformed adult females of Tripaphylus probably possess a full complement of cephalic appendages and maxillipeds. All limbs, with the exception of the maxillae share a general morphological similarity to the corresponding appendages of conspecific males. The maxilla of the transformed adult female of Tripaphylus is a small digitiform protuberance associated with a swelling in some species.

A New Species of Hyperbenthic Cyclopoid Copepod from Japan: First Record of the Genus Cyclopicina in the Indo-Pacific Region.

A new species of the cyclopinid genus Cyclopicina, C. toyoshioae sp. nov., was collected from the hyperbenthic layer off northern Kyushu Island, Japan; its description is based on two adult female specimens. This is the first record of the genus from the Indo-Pacific region. The new species can be distinguished from its two known congeners in: (1) the relatively short antennules which do not reach the posterior margin of the dorsal cephalothoracic shield; (2) the shape of seminal receptacles; (3) the segmentation and armature of the cephalothoracic appendages; (4) the shape of the basal protrusion between the rami of legs 1-4; (5) the presence of three outer spines on the third exopodal segment of leg 4; and (6) the presence or absence of outer setae on the free exopodal segment of leg 5. The genus Cyclopicina shows a wide but scattered distribution in hyperbenthic layers, from the continental shelves to deep-sea basins, in the northern hemisphere.

Screening of candidate genes encoding proteins expressed in pectoral fins of fugu Takifugu rubripes, in relation to habitat site of parasitic copepod Caligus fugu, using suppression subtractive hybridization.

Caligus fugu is a parasitic copepod specific to the tetraodontid genus Takifugu including the commercially important Takifugu rubripes. Despite the rapid accumulation of knowledge on other aspects of its biology, the host and settlement-site recognition mechanisms of this parasite are not yet well understood. Since the infective copepodid stage shows preferential site selection in attaching to the fins, we considered it likely that the copepodid recognizes chemical cues released or leaking from the fins, and/or transmembrane protein present on the fins. To isolate molecules potentially related to attachment site specificity, we applied suppression subtractive hybridization (SSH) PCR by identifying genes expressed more highly in pectoral fins of T. rubripes than in the body surface skin. We sequenced plasmid DNA from 392 clones in a SSH library. The number of non-redundant sequences was 276, which included 135 sequences located on 117 annotated genes and 141 located in positions where no genes had been annotated. We characterized those annotated genes on the basis of gene ontology terms, and found that 46 of the identified genes encode secreted proteins, enzymes or membrane proteins. Among them nine showed higher expression in the pectoral fins than in the skin. These could be candidate genes for involvement in behavioral mechanisms related to the site specificity shown by the infective copepodids of C. fugu.

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.

Historical biogeography of the neotropical Diaptomidae (Crustacea: Copepoda).

INTRODUCTION: Diaptomid copepods are prevalent throughout continental waters of the Neotropics, yet little is known about their biogeography. In this study we investigate the main biogeographical patterns among the neotropical freshwater diaptomid copepods using Parsimony Analysis of Endemicity (PAE) based on species records within ecoregions. In addition, we assess potential environmental correlates and limits for species richness. RESULTS: PAE was efficient in identifying general areas of endemism. Moreover, only ecoregion area showed a significant correlation with diaptomid species richness, although climatic factors were shown to provide possible upper limits to the species richness in a given ecoregion. CONCLUSION: The main patterns of endemism in neotropical freshwater diaptomid copepods are highly congruent with other freshwater taxa, suggesting a strong historical signal in determining the distribution of the family in the Neotropics.

MicroCT illuminates the unique morphology of Shiinoidae (Copepoda: Cyclopoida), an unusual group of fish parasites.

The copepod family Shiinoidae Cressey, 1975 currently comprises nine species of teleost parasites with unusual morphology and a unique attachment mechanism. Female shiinoids possess greatly enlarged antennae that oppose a rostrum, an elongate outgrowth of cuticle that originates between the antennules. The antennae form a moveable clasp against the rostrum which they use to attach to their host. In this study, we use micro-computed tomography (microCT) to examine specimens of Shiinoa inauris Cressey, 1975 in situ attached to host tissue in order to characterize the functional morphology and specific muscles involved in this novel mode of attachment and to resolve uncertainty regarding the segmental composition of the regions of the body. We review the host and locality data for all reports of shiinoids, revise the generic diagnoses for both constituent genera Shiinoa Kabata, 1968 and Parashiinoa West, 1986, transfer Shiinoa rostrata Balaraman, Prabha & Pillai, 1984 to Parashiinoa as Parashiinoa rostrata (Balaraman, Prabha & Pillai, 1984) n. comb., and present keys to the females and males of both genera.

Ectoparasites of the Critically Endangered green sawfish Pristis zijsron and sympatric elasmobranchs in Western Australia.

This study reports the metazoan ectoparasite fauna of juvenile Critically Endangered green sawfish, Pristis zijsron, and sympatric elasmobranchs in Western Australia. Five parasite taxa were found on 76 screened P. zijsron: Caligus furcisetifer (Copepoda: Caligidae), Dermopristis pterophila (Monogenea: Microbothriidae), Branchellion plicobranchus and Stibarobdella macrothela (Hirudinea: Piscicolidae), and praniza larvae of an unidentified gnathiid isopod. Only C. furcisetifer and D. pterophila were common, exhibiting discrepant site-specificity, with C. furcisetifer occurring mostly on the head and rostrum, and D. pterophila around the pectoral and pelvic fins. Intensity of infection for C. furcisetifer and D. pterophila increased with host total length and was influenced by host sex, but in opposite directions; intensity of C. furcisetifer was greater on female P. zijsron, whereas intensity of D. pterophila was greater on males. In the Ashburton River, likelihood of infection for C. furcisetifer and D. pterophila on P. zijsron increased with time since substantial freshwater discharge events, suggesting decreased salinity impacts both taxa. In addition to P. zijsron, five other sympatric elasmobranch species were opportunistically screened for ectoparasites in the study area: the giant shovelnose ray, Glaucostegus typus, the eyebrow wedgefish, Rhynchobatus palpebratus, the nervous shark, Carcharhinus cautus, the lemon shark, Negaprion acutidens, and the graceful shark, Carcharhinus amblyrhynchoides. Caligus furcisetifer was found on R. palpebratus; no other parasites of P. zijsron were found on other sympatric elasmobranch species. Conversely, Perissopus dentatus (Copepoda: Pandaridae) was found on all three carcharhinids but not on batoid rays (P. zijsron, G. typus or R. palpebratus).

Resolving taxonomic and nomenclatural problems in the genus Caligus O.F. Mller, 1785 (Copepoda: Caligidae).

Supplementary descriptions are provided for six poorly known species of Caligus, based on a study of type and other material carried out by the late Roger F. Cressey but never published. As part of that study new illustrations were produced by Hillary Boyle Cressey who has kindly made these previously unpublished drawings available to this paper. The present account also contains critical re-assessments of the validity of several other species of Caligus Mller, 1785. It is proposed to recognise that: C. glacialis Gadd, 1910 and C. raniceps Heegaard, 1943 are junior subjective synonyms of the type species C. curtus Mller, 1785 and we consider the published geographical locality given for C. raniceps by Heegaard (1943) to be erroneous; C. guerini Guiart, 1913 is a junior subjective synonym of C. elongatus von Nordmann, 1832; C. mordax Leigh-Sharpe, 1934 is a junior subjective synonym of C. coryphaenae Steenstrup & Ltken, 1861; C. lessonius Risso, 1826 is not a caligid and is probably a junior synonym of the pandarid Demoleus heptapus (Otto, 1821); C. clavatus Kirtisinghe, 1964 is a junior subjective synonym of C. sphyraeni Pillai, 1963; C. rotundigenitalis Y, 1933 is a junior subjective synonym of C. torpedinis Heller, 1865; C. hyalinae Heegaard, 1966 is a junior subjective synonym of C. chelifer Wilson, 1905; C. biseriodentatus, Shen, 1957 is a junior subjective synonym of C. pauliani Nues-Ruivo & Fourmanoir, 1956; and C. cornutus Heegaard, 1962 can be formally treated as a junior subjective synonym of C. lobodes (Wilson, 1911) because the name C. cornutus belongs with the male holotype; the female allotype collected by Heegaard (1962) remains unidentified. We also conclude that C. mebachii Marukawa, 1927 was based on a young male of Euryphorus brachypterus (Gerstaecker, 1853) and a male of Caligus coryphaenae Steenstrup & Ltken, 1861 which was mistakenly identified as the female. A lectotype is designated for C. mebachii and this species is treated as a synonym of Euryphorus brachypterus. It is noted that C. hamatus Heegaard, 1955 is conspecific with, and has priority over, C. undulatus Shen & Li, 1959. However, given that C. undulatus is a high profile and well known species, frequently recorded from across the Pacific, Indian and Atlantic oceans, a case has been submitted to the ICZN to grant precedence of C. undulatus over C. hamatus. We reject the transfer of Chalimus tenuis Leidy, 1889 to Caligus by Fowler (1912) on the basis of lack of evidence supporting the transfer, and return it to Chalimus, where it can be treated as a species inquirendum within a genus that is no longer considered as valid. We consider that C. alalongae Kryer, 1863 and C. gracilis Dana, 1852 are species inquirenda. Caligus truttae is a nomen nudum because Giard (1890) provided no morphological information or illustration associated with the new name.

A new species of Paramacrochiron (Copepoda: Cyclopoida: Macrochironidae) associated with the rhizostome medusa Rhopilema hispidum collected from the Gulf of Thailand, with a phylogenetic analysis of the family Macrochironidae.

Paramacrochiron thailandicum n. sp. (Copepoda: Cyclopoida: Macrochironidae) is described from the rhizostome medusa Rhopilema hispidum occurring in the Gulf of Thailand. The new species is distinguishable from other congeners mainly by detailed features of the fourth legs and the urosome in both sexes. Copepodid and adult stages of the genus Paramacrochiron seem to be host-specific to rhizostome medusae, but may spend periods free in the plankton or benthos during the absence of the host. A cladistic analysis shows that the Macrochironidae comprises two main lineages. Paramacrochiron is recovered as a monophyletic group, located on one lineage together with Pseudomacrochiron, which appears as a paraphyletic taxon with the limited character set used. The other main lineage comprises the genera Macrochiron and Sewellochiron, but the sole species of the latter genus, Sewellochiron fidens, is nested within Macrochiron. This analysis provides little support for maintaining Sewellochiron as a separate genus.

A new species of Sabellacheres M. Sars, 1862 (Copepoda: Gastrodelphyidae) from a deep-water benthic polychaete in Antarctic waters, with a key to the species of the genus.

Specimens of a deep-living sabellid polychaete of the genus Perkinsiana Knight-Jones dredged in Antarctic waters were found to be parasitised by an undescribed species of the cyclopoid copepod genus Sabellacheres M. Sars, 1862. Specimens of both sexes were studied using light microscopy and SEM, and compared with its congeners. The new species, Sabellacheres antarcticus n. sp., can be distinguished from its congeners by the shape and proportions of the body and brood-pouch, its 4-segmented antennae, the shape and length of the distal process of the second antennular segment, the position of leg 3, and the structure of the male maxilliped. This is only the second record of a species of this genus from the southern hemisphere. The new species was found on a single host species, as is typical for most species of Sabellacheres. A key for the identification of both sexes of the species of Sabellacheres is included.

Sagum posteli Delamare-Deboutteville & Nunes-Ruivo, 1954 (Copepoda: Siphonostomatoida: Lernanthropidae) parasitic on Epinephelus aeneus (Geoffroy Saint-Hilaire) in Turkish waters, with a key to the species of Sagum Wilson, 1913.

Sagum posteli Delamare-Deboutteville & Nunes-Ruivo, 1954 (Copepoda: Lernanthropidae) is reported from the white grouper Epinephelus aeneus Geoffroy Saint-Hilaire caught off the Turkish Mediterranean coast. This documents the first discovery of this species in the Mediterranean and is only the second record. The species is redescribed from adult females and the cephalothoracic limbs are described for the first time. The valid species of the genus Sagum Wilson, 1913 are reviewed, and the poorly described species S. poeyi Ortiz, Lalana & Suarez, 2003 is relegated as a junior synonym of S. texanum Pearse, 1952, described from the same host. A key is provided to females of the ten valid species of Sagum and the known hosts for all species are summarised.

A synthesis tree of the Copepoda: integrating phylogenetic and taxonomic data reveals multiple origins of parasitism.

The Copepoda is a clade of pancrustaceans containing 14,485 species that are extremely varied in their morphology and lifestyle. Not only do copepods dominate marine plankton and sediment communities and make up a sizeable component of the freshwater plankton, but over 6,000 species are symbiotically associated with every major phylum of marine metazoans, mostly as parasites. Unfortunately, our understanding of copepod evolutionary relationships is relatively limited in part because of their extremely divergent morphology, sparse taxon sampling in molecular phylogenetic analyses, a reliance on only a handful of molecular markers, and little taxonomic overlap between phylogenetic studies. Here, a synthesis tree method is used to integrate published phylogenies into a more comprehensive tree of copepods by leveraging phylogenetic and taxonomic data. A literature review in this study finds fewer than 500 species of copepods have been sampled in molecular phylogenetic studies. Using the Open Tree of Life platform, those taxa that have been sampled in previous phylogenetic studies are grafted together and combined with the underlying copepod taxonomic hierarchy from the Open Tree of Life Taxonomy to make a synthesis phylogeny of all copepod species. Taxon sampling with respect to molecular phylogenetic analyses is reviewed for all orders of copepods and shows only 3% of copepod species have been sampled in phylogenetic studies. The resulting synthesis phylogeny reveals copepods have transitioned to a parasitic lifestyle on at least 14 occasions. We examine the underlying phylogenetic, taxonomic, and natural history data supporting these transitions to parasitism; review the species diversity of each parasitic clade; and identify key areas for further phylogenetic investigation.

The cephalothoracic sucker of sea lice (Crustacea: Copepoda: Caligidae): The functional importance of cuticular membrane ultrastructure.

Sea lice adhere to the body surface of host fish with a cephalothoracic sucker. Caligus adheres to this substrate using legs 2 and 3, and the action of cephalothoracic muscles. Lunules, small, paired, anterior sucker-like structures, have a vital function in the initial step of adhering and contain a unique endocuticule containing elements that may behave like active matter and serve as the actuating mechanism. Cuticular membranes bordering the cephalothorax have a unique endocuticule with an undulating dorsal surface and a smooth ventral surface. A high-speed camera revealed that this undulation likely facilitates rapid automatic application of the sucker to the substrate. The cuticular membranes on the posterior margin of the first exopodal segment of leg 2 have a specialized endocuticle with tubules each surrounded by fine fibers. This reinforcement helps them to generate a posteriorly-directed jet of water. Opening-closing of these membranes is controlled by postero-anterior motion of the distal exopodal segments of leg 2. The outer cuticular membrane of leg 3 is simple, presumably effected by powerful extrinsic muscles. The consistency of sucker morphology within Caligus implies a highly stereotyped attachment behavior that is effective across a remarkable variety of fishes.

A new genus of endoparasitic copepods (Cyclopoida: Enterognathidae), forming a gall in the calyx of deep-sea crinoids.

A new genus and species of cyclopoid copepod belonging to the family Enterognathidae, Parenterognathus troglodytes, is described from a gall on the calyx of the deep-sea crinoid Glyptometra crassa (Clark, 1912) collected at depths of 775-787 m off Kumano-nada, middle Japan. The new genus can be distinguished from the three known genera of the family by body tagmosis and by the segmentation and armature of the appendages. This is the first record of this family from the Pacific Ocean. This family seems to be host-specific to relatively basal deuterostomes, such as echinoderms and hemichordates. The evolutionary transformation and history of the Enterognathidae are briefly discussed.

An annotated list of parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda and Nematoda) collected in groupers (Serranidae, Epinephelinae) in New Caledonia emphasizes parasite biodiversity in coral reef fish.

Abstract: Over a 7-year period, parasites have been collected from 28 species of groupers (Serranidae, Epinephelinae) in the waters off New Caledonia. Host-parasite and parasite-host lists are provided, with a total of 337 host-parasite combinations, including 146 parasite identifications at the species level. Results are included for isopods (5 species), copepods (19), monogeneans (56), digeneans (28), cestodes (12), and nematodes (12). When results are restricted to those 14 fish species for which more than five specimens were examined and to parasites identified at the species level, 109 host-parasite combinations were recorded, with 63 different species, of which monogeneans account for half (32 species), and an average of 4.5 parasite species per fish species. Digenean records were compared for 16 fish species shared with the study of Cribb et al. (2002); based on a total of 90 parasite records identified at the species level, New Caledonia has 17 new records and only seven species were already known from other locations. We hypothesize that the present results represent only a small part of the actual biodiversity, and we predict a biodiversity of 10 different parasite species and 30 host-parasite combinations per serranid. A comparison with a study on Heron Island (Queensland, Australia) by Lester and Sewell (1989) was attempted: of the four species of fish in common and in a total of 91 host-parasite combinations, only six parasites identified at the species level were shared. This suggests strongly that insufficient sampling impairs proper biogeographical or ecological comparisons. Probably only 3% of the parasite species of coral reef fish are already known in New Caledonia.

Two new species of the genus Caligus (Crustacea, Copepoda, Siphonostomatoida) from the Sea of Japan, with a note on the establishment of a new species group.

Two new species of Caligus are described from the Japanese coast of the Sea of Japan. Caligus chinglonglini sp. nov. is based on a male specimen found in a plankton sample, whereas C. kajii sp. nov. was collected from the body surface of the host flathead Platycephalus sp. These two new species can be assigned to a distinct species group, the pseudorhombi group newly named and defined by the morphology of the genital complex in both sexes, and by the structure and armature of legs 2 and 4. The species group so far accommodates 19 species including these two new species. The morphology, host specificity and zoogeography of the species group are discussed herein and keys to species groups of Caligus and to species of the C. pseudorhombi species group are provided.

Re-description of Azygokeras columbiae Koeller amp; Littlepage, 1976 (Calanoida: Aetideidae) and musculature of the male grasping antennule.

Azygokeras columbiae from Bute Inlet, British Columbia, Canada, is re-described, correcting some details and adding information not available in the original description. Azygokeras columbiae is unique amongst male Aetideidae in having the right antennule modified for grasping but without a true knee joint (geniculation) between segments XX and XXI nor a hiatus in the musculature at this joint, typical of taxa with a geniculate male antennule. Male Azygokeras have wide pivot points and arthrodial membranes between segments XXI and XXII, XXIII and XXIV and XXV and XXVI that allow greater movement in several planes than in homologous segments of Euaugaptilus and Heterorhabdus. Modifications of the terminal antennular joints allow for extensive movement in several planes associated with a series of short muscles in segments XIX to XXVI. These muscles become progressively more massive from proximal to distal on the antennule and are paired with an antagonistic muscle also increasing in mass distally.