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.

Pathology caused by introduced Neoergasilus japonicus (Copepoda: Ergasilidae) to the skin of indigenous Tilapia sparrmanii in South Africa and scanning electron microscopy study of wound-inflicting structures

Neoergasilus japonicus, a fish ectoparasite indigenous to eastern and southern Asia, has been introduced to various regions, including Europe and North and South America, where it spreads at an alarming rate. The parasite is not host-specific. It was also collected from the Vaal-Orange and Limpopo river systems in South Africa. This report describes the morphology of the wound-inflecting structures in N. japonicus and relates their morphology to the pathological effect on Tilapia sparrmanii. Host tissue with parasites attached was imbedded in resin for histological sectioning and stained with haematoxylin and eosin. Additional specimens were prepared for scanning electron microscopy. Adult female parasites attach by inserting the hooked tips of the antennae into the epidermis. The maxillulae are minute but have sharp tips. The maxillae have sharp tips on the endopod and brush-like setae on the exopod. The mandibles are armed with sharp tips. These structures are used to remove the epidermis of the host and brush it into the buccal cavity. Host tissue in the intestine confirms that adult females consume host tissue leaving the dermis exposed to opportunistic diseases. The microscopic size of the parasite prevents casual observation, and its occurrence in Africa is, therefore, probably underreported.

Mastigodiaptomus galapagoensis n. sp. (Crustacea: Copepoda: Diaptomidae), a possibly extinct copepod from a crater lake of the Galápagos archipelago

Background

A new species of a Neotropical diaptomid copepod is described based on individuals recovered from a small, almost forgotten collection of unique plankton samples from El Junco, a crater lake in San Cristóbal island, Galápagos archipelago. This copepod was regularly reported (1966-2004) as an abundant zooplankter in the lake, but it was not found in subsequent plankton surveys (2007-2018), and its specific identity remained unknown. In 2020, it was declared extinct because of introduced fish predation, rotenone treatment, and other major disturbances. The taxonomic examination of these invaluable specimens allowed us to recognize them as representing an undescribed species of the freshwater diaptomid genus Mastigodiaptomus Light, 1939.

Methods

Here, we describe the new species from El Junco crater lake, located in the San Cristóbal island a part of the Galápagos archipelago, collected with plankton nets. The description is based on detailed morphology, based on SEM and light microscopy.

Results

The taxonomic examination of these invaluable specimens allowed us to recognize them as representing an undescribed species of the freshwater diaptomid genus Mastigodiaptomus Light, 1939. The new species was readily assigned to this genus and is distinguished from its known congeners by details of (1) the male right fifth leg terminal claw and aculeus, (2) spiniform processes pattern of the right geniculate antennule segments 10-16, (3) length and structure of the spiniform process of the antepenultimate segment of the male right antennule, and (4) details of the dorsal process on the female fourth pediger. This finding represents the first report of this Neotropical copepod genus outside its original biogeographic region, the third species of a diaptomid copepod reported from insular freshwater systems, the southernmost record of Mastigodiaptomus, and the only freshwater calanoid in the Galápagos. The intriguing presence of this chiefly Neotropical copepod genus here could be related either to (1) human agency linked to pirate activities, commercial travelling by Spaniard ships, whaling activities, and intense tortoise hunting in San Cristóbal island. In the past, El Junco was the only freshwater source 600 nautical miles around, or (2) zoochory of resistant dormant stages passively transported by more than 65 migrating bird species known to settle in San Cristóbal. These two hypotheses cannot be properly tested at this time, so the explanation of the presence of this copepod will remain as a new open question in the fascinating natural history of the Galápagos.

Morphological and mitochondrial approaches of Hatschekia sargi (Copepoda: Hatschekiidae) as a parasite of Epinephelus chlorostigma

Little information is available until now about the copepods infecting different fish species. Therefore, this study aimed to provide light on siphonostomatoids infecting Epinephelus chlorostigma. Twenty fish specimens were taken from the Red Sea coast (Jeddah, Saudi Arabia), and ectoparasitic copepods were investigated. Light microscopy and molecular tools were used to examine copepods isolated from fish. Parasitological indexes were calculated and showed that 60% of the examined fish were infected with a mean intensity of 12 parasite/fish. Morphological examination revealed that this copepod species is characterized by all unique features of the genus Hatschekia with special reference to Hatschekia sargi. The taxonomic position of the recovered species in the Hatschekiidae family within Siphonostomatoida was confirmed using phylogenetic analysis based on partial mitochondrial cytochrome c oxidase subunit I (mt COI) gene sequences. The mt COI gene query revealed that the recovered Hatschekia species is closely related to Hatschekia maculatus (gb| JQ664005.1). This study discovers a new host for Hatschekia species isolated from Saudi Arabia and conducts the first genomic investigation of the mt COI gene.

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.

Genetic homogeneity coupled with morphometric variability suggests high phenotypic plasticity in the sea louse Caligus rogercresseyi (Boxshall and Bravo, 2000), infecting farmed salmon (Salmo salar) along a wide latitudinal range in southern Chile

The sea louse Caligus rogercresseyi is the most important pathogen causing "caligidosis" in the Chilean salmon industry. In this study, using cox1 gene, we evaluate the genetic variation of C. rogercresseyi from farmed Salmo salar along a latitudinal range (40°-52°S) in south Chile to determine whether morphological differences are explained by genetic or environmental factors. Female parasites were randomly collected from S. salar at five farms. Body variation was examined using multivariate analyses and genetic heterogeneity was explored with AMOVA. C. rogercresseyi exhibited significant morphometric variability among sites and parasites collected from >54°S were the longest ones. Parasites did not show genetic structure among farms. Thus, C. rogercresseyi infesting salmons is panmictic along an extensive latitudinal range in south Chile. The same genetic pattern can be explained by the frequent movement of parasitized S. salar among farms in that region. Phenotypic plasticity in parasites could be explained by natural or aquaculture-mediated environment variability. C. rogercreseyi from 54°S could favor the local spread of this disease, suggesting an immediate health risk for the recent salmon industry in that region. Further research is required to confirm genetic homogeneity of this parasite along its geographical distribution using more powerful markers (e.g. SNPs).

New species of Ergasilus von Nordmann, 1832 (Copepoda: Ergasilidae) from the gills of freshwater fishes in Patagonia, Argentina

A new parasitic copepod, Ergasilus yandemontei n. sp., is described based on 10 adult females collected from the gills of the atherinid silverside Odontesthes hatcheri (Eigenmann), in Lake Pellegrini, Neuquén Province, Patagonia, Argentina. This new copepod species is characterized by having: (i) a 2-segmented endopod on leg 1; (ii) a semi pinnate seta on the terminal segment of the exopod of leg 1; (iii) a reduced leg 5 with a single seta; (iv) aesthetascs on antennule, 1 aesthetasc on the sixth segment and 1 on the fourth segment. Ergasilus yandemontei n. sp. represents the first species described from Patagonian freshwaters. Ergasilus sieboldi var. patagonicus Szidat, 1956 described from Lake Pellegrini, should be considered a synonym of the new species described herein.

Size, not temperature, drives cyclopoid copepod predation of invasive mosquito larvae

During range expansion, invasive species can experience new thermal regimes. Differences between the thermal performance of local and invasive species can alter species interactions, including predator-prey interactions. The Asian tiger mosquito, Aedes albopictus, is a known vector of several viral diseases of public health importance. It has successfully invaded many regions across the globe and currently threatens to invade regions of the UK where conditions would support seasonal activity. We assessed the functional response and predation efficiency (percentage of prey consumed) of the cyclopoid copepods Macrocyclops albidus and Megacyclops viridis from South East England, UK against newly-hatched French Ae. albopictus larvae across a relevant temperature range (15, 20, and 25°C). Predator-absent controls were included in all experiments to account for background prey mortality. We found that both M. albidus and M. viridis display type II functional response curves, and that both would therefore be suitable biocontrol agents in the event of an Ae. albopictus invasion in the UK. No significant effect of temperature on the predation interaction was detected by either type of analysis. However, the predation efficiency analysis did show differences due to predator species. The results suggest that M. viridis would be a superior predator against invasive Ae. albopictus larvae due to the larger size of this copepod species, relative to M. albidus. Our work highlights the importance of size relationships in predicting interactions between invading prey and local predators.

Pseudanuretes anfoozi n. sp. (Copepoda: Siphonostomatoida: Caligidae) from the yellowbar angelfish Pomacanthus maculosus (Forsskål) in coral reefs off Iraq

A new species of Pseudanuretes Yamaguti, 1936 (Copepoda: Caligidae) parasitic on the gills of the yellowbar angelfish Pomacanthus maculosus (Forsskål) from a coral reef off Iraq, north-western Arabian Gulf, is described. Pseudanuretes anfoozi n. sp. belongs within a group of species characterised by the spear-like structure of leg 4. Morphologically P. anfoozi n. sp. is similar to P. papernai Kabata & Deets, 1988 in possessing an armature of I,6 on the third exopodal segment of leg 2 rather than I,7 in the other species of this group. However, P. anfoozi n. sp. can be distinguished from P. papernai by the possession of only 5 caudal setae instead of 6, and in the shape of the caudal rami, which are shorter and wider in new species. In addition, these two species differ in the shape of the genital complex of the adult female.

A new species of Brachiella (Copepoda, Siphonostomatoida, Lernaeopodidae) from Peninsular Malaysia, with relegation of two genera Charopinopsis and Eobrachiella to junior synonyms of Brachiella

Both sexes of Brachiella malayensis n. sp. are described on the basis of specimens found in the nostrils of narrow-barred Spanish mackerel Scomberomorus commerson (Lacepède) collected off Besut, Malaysia. The female of this species closely resembles those of B. magna Kabata, 1968 and B. cybii Pillai, Prabha et Balaraman, 1982 but is distinguishable mainly by the body size and the proportions of the cephalosome, posterior processes and caudal rami. While examining the male, we noticed a systematic inconsistency in some lernaeopodid genera. The genus Brachiella Cuvier, 1830, represented by its type-species Brachiella thynni Cuvier, 1830, and two monotypic genera Charopinopsis Yamaguti, 1963 and Eobrachiella Ho et Do, 1984, represented by Charopinopsis quaternia (Wilson, 1935) and Eobrachiella elegans (Richiardi, 1880), respectively, share distinct synapomorphies in the embracing (vs. pinching) elongate male maxilliped and the female trunk with a pair of long, cylindrical ventroposterior processes (in addition to a pair of modified caudal rami), both of which are involved in their unique reproductive strategy. The latter two genera are herewith relegated to junior synonyms of Brachiella.

Occurrence of Caligus asperimanus Pearse, 1951 (Copepoda: Caligidae) parasitic Lutjanus spp. (Perciformes: Lutjanidae) in the western South Atlantic

Sea lice are widespread copepods in marine teleost around the world. In this paper the first record of Caligus asperimanus Pearse, 1951 in the Western South Atlantic is documented parasitizing Lutjanus jocu and Lutjanus vivanus caught from coastal zones of Espírito Santo and Rio de Janeiro State, respectively.

Acusicola margulisae n. sp. (Copepoda: Ergasilidae) from freshwater fishes in a Nicaraguan crater lake based on morphological and molecular evidence

The ergasilid copepod Acusicola margulisae n. sp. is described based on material from three species of cichlid, Amphilophus citrinellus (Günther), Parachromis managuensis (Günther), and Oreochromis sp., and from the poecilid Poecilia mexicana (Steindachner), in the crater Lake Asososca León, Nicaragua. This constitutes the 15th species described in the genus Acusicola Cressey, 1970. The new species differs from all its congeners by the relatively longer first endopodal segment of leg 1, and the size and number of setae on second endopodal segment of leg 1. We provide the first gene sequence for a species of Acusicola. To examine the intraspecific genetic variation of the new species collected from different host species, sequences of the mitochondrial barcode region cox1 were generated. In addition, partial regions of the 18S and 28S ribosomal RNA genes were sequenced and used to infer the phylogenetic relationships of the genus Acusicola within the family Ergasilidae Burmeister, 1835. The phylogenetic trees yielded the isolates of Acusicola margulisae n. sp. as a reciprocally monophyletic lineage, and as the sister taxa of five genera of ergasilid copepods. The genus Ergasilus von Nordmann, 1832 was recovered as a paraphyletic group. These analyses indicate that phylogenetic relationships are not yet well resolved and more representative species and genera of the family are required to provide a robust classification of this highly diverse group of copepods.

The brain and the corresponding sense organs in calanoid copepods - Evidence of vestiges of compound eyes

Copepoda is one of the crustacean taxa with still unresolved phylogenetic relationships within Tetraconata. Recent phylogenomic studies place them close to Malacostraca and Cirripedia. Little is known about the morphological details of the copepod nervous system, and the available data are sometimes contradictory. We investigated several representatives of the subgroup Calanoida using immunohistochemical labeling against alpha-tubulin and various neuroactive substances, combining this with confocal laser scanning analysis and 3D reconstruction. Our results show that the studied copepods exhibit only a single anterior protocerebral neuropil which is connected to the nerves of two protocerebral sense organs: the frontal filament organ and a photoreceptor known as the Gicklhorn's organ. We suggest, on the basis of its position and the innervation it provides, that Gicklhorn's organ is homologous to the compound eye in arthropods. With regard to the frontal filament organ, we reveal detailed innervation to the lateral protocerebrum and the appearance of spherical bodies that stain intensely against alpha tubulin. A potential homology of these bodies to the onion bodies in malacostacan crustaceans and in Mystacocarida is suggested. The nauplius eye in all the examined calanoids shows the same basic pattern of innervation with the middle cup sending its neurites into the median nerve, while the axons of the lateral cups proceed into both the median and the lateral nerves. The early development of the axonal scaffold of the nauplius eye neuropil from the proximal parts of the nauplius eye nerves follows the same pattern as in other crustaceans. In our view, this specific innervation pattern is a further feature supporting the homology of the nauplius eye in crustaceans.

A new species of bomolochid Orbitacolax brevispinus n. sp. and redescription of taeniacanthid Cirracanthus inimici (Yamaguti et Yamasu, 1959) (Crustacea: Copepoda: Cyclopoida) parasitic on marine fishes of Korea

Two species of cyclopoid copepods are recorded in this study. (1) A new species of bomolochid, Orbitacolax brevispinus n. sp. (Crustacea) is described based on adult females collected from the gill filaments and inner surface of the opercula of red barracuda, Sphyraena pinguis Günther (Perciformes: Sphyraenidae), captured in Korean waters. The new species differs from its congeners by the possession of two pairs of spines on the dorsal surface of the cephalothorax located just posterior to the rostrum and a different setal formula on the distal exopodal segments of legs 2-4. (2) A taeniacanthid Cirracanthus inimici (Yamaguti et Yamasu, 1959) (Crustacea) is redescribed based on the specimens collected from the gill filaments and inner surface of the opercula of devil stinger, Inimicus japonicus (Cuvier) (Scorpaeniformes: Synancellidae). This finding is the first record in Korean waters and the first description of male. A checklist of parasitic copepods of the families Bomolochidae Sumpf, 1871 and Taeniacanthidae Wilson, 1911of Korea is also provided.

A new species of Chondracanthus (Cyclopoida: Chondracanthidae) parasitic on deep-sea Dibranchus spongiosa(Lophiiformes: Ogcocephalidae) from the Eastern Central Pacific

A total of 228 sampling stations were visited for benthic fauna during a series of oceanographic cruises in the Gulf of California, west coast of the Baja California Peninsula, and Eastern Central Pacific from year 1991 to 2014. Among others, three fish species of the genus Dibranchus were caught in 28 stations. Of these, D. spongiosa was the most common and abundant. Close inspection of this fish revealed the presence of a new species of parasitic copepod, Chondracanthus dibranchi sp. nov., found in the gill cavity of seven specimens of D. spongiosa. Chondracanthus dibranchi sp. nov. seems to be morphologically related to C. psetti and C. janebennettae. The female of C. janebennettae can be separated from these other two congeners by the general shape of the head and abdomen, by the number of teeth on the mandibular blade, and by the general body shape. Chondracanthus psetti and C. dibranchi sp. nov. share the relative lengths of legs 1 and 2, the relative size and shape of the genito-abdomen, and the conical attenuating lateral processes on the trunk of the female. The females of these two species can be separated by the shape and armature of the antennule, shape of the antenna, the claw of the maxilliped, the rami of leg 1 and 2 and posterior processes, the head region, and by the position of the lateral processes of the trunk. An amendment to Tang's (2007) key to the species of Chondracanthus is proposed.

From local adaptation to ecological speciation in copepod populations from neighboring lakes

Continental copepods have been derived from several independent invasive events from the sea, but the subsequent evolutionary processes that account for the current diversity in lacustrine environments are virtually unknown. Salinity is highly variable among lakes and constitutes a source of divergent selection driving potential reproductive isolation. We studied four populations of the calanoid copepod Leptodiaptomus cf. sicilis inhabiting four neighboring lakes with a common history (since the Late Pleistocene) located in the Oriental Basin, Mexico; one lake is shallow and varies in salinity periodically (1.4-10 g L(-1)), while three are deep and permanent, with constant salinity (0.5, 1.1 and 6.5 g L(-1), respectively). We hypothesized that (1) these populations belong to a different species than L. sicilis sensu stricto and (2) are experiencing ecologically based divergence due to salinity differences. We assessed morphological and molecular (mtDNA) COI variation, as well as fitness differences and tests of reproductive isolation. Although relationships of the Mexican populations with L. sicilis s.s. could not be elucidated, we identified a clear pattern of divergent selection driven by salinity conditions. The four populations can still be considered a single biological species (sexual recognition and hybridization are still possible in laboratory conditions), but they have diverged into at least three different phenotypes: two locally adapted, specialized in the lakes of constant salinity (saline vs. freshwater), and an intermediate generalist phenotype inhabiting the temporary lake with fluctuating salinity. The specialized phenotypes are poorly suited as migrants, so prezygotic isolation due to immigrant inviability is highly probable. This implication was supported by molecular evidence that showed restricted gene flow, persistence of founder events, and a pattern of allopatric fragmentation. This study showed how ecologically based divergent selection may explain diversification patterns in lacustrine copepods.

Factors determining the average body size of geographically separated Arctodiaptomus salinus (Daday, 1885) populations

Arctodiaptomus salinus inhabits water bodies across Eurasia and North Africa. Based on our own data and that from the literature, we analyzed the influences of several factors on the intra- and inter-population variability of this species. A strong negative linear correlation between temperature and average body size in the Crimean and African populations was found, in which the parameters might be influenced by salinity. Meanwhile, a significant negative correlation between female body size and the altitude of habitats was found by comparing body size in populations from different regions. Individuals from environments with highly varying abiotic parameters, e.g. temporary reservoirs, had a larger body size than individuals from permanent water bodies. The changes in average body mass in populations were at 11.4 times, whereas, those in individual metabolic activities were at 6.2 times. Moreover, two size groups of A. salinus in the Crimean and the Siberian lakes were observed. The ratio of female length to male length fluctuated between 1.02 and 1.30. The average size of A. salinus in populations and its variations were determined by both genetic and environmental factors. However, the parities of these factors were unequal in either spatial or temporal scales.

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.

Parasitic copepods from two species of commercial fishes collected off Iraq, with description of Hatschekia shari n. sp

Two species of parasitic copepods, including one new species, are described based on specimens collected from off Basrah, Iraq (Arabian Gulf). Hatschekia shari n. sp. (Siphonostomatoida: Hatschekiidae) was found from the gill filaments of the spangled emperor Lethrinus nebulosus (Forsskål) (Perciformes: Lethrinidae). The new species is characterised by the following characters in the female: a rectangular cephalothorax with dorsal frame composed of two short and one long bifid longitudinal bars, connecting to one short and one long latitudinal bars; elongate, cylindrical trunk without posterolateral processes or lobes; absence of parabasal papillae; and antennae bearing middle segments without narrow median part and with terminal claws without basal conical processes. Bactrochondria formosana Ho, Lin & Liu, 2011 (Cyclopoida: Chondracanthidae) was found on the gill filaments of the largescale tonguesole Cynoglossus arel (Bloch & Schneider) (Pleuronectiformes: Cynoglossidae). Close comparison of the specimens of B. formosana collected from off Iraq with the original description revealed some differences in elements and ornamentations on the body and appendages. Our finding of B. formosana represents not only a new record from the Indian Ocean but also from a new host.

Variation in Body Shape across Species and Populations in a Radiation of Diaptomid Copepods

Inter and intra-population variation in morphological traits, such as body size and shape, provides important insights into the ecological importance of individual natural populations. The radiation of Diaptomid species (~400 species) has apparently produced little morphological differentiation other than those in secondary sexual characteristics, suggesting sexual, rather than ecological, selection has driven speciation. This evolutionary history suggests that species, and conspecific populations, would be ecologically redundant but recent work found contrasting ecosystem effects among both species and populations. This study provides the first quantification of shape variation among species, populations, and/or sexes (beyond taxonomic illustrations and body size measurements) to gain insight into the ecological differentiation of Diaptomids. Here we quantify the shape of five Diaptomid species (family Diaptomidae) from four populations each, using morphometric landmarks on the prosome, urosome, and antennae. We partition morphological variation among species, populations, and sexes, and test for phenotype-by-environment correlations to reveal possible functional consequences of shape variation. We found that intraspecific variation was 18-35% as large as interspecific variation across all measured traits. Interspecific variation in body size and relative antennae length, the two traits showing significant sexual dimorphism, were correlated with lake size and geographic location suggesting some niche differentiation between species. Observed relationships between intraspecific morphological variation and the environment suggest that divergent selection in contrasting lakes might contribute to shape differences among local populations, but confirming this requires further analyses. Our results show that although Diaptomid species differ in their reproductive traits, they also differ in other morphological traits that might indicate ecological differences among species and populations.

Effect of temperature and salinity on egg hatching and description of the life cycle of Lernanthropus latis (Copepoda: Lernanthropidae) infecting barramundi, Lates calcarifer

The parasite Lernanthropus latis (Copepoda: Lernanthropidae) is a major threat to the sustained mariculture of barramundi, Lates calcarifer (Perciformes: Latidae). We investigated the effect of water temperature and salinity on egg hatching success of L. latis and describe the life cycle for the first time. Wild and sea-caged L. calcarifer examined in tropical north Australia exhibited similar parasite prevalence (range: 80-100%) and mean parasite intensity (range: 3-6), whereas land-based maricultured fish were not infected. Hatching success and time to first and last hatch was determined for a range of water temperature (22, 30, 32 and 34°C) and salinity (0, 11, 22, 35 and 40‰) combinations representing current and predicted climate conditions. There was a significant interaction between water temperature and salinity on the hatching success of L. latis nauplii. Eggs hatched in all temperature treatments, with the greatest hatching success at 30°C and 32°C (98 and 92% success, respectively) in 35‰. Hatching did not occur at 0‰ and was severely reduced at 11‰ (1.6% success). Hatching began within 6h at all water temperatures with >95% of eggs hatched within 30h at 30, 32 and 34°C and within 60h at 22°C. Adult parasites differed from the original description by the presence of the parabasal flagellum, small setae on the legs and caudal rami and minor incongruences regarding morphological measurements. The life cycle of L. latis includes three free living stages and five parasitic stages. Although L. latis exhibits broad environmental tolerance, freshwater can be used as an effective management strategy to break the life cycle in aquaculture.

Infestation of gill copepod Lernanthropus latis (Copepoda: Lernanthropidae) and its effect on cage-cultured Asian sea bass Lates calcarifer

Twenty Asian sea bass Lates calcarifer from a floating cage in Bt. Tambun, Penang were examined for the presence of parasitic gill copepod, Lernanthropus latis. The prevalence of L. latis was 100% with the intensity of infection ranging from 1 to 18 parasites per host or 3.75 of mean intensity. Female parasites having oblong cephalothorax and egg-strings were seen mainly on the entire gill of examined Asian sea bass. The infected gill of Asian sea bass was pale and had eccessive mucus production. Under light and scanning electron microscopies (SEM), L. latis was seen grasping or holding tightly to the gill filament using their antenna, maxilla and maxilliped. These structures are characteristically prehensile and uncinate for the parasite to attach onto the host tissue. The damage was clearly seen under SEM as the hooked end of the antenna was embedded into the gill filament. The parasite also has the mandible which is styliform with eight teeth on the inner margin. The pathological effects such as erosion, haemorrhages, hyperplasia and necrosis along the secondary lamellae of gill filaments were seen and more severe at the attachment site. The combined actions of the antenna, maxilla and maxilliped together with the mandible resulted in extensive damage as L. latis attached and fed on the host tissues.

Contrasting ecosystem-effects of morphologically similar copepods

Organisms alter the biotic and abiotic conditions of ecosystems. They can modulate the availability of resources to other species (ecosystem engineering) and shape selection pressures on other organisms (niche construction). Very little is known about how the engineering effects of organisms vary among and within species, and, as a result, the ecosystem consequences of species diversification and phenotypic evolution are poorly understood. Here, using a common gardening experiment, we test whether morphologically similar species and populations of Diaptomidae copepods (Leptodiaptomus ashlandi, Hesperodiaptomus franciscanus, Skistodiaptomus oregonensis) have similar or different effects on the structure and function of freshwater ecosystems. We found that copepod species had contrasting effects on algal biomass, ammonium concentrations, and sedimentation rates, and that copepod populations had contrasting effects on prokaryote abundance, sedimentation rates, and gross primary productivity. The average size of ecosystem-effect contrasts between species was similar to those between populations, and was comparable to those between fish species and populations measured in previous common gardening experiments. Our results suggest that subtle morphological variation among and within species can cause multifarious and divergent ecosystem-effects. We conclude that using morphological trait variation to assess the functional similarity of organisms may underestimate the importance of species and population diversity for ecosystem functioning.

Species of Taeniacanthus Sumpf, 1871 (Crustacea: Copepoda: Taeniacanthidae) parasitic on boxfishes (Tetraodontiformes: Aracanidae and Ostraciidae) from the Indo-West Pacific region, with descriptions of two new species

Two new copepod species of the genus Taeniacanthus Sumpf, 1871 (Cyclopoida: Taeniacanthidae) are described from boxfishes (Aracanidae and Ostraciidae) caught in the Indo-West Pacific region: T. larsonae n. sp. from Ostracion nasus Bloch in the Arafura Sea and off Australia and Tetrosomus concatenatus (Bloch) off Japan; and T. thackerae n. sp. from O. immaculatus Temminck & Schlegel off Palau, O. rhinorhynchos Bleeker off Australia, Lactoria cornuta (Linnaeus) and Ostracion sp. off Japan, and Kentrocapros aculeatus (Houttuyn) in the East China Sea. T. larsonae n. sp. differs from its congeners by having several rows of spinules on the large pectinate process of the antenna and by differences in the shape of the sclerotised plates on the rostral area and structure of the maxilliped. T. thackerae n. sp. can be distinguished from its congeners by differences in the shape of the sclerotised plates on the rostral area, the structure of the maxilliped and ornamentation pattern of legs 1-4. Supplemental information for the female of Taeniacanthus ostracionis (Richiardi, 1870) and T. moa (Lewis, 1967), as well as the first description of the male of T. moa, are also provided based on new material collected from ostraciid hosts caught in the Arafura Sea and off Australia, Indonesia and Japan. The four taeniacanthid species reported from boxfishes exhibit variable levels of host-specificity and have broad geographical ranges within the Indo-West Pacific region.

Diversity of the Monstrilloida (Crustacea: Copepoda)

Monstrilloid copepods are protelean parasites of different groups of marine benthic invertebrates. Only their first naupliar, preadult, and adult phases are planktonic. Monstrilloids are currently represented by more than 115 nominal species contained in four genera. Its taxonomic knowledge has been hampered by nomenclatural and descriptive problems derived from their peculiar ontogeny and poor definitions of taxa. One of the most important difficulties is that of matching males to females. The only reliable methods to link the sexes of a species are the confirmation of particular apomorphies shared by both sexes, finding both sexes in the same host or as a pre-copulatory male-female pair in the plankton, or by the use of molecular markers. A general overview of the morphology of the group and its life cycle is provided herein. Recently, upgraded descriptive standards have been established and the relevance of redescribing taxa based on type and museum specimens has been demonstrated. The rate of species description per decade has had several peaks between 1840 and 2010: (1971–1980, 1991–2000, 2001–2010), each related to the activity of a few researchers. An analysis of the world distribution of published records of the Monstrilloida revealed that the Northeast Atlantic is the best studied region (45% of all records), followed by the Northwestern Atlantic (17%); the least surveyed areas include regions of the southern hemisphere (less than 3%). The Northeast Atlantic region harbors the highest number of known species (32 nominal species), followed by the Caribbean Sea/Gulf of Mexico (24), the Mediterranean/Black Sea (19), Indonesia-Malaysia-Philippines region (17), Japanese waters (17), and the Brazil-Argentina area (16). Other than these generalized patterns, little can be concluded concerning the biogeography of the group. Many species records are doubtful or improbable, and purportedly cosmopolitan nominal species are being revealed as species complexes yet to be studied.

Ergasilus boleophthalmi sp. n. (Copepoda: Ergasilidae) parasitic on gobiid fishes from Shatt Al-Basrah Canal, South of Iraq

A new species of Ergasilus von Nordmann, 1832 (Copepoda: Ergasilidae) parasitic on the gills of two gobiid fishes Boleophthalmus dussumieri Valenciennes and Bathygobius fuscus (Rüppell, 1930) from Shatt Al-Basrah Canal, Iraq, is described. The new species differs from all its congeners by a combination of character states including the shape of the body, and the structure and armature of the swimming legs.

Three new species of Hatschekia Poche, 1902 (Copepoda: Siphonostomatoida: Hatschekiidae) parasitic on boxfishes (Pisces: Tetraodontiformes: Aracanidae and Ostraciidae) in Japanese waters

Three new species of Hatschekia Poche, 1902 are described from the gill filaments of three species of boxfishes captured off southern Japan: H. pseudostracii n. sp. on Kentrocapros aculeatus (Houttuyn) (Aracanidae); H. bibullae n. sp. on Lactoria diaphana (Bloch & Schneider) (Ostraciidae); and H. kuroshioensis n. sp. on Tetrosomus concatenates (Bloch) (Ostraciidae). Of the 93 currently valid species in the genus, these new species differ from the 87 species which lack four stout processes on the posterior margin of the intercoxal sclerites of legs 1 and 2. Those processes are present on the remaining six species and the three new species. Of these nine species, H. pseudostracii n. sp. is distinguished by having a T-shaped chitinous frame on the cephalothorax, the leg 1 exopod twice as long as the endopod and a small parabasal papilla. H. bibullae n. sp. can be differentiated by a combination of morphological features as follows: a well-developed, thumb-shaped parabasal papilla, the leg 1 exopod twice as long as the endopod and a trunk lacking posterior lobes. H. kuroshioensis n. sp. can be recognised by bearing a T-shaped chitinous frame on the cephalothorax, the leg 1 exopod is three times as long as the endopod and the trunk lacks posterior lobes.

Three new species of Hatschekia Poche, 1902 (Copepoda: Siphonostomatoida: Hatschekiidae) parasitic on Abalistes filamentosus (Pisces: Tetraodontiformes: Balistidae) from off Okinawa, Japan

Three new species of the copepod genus Hatschekia Poche, 1902, H. lima n. sp., H. cylindrus n. sp. and H. sunaoi n. sp., are described from the gill filaments of a triggerfish, Abalistes filamentosus Matsuura & Yoshino, caught off the Ryukyu Islands, Okinawa, Japan. These new species share an unusual morphological character, i.e. four stout posterior spines on the intercoxal sclerites of legs 1 and 2. H. lima n. sp. differs from its congeners in having a robust inner lobe on the maxillule and leg 3 with a swollen basal lobe. H. cylindrus n. sp. is distinguishable from its congeners by having a cephalothorax fused to the trunk and a double-semicircular chitinous frame. H. sunaoi n. sp. is characterised by leg 3 with a swollen basal lobe and an oval cephalothorax.

Serial EM analysis of a copepod larval nervous system: Naupliar eye, optic circuitry, and prospects for full CNS reconstruction

The medial eye and optic center of the first nauplius of Dactylopusia (=Dactylopodia) tisboides, a harpacticoid copepod, were reconstructed from serial EM micrographs. Axons from the eye project to a set of matching cartridges defined by glial cells processes, and input is then processed in sequence through two synaptic fields. A single class of local relay neurons provides the main pathway between these, subject to modulatory input from a class of densely stained neurons with distinctive dense terminals. The importance of other outside sources of synaptic input to the second synaptic field indicates that the latter is a major site for integrating the optic input with signals originating elsewhere in the CNS. This accords with physiological data on the shadow response in barnacles, whose visual system is also derived from a naupliar eye. With a body length of ca. 80microns, copepod larvae like that of Dactylopusia are arguably among the smallest functional metazoans with a complex nervous system. Hence they are promising subjects for full reconstruction of neural circuitry at the EM level that could, in principle, reveal where key decision-making functions are localized.

Parasitic fauna of the lake brown trout, Salmo trutta lacustris (Salmonidae), a little known endemic fish from Polish waters

The lake brown trout is a salmonids fish regarded as a stationary form of the migratory trout. Within 2003-2004, 31 lake brown trout (Salmo trutta lacustris L.) from Lake Wdzydze (Poland), were examined for the presence of parasites following commonly used procedures. The parasites found represented Digenea: Diplostomum sp., Posthodiplostomum cuticola (Nordmann, 1832), Sphaerostomum globiporum (Rudolphi, 1802); Cestoda: Eubothrium crassum (Bloch, 1779), Triaenophorus nodulosus (Pallas, 1781); Acanthocephala: Acanthocephalus lucii (Müller, 1776); Copepoda: Ergasilus sieboldi Nordmann, 1832, and Hirudinea: Piscicola geometra (Linnaeus, 1761). The overall infection level amounted to 96.7%, 249.4, and 1-440. The copepod E. sieboldi was the most frequent parasite (93.5%, 257.4, 64-438). Lake brown trout from the Lake Wdzydze are very heavily infected by parasites dominated by the copepod E. sieboldi.

A new species of Ergasilus (Copepoda:Cyclopoida:Ergasilidae) from coastal fishes of the Mexican Pacific

A new species of the cyclopoid copepod genus Ergasilus von Nordmann, 1832 is described based on adult female specimens removed from the gills of the yellow snapper Lutjanus argentiventris (Peters) and the yellowfin snook Centropomus robalito Jordan et Gilbert from a Pacific coastal system of Mexico. The new species Ergasilus davidi sp. n. has a combination of characters that includes a two-segmented first leg endopod, a three-segmented fourth leg endopod, and the presence of a single seta on the first antennular segment. These characters are shared with 14 other congeners known mainly from Brazil and North America. It differs from these other species in the armature and ornamentation of legs 1 and 4, the shape of the body, and the structure and ornamentation of the antennae. Additional characters include a maxillar basis armed with blunt teeth, distally bent maxillular setae, and naked margins of first exopodal segments of legs 2-4. Previous regional records of Ergasilus sp. from both fish species are probably assignable to E. davidi. The prevalence and intensity of infection was estimated for both teleost species and agrees to previous data. Based on other records of the genus from several other teleost species in the surveyed area and adjacent zones of the Eastern Pacific, it is presumed that the new species could have a wider range of hosts. The new species represents the first Ergasilus described from Mexican waters of the Pacific. Overall, the genus remains poorly known in Central America and Mexico.

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.

Naricolax hoi n. sp. (Cyclopoida: Bomolochidae) from Arius maculatus (Siluriformes: Ariidae) off Taiwan and a redescription of N. chrysophryenus (Roubal, Armitage & Rohde, 1983) from a new host, Seriola lalandi (Perciformes: Carangidae), in Australian waters

We propose that Naricolax stocki (Roubal, 1981) (Cyclopoida: Bomolochidae) of Ho & Lin (2005), reported from the spotted catfish Arius maculatus (Thunburg) off Taiwan, represents a new species, N. hoi n. sp. N. hoi can be distinguished from six known congeners by the shape of the rostral area, the maxillary armature and the structural details of legs 3 and 4. N. chrysophryenus (Roubal, Armitage & Rohde, 1983) is redescribed on the basis of recently collected material from wild and farmed yellowtail kingfish Seriola lalandi Valenciennes in southern and eastern Australian waters, providing the first record of Naricolax Ho, Do & Kasahara, 1983 from a carangid host. A key to the species of Naricolax is provided.

Extraordinary host switching in siphonostomatoid copepods and the demise of the Monstrilloida: Integrating molecular data, ontogeny and antennulary morphology

Copepods exhibit an astounding variety of lifestyles, host associations and morphology, to the extent that their crustacean affinities may be obscured. Relationships among the ten copepod orders based on morphological characters remain equivocal. Here we test the ordinal status of the enigmatic Monstrilloida using SSU rDNA gene sequences, comparative morphological data (antennulary sensory interface) and ontogenetic data (caudal ramus setation patterns). Bayesian analysis unexpectedly revealed the Monstrilloida are nested within a fish-parasitic clade of the Siphonostomatoida and share a common ancestor with the stem species of the caligiform families (sea-lice). This unforeseen relationship is congruent with both antennulary and caudal ramus morphology. The divergence of the monstrilloids from an ectoparasitic, vertebrate-associated ancestor involved radical changes in host utilization, body plan and life cycle strategy, a combination rarely observed and probably unique in metazoan parasites. Adult monstrilloids secondarily returned to a free-living, predator-exposed mode of life and we postulate the pressure on maintaining a functional approaching-predator detection system has progenetically delayed the suppression (as in post-copepodid caligiform instars) of the 5-point antennulary sensory array. The homoplastic evolution of the frontal filament in Siphonostomatoida is discussed.

New genus and species of eudactylinid (Siphonostomatoida: Copepoda) from gill lamellae of ornate eagle rays, Aetomylaeus vespertilio (Myliobatidae), collected in the Beagle Gulf off northern Australia

Janinecaira darkthread n. gen., n. sp. (Eudactylinidae, Siphonostomatoida, Copepoda) infects gills of the ornate eagle ray Aetomylaeus vespertilio (Bleeker, 1852) (Myliobatidae, Myliobatiformes) in the Beagle Gulf (Timor Sea, eastern Indian Ocean) off northern Australia. The adult female of Janinecaira darkthread n. sp. is most easily distinguished from other eudactylinids (Eudactylinidae) by its long genital complex that comprises about 86-90% of the total body length. A diagnostic key to genera of Eudactylinidae based on adult females is provided.

Three species of Caligus Müller, 1785 (Copepoda: Caligidae) parasitic on Caranx spp. (Teleostei: Carangidae) off Taiwan

Three species of sea-lice (Siphonostomatoida: Caligidae) parasitic on marine fishes of the genus Caranx off Taiwan are reported. They are: Caligus fortis Kabata, 1965 on Caranx ignobilis (Forsskål); Caligus robustus Bassett-Smith, 1898 on Caranx sexfasciatus Quoy & Gaimard; and Caligus inanis n. sp. on Caranx ignobilis. Caligus robustus is a widely distributed species, but this is the first report of C. fortis outside the Australian and Indian regions. The new species is distinguished from its congeners in lacking postantennal process and carrying a pair of tiny, tooth-like, sharp protuberances on the posterior margin of the cephalothoracic shield.

A new genus and species of hyponeoid (Copepoda) from the olfactory sac of a gulper shark Centrophorus sp. (Squaliformes: Centrophoridae) captured off Madagascar

Greeniedeets buccaneer n. gen., n. sp. (Hyponeoidae, Siphonostomatoida, Copepoda) infects the olfactory sac of a gulper shark, Centrophorus sp. (Centrophoridae, Squaliformes) off Madagascar. The adult female of Greeniedeets buccaneer n. gen., n. sp. is most easily distinguished from other hyponeoids (Hyponeoidae) by its possession of a genital complex that is horseshoe shaped in dorsal view. An amended family diagnosis for Hyponeoidae and diagnostic key to hyponeoids based on adult females are provided.

Two new species of taeniacanthid copepods (Poecilostomatoida) parasitic on marine fishes of Taiwan

Two new species of copepods (Poecilostomatoida Taeniacanthidae) parasitic on fishes of Taiwan are reported. They are: Irodes parupenei n. sp. from Parupeneus spilurus (Bleeker) and P. multifasciatus (Quoy & Gaimard), and Taeniacanthus spiniferus n. sp. from Acanthocepola limbata Valenciennes. I. parupenei is characteristic in having nine (instead of eight) elements on the terminal segment of leg 2 exopod, a spiniform element (instead of a long, plumose seta) on the medial margin of the proximal segment of leg 4 endopod, and thee spines and one long, naked seta (rather than four short setae) on the slender (rather than spatula-like), terminal segment of leg 5. T. spiniferus is distinguished from its 38 congeners in carrying a pair of sharp tines in the ventral area of the rostrum.

First report of Pennella balaenopterae Koren and Danielssen, 1877 (Copepoda: Pennelidae) from Turkey

A parasitic copepod, Pennella balaenopterae Koren and Danielssen, 1877 (Copepoda: Pennelidae), has been reported from the fin whale, Balaenoptera physalus (Cetacaea: Mysticeti), which was found dead on the Avluk beach (Yumurtalik seaport, Iskenderun Bay, Northeastern Mediterranean coast of Turkey) in 6 May, 2002. This is the first report of Pennella balaenopterae in the Turkish seas.

A new species of Prohatschekia Nunes-Ruivo, 1954 (Copepoda: Hatschekiidae) parasitic on Scorpaena elongata (Cadenat) off Algeria

A new species of parasitic copepod, Prohatschekia mediterranea n. sp. (Siphonostomatoida: Hatschekiidae), is described from a scorpaenid fish, Scorpaena elongata, collected off Algeria. This is the seventh species of Prohatschekia Nunes-Ruivo, 1954 to be described and the first record of the genus from the Mediterranean Sea. The new species is most closely related to P. cremouxi Nunes-Ruivo, 1954, known from a congeneric host collected in Senegal. A key is provided to distinguish the new species from other members of the genus.

Lamproglena hepseti n. sp. (Copepoda: Lernaeidae), a gill parasite of the African pike Hepsetus odoe (Bloch) from the Okavango River and Delta, Botswana

During surveys of the biodiversity of fish parasites in the Okavango River and Delta, Botswana, specimens of Lamproglena von Nordmann, 1832 were found associated with the African pike Hepsetus odoe (Bloch). This Lamproglena species distinctly differs from all known species based on morphological features, in particular the cephalothorax and the maxilliped; it is described as L. hepseti n. sp. and is specific to its host, the African pike.

Comparative description of males of two species of Achtheres von Nordmann, 1832 (Copepoda: Siphonostomatoida: Lernaeopodidae) infecting zander and European perch

Achtheres percarum von Nordmann, 1832 and Achtheres sandrae Gadd, 1901 (Lernaeopodidae) are common parasitic copepods infecting fishes in Eurasia. The former is specific to perch, Perca fluviatilis L., while the latter, to zander, Sander lucioperca (L.). Until recently these copepods have been regarded a single species. The present study was intended to analyse details of male morphology and provide their complete descriptions with differential diagnosis. Males of A. percarum and A. sandrae were collected from perch and zander at Lake Dabie (north-western Poland). The males of A. sandrae are larger than those of A. percarum. They also differ in proportions of the first antenna, mandibular denticulation, structure of the first maxilla, and the armament of caudal ramus. The reported differences in male morphology constitute a conclusive confirmation of the separate identity of the two species.

Nesippus orientalis Heller, 1868 (Pandaridae: Siphonostomatoida): descriptions of the adult, young and immature females, a first description of the male and aspects of their functional morphology

Nesippus orientalis Heller, 1868, a cosmopolitan species found in the mouth and on the gill-arches of a number of shark hosts, is distinguished from other species by the presence of dorsal plates on the fourth thoracic segment. Specimens were collected from various sharks caught in the nets of the Natal Sharks Board, off the coast of KwaZulu-Natal, South Africa. Collected specimens were preserved in 70% ethanol and studied using the wooden slide technique and scanning electron microscopy. Careful examination of adult females revealed features previously not described in detail. Furthermore, some female specimens were still grasping the placoid scales of their hosts. These specimens showed how the maxillipeds are used to clasp the host. Immature, young females and males, some still attached to the young females, were also collected. The males use their maxillipeds, which have a slightly different structure to those of the female, to hold onto the females.