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Variation and Systematic Problems in a Group of Lernaeid Copepods
Abstract
Les Copépodes parasites du complexe cyprinacea-barnimiana du genre Lernaea sont discutés. L'ancre de L. barnimiana est extrêmement variable en forme. Cette variabilité est en grande partie en corrélation avec l'emplacement de l'attache. La variabilité de l'ancre de L. cyprinacea, également bien marquée, présente une corrélation moindre avec l'emplacement de l'attache, peut-être parce qu'elle est plus petite que celle de L. barnimiana. Une Lernaea qui, trouvée dans le Lac Victoria (Afrique orientale), est très étroitement liée à son hôte (deux espèces de Tilapia), n'est a mon avis qu'une forme de L. cyprinacea. C'est la première fois qu'on signale cette espèce en Afrique, et il est possible qu'elle ait envahi récemment ce continent par la voie du Nil.
... Cosmopolitan parasitic copepods belonging to the genus Lernaea Linnaeus, 1758 (Cyclopoida: Lernaeidae) can infect many different freshwater fish species [1][2][3], causing lernaeosis, a disease that can cause serious pathogenic effects on their hosts. The taxonomy of this genus is still largely unresolved due to the existence of an exceptionally large number (109) of recorded nominal species [4], a small number of morphological traits useful for species identification, a high degree of intraspecific morphological variability, and a lack of clear morphological distinction between some species [5][6][7][8]. As a result, almost half (48) of the nominal species are believed to be synonymous [4]. ...
... However, experimental infection studies put a major question mark over the validity of the prevailing taxonomy of the genus by showing that the anchor exhibits high intraspecific variation [5,11]. For example, Harding [6] and Fryer [7] have shown that the growth and orientation of the anchor are affected by the anatomy of the host. As discussed by Fryer [7], Yashouv [12] collected larvae from adults settled on one host and then successfully infected another fish species (host not specified by Fryer) and tadpoles with these larvae; most of the specimens from carp and buffalo fish were assignable to L. cyprinacea, but specimens from Gambusia were morphologically notably different from L. cyprinacea. ...
... For example, Harding [6] and Fryer [7] have shown that the growth and orientation of the anchor are affected by the anatomy of the host. As discussed by Fryer [7], Yashouv [12] collected larvae from adults settled on one host and then successfully infected another fish species (host not specified by Fryer) and tadpoles with these larvae; most of the specimens from carp and buffalo fish were assignable to L. cyprinacea, but specimens from Gambusia were morphologically notably different from L. cyprinacea. A subsequent study of Poddubnaya (1973) even further casted the shadow of doubt over the usefulness of the anchor for species identification: when different hosts were infected by larvae from a single batch of L. elegans (a synonym of L. cyprinacea) eggs, adult parasites exhibited different anchor characteristics, some of which corresponded to other described species of Lernaea [13]. ...
Background:
Species belonging to the genus Lernaea are cosmopolitan parasites that can infect many different freshwater fish hosts. Due to a high degree of morphological intraspecific variability and high levels of interspecific similarities, their classification is extremely difficult and controversial. Although the suitability of the shape of cephalic horns has been questioned decades ago by some experimental infection studies, this character still plays the central role in the identification of Lernaea spp.
Methods:
We used the nominal species Lernaea cyprinacea and Lernaea cruciata to test the hypothesis that the shape of the anchor can exhibit host-induced morphological variability, and that the two taxa may be synonymous.
Results:
We examined 517 wild or farmed specimens of five host fish species (four cyprinids and a mosquitofish), and found that all 16 parasite specimens collected from mosquitofish could be morphologically identified as L. cruciata, whereas the remaining 25 parasite specimens were all identified as L. cyprinacea. We experimentally infected goldfish and mosquitofish specimens with offspring (copepodids) of a single L. cyprinacea specimen: the adult parasites from goldfish were morphologically identified as L. cyprinacea, and those from mosquitofish as L. cruciata. We then used molecular data to corroborate that all these specimens are conspecific.
Conclusions:
Our results suggest that L. cyprinacea and L. cruciata may be synonyms, misidentified as different species as a result of host-induced morphological variation. Given the current shortage of molecular data for the genus Lernaea, in order to resolve the taxonomy of this genus (determine the exact number of species), future studies should aim to sequence as much molecular data as possible, and conduct further experimental infections.
... Kabata (1983) da una clave para los géneros de la Familia Lernaeidae. Debido a la variabilidad en la morfología de las anclas, y a que ésta se modifica según la resistencia que encuentran durante su desarrollo en el pez (Fryer, 1961;Thurston, 1969), se recomienda que la identificación se realice a partir de una variedad de especímenes y muestras (Shariff y Sommerville, 1990). ...
... Las hembras de la Familia Lernaeidae introducen sus extremos anteriores en los tejidos de los hospedadores, profundizando hasta varios centímetros, donde se fijan mediante el desarrollo del órgano de anclaje al que le debe el género su nombre vulgar de gusanos ancla (Kabata, 1970). La taxonomía del grupo es compleja, siendo el tamaño y la forma del órgano de anclaje dos de las características morfológicas principales utilizadas para su diferenciación a nivel de especie; sin embargo, esta estructura muestra diferencias morfológicas dentro de la misma especie según las especies hospedadoras, el sitio de anclaje (Hoole y cols., 2001) e incluso según la resistencia que encuentren durante su desarrollo en el pez (Fryer, 1961;Thurston, 1969). ...
The current PhD Thesis has a double approach: qualitative and quantitative. The
qualitative part was based on the identification of the different parasites found in the
fish of the mid and upper river Duero basin, through the morphological description
and classification in different taxonomic groups. The quantitative part was designed as
a transversal epidemiological study, with the aim of establishing the prevalence and
intensity of infection of the different parasite groups identified, as well as establishing
the most important associations between those groups and the risk factors that could
be involved.
The aim of the study was the species belonging to the Family Cyprinidae, the most
characteristic and diverse in its aquatic ecosystems: Iberian barbel (Barbus bocagei),
“bermejuela” (Chondrostoma arcasii), Duero nase (Chondrostoma duriense), Iberian chub
(Squalius carolitertii), Iberian gudgeon (Gobio lozanoi), Eurasian minnow (Phoxinus
phoxinus) and tench (Tinca tinca). The fish was chosen as sampling unit, and sampling
which was randomized, stratified and distributed through three seasons (spring,
summer and autumn), since 2005 to 2007.
Seven sampling stations were selected: two of them in the upper part of the rivers
Revinuesa and Ucero; four in the middle part of the rivers Arlanza, Duratón, Eresma y
Ucero; and a single station in a tench fish farm.
In total, eleven taxonomic groups were identified: three protozoans (Ichthyophthirius
multifiliis, Tripartiella sp. y Myxobolus sp.), two monogeneans (Gyrodactylus sp. y
Dactylogyrus sp.), two crustacean copepods (Ergasilus sieboldi y Lernaea cyprinacea), one
digenetic trematode (Hysteromorpha triloba) and one mollusc glochidium (Unio sp.).
For every parasite, prevalences and intensities of infection were measured in those fish
in which they were identified, as well as the main risk factors associated to its presence,
both intrinsic (species, sex, reproductive state (spawning), somatic condition factor…)
and extrinsic (location, seasonality, water physic-chemical and microbiological water
quality…).
In general terms, our results show the close link between the different environmental
parameters which are characteristic of the studied region, the adaptations in the life
cycles and strategies of the different species of cyprinids to them, as well as the
adaptation of the different taxonomic groups of parasites both to the environment and
to the host in/on which they develop their life cycles.
... Due to these factors and some morphological differences between northwestern (Asian) and northeastern (North-American) Pacific populations, it remains unclear whether these populations all belong to the same species, or whether the Asian populations may have to be renamed to Argeia pingi [30,31]. Previously, taxonomic hypotheses for this genus were put forward exclusively on the basis of morphology, but this approach is often an unreliable taxonomic tool in parasitic crustaceans due to a limited number of taxonomically informative traits and hostinduced morphological variability [19,32,33]. However, molecular data for this genus remain remarkably scarce: only two GenBank entries are currently (May 2020) available for the entire genus, cox1 (mitochondrial) and 18S (nuclear) genes (both for A. pugettensis), and 6 barcode (cox1) sequences in the BOLD database (Argeia spp.). ...
... In the 13 PCG dataset, the above four species were among the 12 species in the narrow k range of 0.19-0.23, but a majority of species (32) was in the k > 5 range. These results correspond relatively well to the branch lengths, but statistical test for relaxation was non-significant with A. pugettensis selected as the test branch, probably as a result of a handful of other species exhibiting similar k values. ...
Background:
Argeia pugettensis is an isopod species that parasitizes other crustaceans. Its huge native geographic range spans the Pacific from China to California, but molecular data are available only for a handful of specimens from North-American populations. We sequenced and characterised the complete mitogenome of a specimen collected in the Yellow Sea.
Results:
It exhibited a barcode (cox1) similarity level of only 87-89% with North-American populations, which is unusually low for conspecifics. Its mitogenome is among the largest in isopods (≈16.5 Kbp), mostly due to a large duplicated palindromic genomic segment (2 Kbp) comprising three genes. However, it lost a segment comprising three genes, nad4L-trnP-nad6, and many genes exhibited highly divergent sequences in comparison to isopod orthologues, including numerous mutations, deletions and insertions. Phylogenetic and selection analyses corroborated that this is one of the handful of most rapidly evolving available isopod mitogenomes, and that it evolves under highly relaxed selection constraints (as opposed to positive selection). However, its nuclear 18S gene is highly conserved, which suggests that rapid evolution is limited to its mitochondrial genome. The cox1 sequence analysis indicates that elevated mitogenomic evolutionary rates are not shared by North-American conspecifics, which suggests a breakdown of cox1 barcoding in this species.
Conclusions:
A highly architecturally disrupted mitogenome and decoupling of mitochondrial and nuclear rates would normally be expected to have strong negative impacts on the fitness of the organism, so the existence of this lineage is a puzzling evolutionary question. Additional studies are needed to assess the phylogenetic breadth of this disrupted mitochondrial architecture and its impact on fitness.
... Although bulla shape is widely used identification of species of the genus Salmincola, its diameter can be easily changed by its attachment sites and host characteristics (Kabata 1969). In other siphonostomatoid copepods, it is also reported that the attachment organs are affected by host body parts, as well as ambient environmental factors like temperature (Fryer 1961, Hogans 1987, Abaunza et al. 2001, Hua et al. 2019, Suyama et al. 2019, González et al. 2021. The ratio of the bulla diameter/cephalothorax length of S. markewitschi was highly variable even within a small geographic range Shedko 2002, Nagasawa 2020b, Nagasawa and Ishiyama 2021) and the high variation may be due to host characteristics and/or physical environmental factors, which affect the parasite's development. ...
Salmincola markewitschi Shedko et Shedko, 2002 (Copepoda: Lernaeopodidae) is an ectoparasitic copepod mainly infecting the buccal cavities of white-spotted charr Salvelinus leucomaenis (Pallas) (Salmonidae). This species has only been recorded from Northeast Asia, where a morphologically similar congener Salmincola carpionis (Krøyer, 1837) is also distributed, using the same host species. These copepods are hard to distinguish from each other because of their similarities. We thus examined the newly collected specimens morphologically and genetically from five populations of white-spotted charr in Japan. Most of the specimens were morphologically consistent with S. markewitschi but showed great variations in the numbers of spines on the exopods of the antennae, shape of the maxilliped myxal palps, and the bulla diameter. Consequently, some specimens shared characteristics with S. carpionis. In addition to the mophological continuities, genetic analyses of 28S rDNA and COI mitochondrial DNA confirmed that all specimens belong to a single species. Further taxonomic revisions are required to draw conclusions of whether S. markewitschi is a valid species different from S. carpionis, by collecting samples from across their wide distributional ranges, such as Europe, North America, and Northeast Asia. A key to identification of species of Salmincola Wilson, 1915 occurring in Japan is also provided.
... This study also found some samples with four simple processes of similar size (Fig. 3e-g), which corresponds morphologically to L. cruciata (Fryer 1961). However, samples obtained from the present study had identical 18S and 28S rRNA sequences and very limited genetic differences in the COXI region (0.37%). ...
Lernaea is a genus of freshwater parasitic copepod, consisting of around 80 species. The anchor worm (L. cyprinacea) is the most well-known species because of its wide distribution beyond its native range and significant effect on freshwater host species. In Australia, nearly all reported Lernaea infections are referred to as L. cyprinacea without molecular evidence. Identification solely based on morphological features is not reliable due to the highly variable morphology of Lernaea species, especially of the most important characteristic, the anchor. In Australia, the species has now been found on many native fish, including in the Murrumbidgee catchment area, which is home to several endangered species. To provide clear identification of Lernaea species, we sampled Lernaea from six fish species from various localities in the Murrumbidgee catchment, southeastern Australia. The Lernaea specimens were described using combined traditional morphological observation and three gene regions. Although significant morphological variations were found, limited genetic differences in all three gene regions suggested they all belong to one species. Phylogenetic analyses of all tested species and those reported from other parts of the world suggested our specimens are L. cyprinacea. This study provides strong evidence for the occurrence of an introduced invasive species in Australia.
... The shape of the anchors is used as the most reliable characteristic for taxonomic comparison, in which the growth of the anchors is considered. This growth depends on the thickness of the tissue to which the parasite is attached (HARDING, 1950;FRYER, 1961FRYER, , 1968. Conversely, this feature is in fact unreliable for distinguishing species within Lernaea, since it may exhibit high intraspecific variation, which creates much taxonomic confusion. ...
Parasitic copepods of the family Lernaeidae are often found infesting freshwater fishes worldwide. They cause lernaeosis, a disease that can lead to serious pathogenic effects on their fish hosts. The most common lernaeid is the Lernaea cyprinacea, which has been widely introduced through importation of tropical fishes, e.g. cyprinids. In South America, it is one of the most common parasites both in wild and in farmed fish in the central region of Argentina. The silverside Odontesthes bonariensis is the most important fish of the sport fisheries of Argentina and one of the fish most affected by lernaeosis. Six specimens of copepods were collected from 30 specimens of O. bonariensis collected in a Pampean shallow lake (33°25'28”S 62°53'56”W) of Córdoba (Argentina). The 28S rRNA gene of L. cyprinacea was amplified by means of PCR to obtain the 28S rDNA sequence. The sequence obtained of this parasite from Argentina showed high genetic similarity with those from various geographical origins. The present study provided molecular characterization of L. cyprinacea in South America for the first time.
... The shape of the anchors is selected as the most important characteristic for identification purposes. However, the growth of the anchors is largely influenced by the consistency of the tissue to which the parasite is attached (Hu, 1948;Harding, 1950;Fryer, 1961Fryer, , 1968. Poddubnaya, (1973Poddubnaya, ( , 1978 further complicated the understanding of the species concept of lernaeids when she showed that offsprings with different phenotypes could be obtained from a single maternal specimen. ...
Isolates of the fish parasitic copepod Lernaea from four different freshwater fishes viz., catla (Catla catla), guppy (Poecilia reticulata), platy (Xiphophorus naculatus) and gold fish (Carassius auratus) were selected for the study. The isolates had considerably differing anchor shapes and were likely to be grouped as different species. Partial nucleotide sequences of the 18S and 28S rDNA regions of the Lernaea isolates were determined. Phylogenetic trees generated by the neighbour joining method revealed that the Lernaea isolates examined in this study were of similar genotype and were identified to be Lernaea cyprinacea.
... L'infection par les espèces les plus opportunistes et dans des conditions difficiles (conditions de l'eau défavorables, la nutrition déficiente et le surpeuplement) est susceptible d'induire des effets cliniques et pathologiques graves. Ces genres de lésions sont provoqués par Ergacilus megacheir et Lernaea cyprinacea infestant les poissons de la famille des Cichlidae et des Cyprinidae(Fryer, 1961(Fryer, et 1968. ...
Cette Thèse montre les retombées positives de l'application des mesures de biosécurité en élevage du tilapia du Nil. Elle montre aussi la possibilité de contrôler les parasites Argulus sp (appelés Poux du poisson) à travers des dispositifs de filtration de l'eau d'alimentation des structures d'élevage et avec des plantes tropicales.
... Fish which were already infected were prone to further infection by a new generation of parasites. Fryer (1961) reported that young adults of Lernaea cyprinacea were often found where old individuals were already present on the host, in this case two different species of Tilapia. A similar pattern occurred in a population of the lernaeopodid copepod Tracheliastes polycolpus infesting dace, Leuciscus leusiscus in Yorkshire rivers (Aubrook & Fryer, 1965). ...
10-spined sticklebacks, Pungitius pungitius, taken from a drainage dyke at Chalk Marshes, Kent, between October 1979 and July 1980 were infested with adult females of the parasitic copepod Thersitina gasterostei. Relative density of the overwintering parasite population fell during the winter months to a minimum in April; however during this winter period the proportion of ovigerous females rose, reaching 100% in April. Young infective adults were first seen in May, and the peak of infection by the first summer generation occurred in June. The parasite was found to be overdispersed within the host population: in 8 of 10 monthly samples the negative binomial distribution was a good model for the observed data. Relative density was related to host length in only 3 of the 10 samples. Evidence is presented to suggest that infected fish are more likely than non-infected fish to recruit young parasite.
Over the past 80 years, tilapia have been translocated globally for aquaculture; active
production is recorded in >124 countries. Of 7 million tonnes of tilapia produced in
aquaculture, 79% is from 79 countries outside the natural range of tilapia. Capture fisheries
account for a further 723,627 tonnes of tilapia, and >47% of this is landed from
established invasive populations outside Africa. Tilapias host a rich fauna of parasites,
many of which have been translocated with their hosts. This review summarises >2500
host–parasite records from 73+ countries and >820 recorded tilapia translocations
(provided in the supplementary materials). This work focuses on the notable pathogens
that threaten the health of cultured populations of tilapia, providing a description of
their pathology and includes species that also have substantial impacts on wild tilapia populations, where relevant. For each major parasite taxonomic group, we highlight
which parasites have been translocated or have been acquired from the new environments into which tilapia have been introduced, together with remarks on standard treatment approaches and research on them and their management and control. Regarding the theme ‘Tilapia health: quo vadis?’, Africa has enormous potential for aquaculture growth, but substantial knowledge gaps about tilapia parasites in many African states remain, which creates associated production and biosecurity risks. For each parasitic group, therefore, the risks of parasite translocation to new regions as tilapia aquaculture industries expand are highlighted.
Lernaea multilobosa sp. nov. is described from a wild, cyprinid fish, Salmostoma bacaila, collected from Manchhar Lake. The ectoparasite was found attached on the lateral side of body above the anal fin. This new species is distinct from other species of anchor worms reported from the Indian sub-continent, on the basis of the cephalic horns, which bear a considerable number of finger-like lobes, distinctive 5th leg, a vestigeal 6th leg and absence of anal laminae and setae on the abdomen.
The external morphology of Lernaea cyprinacea L. in Vigo Co., Indiana, was more variable than has been previously reported. The pregenital prominence was absent in small lernaeids, then developed as a single protuberance, which doubled as the female copepod lengthened and matured. No correlation was found between the location on the host fish and the direction of torsion. Sixteen species of fishes, taken in Vigo Co., were parasitized by L. cyprinacea. They were: Notropis blennius,* N. atherinoides,* N. spilopterus,* N. volucellus,* Semotilus atromaculatus,* Phenacobius mirabilis,* Hybognathus nuchalis,* Ictiobus niger,* I. cyprinellus,* Lepomis macrochirus, Micropterus salmoides, Pomoxis annularis,* Catostomus commersoni, Esox americanus,* Moxostoma erythrurum,* and Percina maculata* (asterisk denotes new host records). L. cyprinacea parasitized 0.8% of the fishes examined. Usually there was one parasite per fish, attached near a fin.
Thirty-eight species of fish were collected seasonally from two southeastern Wisconsin lakes between 1976 and 1978 and examined for crustacean parasites; five species (Copepoda, Branchiura) are reported. New records include two host (H) and two state (S) records: Branchiura, Argulus japonicus (H,S); Copepoda, Lernaea cruciata (S) and L. cyprinacea (H). Two other species recovered were A. appendiculosus and A. catostomi. All records (except L. cyprinacea) are new for southeast Wisconsin. Morphological variations and ecological observations, as well as notes on some host tissue reactions, are reported. Thriving populations of epizoic protozoans, diatoms, fungi, and filamentous algae associated with L. cyprinacea are described for the first time.
The known distribution of the parasitic crustaceans of African freshwater fishes, which now include some 80 more or less adequately described taxa, is summarized, and the significance of some of the patterns which they exhibit is discussed. Information is given on the taxonomy biology and evolution of certain species.
Four species of parasitic Crustacea, collected from various inland water fishes of Israel, are described: Pseudolepeophtheirus mediterraneas n.sp. from the gills of Mugil capito Ergasilus fryeri n.sp. from the gills of mullets, cichlids and the common eel; Lamproglena jordani n.sp. from gills of cyprinid fishes; Argulus tristramellae n.sp. from the gill cavity of Tristramella simonis.
This chapter describes the important viral, bacterial, fungal, and parasitic agents affecting cultured ictalurid catfish emphasizing each etiologic agent, significance of the disease, clinical signs and pathology, and epizootiology; and the role of the environment and host-pathogen interactions. Viral diseases discussed include channel catfish virus disease and catfish reovirus. Bacterial diseases discussed include enteric septicemia of catfish, columnaris disease, motile aeromonad septicemia (MAS) disease, and Edwardsiella tarda septicemia disease. Oomycete (fungal) diseases discussed include saprolegniasis, aphanomycosis, and branchiomycosis. Several myxozoan parasites infect channel catfish. Proliferative gill disease (PGD), or “hamburger gill,” is the myxozoan disease that results in tremendous economic losses in the industry. Although several other Henneguya species also infect catfish, extensive mortalities are rarely associated with these species. These histozoic myxosporidians have spores that are characteristically elongated and are rounded and ellipsoid or spindle-shape in valvular view, and biconcave in sutural view.
A morphological study on the ectoparasite Lernaea cyprinacea, found on Labeo rosae and Oreochromis mossambicus in the Olifants River in the Kruger National Park, South Africa, was done with the use of Scanning Electron Microscopy. Detailed descriptions are given of the appendages and their associated ornamentation. Significant morphological findings include the exact structure of the mandibles and the ornamentation on first pair of maxillae. Statistical analysis of the morphometrical data as well as the geographical distribution in Africa are shown.
Des études morphométriques ont été effectuées sur les stades larvaires de Lernaea polymorpha et L. cyprinacea pour déterminer si elles pouvaient constituer une méthode fiable pour l'identification spécifique. Elles ont porté sur huit caractéristiques des stades de dévelopement chez L. polymorpha, sur Aristichthys nobilis, et chez L. cyprinacea, sur A. nobilis et Carassius auratus. Les résultats ont montré des variations morphométriques des différents stades larvaires de L. cyprinacea obtenus sur des hôtes différent, alors que des similitudes étaient observées entre les stades larvaires de L. cyprinacea et L. polymorpha élevés dans les mêmes conditions. Certaines caractéristiques n'étaient pas influencées par l'espéce hôte, ni chez l'une, ni chez l'autre Lernaea. Ceci inclut la longueur du segment génital chez le cinquième copépodite femelle et la longueur de l'antennule chez les stades cyclopoïdes des deux sexes. Les résultats sont comparés à ceux obtenus dans d'autres études.
Parasitic infections of fish cultured in fresh and marine waters of subtropical and tropical geographic regions are reviewed. The following parasites are discussed: Ectoparasitic protozoa, Coccidia, Myxosporea, Monogenea, Metacercariae of trematodes, the Asian tapeworm, nematodes, ergasilids, lernaeids, and argulids. Criteria for selection were their impact on farmed fish and the availability of data beyond case reports and surveys. Epizootic ectoparasitic infections are usually the outcome of adverse growth conditions, either climatic or resulting from management practices. Epizootiology of infections by internal parasites, heteroxenous in particular, is more complex, particularly in man-made systems, as it is determined by a wider range of interacting ecological parameters. Exotic species, particularly cyprinids, comprise the bulk of freshwater fish farmed in warm water systems. Most important diseases affecting fishes in such systems are caused by introduced pathogens. Only a few of the autochthonous parasites become involved in epizootic infections, also where indigenous species are farmed. Marine farming is usually based on indigenous species. The relatively short history of piscine mariculture has already recorded epizootic infections and mortalities both by parasites contracted from the local environment and by specific parasites associated with the cultured species. As in freshwater systems, culture practices often create an environment favorable to epizootic infection.
New crustaceans parasitie on African freshwater fishes of the Nile, or former Nile, and Niger systems are described. The taxonomy of a group of closely related species of Argulus is clarified, and errors in the older literature are corrected. Additional information on distribution is presented.
A new species of Lernaea, closely related to L. cyprinacea, is described from both native and introduced fish species at a fish farming facility in Rio Grande do Sul, Brazil. All life-cycle stages of the new species, L. devastatrix, can be distinguished from L. cyprinacea by the reflexed claw on its antenna. A partial scheme of homologies of the antennulary segments is proposed, and the development of the segmentation and setation patterns is traced from CoIII to adults of both sexes. New interpretations are proposed of the homology of the antennary claw and of the maxillipedal endopod in lernaeids.
This book is the second edition of the first of three proposed volumes on diseases and disorders in freshwater and marine fishes (fin and shellfish). Since the publication of the first edition, a tremendous volume of research has been conducted on parasites, especially those that cause morbidity and mortality in fish. Like the first edition, this book deals with parasitic infections caused by protozoans and metazoans and each chapter deals with a specific disease/disorder or a group of closely related diseases. Its primary objective is to produce a comprehensive and authoritative review from experts who are actively working in the area or have contributed to the understanding of fish diseases/disorders. Significant changes to this second edition include the addition of three new chapters and four of the original chapters have new authors. All other chapters have been thoroughly updated since the first edition was published in 1995. The book will be of significant interest to researchers and students of aquaculture, fisheries, parasitology and veterinary medicine.
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