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      The caligid life cycle: new evidence from Lepeophtheirus elegans reconciles the cycles of Caligus and Lepeophtheirus (Copepoda: Caligidae) Translated title: Le cycle des vie des caligides : de nouvelles données obtenues chez Lepeophtheirus elegans réconcilient les cycles de Caligus et Lepeophtheirus (Copepoda : Caligidae)

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          Abstract

          The developmental stages of the sea louse Lepeophtheirus elegans (Copepoda: Caligidae) are described from material collected from marine ranched Korean rockfish, Sebastes schlegelii. In L. elegans, setal number on the proximal segment of the antennule increases from 3 in the copepodid to 27 in the adult. Using the number of setae as a stage marker supports the inference that the post-naupliar phase of the life cycle comprises six stages: copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, and the adult. We observed variation in body length in both of the chalimus stages which we consider represents an early expression of sexual size dimorphism. We interpret the larger specimens of chalimus I as putative females, and the smaller as putative males; similarly with chalimus II, larger specimens are putative females and the smaller are males. Two patterns of life cycle are currently recognized within the Caligidae but the evidence presented here reconciles the two. We conclude that the typical caligid life cycle comprises only eight stages: two naupliar, one copepodid, and four chalimus stages preceding the adult in Caligus, but with the four chalimus stages represented by two chalimus and two pre-adult stages in Lepeophtheirus. This is a profound change with significant implications for the aquaculture industry, given that lice monitoring protocols include counts of chalimus stages and use temperature to predict when they will moult into the more pathogenic, mobile pre-adults. Lice management strategies must be tailored to the precise life cycle of the parasite.

          Translated abstract

          Les stades de développement du copépode parasite Lepeophtheirus elegans (Copepoda : Caligidae) sont décrits à partir de matériel collecté sur des spécimens du Sébaste coréen Sebastes schlegelii élevés en mer. Chez L. elegans, le nombre de soies sur le segment proximal de l’antennule croît de trois au stade copépoditique à 27 chez l’adulte. L’utilisation du nombre de soies comme marqueur du stade permet d’établir que la phase post-nauplienne du cycle de vie comprend six stades: copépodite, chalimus I, chalimus II, pré-adulte I, pré-adulte II et adulte. Nous avons observé une variation de la longueur du corps chez les deux stades chalimus qui représentent, à notre avis, une expression précoce du dimorphisme sexuel concernant la taille. Nous interprétons les plus grands spécimens de chalimus I comme de futures femelles, et les plus petits comme de futurs mâles; de même, pour les chalimus II, les plus grands spécimens sont femelles et les plus petits sont mâles. Deux modèles de cycles de vie sont actuellement reconnus chez les Caligidae, mais les observations présentées ici réconcilient les deux. Nous concluons que le cycle de vie typique des Caligidae comprend seulement huit stades : deux naupliens, un copépodite et quatre stades chalimus précédant l’adulte chez Caligus, mais avec les quatre stades chalimus représentés par deux stades chalimus et deux stades pré-adultes chez Lepeophtheirus. Ceci est un changement profond avec des implications significatives pour l’industrie de l’aquaculture, puisque la surveillance des poux de mer implique des comptages des stades chalimus et utilise la température pour prédire quand ils vont muer en pré-adultes mobiles, qui sont plus pathogènes. Les stratégies de contrôle des copépodes parasites doivent être adaptées au cycle de vie exact du parasite.

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          Most cited references 2

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          Chalimus stages of Caligus latigenitalis (Copepoda:Caligidae) parasitic on blackhead seabream from Japanese waters, with discussion of terminology used for developmental stages of caligids.

          The first and third chalimus stages and chalimus adult (previously known as young adult) of Caligus latigenitalis are described based on new material collected from the body surface of a heavily infected wild blackhead seabream Acanthopagrus schlegelii schlegelii from Hiroshima Bay, Japan. The second and fourth chalimus stages of the same species are redescribed. Adults of C. latigenitalis are characterized by possessing 2 stout marginally indented processes at the base of 2 terminal spines at distal exopodal segment of leg 4. The chalimi were identified to stage based on the structure of the frontal filament and the discrete ranges in body length. Sexual dimorphism is first observed at the third chalimus stage in the shape of the distal segment of the antenna. The total number of postnaupliar stages of C. latigenitalis is 6, including 4 semaphoronts, i.e., 1 copepodid stage consisting of 1 infective copepodid and the chalimus copepodid, 4 chalimus stages, and 1 adult stage with 1 chalimus adult and 1 mobile adult. New terminology for the developmental stages of caligid copepods is proposed herein by amending the definition of chalimus as the postnaupliar stages, as well as semaphoronts having a frontal filament for host attachment.
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            Caligus sclerotinosus (Copepoda: Caligidae), a serious pest of cultured red seabream Pagrus major (Sparidae) in Korea.

            Caligid copepods (Crustacea) known as sea lice are pests of cultured fish, causing serious diseases and economic losses in fish aquaculture worldwide. One species, Caligus sclerotinosus Roubal, Armitage & Rohde, 1983 (Caligidae), is considered a serious pest of the highly prized red seabream Pagrus major (Temminck and Schlegel, 1843) (Sparidae) cultured in Japan. Recently, in neighboring Korea, red seabream culture has intensified and almost replaced yellow tail culture. However, until now, there have been no reports on infection of this sea louse from red seabream in Korea. We surveyed 120 (20 fish per month) P. major from a sea ranched Tongyeong Marine Research Center aquaculture facility, Gyeongsangnamdo, Korea for six months in 2011 (June to November). We recorded severe infection by the sea louse C. sclerotinosus on the skin of P. major. Prevalence was 100%, mean intensity 7.06, maximum intensity 49, and minimum intensity 2. Adult females (624), males (219) and few chalimi (5) were observed and identified by their morphology. As an average of all our collections, less than 0.6% of individuals were chalimi. We suggest, therefore, that adults of C. sclerotinosus undergo ontogenetic host switching after their final moult. No infection of C. sclerotinosus was found on wild P. major collected from Tongyeong and Yeosu fish markets on the southern coast of Korea. Severe infection by this sea louse may cause secondary infections of the host. This copepod is already reported from Australia and Japan and hence, this is the first report from Korea. We expect this pest to have an impact on Korean red seabream fisheries equally serious to that being experienced in Japan. Copyright © 2012 Elsevier B.V. All rights reserved.
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              Author and article information

              Journal
              Parasite
              Parasite
              parasite
              Parasite
              EDP Sciences
              1252-607X
              1776-1042
              2013
              07 May 2013
              : 20
              : ( publisher-idID: parasite/2013/01 )
              Affiliations
              [1 ] Marine Ecosystem Research Division, Korea Institute of Ocean Science & Technology P.O. Box 29 Seoul 425-600 Korea
              [2 ] Faculty of Marine Technology, Chonnam National University Yeosu 550-749 Korea
              [3 ] Takehara Marine Science Station, Setouchi Field Science Centre, Graduate School of Biosphere Science, Hiroshima University 5-8-1 Minato-machi Takehara, Hiroshima 725-0024 Japan
              [4 ] Marine Ecology Department, Institute of Oceanology Polish Academy of Sciences Powstańców Warszawy 55 81-712 Sopot Poland
              [5 ] Department of Life Sciences, Natural History Museum Cromwell Road London SW7 5BD UK
              Author notes
              [* ]Corresponding author: g.boxshall@ 123456nhm.ac.uk
              Article
              parasite130014 10.1051/parasite/2013015
              10.1051/parasite/2013015
              3718518
              23647664
              © B. Venmathi Maran et al., published by EDP Sciences, 2013

              This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

              Page count
              Figures: 15, Tables: 6, Equations: 0, References: 49, Pages: 22
              Categories
              Research Article

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