Life cycle of the fish parasite Gnathia maxillaris (Crustacea: Isopoda: Gnathiidae)

Parasites significantly influence food webs and ecosystems and occur all over the world in almost every animal group. Within crustaceans there are numerous examples of ectoparasites; for example, representatives of the isopod group Cymothoidae. These obligatory parasitic isopods are relatively poorly studied regarding their functional morphology. Here we present new details of the morphological adaptations to parasitism of the cymothoiid ingroup Nerocila with up-to-date imaging methods (macro photography, stereo imaging, fluorescence photography, micro CT, and histology). Central aspects of the study were (1) the morphology of the mouthparts and (2) the attachment on the host, hence the morphology of the thoracopods. The mouthparts (labrum, mandibles, paragnaths, maxillulae, maxillae, maxillipeds) form a distinct mouth cone and are most likely used for true sucking. The mouthparts are tightly “folded” around each other and provide functional rails for the only two moving mouthparts, mandible and maxillula. Both are not moving in an ancestral-type median-lateral movement, but are strongly tilted to move more in a proximal-distal axis. New details concerning the attachment demonstrate that the angular arrangement of the thoracopods is differentiated to impede removal by the host. The increased understanding of morphological adaptation to parasitism of modern forms will be useful in identifying disarticulated (not attached to the host) fossil parasites.

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“…Representatives of Gnathiidae also act in a comparable way to aegiids but only during a specific larval phase ( Hispano, Bulto & Blanch , 2014 ).…”

Section: The Group Of Interest: Cymothoidaementioning

confidence: 99%

Functional morphology of parasitic isopods: understanding morphological adaptations of attachment and feeding structures inNerocilaas a pre-requisite for reconstructing the evolution of Cymothoidae

Nagler

Haug

2016

PeerJ

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“…There are some additional sampling techniques that should be considered. Suction trapping is an effective method of removing gnathiids and other small benthic invertebrates from substrate ( Purcell, 1996 , Kramer et al., 2012 , Hispano et al., 2014 , Wetzer, 2015 ). Unlit suction traps may reduce sampling bias due to sensory cues such as ambient light level.…”

Section: Introductionmentioning

confidence: 99%

Comparison of sampling methodologies and estimation of population parameters for a temporary fish ectoparasite

Artim

Sikkel

2016

International Journal for Parasitology: Parasites and Wildlife

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Characterizing spatio-temporal variation in the density of organisms in a community is a crucial part of ecological study. However, doing so for small, motile, cryptic species presents multiple challenges, especially where multiple life history stages are involved. Gnathiid isopods are ecologically important marine ectoparasites, micropredators that live in substrate for most of their lives, emerging only once during each juvenile stage to feed on fish blood. Many gnathiid species are nocturnal and most have distinct substrate preferences. Studies of gnathiid use of habitat, exploitation of hosts, and population dynamics have used various trap designs to estimate rates of gnathiid emergence, study sensory ecology, and identify host susceptibility. In the studies reported here, we compare and contrast the performance of emergence, fish-baited and light trap designs, outline the key features of these traps, and determine some life cycle parameters derived from trap counts for the Eastern Caribbean coral-reef gnathiid, Gnathia marleyi. We also used counts from large emergence traps and light traps to estimate additional life cycle parameters, emergence rates, and total gnathiid density on substrate, and to calibrate the light trap design to provide estimates of rate of emergence and total gnathiid density in habitat not amenable to emergence trap deployment.

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“…The OR results >1 indicated a significant effect of the products employed as regards inducing deformities in zuphea and praniza. The mortality in adult forms developed from treated larvae was higher than the mortality observed during the life cycle in the laboratory (Hispano et al, 2014). However, the results obtained for zuphea may have been affected by the use of anaesthetic (clove oil) to sedate the host and facilitate larvae attachment.…”

Section: Discussionmentioning

confidence: 87%

“…G. maxillaris has a biphasic life cycle: a reproductive stage as free‐living adults (usually benthic) and an ectoparasitic larval stage. Two larvae forms are differentiated: zuphea, the larval form that attaches to the fish host and sucks blood; and praniza, the larval form during moulting and transition to the next phase of the life cycle (Hispano, Bulto, & Blanch, ).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of chemical treatments to mitigate or eradicate Gnathia maxillaris infestations

Hispano¹,

Méndez

Bultó³

et al. 2016

J. Appl. Ichthyol.

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Summary The eradication of the haematophagous isopod ectoparasite Gnathia maxillaris was not achieved after several years of physical elimination of larvae by filtration and chemical treatment with trichlorfon in a captive marine fish population in exhibition aquaria. In this study, different in vitro laboratory assays were performed to find effective alternative anti‐parasitic treatments to trichlorfon (lufenuron, emamectin benzoate, cypermethrin and abamectin). The lethal concentration 50 (LC50) values at 96 hr were calculated for each compound using both larval stages (zuphea and praniza); morphological deformities generated throughout the life cycle, reduction in egg laying and survival of adult forms were also determined. Abamectin, cypermethrin and emamectin benzoate proved effective at limiting further Gnathia maxillaris development, but their efficacy at eradicating an infestation in large tanks was not supported by laboratory assays. However, the use of lufenuron proved to be a good substitute for trichlorfon when treating this type of infestation in large‐volume tanks (LC50 55.8 mg m−3 for praniza). Routine lufenuron treatment once a month via an oral dose at 10 mg kg−1 body weight eradicated G. maxillaris from the exhibition aquaria.

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Life cycle of the fish parasite Gnathia maxillaris (Crustacea: Isopoda: Gnathiidae)

Cited by 11 publications

References 32 publications

Functional morphology of parasitic isopods: understanding morphological adaptations of attachment and feeding structures inNerocilaas a pre-requisite for reconstructing the evolution of Cymothoidae

Functional morphology of parasitic isopods: understanding morphological adaptations of attachment and feeding structures inNerocilaas a pre-requisite for reconstructing the evolution of Cymothoidae

Comparison of sampling methodologies and estimation of population parameters for a temporary fish ectoparasite

Evaluation of chemical treatments to mitigate or eradicate Gnathia maxillaris infestations

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