Gill Chamber Research Articles

Chronic Toxicity of Microplastics on Fish (Labeo rohita) and Their Impact on the Freshwater Ecosystem: A Case Study of Gangasagar Pond, Darbhanga, India

The present investigation was conducted to evaluate the chronic toxicity of microplastics on fish, Labeo rohita and isolation, identifications and estimation of microplastics in freshwater pond, Gangasagar Pond, Darbhasnga. traceable clinical, anatomical (morphological) and histopathological alterations. The data were analyzed and found that microplastic fibre (ranging between 12 to 56/m3) were dominated followed by microplastic film (ranging between 10 to 38), fragment (ranging between 8-22). The number of foam, beads (spherical) and coloured were relatively low. The sources of these plastic contaminations are mainly domestic wastes, discarded packaging materials and medical wastes. Trace of microplastics in gill chamber as well as buccal cavity was well marked causing edematous changes. The Histopathological studies suggest that intestine and stomach were the most affected organs in response to microplastics abuse. Microplastics will ultimately affect the aquatic fauna of the pond adversely.

Evaluation of novel PCR-based method to assess gill injuries in fish caused by the cnidarian Ectopleura larynx

Gill disease is a major threat to aquaculture of Atlantic salmon, with an unknown and likely underestimated contribution from cnidarians such as jellyfish and biofouling hydroids. To better understand the risk and thus enable mitigation, technology for the certain identification of cnidarian-related gill damage is needed. We used the hydroid Ectopleura larynx in a case study to determine whether the exposure of salmon to nematocyst-bearing hydrozoans can be deducted via non-destructive PCR-based methods. In a field experiment, we evaluated (i) whether swabbing the inside of the gill operculum in farmed Salmo salar and subsequent PCR analysis can provide quantifiable information about the presence of E. larynx material in the gill chamber and, if so, (ii) whether the screening results correlate with histological assessments of gill damage. The developed PCR methods were able to detect the presence of biofouling hydroids in ambient water. However, despite exposure to suspended hydroid particle concentrations that did result in gill damage in some salmon, quantitative PCR results did not correlate with histological gill assessments. For opercular swabs to serve as a diagnostic tool for detecting biofouling-mediated gill damage in live salmon, increased specificity of genetic markers and improved sampling methods are needed.Animal trial permit no. 24252 (granted 06.07.2020, Norwegian Food Safety Authority).

A multidisciplinary study on Clinostomum infections in Nile tilapia: micro-morphology, oxidative stress, immunology, and histopathology

Yellow grub disease, caused by Clinostomum metacercaria, is an endemic zoonotic infection in freshwater fish, responsible for Halzoun syndrome transmitted through the consumption of raw infected fish. This study aimed to conduct a multidisciplinary investigation integrating detailed morphology, oxidative stress, immunology, and histopathology alteration to advance our understanding of Clinostomum infection. In this annual study, 400 Nile tilapia (Oreochromis niloticus) were collected from the Nile River at Al Bahr Al Aazam, Giza Governorate to assess Clinostomum infection prevalence. Of the examined fish, 160 individuals (40.0%) harboured larval Clinostomum infections. Clinostomum metacercariae were observed in various anatomical locations, with 135 fish (33.8%) in buccal cavities, 21 fish (5.25%) in gill chambers, and 4 fish (1.0%) on the skin. Infection intensity ranged from 2 to 12 cysts per fish, averaging 5 cysts, notably with skin infections characterized by a single cyst in each fish. Macroscopic encysted metacercariae were collected from buccal cavities, gills, and skin. Micro-morphology revealed distinct features in C. complanatum, including an elliptical oral sucker with collar-like rings and large sensory papilla-like structures, contrasting with the absence of these features in C. phalacrocoracis. Oxidative stress, assessed through malondialdehyde (MDA) and nitric oxide levels, revealed an elevation in MDA to 35.13 ± 6 nmol/g and nitric oxide to 25.80 ± 3.12 µmol/g in infected fish. In infected fish, MHC-I gene expression increased approximately 13-fold, MHC-II peaked at 19-fold, and IL-1β significantly upregulated by 17-fold, compared to control levels. Histopathology detailed associated lesions, such as cyst encapsulation and eosinophilic infiltration. Clinstomiasis and its impacts on fish hosts offer crucial insights to control this emerging fish-borne zoonotic disease, threatening wildlife, aquaculture, and human health.

Parasitic fish embryos do a “front-flip” on the yolk to resist expulsion from the host

Embryonic development is often considered shielded from the effects of natural selection, being selected primarily for reliable development. However, embryos sometimes represent virulent parasites, triggering a coevolutionary "arms race" with their host. We have examined embryonic adaptations to a parasitic lifestyle in the bitterling fish. Bitterlings are brood parasites that lay their eggs in the gill chamber of host mussels. Bitterling eggs and embryos have adaptations to resist being flushed out by the mussel. These include a pair of projections from the yolk sac that act as an anchor. Furthermore, bitterling eggs all adopt a head-down position in the mussel gills which further increases their chances of survival. To examine these adaptations in detail, we have studied development in the rosy bitterling (Rhodeus ocellatus) using molecular markers, X-ray tomography, and time-lapse imaging. We describe a suite of developmental adaptations to brood parasitism in this species. We show that the mechanism underlying these adaptions is a modified pattern of blastokinesis-a process unique, among fish, to bitterlings. Tissue movements during blastokinesis cause the embryo to do an extraordinary "front-flip" on the yolk. We suggest that this movement determines the spatial orientation of the other developmental adaptations to parasitism, ensuring that they are optimally positioned to help resist the ejection of the embryo from the mussel. Our study supports the notion that natural selection can drive the evolution of a suite of adaptations, both embryonic and extra-embryonic, via modifications in early development.

Integrative taxonomy of Anaporrhutum mundae sp. nov. (Trematoda: Gorgoderidae), a parasite of the Munda round ray Urotrygon munda (Urotrygonidae) in Costa Rica.

A new species of trematode of anaporrhutine gorgoderid, from the gill chambers of the Munda round ray Urotrygon munda in Costa Rica is described, based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, ITS2 and 28S rDNA sequencing, and phylogenetic analysis. Anaporrhutum mundae sp. nov. can be distinguished from congeneric species by a combination of morphological traits and particularly by having the genital pore opening at the level of the intestinal bifurcation. The new species also can be distinguished from all other species of Anaporrhutum, except A. euzeti Curran, Blend & Overstreet, 2003, by having fewer testicular follicles per testis. Anaporrhutum mundae sp. nov. also differs from A. euzeti in its forebody shape and by having different morphology and location of the vitellaria. The study of the tegumental surface of A. mundae sp. nov., as revealed by scanning electron microscopy, allowed detection of new morphological characters for a member of Anaporrhutinae that may be of taxonomic value. These are: a stylet cavity dorsal to the oral sucker with a large penetration gland opening on each side of the cavity and small penetration gland openings located ventral to the stylet cavity, arranged in a circle around the mouth. This represents the first record of an Anaporrhutum species from Costa Rica. Further, A. mundae sp. nov. represents the first parasite described or reported in this host.

NEW DATA ON RELATIONSHIPS BETWEEN FISHES (CYPRINIDAE) AND MOLLUSKS (BIVALVIA, MARGARITIFERIDAE, UNIONIDAE) IN THE RUSSIAN FAR EAST

The fi ndings of bitterling (Rhodeus sericeus) eggs and larvae in the gill chambers of freshwater bivalve mollusks from Razdolnaya River basin are discussed. Bitterling eggs and larvae were registered in Margaritifera dahurica pearl mussels from Komarovka river, a tributary of Razdolnaya River, on the territory of the Ussuriysky Nature Reserve. Bitterling larvae at diff erent stages of development were also found in Nodularia douglasiae mussels from Razdolnaya River.

Reproductive potential of the blue crab spawning stock in Chesapeake Bay across eras and exploitation rates using nemertean worms as biomarkers

Assessments of reproductive potential and spawning history of marine and estuarine crabs are limited due to issues with determination of age and spawning history. The spawning stock of the blue crab Callinectes sapidus in Chesapeake Bay was heavily fished and declined in the 1990s. Management actions were implemented between 2001 and 2008 to reduce spawning stock exploitation and trigger recovery. Whether these actions impacted the demography of female spawners is unknown. We assessed demographics of overwintering mature female crabs in 1992-1996 and 2020-2022 by classifying them as first-year (imminent primiparous) or second-year (primiparous and multiparous) spawners based on presence of mature nemertean worms (Carcinonemertes carcinophila) in their gill chambers. We also investigated organismal and environmental predictors of second-year spawners. We provide the first annual estimates of the proportion of multi-year spawners at the population level. Management actions reduced exploitation rates by 41% after 2008, and the proportion of second-year spawners was greater than in the 1990s. Nonetheless, exploitation rate in a given year did not predict proportion of second-year spawners in the following year. Second-year spawners tended to be smaller females, or females with a high gonadosomatic index or longevity indicators (i.e. fouling by barnacles). High proportions of large, highly fecund, overwintering first-year spawners in the 2020s support the need for enhanced protection of females in spring to allow these females to spawn. Finally, nemertean worms are a useful, easily implemented tool to determine spawning history and age-specific reproductive potential of crabs that undergo a terminal molt prior to spawning.

​Identification of Gnathiid Isopods as Ectoparasites of the Brown-spotted Grouper Epinephelus chlorostigma from the Red Sea of Saudi Arabia

Background: Gnathiids are considered excellent ectoparasites widely distributed along the fish body with a biphasic life cycle including parasitic larval stages and free-living adults. This study focused on gnathiids infecting the brown-spotted grouper fish and confirming the identity of the host species. Methods: Twenty Epinephelus chlorostigma (Serranidae) were collected from the Red Sea Coast (especially off Jeddah, Saudi Arabia) and examined for gnathiid fish parasites. Species identification of the larvae was based on morphological criteria of Smit and Basson (2002). In contrast, the taxonomy of fish species was supported by amplification and sequencing of host DNA via the mitochondrial DNA genes (COI and 16S rRNA) using gnathiids’ blood meals. Result: Praniza larvae of a gnathiid isopod were collected from the gill chambers of the examined fish. The prevalence rate was 60% and mean intensity of the pranzia larvae was 16. The pranzia larva is described microscopically and distinguished by large body size (3.51-5.90 mm), the presence of 8th teeth in the mandible, maxilliped with 5-7th teeth on the first palp and the endite hooked, pleotelson with concave anterolateral margins and rami of uropods extend its apex. The recovered larvae could be identified as pranzia larvae of Gnathia pantherina Smit and Basson, 2002 due to the morphological resemblance. The host species identity was confirmed molecularly with COI and 16S rRNA genes and showed highly stringent criteria with the previously E. chlorostigma sequence data. The obtained host DNA sequences were deposited in NCBI database under accession numbers ON384530.1 for COI and ON384544.1 for 16S rRNA.

A novel and dual digestive symbiosis scales up the nutrition and immune system of the holobiont Rimicaris exoculata

BackgroundIn deep-sea hydrothermal vent areas, deprived of light, most animals rely on chemosynthetic symbionts for their nutrition. These symbionts may be located on their cuticle, inside modified organs, or in specialized cells. Nonetheless, many of these animals have an open and functional digestive tract. The vent shrimp Rimicaris exoculata is fueled mainly by its gill chamber symbionts, but also has a complete digestive system with symbionts. These are found in the shrimp foregut and midgut, but their roles remain unknown. We used genome-resolved metagenomics on separate foregut and midgut samples, taken from specimens living at three contrasted sites along the Mid-Atlantic Ridge (TAG, Rainbow, and Snake Pit) to reveal their genetic potential.ResultsWe reconstructed and studied 20 Metagenome-Assembled Genomes (MAGs), including novel lineages of Hepatoplasmataceae and Deferribacteres, abundant in the shrimp foregut and midgut, respectively. Although the former showed streamlined reduced genomes capable of using mostly broken-down complex molecules, Deferribacteres showed the ability to degrade complex polymers, synthesize vitamins, and encode numerous flagellar and chemotaxis genes for host-symbiont sensing. Both symbionts harbor a diverse set of immune system genes favoring holobiont defense. In addition, Deferribacteres were observed to particularly colonize the bacteria-free ectoperitrophic space, in direct contact with the host, elongating but not dividing despite possessing the complete genetic machinery necessary for this.ConclusionOverall, these data suggest that these digestive symbionts have key communication and defense roles, which contribute to the overall fitness of the Rimicaris holobiont.FJvM6igKFE6x_yqS3roQ38Video

Four new species of the frogmouth genus Chaunax (Lophiiformes: Chaunacidae) from Taiwan and the Philippines

Four new species of the genus Chaunax found in Taiwan and the Philippines are described. Chaunax albatrossae sp. nov. belongs to the C. abei species group and is distinct from its congeners in having a dark gray mouth cavity, a dark brown to black gill chamber and gill rakers and skin covered with only short, simple spinules. Three new species belong to the C. fimbriatus species group: Chaunax erythraeus sp. nov. is distinct in having a uniformly pinkish-red body and an entirely black gill chamber; Chaunax obscurus sp. nov. is distinct in having a dark gray mouth cavity and orange-red marbling on the dorsal surface that fades after fixation; and Chaunax viridiretis sp. nov. is distinguished by its green reticulate pattern with some small, bright-white patches on the dorsal surface. The diagnostic characters used to identify the chaunacids are summarized and a key to all Chaunax species found in Taiwan and adjacent waters is provided.

A new species of the congrid eel genus Bathycongrus (Order Anguilliformes) from eastern Taiwan

A new species of the congrid eel genus Bathycongrus is described on the basis of three specimens collected from the deep waters of eastern Taiwan. Bathycongrus melanostomus sp. nov., belongs to the few vertebrae species complex and is distinct in having a short and broad snout; a much reduced caudal fin; abdomen, mouth cavity and gill chamber blackish; small conical blunt teeth on vomer forming an elongate patch; total vertebrae 133-135, and total lateral-line pores 108-109.

Functional Morphology of the Urohyal Shunt for Symmetrical and Asymmetrical Ventilation in the Flatfish, Isopsetta isolepis.

Flatfishes are benthic fishes that are well known for their ability to bury in the sediment, making the transition from above to below the sediment in a matter of seconds. Laterally flattened bodies allow flatfishes to lay flush against the substrate, a behavior facilitated by having an asymmetrical neurocranium with two eyes on one side of the head. Despite neurocranial asymmetry, their gill chambers are highly symmetrical. Additionally, most flatfishes have a uniquely shaped urohyal bone that forms passageway for water to travel ventrally between the "eyed-side" and "blind-side" gill chambers. Our study examines whether the kinematics and pressures generated by the gill chambers are also symmetrical during breathing above and below the sediment and during rapid burial in sediment. We studied Isopsetta isolepis individuals using sonomicrometry crystals to measure the changes in positions of the opercle bones relative to the urohyal and pressure transducers to record gill chamber pressures during burial. We conclude I. isolepis exhibit both symmetrical and asymmetrical breathing above and below the sediment. Pressures and movements were highly asymmetrical during burial jetting. We observed motions that indicate that the urohyal is an active shunt to allow passage of water between the eyed to the blind-side gill chambers.

Eradication of Livoneca redmanii infestation in cultured Argyrosomus regius

Two Argyrosomus regius nursery ponds suffered from high mortality during the summer season of 2020. Diseased fish showed signs of respiratory distress, mainly during hot days. Physiochemical pond water parameters were normal, except dissolved oxygen was lower than the optimum level. Livoneca redmanii (Cymotidae, Isopoda) was isolated from the gill chamber of infested fish. The infestation percent was 41 and 33%, and the intensity was 1.146 and 1.06 in the first and second ponds, respectively. The diseased fingerlings were infested in the natural habitat (Mediterranean Sea) before collection for culture. L. redmanii infestation was associated with high economic losses due to direct fish mortality, reduced growth rates and lower condition factor. The molecular study confirmed the presence of L. redmanii based on the phylogenetic analysis of 16S rRNA and COI gene sequences. Infested fish gills showed massive destruction in gill filaments, sloughing and curling of secondary gill lamellae with the detachment of the cartilaginous core supporting the primary gill filaments. Deltamethrin and trichlorfon effectively eradicated L. redmanii at concentrations of 12.5 μg.l−1 and 0.5 mg.l−1, respectively. The lowest detectable deltamethrin residue in treated pond water was 2.18 μg.l−1 at 120 h, with a half-life of 47.63 h.

Developmental neuroanatomy of the rosy bitterling Rhodeus ocellatus (Teleostei: Cypriniformes)-A microCT study.

Bitterlings are carp‐like teleost fish (Cypriniformes: Acheilanathidae) known for their specialized brood parasitic lifestyle. Bitterling embryos, in fact, develop inside the gill chamber of their freshwater mussel hosts. However, little is known about how their parasitic lifestyle affects brain development in comparison to nonparasitic species. Here, we document the development of the brain of the rosy bitterling, Rhodeus ocellatus, at four embryonic stages of 165, 185, 210, 235 hours postfertilization (hpf) using micro‐computed tomography (microCT). Focusing on developmental regionalization and brain ventricular organization, we relate the development of the brain divisions to those described for zebrafish using the prosomeric model as a reference paradigm. Segmentation and three‐dimensional visualization of the ventricular system allowed us to identify changes in the longitudinal brain axis as a result of cephalic flexure during development. The results show that during early embryonic and larval development, histological differentiation, tissue boundaries, periventricular proliferation zones, and ventricular spaces are all detectable by microCT. The results of this study visualized with differential CT profiles are broadly consistent with comparable histological studies, and with the genoarchitecture of teleosts like the zebrafish. Compared to the zebrafish, our study identifies distinct developmental heterochronies in the rosy bitterling, such as a precocious development of the inferior lobe.

Air sac and gill vasotocin receptor gene expression in the air-breathing catfish Heteropneustes fossilis exposed to water and air deprivation conditions.

Heteropneustes fossilis is a facultative air-breathing freshwater catfish and inhabits ponds, ditches, swamps, marshes and rivers that dry up in summers. It possesses a pair of unique tubular accessory respiratory organ (air sac), which is a modification of the gill chamber and enables it to live in water-air transition zones. In the catfish, three vasotocin (Vt) receptor gene paralogs viz., v1a1, v1a2 and v2a were identified for Vt actions. In the present study, the receptor gene transcripts were localized in the gill and air sac by in situ hybridization, and their expression levels in relation to water and air deprivation conditions were investigated by quantitative RT-PCR. The catfish were exposed to 1h and 2h in gonad inactive (resting) and gonad active (prespawning) phases. The gene paralogs showed overlapping distribution in the respiratory epithelium of primary and secondary lamellae of gills and reduced lamellae of the air sacs. In water deprivation (forced aerial mode of respiration) experiment, v2a expression showed a high fold increase in the air sac, which was unchanged or inhibited in the gill. Both v1a1 and v1a2 expression was significantly upregulated in the air sac but showed varied responses in the gill. The gill v1a1 expression was unchanged in the resting phase and modestly upregulated in the prespawning phase. The gill v1a2 expression was modestly upregulated at 1h in both phases but unchanged at 2h. In the air deprivation experiment (forced aquatic respiration), the v2a expression in the air sac was inhibited except for a mild stimulation at 1h in the prespawning phase. In the gill, the v2a expression was stimulated with a steep upregulation at 2h in the prespawning phase. Both v1a1 and v1a2 expression was significantly high in the gill but only modestly increased or unchanged in the air sac. The expression patterns point to a functional distinction; the V2 type receptor expression was higher in the air sac during forced aerial respiration, and the V1 type receptor expression was highly prominent in the gill during forced aquatic respiration. Water and air deprivation treatments caused a significant increase in plasma cortisol level, and the stimulation was higher in the water deprivation fish in the resting phase but equally prominent in the water and air deprivation groups in the prespawning phase. The results indicate that the changes in the expression patterns of Vt receptor genes may be a sequel to stress (hypoxic, metabolic and osmotic), and both Vt and cortisol may interact to counter the stress responses. This study shows that Vt has a new role in the control of air sac functions.

Two New Parasitic Copepod Species, Clavella (Lernaeopodidae) and Haemobaphes (Pennellidae), on the Nototheniid Fish Patagonotothen cornucola (Richardson, 1844) from the Strait of Magellan, Southern Chile.

The parasitic diversity on the intertidal fish of the Southern American Cone is barely known. The present study describes two new parasitic copepod species, a Clavella and a Haemobaphesfound on the nototheniid fish Patagonotothen cornucola. The fish were collected from the intertidal zone of the Strait of Magellan, Southern Chile. The copepods were found on the fins and in the gill chamber of the fish, which were morphologically analyzed using optical and electronic microscopy. Clavella cornucola sp. nov. and Clavella bowmani are similar but differ in the number of setae found on the maxillule (two setae on the inner lobe vs. three on C. bowmani), and a pad of spinules on the dorsal margin as opposed to the outer lobe (no pad vs. one pad, respectively). Haemobaphes puntaarenensis sp. nov. is distinguished from its congeners based on the lobe shapes of the head and the clear separation between the pedigerous somites (first, second, and third). The maxilla on H. puntaarenensis sp. nov. lacks a pad of spinules on the second segment, but it is found in all the other congeneric species. Clavella cornucola sp. nov. is the 10th species of the genus in Chile, whereas Haemobaphes puntaarenensis sp. nov. is the first species of the genus recorded in Chile and the Southern Cone coasts.

Gammarinema scyllae sp. n. and Monhystrium mangrovi sp. n. (Nematoda: Monhysteridae) from land crabs from New Caledonia

Two new species of nematodes associated with crabs are described from New Caledonia. Gammarinema scyllaesp. n. from the gill chambers of Scylla serrata (Forsskål) is characterised by 3–4 mm long body, small outer labial and cephalic sensilla, distinct ocelli, short straight spicules and sub-cylindrical tail. Monhystrium mangrovisp. n. from the gill chambers and body cavity of mangrove crab Neosarmatium sp. is characterised by 1–1.4 mm long body; outer labial sensilla longer than cephalic sensilla, amphid located at level with posterior stoma chamber, denticles in posterior stoma chamber and five pairs of genital papilla on tail. Phylogenetic relationships of two new species and other nematodes from the family Monhysteridae are analysed based on 18S and partial 28S rDNA sequences.

Anuran development: A reinvestigation of the conus arteriosus and gill formation in Bufo bufo throughout metamorphosis using micro-CT.

Using high‐resolution X‐ray micro‐CT imaging of whole Bufo bufo specimens, we acquired detailed 3D descriptions of the changing morphology of the cardiac outflow structures, in particular the conus arteriosus through larval development and the transition. Previous findings regarding anuran conal structures were contradictory, depending on the specifics of the 2D imaging methods used by different authors. Our descriptions of conal morphology at different developmental stages show that early tadpoles initially only have one opening at the ventricular‐conal junction and only one cavum within their conus; however, the forming septum coni soon divides the conus into two chambers, the cavum pulmocutaneum and the cavum aorticum. This is accompanied by the development of a second small opening at the ventricular‐conal junction. The separated chambers continue into the aortic arches. Following the aortic arches into the area where gills will form, we describe how blood vessels associated with the external gills develop from vessels arising from the truncus arteriosus. The external gills soon undergo partial absorption. During the transition from external to internal gills, the gill filaments retreat asymmetrically into a gill chamber formed by a hyoidal cover contacting the animal's ventral side, leaving only a single opening on the animal's left side, the opercular spout. B. bufo retains its internal gills up to metamorphic climax, with the aortic arches arising from the conus arteriosus still leading into the gills. Our 3D image data are publicly available and will provide a sound morphological basis for future studies.

Normal stages of embryonic development of a brood parasite, the rosy bitterling Rhodeus ocellatus (Teleostei: Cypriniformes).

Bitterlings, a group of freshwater teleosts, provide a fascinating example among vertebrates of the evolution of brood parasitism. Their eggs are laid inside the gill chamber of their freshwater mussel hosts where they develop as brood parasites. Studies of the embryonic development of bitterlings are crucial in deciphering the evolution of their distinct early life‐history. Here, we have studied 255 embryos and larvae of the rosy bitterling (Rhodeus ocellatus) using in vitro fertilization and X‐ray microtomography (microCT). We describe 11 pre‐hatching and 13 post‐hatching developmental stages spanning the first 14 days of development, from fertilization to the free‐swimming stage. In contrast to previous developmental studies of various bitterling species, the staging system we describe is character‐based and therefore more compatible with the widely‐used stages described for zebrafish. Our bitterling data provide new insights into to the polarity of the chorion, and into notochord vacuolization and yolk sac extension in relation to body straightening. This study represents the first application of microCT scanning to bitterling development and provides one of the most detailed systematic descriptions of development in any teleost. Our staging series will be an important tool for heterochrony analysis and other comparative studies of teleost development, and may provide insight into the co‐evolution of brood parasitism.

Infection prevalence and pathology of the cymothoid parasite Olencira praegustator in Atlantic menhaden

AbstractIsopod parasites in the family Cymothoidae can cause reduced growth, castration, or even mortality in their hosts. Olencira praegustator is a cymothoid that parasitizes the mouth and gill chamber of Brevoortia tyrannus (Atlantic menhaden), which is the basis for the largest fishery along the eastern coast of the USA and an important link within estuarine food webs. To better characterize interactions between O. praegustator and B. tyrannus, including parasite‐induced pathology, we sampled hosts and parasites from three estuarine sites on Kiawah Island, South Carolina. Over 5 weeks, we collected, measured, and weighed 169 juvenile menhaden; remarkably, 96% of these fish were infected with O. praegustator, typically with one isopod found in the mouth of each host. Based on the external morphologies of 163 examined isopods, 58 were female (35.6%), 9 of which were gravid, and 105 were male (64.4%). Although fish size was unrelated to isopod length or mass, isopod length was a direct predictor of the amount of damage observed on the host operculum, which in severe cases involved tissue atrophy and hemorrhage. Considering the high infection prevalence, significant damage associated with infections, as well as the impairing effects of other cymothoids on their hosts, the consequences of interactions between B. tyrannus and O. praegustator warrant additional investigation for understanding the management and ecology of Atlantic menhaden.