Parasitic Crustaceans Research Articles

Simple method to remove contamination of the host DNA in parasitic crustaceans using DNA AWAY

Simple method to remove contamination of the host DNA in parasitic crustaceans using DNA AWAY

Ectoparasite infection levels differ between fish from upwelling-exposed and sheltered rocky reefs areas in Brazil

Ubiquitous and abundant within marine ecosystems, parasites play essential ecological roles such as shaping host population dynamics, altering competition between species, and influencing energy flows through communities. Their diversity and population dynamics are demonstrably shaped by both seasonal and geographic variations. These variations have been often explored at broad spatial scale. However, parasite communities can exhibit significant disparities even at small spatial scales, driven by factors such as wave exposure, temperature fluctuations, and benthic habitat composition. We investigated how crustacean parasites of fish – caligids and gnathiids - differed between two distinct habitats, which are separated solely by a few kilometres, at Arraial do Cabo, Brazil. These two habitats are characterised by a sheltered embayment (hereinafter referred to as “inside”) or an exposed upwelling habitat (hereinafter referred to as “outside”). Individual fish from four species were examined in both habitats. We found that the infestation rate of caligids varied among fish species and, gnathiids varied between the two sampling sites. Gnathiids were absent from fish outside, while they were present on fish inside the embayment. This disparity suggests a critical role of local environmental factors in shaping gnathiid distribution. Potential drivers include temperature fluctuations, substrate composition, and wave exposure, which differed markedly between the two sites. Conversely, caligid parasites infected fish in both locations. While environmental factors may also influence caligid abundance, they appear to exhibit greater tolerance compared to gnathiids. These findings emphasize the importance of incorporating fine-scale environmental heterogeneity when investigating parasite distribution patterns.

Transcriptomic analysis of sexually dimorphic cypris larvae of the rhizocephalan barnacle Peltogasterella gracilis

Peltogasterella gracilis (Cirripedia: Rhizocephala), a crustacean parasite of hermit crabs, displays genotypic sex determination. Its larvae are planktonic, and female larvae settle on the host. Subsequently, the females control the host's behavior by spreading a root-like structure called “the interna” within the host's body, and form sacs containing eggs called “the externae” outside the host's body. On the other hand, male larvae settle on immature externae and become dwarf males. The cypris larvae of P. gracilis show sexual dimorphism in size and morphology. However, there is no understanding of the molecular mechanisms underlying the sexual dimorphism observed at the larval stage. Here, we conducted a transcriptome analysis and compared the expression of genes in male and female cyprids to better understand their sexual differentiation and settlement processes. A total of 2870 differentially expressed transcripts, comprising 456 female- and 2414 male-biased transcripts were identified. Among the male-biased ones, ionotropic glutamate receptor-, heat shock protein-, acetylcholine-, and homeobox-, cuticle-related transcripts were included. Additionally, 29 gene ontology terms were associated with the sex-specific traits. The present study improves our understanding of sex determination, sexual differentiation, and settlement processes of rhizocephalans.

Crustacean endocrinology: Sexual differentiation and potential application for aquaculture

Crustaceans, which represent a significant subset of arthropods, are classified into three major classes: Ostracoda, Malacostraca, and Branchiopoda. Among them, sex manipulation in decapod species from the Malacostraca class has been extensively researched for aquaculture purposes and to study reproductive physiology and sexual plasticity. Some decapods exhibit sexual dimorphism that influences their biological and economic value. Monosex culture, in which only one sex is cultivated, increases production yields while reducing the risk of invasiveness, as genetic leakage into natural waters is less likely to occur. Differences in yield are also observed when cultivating different sexes, with all-male cultures of Macrobrachium rosenbergii being more profitable than both mixed and all-female cultures. Research on decapod sexual differentiation has led to a better understanding of sex determination and sexual differentiation processes in arthropods. Similar to most mammals and other vertebrate classes, Malacostraca crustaceans, including decapods, exhibit a cell-non-autonomous mode of sexual development. Genetic factors (e.g., sex chromosomes) and endocrine factors (e.g., insulin-like androgenic gland factor and crustacean female sex hormone) play pivotal roles in the development of sexually dimorphic traits. This review synthesizes the existing understanding of sex determination mechanisms and the role of sex hormones in decapod species. Additionally, it provides an overview of the methyl farnesoate, which has been suggested to be involved in male sex differentiation in some crab species, as well as the phenomenon of male-to-female sex reversal in host decapods caused by parasitic crustaceans.

Hematodinium perezi (Dinophyceae: Syndiniales) in Morocco: The First Record on the African Atlantic Coast and the First Country Record of a Parasite of the Invasive Non-Native Blue Crab Callinectes sapidus

Dinoflagellates belonging to the genus Hematodinium are key parasites of marine crustaceans, primarily decapods. In this study, we document the first report of H. perezi Chatton & Poisson, 1930 on the African Atlantic coast. This is also the first parasite record in the invasive non-native Atlantic blue crab Callinectes sapidus Rathbun, 1896 in Morocco. Specimens of C. sapidus were sampled in winter 2023 from two Ramsar sites on the Moroccan Atlantic, namely Merja Zerga and Oualidia Lagoons, and were screened to detect the presence of parasites in their hemolymph. Based on staining fresh hemolymph smears, we did not detect Hematodinium in any of the 36 investigated individuals (20 and 16 from Merja Zerga and Oualidia Lagoons, respectively), probably due to methodological artifacts. The PCR-based method was revealed to be more accurate in diagnosing the Hematodinium parasite. It showed that at Merja Zerga Lagoon, 13 individuals of C. sapidus were infected by the parasite (prevalence: 65%) in comparison to four at Oualidia Lagoon (25%). Genetic analysis, based on the ITS1 rDNA gene from Hematodinium, confirmed the sequences as being those of Hematodinium perezi.

Site-specific Parasitism of Crustaceans on the Black Pomfret, Parastromateus niger (Carangidae) from Indian Waters

An extensive parasitic survey on the Black Pomfret Parastromateus niger (Bloch) (Carangidae) was carried out along the coastal waters of India. A total of 162 host fish (P. niger) were collected, in which 72.2% of the fish were infested with parasitic crustaceans. Six species of parasitic crustaceans were collected, including one species of cymothoid isopod Cymothoa eremita (Brünnich, 1783), and five species of copepods belonging to five different families such as Bomolochus megaceros Heller, 1865 (Bomolochidae), Lernaeenicus stromatei Gnanamuthu, 1953 (Pennellidae), Lernanthropus koenigii Steenstrup and Lütken, 1861 (Lernanthropidae), Synestius caliginus Steenstrup and Lütken, 1861 (Caligidae) and Thysanote appendiculata. (Steenstrup and Lütken, 1861) (Lernaeopodidae). Even though six species of parasitic crustaceans were recovered from the host fish, simultaneous multiple parasitism seldom occurred (only 10%). The prevalence, mean intensity, and mean abundance of each parasite were calculated. The taxonomic account, host, site, and niche-specific parasitization of each species, are discussed. The present study also reviewed and discussed the simultaneous multiple co-occurrence of parasitic crustaceans.

External Parasites of Fish: A Comprehensive Overview

Fishes are a diverse group of gill-bearing aquatic craniate animals characterized by their limbless bodies. These creatures are susceptible to various diseases, both infectious and non-infectious, which can significantly impact fish populations. One critical factor contributing to reduced fish productivity is parasitic infestation. This paper aims to provide a comprehensive overview of the external parasites that affect fish. In aquatic environments, host-parasite interactions are complex, with crustacean parasites often playing a prominent role in fish diseases and the management of captive and cultured fish stocks. Among the most common crustacean parasites of fish, we find copepods, brachiura, and isopods. Copepods, for example, encompass two major crab families: Ergasilidae and Lernaeidae. In contrast, Branchiura (Argulidae) and Isopoda members, both parasitic, generally exhibit larger body sizes than copepods. While these parasites may cause only mild harm to their hosts when present in small quantities, copepods are the most prevalent crustacean parasites in various aquatic habitats, including freshwater, brackish water, and saltwater. In the context of fish health and productivity, prevention often proves more effective than treatment. Implementing strategies such as strict controls when introducing new fish to a newly established tank, robust quarantine procedures, mechanical removal using forceps, freshwater or saltwater dips, and water treatments involving organophosphates can significantly reduce the incidence of external parasite infestations. Therefore, exercising caution when introducing new fish into a population is essential.

Long amplicons as a tool to identify variable regions of ribosomal RNA for improved taxonomic resolution and diagnostic assay design in microeukaryotes: using ascetosporea as a case study

IntroductionThere is no universally appropriate basis for delimiting species in protists, including parasites. Many molecular markers used for species delimitation are part of the ribosomal RNA (rRNA) array, with different regions of the array being used for different parasitic protist taxa. However, little is known about sequence variability across the rRNA in most organisms, and there is no standard threshold at which divergence in the sequence of a particular gene can be used as a basis for species delimitation. MethodsHere we demonstrate a method to generate the full rRNA array of parasitic protists by amplification of the array in two long, overlapping fragments followed by Illumina and Nanopore sequencing to produce high quality assemblies, to determine variations in sequence variability across the array. We apply this approach to two pairs of closely related ascetosporean parasites of crustaceans and molluscs [respectively Paramarteilia canceri/P. orchestiae and Marteilia cochillia/M. cocosarum (Rhizaria; Endomyxa; Ascetosporea)] and Bonamia ostreae and demonstrate how full-length rRNA sequences can be used to determine regions of the rRNA array that are most discriminatory, and robustly differentiate between species in combination with other lines of evidence. ResultsPhylogenetic analyses of the transcribed regions of the rRNA array demonstrate maximal support for, and separation of, all four parasite species. Sliding window global alignment analysis determined the regions of the rRNA array that had the most consistent nucleotide differences between the closely related parasites in a 1 kb region of the array. For Paramarteilia, this region was a combined internal transcribed spacer 1-5.8S-internal transcribed spacer 2 alignment, and for Marteilia, it was the external transcribed spacer. Phylogenetic analysis of these regions were able to recover the respective species, demonstrating that these regions could be used for improved diagnostic PCR assays.DiscussionOur method could be adapted to quickly generate sequence data and determine regions more suitable for diagnostic assays for a wide diversity of parasite groups. It also allows the generation of sequence data for regions of the rRNA not commonly studied (e.g. regions of the intergenic spacer), thus enabling research into their suitability as marker regions.

Sacculina-Induced Morphological Feminization in the Grapsid Crab Pachygrapsus crassipes.

Rhizocephalan barnacles (Thecostraca: Cirripedia) are parasitic crustaceans that lack appendages, segmentation, and a digestive system in adults, while instead infiltrating their hosts with a nutrient-absorbing system of rootlets. Sacculinids, belonging to the Rhizocephala order, are known for their various parasitization-induced effects on their decapod hosts, such as parasitic castration, reduction in the growth of secondary sexual characteristics, feminization of male crabs, and alteration of host behavior. In this study, we conducted field surveys in Japan at Manazuru Town (Kanagawa) on the Pacific coast, and on Sado Island and Noto Peninsula on the Sea of Japan side, and found that sacculinid-parasite-ratios on the grapsid crab Pachygrapsus crassipes were particularly high on the Sea of Japan coast. Molecular phylogenetic analysis revealed that the Manazuru population forms a single clade with Sacculina yatsui, and both Sado and Noto populations form a single clade with S. confragosa. We further demonstrated that external morphologies of male P. crassipes parasitized by sacculinids were changed to female phenotypes. This host-parasite interaction will be a useful model for understanding molecular mechanisms underlying rhizocephalan-driven morphological and behavioral feminization and castration.

110-million-years-old fossil suggests early parasitism in shrimps

Direct evidence of paleo-parasitism in crustaceans is very scarce. Epicaridean isopods are obligatory parasites of crustaceans, including decapods such as crabs, shrimps, and lobsters. Their interaction with hosts is known from fossils as far back as the Jurassic through deformations of the branchial cuticle on the hosts. Their small size and low fossilization potential, outside of those larvae that have been found in amber, makes understanding the group’s evolution challenging. Here, we report the oldest evidence of paleo-parasitism in marine shrimps and an imprint of a putative adult parasite that appears to be an epicaridean isopod. Our results suggest that the parasite–host interaction between epicaridean isopods and marine shrimps started at least 110 million years ago, and the Tethys Sea was a possible dispersal pathway for this lineage of parasites during the Jurassic and Cretaceous, as known for other marine organisms through most of the Mesozoic and Cenozoic. The oldest fossil records of bopyrid swellings associated with a large number of decapods from the Jurassic in Europe suggest that the Tethys region was a center of epicaridean distribution as a whole. Recent parasitic isopods found on dendrobranchiate shrimps are restricted to the Indo-Pacific and may represent a relict group of a lineage of parasites more widely distributed in the Mesozoic.

Fossil relatives of extant parasitic crustaceans from the Mesozoic of Europe

The fossil record of Isopoda includes remains of presumed parasites. Among the fossils which have been discussed as potential parasites are those termed as Urda Münster, 1840. Some of these fossils have been discussed as possibly related to an extant group of parasites, Gnathiidae Leach, 1814. The type species of Urda – Urda rostrata Münster, 1840 – is herein interpreted as a close relative of the group Gnathiidae, based on the shared occurrence of a number of apomorphic features. This is with Urda punctata (Münster, 1842) herein being interpreted as a junior subjective synonym of U. rostrata. However, not all of the fossils associated with the name Urda can safely be identified as close relatives of Gnathiidae. Moreover, it is unclear whether the extinct species, which can be identified as close relatives of U. rostrata and Gnathiidae form a monophyletic group, as we could not identify an autapomorphy for a natural group Urda. A new species of close relatives of Urda rostrata and Gnathiidae – Urda buechneri n. sp. – is formally described based on µCT image data. Palaega suevica Reiff, 1936 and Palaega kessleri Reiff, 1936 are found to be subjective synonyms and are re-interpreted as Urda suevica n. comb. – a species closely related to U. rostrata. Due to the documented destruction of the holotype, a herein figured fossil specimen is designated as the neotype of Urda suevica. Palaega? stemmerbergensis Malzahn, 1968 is also interpreted as a close representative of U. rostrata and herein treated as Urda stemmerbergensis n. comb. Another already formally described species – Eobooralana rhodanica gen. et comb. nov. – is interpreted as a more distant relative, which is likely to be closer related to other extant species of Isopoda than those within Gnathiidae. For three species there are not enough characters preserved to interpret them as closely related to U. rostrata and Gnathiidae: Urda? liasica Frentzen, 1937 nom. dub. (type material destroyed, description insufficient for proper diagnosis), Urda? moravica Remeš, 1912 and Urda? zelandica Buckeridge and Johns, 1996.

A Rhizocephalan Parasite Induces Pervasive Effects on Its Shrimp Host.

AbstractRhizocephalan barnacles are parasites of crustaceans that are known for dramatic effects on hosts, including parasitic castration, feminization, molt inhibition, and the facilitation of epibiosis. Most research on rhizocephalans has focused on carcinized hosts, with relatively little research directed to shrimp hosts that may experience distinct consequences of infection. Here, we describe a high-prevalence rhizocephalan-shrimp system in which multiple host changes are associated with infection: the dock shrimp Pandalus danae infected by the rhizocephalan Sylon hippolytes. In field-collected P. danae, infection by Sylon was associated with development of female sex characters at a smaller size and greater probability of epibiosis. Standardized video observations showed that infected P. danae performed grooming activities at higher rates than uninfected shrimp, suggesting that inhibited molting rather than direct behavioral modification is a likely mechanism for higher epibiosis rates. There was no difference in the composition of grooming behavior types or in general activity between infected and uninfected shrimp. Fatty acid compositions differed with infection, but total lipid concentrations did not, suggesting that parasite-driven shifts in host resource allocation were compensated or redirected from unmeasured tissues. Our results show that Sylon alters its host's role by provisioning an epibiotic substrate and also that it influences host physiology, resulting in feminization and fatty acid shifts. This study lays the groundwork for expanding rhizocephalan-shrimp research and encourages recognition of oft-ignored roles of parasitism in ecological communities.

Update of the parasitic crustacean holdings of the Museo de la Plata, Argentina

The Carcinological Collection of the División Zoología Invertebrados, Museo de La Plata (FCNyM UNLP) currently contains 2446 lots, of which 124 represent type material. There is a total of 162 batches corresponding to parasitic crustaceans. Six orders are represented in the collection and recorded here: Arguloida, Cyclopoida, Siphonostomatoida, Harpacticoida, Isopoda, and the infraclass Rizocephala, belonging to four classes of the Suphylum Crustacea. The species names are listed in systematical order, and the type locality, collection number, current taxonomic status and original bibliographic reference are given. Host and site of infection are also provided.

Response of Parasite Community Composition to Aquatic Pollution in Common Carp (Cyprinus carpio L.): A Semi-Experimental Study.

The response of parasite communities to aquatic contamination has been shown to vary with both type of pollutant and parasite lifestyle. In this semi-experimental study, we examined uptake of pharmaceutical compounds in common carp (Cyprinus carpio L.) restocked from a control pond to a treatment pond fed with organic pollution from a sewage treatment plant and assessed changes in parasite community composition and fish biometric parameters. The parasite community of restocked fish changed over the six-month exposure period, and the composition of pharmaceutical compounds in the liver and brain was almost the same as that in fish living in the treatment pond their whole life. While fish size and weight were significantly higher in both treatment groups compared to the control, condition indices, including condition factor, hepatosomatic index, and splenosomatic index, were significantly higher in control fish. Parasite diversity and species richness decreased at the polluted site, alongside a significant increase in the abundance of a single parasite species, Gyrodactylus sprostonae. Oviparous monogeneans of the Dactylogyridae and Diplozoidae families and parasitic crustaceans responded to pollution with a significant decrease in abundance, the reduction in numbers most likely related to the sensitivity of their free-living stages to pollution.

Insights into the diversification of deep-sea endoparasites: Phylogenetic relationships within Dendrogaster (Crustacea: Ascothoracida) and a new species description from a western Pacific seamount

Parasitic crustacean Dendrogaster is completely endoparasitic and is not known from any marine invertebrates other than asteroids. Understanding the diversity of this group is considerably lagging, as it is an internal parasite that is not easily detected without dissecting the host. The group is thought to have coevolved with asteroids due to its endoparasitism; however, this has not been verified due to a lack of phylogenetic studies. A molecular phylogenetic analysis was required to understand the evolution of this very specialized genus. During a biodiversity survey at An'ei Seamount established as an offshore marine protected area in Japan, we discovered an unknown species of Dendrogaster inside a recently described species of asteroids. In this study, we attempted to elucidate the phylogenetic relationships of multiple species of Dendrogaster, including a new species, Dendrogaster nike sp. nov., collected from the An'ei Seamount of the Nishi-Shichito Ridge. We determined the COI and 18S gene sequences of some Dendrogaster species and reconstructed a phylogenetic tree. Upon plotting the information of the host and habitat depth onto the phylogenetic tree, evidence of coevolution between Dendrogaster and its host, which is commonly observed in endosymbiotic organisms, was not observed. Instead, our findings suggest that species diversification in Dendrogaster may have occurred based on habitat depth rather than coevolution with the host.

Investigation of Parasitic Crustacean in the Culture Management of Clarias Gariepinus in Lagos Fish Farms

The major parasitic crustaceans infecting cultured fish species comprise Branchiurans, Leaneids, Ergasilids and Isopods causing wounds that serve as portal entry for bacterial, fungi and viral infections eventually result to morbidity, mortality and economic loss thereby necessitating investigation on prevalence and effects on predilection site of Clarias gariepinus in this study. Four hundred and eighty four fish samples of Clarias gariepinus at various developmental stages were randomly selected from fish farms across the three agro – ecological zones in Lagos Stata, Nigeria. The samples collection lasted eighteen months covering both wet and dry season while parasitology and histology examinations were carried out in a laboratory using standard methods.. The wet mounts were prepared for skin and gills. Water quality parameters monitored were pH, water temperature, dissolved oxygen, ammonia, nitrite, iron concentration, alkalinity, hardness and turbidity according to respective manual guidelines. Descriptive statistics such as frequency count, percentages, standard deviation were used to determine the level of prevalence, occurrence and distribution of the parasites. Argulus species (Branchiuran) was the only parasitic crustacean observed in this study with low prevalence and intensity of infection of 1.05% and 2 respectively found on the gills of fingerlings during the rainy season. The histological examination on infected gill revealed no alteration. The water parameters were within the acceptable limit for fish survival. The low prevalence and loads of Argulus sp indicated good management practices which possibly suppress the propagation of the parasites despite the expected influence of optimum temperature and low dissolved oxygen in favour of the parasites. Therefore, good management practices should be encouraged to reduce rate of parasitic infection that often being a primary pathway to secondary infections.

Molecular and Morphological Characterizations of the Fish Parasitic Isopod Mothocya parvostis (Crustacea: Cymothoidae) Parasitizing Optional Intermediate Hosts: Juveniles of the Cobaltcap Silverside Hypoatherina tsurugae and Yellowfin Seabream Acanthopagrus latus.

Mothocya parvostis (Isopoda: Cymothoidae) is a parasitic crustacean that infests the opercular cavities of fishes. Its main final host is the Japanese halfbeak, Hyporhamphus sajori. However, M. parvostis also infests the black sea bream, Acanthopagrus schelgelii, as an optional intermediate host. Understanding the use of optional intermediate hosts is important for understanding the life history of Cymothoidae, and further information should be obtained. In this study, we aim to investigate the life cycle of M. parvostis. We collected and examined 20 mancae and 144 juveniles of M. parvostis from 129 cobaltcap silversides, Hypoatherina tsurugae, and 494 yellowfin seabreams, Acanthopagrus latus. Molecular analysis of the cytochrome c oxidase subunit I gene and 16S rRNA genes revealed that cymothoid mancae and juveniles from the two fish species were identified to be M. parvostis. All M. parvostis on H. tsurugae and A. latus might be mancae or juveniles, with no adult parasites; thus, H. tsurugae and A. latus juveniles were optional intermediate hosts of M. parvostis. In the results of morphological description, M. parvostis juveniles infesting the final host H. sajori lacked swimming setae, while juveniles parasitizing the two optional intermediate hosts had them. Mothocya parvostis mancae infested juveniles of both species just after metamorphosis, grew with the host. As the fish grows further, the parasite detached from the fish. The parasitic status of M. parvostis in the three optional intermediate hosts indicated that M. parvostis likely reproduced from June to December, and different optional intermediate hosts were used depending on the time of year in Hiroshima Bay. Therefore, a parasitic strategy involving optional intermediate hosts might increase the infestation success of M. parvostis to H. sajori.

Freshwater fish parasite diversity in West Bengal – A review

Aquaculture has the potential to meet the need of growing demand of fish in an affordable price. But in capture and in culture fisheries the fishes face diseases that interfere in the production of fish. The occurrence of disease causes the reduced production in aquaculture or reduce the marketable value of fish because of change of flesh quality, thus hampering the production. Freshwater fishes whether they are cultured or wild face different types of diseases in their skin, gills, fins, blood, and internal organs. The parasites that cause the diseases may be protozoans or metazoans.The main protozoan freshwater fish diseases are ichthyophthiriasis, trichodiniasis, costiosis, chilodonellosis. The most common metazoan parasitic diseases of freshwater fishes are dactylogyrusis, gyrodactylosis, argulosis, myxosporidiasis, ligulosis, ergasilosis, lernaesis, etc. The focus of this review is to screen the research studies that takes place on freshwater fish parasites of West Bengal. The review also aims to study the diversity of freshwater fish parasites in West Bengal, so that it will helps the researcher to get an idea about the freshwater fish parasites and their mode of infection in the fishes. The research work that takes place in different regions of West Bengal. Some of them reveal new species of parasites in fishes. Protozoan, cnidarian, acanthocephalan, nematode, cestode, trematode, crustacean parasites are identified in freshwater fishes of West Bengal. Among the protozoans cailiates, flagellates are identified. Trichodinids are very common protozoan fish parasites in most districts. Parasites under genus Myxobolus, Dactylogyrus, Gyrodactylus, Argulus, Lernea are common among the metazoans.

An Investigation on Argulus foliaceus (Crustacea) Infestation of Fishes in the Kunduzlar Dam Lake

In this study, crustacean parasite species, Argulus foliaceus was investigated on the seven fish species (Alburnus escherichii, Barbus plebejus, Capoeta tinca, Carassius gibelio, Chondrostoma nasus, Cyprinus carpio, Squalius cephalus) from the Kunduzlar Dam Lake in Kırka-Eskişehir, Türkiye. The parasite was found on the gills, fins, and skin of all of the host fish species except Chondrostoma nasus. Its prevalence and mean intensity of the parasitic infection value for the infected six fish species are as follows: 3 out of 38 Alburnus escherichii (prevalence 7.9%, mean intensity 4.3±3.1), 9 out of 16 Barbus plebejus (56.2%, 47.9±28.5), 12 out of 47 Capoeta tinca (25.5%, 27.5±18.9), 7 out of 17 Carassius gibelio (41.1%, 6.9±5.3), 4 out of 4 Cyprinus carpio (100%, 4.3±4.2) and 6 out of 14 Squalius cephalus (42.8%, 2.3±1.8). Argulus foliaceus was recorded for A. escherichii among the six host fish species for the first time within the study area from Türkiye. Thus, a new host fish species and a new locality have been added to the geographical infestation zone of the A. foliaceus species from Türkiye, which is located in the southeast region of Eurasia. Parasitological findings were evaluated concerning seasonal, age, and gender groups of the host fishes. In conclusion, A. foliaceus infestation was observed higher in summer due to the increased in water temperature, which is significantly different from winter, spring, and autumn. The infestation of A. foliaceus was more common in larger fish than in smaller fish. Moreover, the similar rates of infestation were recorded between the male and female fish.

Giáp xác ký sinh trên ghẹ chữ thập Charybdis feriata Linnaeus, 1758 khu vực vịnh Nha Trang

Charybdis feriata (Linnaeus, 1758) is wide distribution and high economic value species in many countries around the world. In Vietnam, Charybdis feriata is on the list of endangered species that need to be conserved. Parasites cause many effects on the growth and development of crabs, which may be one of the causes leading to the decline of host populations. This paper presents the species composition, parasitic sites and infection status of parasitic crustaceans on C. feriata in Nha Trang Bay. From 113 individuals of Charybdis feriata collected in June and July 2022, we have identified 6 species of parasitic crustaceans, of which 2 species have been recorded for the first time on this crab, including: Octolasmis neptuni, Semibalanus sp.. Each infested crab is infected with up to 5 species of parasites. Octolasmis angulata was the dominant species with the highest prevalence and median intensity of infection at 44.4% and 6.5 individuals/infected crabs, respectively. Comparison of infection status by sex and host size showed that Sacculina serenei infection rate was higher in female crabs than male crabs, while infection intensity in male crabs was higher than female crabs. The prevalence and intensity of infection with Octolasmis angulata species increased significantly with host size. There was no statistical difference between the different host groups of sex and size. The data on parasitic crustaceans on Charybdis feriata contribute to the basis for the recovery, sustainable development of this endangered species.