Life Cycle and Life History Strategies of Parasitic Crustacea

Isopods infesting Atlantic bonefish (Albula vulpes) host novel viruses, including reoviruses related to global pathogens, and opportunistically feed on humans

Isopods infest fish worldwide, but their role as disease vectors remains poorly understood. Here, we describe infestation of Atlantic bonefish (Albula vulpes) in Belize with isopods in two of three locations studied, with infestation rates of 15 and 44%. Isopods fed aggressively, and infested fish showed missing scales and scars. Gross morphologic and molecular phylogenetic analyses revealed the isopods to cluster within the family Aegidae and to be most closely related to members of the genus Rocinela, which are globally distributed micro-predators of fish. Metagenomic analysis of 10 isopods identified 11 viruses, including two novel reoviruses (Reovirales) in the families Sedoreoviridae and Spinareoviridae. The novel sedoreovirus clustered phylogenetically within an invertebrate-specific clade of viruses related to the genus Orbivirus, which contains arboviruses of global concern for mammal health. The novel spinareovirus clustered within the fish-infecting genus Aquareovirus, which contains viruses of global concern for fish health. Metagenomic analyses revealed no evidence of infection of bonefish with the novel aquareovirus, suggesting that viremia in bonefish is absent, low, or transient, or that isopods may have acquired the virus from other fish. During field collections, isopods aggressively bit humans, and blood meal analysis confirmed that isopods had fed on bonefish, other fish, and humans. Vector-borne transmission may be an underappreciated mechanism for aquareovirus transmission and for virus host switching between fish and other species, which has been inferred across viral families from studies of deep virus evolution.

Investigating dynamics, etiology, pathology, and therapeutic interventions of Caligus clemensi and Vibrio alginolyticus co-infection in farmed marine fish

This study investigated a disease outbreak characterized by caligid copepod infestations and subsequent secondary bacterial infections in European seabass (Dicentrarchus labrax) and flathead grey mullet (Mugil cephalus) cultivated at a private facility in the Deeba Triangle region of Egypt. Moribund fish displayed brown spots on the skin, tongue, and gills, along with lethargy and excess mucus. The fish suffered severe infections, exhibiting external hemorrhages, ulcers, and ascites. The fish had pale, enlarged livers with hemorrhaging. Comprehensive parasitological, bacteriological, molecular, immunity and histopathological analyses were conducted to identify the etiological agents and pathological changes. Caligid copepod infestation was observed in wet mounts from the buccal and branchial cavities of all examined fish, and the caligids were identified as Caligus clemensi through COI gene sequencing and phylogenetic analysis. Vibrio alginolyticus was confirmed as a secondary bacterial infection through biochemical tests, recA gene sequencing, and phylogenetic analyses. Antibiotic susceptibility testing revealed resistance to β-lactams, aminoglycosides, and trimethoprim-sulfamethoxazole in V. alginolyticus isolates. Upregulation of the inflammatory marker IL-1β in gill and skin tissues indicated a robust cell-mediated immune response against the pathogens. Histopathological examination revealed severe tissue damage, hyperplasia, hemorrhage, and congestion in the gills, along with hepatocellular degeneration and steatosis in the liver, providing initial insights into this outbreak. A comprehensive therapeutic regimen was implemented, comprising prolonged hydrogen peroxide immersion baths, followed by the application of the nature-identical plant-based compound Lice-less and probiotic Sanolife Pro-W supplementation. This integrated approach effectively eliminated C. clemensi infestations, controlled secondary bacterial infections, and restored fish health, reducing morbidity and mortality rates to minimal levels.

Niche partitioning and host specialisation in fish-parasitising isopods: Trait-dependent patterns from three ecosystems on the east coast of India

Due to their large size and obligate nature, Cymothoid isopods inflict a high degree of tissue damage to fish. Still, they are understudied at an ecosystem level despite their global presence and ecological role. In this work, we collected fish host-isopod parasite data, along with their life history and ecological traits, from the northern part of the east coast of India and investigated patterns in host specialisation and preference of isopod parasites using a trait-based network perspective. We observed that the region of attachment of the parasite (buccal cavity, branchial cavity, and skin) and host fish ecology (schooling behaviour and habitat characteristics) influenced host specialisation and preference. We found that branchial cavity-attaching parasites preferred schooling, pelagic fishes, whereas buccal cavity-attaching parasites preferred mostly non-schooling, demersal fishes. Skin-attaching parasites were found to be generalists and had no preference based on our examined host traits.

New occurrence of Cirolana capricornica (Isopoda: Cirolanidae) from Epinepheluschlorostigma in Suez Governorate, Egypt

Background and Aim

The isopods of the Crustacea are noteworthy. All marine, fresh, and brackish waterways at all depths are home to aquatic organisms. This order also includes species that live on land. This study aimed to report a new occurrence of the isopod Cirolana capricornica on the operculum, mouth, and body cavities of Epinephilus chlorostigma in the Suez Governorate, Egypt.

Materials and Methods

With the help of fishermen, 50 live E. chlorostigma (Linnaeus, 1758) were randomly gathered along the Red Sea coast of the Suez Governorate during November and December 2019 for the current investigation. Isopods were isolated from the fish samples and captured using light and electron microscopy for morphological identification.

Results

Some fish were emaciated, and minute white isopods were attached externally to the skin near the gills and mouth cavity, and internally to the mouth cavity. No correlation was observed between body cavity attachment and gross lesions. The prevalence of infestation was 16%.

Conclusion

C. capricornica was identified using optical and electron microscopy to analyze the isopod specimens' morphology. This scavenging isopod species is newly discovered in Egypt.

Component communities and annual and seasonal variations of metazoan parasites in Eleotris pisonis (Gmelin, 1789) (Gobiiformes: Eleotridae) in the Amazon River, Brazil

Our hypothesis for this study was that annual and seasonal variations do not influence the structure of the component communities and the diversity of metazoan parasites of spinycheek sleeper (Eleotris pisonis) in the Amazon River, state of Amapá, Brazil. A total of 164 fish were collected between 2020 and 2021, from which 888 parasites were found. In 2020, five species of parasites were found (one Nematoda, one Digenea, one Acanthocephala, one Arachnida and one Crustacea); and in 2021, five species were also found (three Nematoda, one Digenea and one Crustacea). Larvae of Contracaecum sp. were the dominant taxon throughout the study. The parasite species richness and Brillouin diversity index were higher in 2021, without significant differences between seasonal periods. Some component communities of parasites showed differences between years and between seasonal periods. These facts do not support the hypothesis that such variables would not influence the component communities of the parasites. Lastly, this report provides the first records of Spirocamallanus inopinatus, Genarchella genarchella, Acari, Ergasilus sp., Neoechinorhynchus sp., larvae of Pseudoproleptus sp. and larvae of Contracaecum sp. in E. pisonis.

Checklist of parasitic isopods from Brazil: Bopyroidea and Cryptoniscoidea (Isopoda: Cymothoida: Epicaridea)

All species of Brazilian parasitic isopods belonging to Epicaridea (Bopyroidea and Cryptoniscoidea) known to date, including references and distribution information, are listed. The list comprises 37 valid species, 18 of which are endemic to the country, 17 are also recorded from other countries in the Americas, and only two species are distributed outside of the American continent as well. Synonym list, known hosts and distribution are given for each of the species, along with taxonomic and ecological remarks when relevant.

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.

Embryonic and post-embryonic development in the parasitic copepod Ive ptychoderae (Copepoda: Iviidae): Insights into its phylogenetic position

Parasitic copepods are frequently discovered in many marine animals, and they exhibit great species diversity with remarkable morphological adaptations to their parasitic lifestyle. Similar to their free-living relatives, parasitic copepods usually develop through complex life cycle, but they eventually transform into a modified adult form with reduced appendages. Although the life cycle and distinct larval stages have been described in a few species of parasitic copepods, particularly those infecting commercially valuable marine animals (such as fishes, oysters, and lobsters), very little is known about the developmental process of the species that transformed into extremely simplified adult body plan. This paucity also causes some difficulties when investigating the taxonomy and phylogeny of this kind of parasitic copepods. Here we describe the embryonic development and a series of sequential larval stages of a parasitic copepod, Ive ptychoderae, which is a vermiform endoparasite living inside the hemichordate acorn worms. We devised laboratory regimes that enable us raising large quantity of embryos and free living larvae, and obtaining post-infested I. ptychoderae samples from the host tissues. Using defined morphological features, the embryonic development of I. ptychoderae can be categorized into eight stages (1-, 2-, 4-, 8-, 16- cell stages, blastula, gastrula, and limb bud stages) and the post-embryonic development comprises six larval stages (2 naupliar and 4 copepodid stages). Based on the comparisons of morphological characters in the nauplius stage, our results provide evidence to support that the Ive-group is more closely related to the Cyclopoida, which represents one of the two major clades that contain many highly transformed parasitic copepods. Thus, our results help to resolve the problematic phylogenetic position of the Ive-group in previous study based on analysis using 18S rDNA sequences. Combining with more molecular data, future comparative analyses on the morphological features of copepodid stages will further refine our understanding of the phylogenetic relationships of parasitic copepods.

Morphological and functional structure of two Ergasilidae parasites determine their microhabitat affinity on the gills of an Anostomidae fish from the Amazon

The aim of this study was to investigate the microhabitat affinities of Ergasilus sp. and Therodamas longicollum on the gills of Leporinus fasciatus ("aracu-piau"), an anostomid fish from the Amazon. A total of 143 specimens of L. fasciatus were examined, of which 35% had their gills parasitized by at least one ergasilid species. A total of 159 specimens of Ergasilus sp. and 97 specimens of T. longicollum were recovered. Both ergasilids species exhibited a greater affinity for attachment in arch 1 of the gills of the host. There was a negative correlation between the abundance of Ergasilus sp. and the abundance of T. longicollum within each gill arch. Analysis of distribution along the gill arch showed a higher occurrence of Ergasilus sp. in Section 5, while T. longicollum occurred mainly in Section 3 of the gills. There was a positive correlation between the abundance of these ectoparasites and the size of the gill arch. Ergasilus sp. occurred only on the filament of the gill arch and exhibited affinity for the proximal region, while T. longicollum occurred only in the gill arch itself. The results reveal that these two parasite species compete in the gills of the host without the overlapping of their niches.

Redescription of the rare, deep-sea hyperiidean amphipod Megalanceoloides remipes (K.H. Barnard, 1932) (Crustacea: Amphipoda: Hyperiidea), including the first description of males

Megalanceoloides remipes is a rare deep-sea species known from very few specimens. Until recently (Zeidler 2019) it was known only from the type, an incomplete female, and one other specimen, probably a juvenile female (Vinogradov 1964). Another specimen, an ovigerous female, described by Gasca Haddock (2016) and compared to the previous two, was later considered to be a new species, M. aequanime Gasca, 2017 (Gasca Browne 2017). More recently, Williams Bunkley-Williams (2019) proposed another new species, M. gascae, for the specimen described by Vinogradov (1964). Thus, a redescription of M. remipes is still required, especially in light of the two new species proposed by these authors. The recent discovery of several specimens of M. remipes, including both sexes, in the USNM (Zeidler 2019) has now made it possible to provide a detailed redescription of the species, together with the first description of males, enabling a better comparison with M. aequanime and M. gascae.

Ectoparasites infecting Mugil curema (Mugiliformes: Mugilidae) in Amapá state estuary, in the northern Brazilian coast region

In fish, one of the most important interactions is that occur between parasite species and environment. Wild fish interactions with parasites of different taxa can result in diseases for fish and consequently damages to the fishing industry. This study investigated the ectoparasite fauna in Mugil curema (Valenciennes, 1836), in Amapá state estuary, in Brazilian coast region. The parasite prevalence was 51.4%, and a total of 282 parasites were collected among Ligophorus brasiliensis (Abdallah, Azevedo & Luque 2009), Excorallana longicornis (Lemos de Castro, 1960), larvae of Gnathia sp. and Ergasilus atafonensis (Amado & Rocha, 1995), but L. brasiliensis was the dominant parasite. The parasites presented highly aggregated dispersion, except for Gnathia sp. that had a random dispersion. There was a predominance of hosts non-parasitized and parasitized by one species. The relative condition factor did not differ between parasitized and non-parasitized fish. The body size of hosts did not influence the parasite abundance. The community of ectoparasites consisted of low species richness with low infection levels. This is the first study on parasites of fish from the coast of the State of Amapá and is the first report of Gnathia sp. for M. curema.

Phanerozoic parasitism and marine metazoan diversity: dilution versus amplification

Growing evidence suggests that biodiversity mediates parasite prevalence. We have compiled the first global database on occurrences and prevalence of marine parasitism throughout the Phanerozoic and assess the relationship with biodiversity to test if there is support for amplification or dilution of parasitism at the macroevolutionary scale. Median prevalence values by era are 5% for the Paleozoic, 4% for the Mesozoic, and a significant increase to 10% for the Cenozoic. We calculated period-level shareholder quorum sub-sampled (SQS) estimates of mean sampled diversity, three-timer (3T) origination rates, and 3T extinction rates for the most abundant host clades in the Paleobiology Database to compare to both occurrences of parasitism and the more informative parasite prevalence values. Generalized linear models (GLMs) of parasite occurrences and SQS diversity measures support both the amplification (all taxa pooled, crinoids and blastoids, and molluscs) and dilution hypotheses (arthropods, cnidarians, and bivalves). GLMs of prevalence and SQS diversity measures support the amplification hypothesis (all taxa pooled and molluscs). Though likely scale-dependent, parasitism has increased through the Phanerozoic and clear patterns primarily support the amplification of parasitism with biodiversity in the history of life.

This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.