Trichodinid ectoparasites (ciliphora: Peritrichida) of some marine fishes from coastal regions of the Yellow Sea and Bohai Sea

Histopathology, immunoenzyme activity and transcriptome analysis of immune response in silver pomfret infected by cryptokaryon (Cryptorchidism irritant)

Cryptorchidism irritant (CI) infection is a major problem in the culturing process of silver pomfret (Pampus argenteus), which can result in rapid and massive death. However, there is limited information available on the immune response of silver pomfret infected by CI. To address this gap, we sampled naturally infected fish and observed milky white translucent oval CI trophozoites on the gills, body surface, and fin rays. Histological analysis showed that CI infection led to vacuolation of epithelial cells and a decrease in blood cells in the gills. We also performed transcriptome profiling of the gill, kidney complex, and spleen, generating 399,616,194 clean reads that assembled into 101,228 unigenes, which were annotated based on public databases. We detected 14,369 differentially expressed genes, and selected several key immune-related genes for further validation using RT-qPCR. The Graft-versus-host pathway and Allograft rejection pathway were enriched in the gills, leading to inflammation and ulceration. CI infection activated the immune system, increasing levels of interleukin-1 beta and MHC class II antigen, and also activated innate and acquired immune genes in silver pomfret. Furthermore, we measured the activities of five immune-related enzymes (SOD, AKP, CAT, CSH and ACP), which all increased to varying degrees after CI infection. Our findings enhance our understanding of the immune response of fish to parasitic infection and may contribute to the development of strategies to prevent high mortality in CI-stimulated fish in aquaculture.

Immune response of silver pomfret (Pampus argenteus) to Amyloodinium ocellatum infection

Amyloodinium ocellatum (AO) infection in silver pomfret (Pampus argenteus) causes extensive mortality. Insufficient information exists on the molecular immune response of silver pomfret to AO infestation, so herein we simulated the process of silver pomfret being infected by AO. Translucent trophosomes were observed on the gills of AO-infected fish. Transcriptome profiling was performed to investigate the effects of AO infection on the gill, kidney complex and spleen. Overall, 404,412,298 clean reads were obtained, assembling into 96,341 unigenes, which were annotated against public databases. In total, 2730 differentially expressed genes were detected, and few energy- and immune-related genes were further assessed using RT-qPCR. Moreover, activities of three immune-related (SOD, AKP and ACP) and three energy-related (PKM, LDH and GCK) enzymes were determined. AO infection activated the immune system and increased interleukin-1 beta and immunoglobulin M heavy chain levels. Besides, the PPAR signalling pathway was highly enriched, which played a role in improving immunity and maintaining homeostasis. AO infection also caused dyspnoea, leading to extensive lactic acid accumulation, potentially contributing towards a strong immune response in the host. Our data improved our understanding regarding the immune response mechanisms through which fish coped with parasitic infections and may help prevent high fish mortality in aquaculture.

Trichodinids (Ciliophora: Trichodinidae) on Rocky-tidal Fishes from the Baja California Peninsula, Mexico

Information regarding trichodinid ectoparasites on marine fishes of North America is relatively scarce. In this study, 5 ciliate species from the family Trichodinidae were found associated with 8 fish hosts from the rocky intertidal zone of the western coast of the Baja California Peninsula (BCP), Mexico. All of the host-parasite relationships recorded here are new. Furthermore, 3 of the trichodinid species found are recorded for the first time for Mexico. Trichodinids taxa do not show a noticeable distributional gradient along the BCP, which suggests a wide-continuous distribution of the species throughout the study area.

Parasites of cartilaginous fishes (Chondrichthyes) in South Africa - a neglected field of marine science

Southern Africa is considered one of the world's 'hotspots' for the diversity of cartilaginous fishes (Chondrichthyes), with currently 204 reported species. Although numerous literature records and treatises on chondrichthyan fishes are available, a paucity of information exists on the biodiversity of their parasites. Chondrichthyan fishes are parasitised by several groups of protozoan and metazoan organisms that live either permanently or temporarily on and within their hosts. Reports of parasites infecting elasmobranchs and holocephalans in South Africa are sparse and information on most parasitic groups is fragmentary or entirely lacking. Parasitic copepods constitute the best-studied group with currently 70 described species (excluding undescribed species or nomina nuda) from chondrichthyans. Given the large number of chondrichthyan species present in southern Africa, it is expected that only a mere fraction of the parasite diversity has been discovered to date and numerous species await discovery and description. This review summarises information on all groups of parasites of chondrichthyan hosts and demonstrates the current knowledge of chondrichthyan parasites in South Africa. Checklists are provided displaying the host-parasite and parasite-host data known to date.

First record of Trichodina heterodentata (Ciliophora: Trichodinidae) from channel catfish, Ictalurus punctatus cultivated in Brazil

This study characterises morphologically Trichodina heterodentata Duncan, 1977 from channel catfish, Ictalurus punctatus (Rafinesque, 1818) in the State of Santa Catarina, Brazil. Body and gill smears were air-dried at room temperature, impregnated with silver nitrate and/or stained with Giemsa. Ten characteristics were selected to compare the present material with other morphological characterisations of T. heterodentata. Prevalence rate was 100%, mean intensity 89,333.70 (3,125 to 299,100 parasites per host). Trichodina heterodentata was considered medium-sized trichodinid with mean body diameter 59.4 ± 8.5 μm, denticulate ring 38.5 ± 4.5 μm, adhesive disc 60.2 ± 6.7 μm diameter and 24.4 ± 1.6 denticles. In relation to previous reports of T. heterodentata this material resembles in 90% of the analysed characters. This work confirms the biometrical variation that exists in the different populations of T. heterodentata. A list of hosts and comparative measurements of T. heterodentata are presented and the channel catfish is considered a new host.

Trichodina magna Van As and Basson, 1989 (Ciliophora: Peritrichia) from cultured Nile tilapia in the state of Santa Catarina, Brazil

Specimens of Trichodina magna Van As and Bassson, 1989 (Ciliophora: Peritrichia) from the Nile tilapia Oreochromis niloticus collected from October 2004 to June 2005 in fish ponds situated in three regions of Santa Catarina State, Brazil are described here. Wet smears of skin and gills were prepared in the field, air dried, impregnated with Klein's dry silver method and Giemsa's solution. From a total of 146 examined fish, 36 were parasitized on the skin, 14 in the gills and 33 on the skin and gills, simultaneously. The mean diameter of the body of the specimens of T. magna was 84.3 +/- 12.6 microm, adhesive disc 60.7 +/- 10.0 microm, denticulate ring, 38.3 +/- 7.4 microm, consisting of 26 (23 to 29) denticles. The only distinguishable difference from the original description was the fact that the ray of the denticle is anteriorly directed and does not extend over the y + 1 axis.

Trichodinid ectoparasites (Ciliophora: Peritricha) from Misgurnus anguillicaudatus (Cantor) and Anodonta woodiana (Lea) in China, with descriptions of two new species of Trichodina Ehrenberg, 1838

During parasitological surveys in Chongqing, China, three trichodinids infecting a freshwater fish, Misgurnus anguillicaudatus (Cantor), and a mollusc, Anodonta woodiana (Lea), were investigated. Two of these species were found to be new. Trichodina lechriodentata n. sp., from the fish, was identified by its small-sized body and irregularly rectangular blade, while T. rara n. sp., from the mollusc, is characterised by its overall dimensions, denticle morphology and the presence of a white speckle in some specimens. T. modesta Lom, 1979 is also described from the fish. Photomicrographs and morphometric data are presented for all of the species.

Taxonomy of trichodinids from the gills of marine fishes in coastal regions of the Yellow Sea, with descriptions of two new species of Trichodina Ehrenberg, 1830 (Protozoa: Ciliophora: Peritrichia)

Seven species of marine fishes from coastal regions of the Yellow Sea were examined for ectoparasitic trichodinids (Protozoa, Ciliophora). A total of seven species belonging to the genus Trichodina Ehrenberg, 1830, including two new species, occurred as gill parasites. These were T. rectispina n. sp., T. circinantis n. sp., T. frequentis Shtein, 1979, T. jarmilae Lom & Laird, 1969, T. hexagrammi Zhukov, 1964, T. minima Shtein, 1979 and T. ovonucleata Raabe, 1958. Each was investigated following silver nitrate and protargol impregnation. Morphometric data and comparative descriptions of these trichodinids are provided along with details of their prevalence and intensity of infestation.