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Juvenile Platax orbicularis switches foraging tactics from diurnal herbivory to nocturnal zooplanktivory within a day. To examine how juvenile fish actively feed on zooplankton prey during nighttime, a field-recorded video analysis was conducted in the reefs off Kuchierabu-jima Island, southern Japan. Juveniles consistently showed fast and sudden attacks that were accurately directed at individual zooplankton prey, and changed feeding frequencies with different prey densities. A negative relationship was observed between feeding frequency and prey density, with higher feeding frequencies occurring at lower prey concentrations, implying a disturbance effect of clouded zooplankton prey on the juvenile fish. A clear transition from a ram-based to a suction-based feeding mode was observed with fish size, suggesting that changes in the feeding behaviors occur even in juveniles fishes, without drastic morphological changes.

The orbicular batfish (Platax orbicularis), also called ‘Paraha peue’ in Tahitian, is the most important marine fish species reared in French Polynesia. Sudden and widespread outbreaks of severe ‘white-patch disease’ have occurred since 2011 in batfish farms one to three weeks after the transfer of juveniles from bio-secured hatcheries to lagoon cages. With cumulative mortality ranging from 20 to 90%, the sustainability of aquaculture of this species is severely threatened. In this study, we report for the first time the isolation from diseased batfish of several isolates belonging to the species Tenacibaculum maritimum, a major pathogen of many marine fish species. Histopathological analysis, an experimental bath challenge and a field monitoring study showed that T. maritimum is associated with ‘white-patch disease’. Moreover, molecular and serological analyses performed on representative isolates revealed some degree of genetic diversity among the isolates, a finding of primary importance for epidemiological studies and the development of management and control strategies such as vaccination.

Although the clinical course and pathogenesis of lymphocystis disease virus (LCDV) infection have been extensively described in freshwater and seawater environments, lymphocystis disease has not been studied in the copperband butterflyfish (Chelmon rostratus) or described at the molecular level in orbicular batfish (Platax orbicularis). The present study aimed to identify LCDV in a copperband butterflyfish and an orbicular batfish using light and electron microscopy (morphological) and molecular methods, namely PCR followed by phylogenetic analysis. We present a case series of two representatives of two distinct fish species with stress-induced chronic LCDV infection, which presented with typical, recurring, macroscopically visible lymphocystis nodules on their pectoral, caudal, and dorsal fins. After collecting lymphocystis nodules from live animals using skin scraping, we processed the hypertrophic giant cells for qualitative analysis using light and electron microscopy. Through our qualitative morphological analysis, we also share intimate observations of putative viral replication and assembly in the intracytoplasmic inclusion bodies of lymphocystis nodules. We present LCDV infection in a novel species, the copperband butterflyfish, and our molecular analysis identified the virus from the orbicular batfish as a novel LCDV species.

Mimesis is a relatively widespread phenomenon among reef fish, but the ontogenetic processes relevant for mimetic associations in fish are still poorly understood. In the present study, the allometric growth of two allopatric leaf-mimetic species of ephippid fishes, Chaetodipterus faber from the Atlantic and Platax orbicularis from the Indo-Pacific, was analyzed using ten morphological variables. The development of fins was considered owing to the importance of these structures for mimetic behaviors during early life stages. Despite the anatomical and behavioral similarities in both juvenile and adult stages, C. faber and P. orbicularis showed distinct patterns of growth. The overall shape of C. faber transforms from a rounded-shape in mimetic juveniles to a lengthened profile in adults, while in P. orbicularis, juveniles present an oblong profile including dorsal and anal fins, with relative fin size diminishing while the overall profile grows rounder in adults. Although the two species are closely-related, the present results suggest that growth patterns in C. faber and P. orbicularis are different, and are probably independent events in ephippids that have resulted from similar selective processes.

Ephippidae fish are characterized by a discoid shape with a very small visceral cavity. Among them has a high economic potential due to its flesh quality and flesh to carcass ratio. Nonetheless, the development of its aquaculture is limited by high mortality rates, especially due to infection, occurring one to three weeks after the transfer of fishes from bio-secure land-based aquaculture system to the lagoon cages for growth. Among the lines of defense against this microbial infection, the gastrointestinal tract (GIT) is less studied. The knowledge about the morphofunctional anatomy of this organ in is still scarce. Therefore, the aims of this study are to characterize the GIT in non-infected juveniles to then investigate the impact of on this multifunctional organ. In the first place, the morpho-anatomy of the GIT in non-infected individuals was characterized using various histological techniques. Then, infected individuals, experimentally challenged by were analysed and compared to the previously established GIT reference. The overlapped shape of the GIT of is probably due to its constrained compaction in a narrow visceral cavity. Firstly, the GIT was divided into 10 sections, from the esophagus to the rectum. For each section, the structure of the walls was characterized, with a focus on mucus secretions and the presence of the Na /K ATPase pump. An identification key allowing the characterization of the GIT sections using histology is given. Secondly, individuals challenged with exhibited differences in mucus type and proportion and, modifications in the mucosal and muscle layers. These changes could induce an imbalance in the trade-off between the GIT functions which may be in favour of protection and immunity to the disadvantage of nutrition capacities.

Examination of three species of batfishes (Teleostei: Epphippidae) from off Lizard and Heron Islands on the Great Barrier Reef led to the discovery of specimens of the trematode genus Paradiscogaster Yamaguti, 1934 (Digenea: Faustulidae). Morphological analysis demonstrated that the new specimens represented four morphotypes which we interpret to be new species: Paradiscogaster martini n. sp., P . vichovae n. sp. and P . brayi n. sp. from Platax orbicularis (Forsskål) and P. pinnatus (Linnaeus) off Lizard Island, and P . nitschkei n. sp. from P. teira (Forsskål) off Heron Island. Published material was re-examined and the specimens identified as P. chaetodontis okinawensis Yamaguti, 1971 from P. pinnatus from Okinawa, Japan, actually represent the new species P . brayi n. sp., demonstrating that some species of Paradiscogaster have wide geographical distributions. ITS2 rDNA data for the four morphotypes differ by 4–39 base pairs confirming the delineation of the four species proposed. A feature of this study is the recognition of Platax spp. as an important host group for Paradiscogaster , with the new species placing them as the second richest host group for these parasites after the Chaetodontidae.

The general morphological shape of plant-resembling fish and plant parts were compared using a geometric morphometrics approach. Three plant-mimetic fish species, Lobotes surinamensis (Lobotidae), Platax orbicularis (Ephippidae) and Canthidermis maculata (Balistidae), were compared during their early developmental stages with accompanying plant debris (i.e., leaves of several taxa) in the coastal subtropical waters around Kuchierabu-jima Island, closely facing the Kuroshio Current. The degree of similarity shared between the plant parts and co-occurring fish species was quantified, however fish remained morphologically distinct from their plant models. Such similarities were corroborated by analysis of covariance and linear discriminant analysis, in which relative body areas of fish were strongly related to plant models. Our results strengthen the paradigm that morphological clues can lead to ecological evidence to allow predictions of behavioural and habitat choice by mimetic fish, according to the degree of similarity shared with their respective models. The resemblance to plant parts detected in the three fish species may provide fitness advantages via convergent evolutionary effects.

Cet ouvrage fait le point sur la biologie du Platax, son cycle de vie, le comportement mimétique de ses juvéniles, sa place dans la filière du poisson lagonaire. Il présente les éléments novateurs en termes de qualité et de production.

Abstract The orbicular batfish (Platax orbicularis), also called ‘Paraha peue’ in Tahitian, is the most important marine fish species reared in French Polynesia. Sudden and widespread outbreaks of severe ‘white-patch disease’ have occurred since 2011 in batfish farms one to three weeks after the transfer of juveniles from bio-secured hatcheries to lagoon cages. With cumulative mortality ranging from 20 to 90%, the sustainability of aquaculture of this species is severely threatened. In this study, we describe for the first time the isolation from diseased batfish of several strains belonging to the species Tenacibaculum maritimum, a major pathogen of many marine fish species. Histopathological analysis, an experimental bath challenge and a field monitoring study showed that T. maritimum is associated with white-patch disease. Moreover, molecular and serological analyses performed on representative strains revealed some degree of genetic diversity among the isolates, a finding of primary importance for epidemiological studies and for the development of management and control strategies such as vaccination.

This work uses scientific work by the Polynesian Fisheries Department (SPE) and Ifremer to enlighten the reader on the biology of the Platax, its life cycle, the mimetic behaviour of its young and its place in the lagoon fish chain. It presents fresh elements: a reliable method of obtaining quality fry and prospects for producing commercially-sized fish with a secure breeding benchmark. The result is an initial transfer of know-how to the profession which is essential if the activity is to develop further.Original Abstract: Cet ouvrage fait le point sur la biologie du Platax, son cycle de vie, le comportement mimetique de ses juveniles, sa place dans la filiere du poisson lagonaire. Il presente les elements novateurs en termes de qualite et de production.