Giuseppe Paladini

Economic costs of protistan and metazoan parasites to global mariculture

Parasites have a major impact on global finfish and shellfish aquaculture, having significant effects on farm production, sustainability and economic viability. Parasite infections and impacts can, according to pathogen and context, be considered to be either unpredictable/sporadic or predictable/regular. Although both types of infection may result in the loss of stock and incur costs associated with the control and management of infection, predictable infections can also lead to costs associated with prophylaxis and related activities. The estimation of the economic cost of a parasite event is frequently complicated by the complex interplay of numerous factors associated with a specific incident, which may range from direct production losses to downstream socio-economic impacts on livelihoods and satellite industries associated with the primary producer. In this study, we examine the worlds major marine and brackish water aquaculture production industries and provide estimates of the potential economic costs attributable to a range of key parasite pathogens using 498 specific events for the purposes of illustration and estimation of costs. This study provides a baseline resource for risk assessment and the development of more robust biosecurity practices, which can in turn help mitigate against and/or minimise the potential impacts of parasite-mediated disease in aquaculture.

Gyrodactylus salinae n. sp. (Platyhelminthes: Monogenea) infecting the south European toothcarp Aphanius fasciatus (Valenciennes) (Teleostei, Cyprinodontidae) from a hypersaline environment in Italy

BackgroundHistorically, non-native species of Gambusia (Poeciliidae) have been used to control larval stages of the Asian tiger mosquito, Stegomyia albopicta Reinert, Harbach et Kitching, 2004 throughout Italy. The potential utility of indigenous populations of Aphanius fasciatus (Valenciennes) (Teleostei: Cyprinodontidae) as an appropriate alternative biological control is currently being explored. A sub-sample of ten fish collected from Cervia Saline, Italy (salinity 65 ppt; 30°C) to assess their reproductive capability in captivity, harboured a moderate infection of Gyrodactylus von Nordmann, 1832 (Platyhelminthes, Monogenea). A subsequent morphological and molecular study identified this as being a new species.ResultsGyrodactylus salinae n. sp. is described from the skin, fins and gills of A. fasciatus. Light and scanning electron microscopical (SEM) examination of the opisthaptoral armature and their comparison with all other recorded species suggested morphological similarities to Gyrodactylus rugiensoides Huyse et Volckaert, 2002 from Pomatoschistus minutus (Pallas). Features of the ventral bar, however, permit its discrimination from G. rugiensoides. Sequencing of the nuclear ribosomal DNA internal transcribed spacers 1 and 2 and the 5.8S rRNA gene and a comparison with all species listed in GenBank confirmed they are unique and represent a new species (most similar to Gyrodactylus anguillae Ergens, 1960, 8.3% pair-wise distance based on 5.8S+ITS2) . This represents the first species of Gyrodactylus to be described from Aphanius and, to date, has the longest ITS1 (774 bp) sequenced from any Gyrodactylus. Additional sampling of Cervia Saline throughout the year, found G. salinae n. sp. to persist in conditions ranging from 35 ppt and 5°C in December to 65 ppt and 30°C in July, while in captivity a low level of infection was present, even in freshwater conditions (0 ppt).ConclusionsThe ability of G. salinae n. sp. to tolerate a wide range of salinities and temperatures shows its potential to readily adapt to several environmental conditions. These findings, together with the fact that A. fasciatus is a protected species and is considered as a biological control organism, necessitate further studies on the ecology and virulence of G. salinae n. sp.

Ieredactylus rivuli gen. et sp. nov. (Monogenea, Gyrodactylidae) from Rivulus hartii (Cyprinodontiformes, Rivulidae) in Trinidad

A new genus and species of Gyrodactylidae, Ieredactylus rivuli gen. et sp. nov. (Platyhelminthes, Monogenea), is described from the skin of Hart’s Rivulus (Rivulus hartii Boulenger), a cyprinodontiform fish collected from streams of the Caroni and Oropouche drainages and the Pitch Lake in Trinidad (prevalence all localities: 16.7–94.6%; mean parasite intensity 1–9 parasites/fish; range 1–34) with the holotype originating from a tributary of the Aripo River. This viviparous monogenean is distinctive from other genera of Gyrodactylidae by its split ventral bar membrane, the shape of its male copulatory organ, the presence of two conical accessory pieces associated with the hamulus root and two differently shaped marginal hook sickles. Its unique rDNA sequence shows the closest ITS2 similarity (70%) to Gyrodactyloides andriaschewii Bychowsky et Poljansky, 1953. The presence of I. rivuli gen. et sp. nov. in the Pitch Lake indicates an adaptation to extreme environmental conditions such as high temperatures and hydrocarbons and adverse pH. Guppies may potentially serve as temporary hosts. The parasite displays distinct behaviours, including a characteristic ‘swimming-like’ movement. The ecology and phylogeny of I. rivuli gen. et sp. nov. is discussed in relation to the diversity of other gyrodactylids in Trinidad.

Efficacy of ginger-based treatments against infection with Gyrodactylus turnbulli in the guppy (Poecilia reticulata (Peters)).

Monogenean infections of commercially farmed fishes are responsible for significant economic losses and existing chemical therapeutants, often stressful to the fish, pose associated risks. As part of a recent trend to move towards the use of alternative, plant-based remedies for commonly occurring aquaculture-related diseases, the efficiency of ginger (Zingiber officinale) was investigated against the monogenean parasite Gyrodactylus turnbulli in the guppy. In vitro trials revealed the clear anti-parasitic effects of ginger. Ethanolic and aqueous extracts, prepared from freeze dried ginger, were tested. An increase in extract concentration was associated with reduced time to parasite immobilisation, with ethanolic extract being more efficient; at 75 and 200ppt aqueous ginger extract parasites died at 65.6±2.8 and 1.8±0.2min, respectively, whereas at 5 and 40ppt ethanolic extract parasites died at 26.1±0.7 and 4.9±0.3min, respectively. Bathing G. turnbulli-infected fish in ethanolic ginger extract (i.e. 5 and 7.5ppt for 90 and 30min, respectively) significantly reduced infection prevalence and intensity when compared to the water and ethanol controls. The higher concentration (i.e. 7.5ppt) proved as equally effective as Praziquantel, the conventionally used chemical treatment for gyrodactylosis, with the fish appearing to be completely cleared of the infection in both cases. Oral treatments of G. turnbulli-infected guppies with diets supplemented with 10 and 20% ginger powder proved to be ineffective in decreasing parasite load. These findings demonstrate that immersion in ginger extract offers an effective, alternative treatment against monogenean infection in fish.

Gyrodactylus longipes n. sp. (Monogenea: Gyrodactylidae) from farmed gilthead seabream (Sparus aurata L.) from the Mediterranean

Gyrodactylus longipes n. sp. (Monogenea, Gyrodactylidae) is described from the gills of farmed juvenile gilthead seabream (Sparus aurata L.) from two sites located in Italy and Bosnia-Herzegovina and represents the second species of Gyrodactylus to be described from S. aurata. Gyrodactylus orecchiae Paladini, Cable, Fioravanti, Faria, Di Cave et Shinn, 2009 was the first gyrodactylid to be described from S. aurata, from populations cultured in Albania and Croatia. In the current study, G. longipes was found in a mixed infection with G. orecchiae on fish maintained in Latina Province, Italy, thus extending the reported distribution of the latter throughout the Mediterranean. The morphology of the opisthaptoral hard parts of G. longipes is compared to those of G. orecchiae, using light and scanning electron microscopy. Gyrodactylus longipes is characterised by having larger, elongated ventral bar processes and long, triangular-shaped toe region to their marginal hook sickles which, by comparison, are rhomboid in G. orecchiae. The marginal hook sickles of G. longipes are almost double the size of G. orecchiae which allows for their rapid discrimination from each other in mixed infections. A comparison of the DNA sequence of the ribosomal internal transcribed spacer 1 and 2 regions (ITS1 and ITS2) of G. longipes with the corresponding sequence from G. orecchiae and with those available in GenBank, supports the separate species status of G. longipes. Part of this study necessitated an overview of the existing Gyrodactylus fauna from Italy and Bosnia-Herzegovina; a summary from each country is provided here to assist future investigations.

Evidence for Cryptic Speciation in Directly Transmitted Gyrodactylid Parasites of Trinidadian Guppies

Cryptic species complexes are common among parasites, which tend to have large populations and are subject to rapid evolution. Such complexes may arise through host-parasite co-evolution and/or host switching. For parasites that reproduce directly on their host, there might be increased opportunities for sympatric speciation, either by exploiting different hosts or different micro-habitats within the same host. The genus Gyrodactylus is a specious group of viviparous monogeneans. These ectoparasites transfer between teleosts during social contact and cause significant host mortality. Their impact on the guppy (Poecilia reticulata), an iconic evolutionary and ecological model species, is well established and yet the population genetics and phylogenetics of these parasites remains understudied. Using mtDNA sequencing of the host and its parasites, we provide evidence of cryptic speciation in Gyrodactylus bullatarudis, G. poeciliae and G. turnbulli. For the COII gene, genetic divergence of lineages within each parasite species ranged between 5.7 and 17.2%, which is typical of the divergence observed between described species in this genus. Different lineages of G. turnbulli and G. poeciliae appear geographically isolated, which could imply allopatric speciation. In addition, for G. poeciliae, co-evolution with a different host species cannot be discarded due to its host range. This parasite was originally described on P. caucana, but for the first time here it is also recorded on the guppy. The two cryptic lineages of G. bullatarudis showed considerable geographic overlap. G. bullatarudis has a known wide host range and it can also utilize a killifish (Anablepsoides hartii) as a temporary host. This killifish is capable of migrating overland and it could act as a transmission vector between otherwise isolated populations. Additional genetic markers are needed to confirm the presence of these cryptic Gyrodactylus species complexes, potentially leading to more in-depth genetic, ecological and evolutionary analyses on this multi-host-parasite system.

A scanning electron microscope technique for studying the sclerites of Cichlidogyrus

The genus Cichlidogyrus (Monogenea: Ancyrocephalidae) includes more than 90 species, most of which are gill parasites of African cichlid fishes. Cichlidogyrus has been studied extensively in recent years, but scanning electron microscope (SEM) investigations of the isolated hard parts have not yet been undertaken. In this paper, we describe a method for isolating and scanning the sclerites of individual Cichlidogyrus worms. Twenty-year-old, formol-fixed specimens of Cichlidogyrus casuarinus were subjected to proteinase K digestion in order to release the sclerites from the surrounding soft tissues. SEM micrographs of the haptoral sclerites and the male copulatory organ are presented. The ability to digest formol-fixed specimens makes this method a useful tool for the study of historical museum collections.

Morphological and molecular characterisation of Gyrodactylus salmonis (Platyhelminthes, Monogenea) isolates collected in Mexico from rainbow trout (Oncorhynchus mykiss Walbaum)

Gyrodactylus salmonis (Yin et Sproston, 1948) isolates collected from feral rainbow trout, Oncorhynchus mykiss (Walbaum) in Veracruz, southeastern Mexico are described. Morphological and molecular variation of these isolates to G. salmonis collected in Canada and the U.S.A. is characterised. Morphologically, the marginal hook sickles of Mexican isolates of G. salmonis closely resemble those of Canadian specimens - their shaft and hook regions align closely with one another; only features of the sickle base and a prominent bridge to the toe permit their separation. The 18S sequence determined from the Mexican specimens was identical to two variable regions of SSU rDNA obtained from a Canadian population of G. salmonis. Internal transcribed spacer (ITS) regions (spanning ITS1, 5.8S and ITS2) of Mexican isolates of G. salmonis are identical to ITS sequences of an American population of G. salmonis and to Gyrodactylus salvelini Kuusela, Ziętara et Lumme, 2008 from Finland. Analyses of the ribosomal RNA gene of Mexican isolates of G. salmonis show 98-99% similarity to those of Gyrodactylus gobiensis Gläser, 1974, Gyrodactylus salaris Malmberg, 1957, and Gyrodactylus rutilensis Gläser, 1974. Mexican and American isolates of G. salmonis are 98% identical, as assessed by sequencing the mitochondrial cox1 gene. Oncorhynchus mykiss is one of the most widely-dispersed fish species in the world and has been shown to be an important vector for parasite/disease transmission. Considering that Mexican isolates of G. salmonis were collected well outside the native distribution range of all salmonid fish, we discuss the possibility that the parasites were translocated with their host through the aquacultural trade. In addition, this study includes a morphological review of Gyrodactylus species collected from rainbow trout and from other salmonid fish of the genus Oncorhynchus which occur throughout North America.

An infection of Gyrodactylus anguillae Ergens, 1960 (Monogenea) associated with the mortality of glass eels (Anguilla anguilla L.) on the north-western Mediterranean Sea board of Spain

The association of Gyrodactylus anguillae Ergens, 1960 with the glass eel stage of Anguilla anguilla (L.) (total body length 61.4 ± 4.9 mm; range 55-70) is reported from the north-western Mediterranean coast of Spain for the first time. A sample of 12,600 glass eels, caught by professional fishermen operating in the mouth of the rivers Fluvià, La Muga and Ter (north-east Spain), was subject to mortalities of ∼ 1.75% of stock/day following transfer to a research facility. Subsequent losses over a 31-day period amounted to 56% of the initial stocked biomass. Although the moderate burdens of G. anguillae/host (20.2 ± 6; range 11-32) were the primary reason for a subsequent treatment, a simultaneous infection with Trichodina jadranica Raabe, 1958, Trichodina anguillae Wu, 1961 and Ichthyophthirius multifiliis Fouquet, 1876, makes it impossible to attribute the high mortality of glass eels in this case to a single pathogen. A histopathological examination of the gills of moribund fish showed them to be swollen, hyperplastic and necrotic. This study also redescribes G. anguillae, providing for the first time a full 27 character morphometric description of the attachment hooks, and importantly, a photographic record of the armature of the haptor and the male copulatory organ.

To each his own: no evidence of gyrodactylid parasite host switches from invasive poeciliid fishes to Goodea atripinnis Jordan (Cyprinodontiformes: Goodeidae), the most dominant endemic freshwater goodeid fish in the Mexican Highlands

BackgroundGoodeid topminnows are live-bearing fishes endemic to the Mexican Highlands (Mesa Central, MC). Unfortunately, in the MC, environmental degradation and introduced species have pushed several goodeid species to the brink of extinction. Invasive fishes can introduce exotic parasites, and the most abundant goodeid, blackfin goodea Goodea atripinnis Jordan, is parasitised by six exotic helminths. Poeciliids are widely dispersed invasive fishes, which exert negative ecological effects on goodeids. Poeciliids host several species of the monogenean genus Gyrodactylus von Nordmann, 1832, including pathogenic, invasive parasites. Here, we looked for evidence of Gyrodactylus species switching hosts from poeciliids to goodeids.MethodsFish were collected in rivers draining the MC into both sides of the continental divide. Hosts were screened for gyrodactylid parasites in localities where G. atripinnis and poeciliids occurred sympatrically. Gyrodactylus specimens were characterised morphologically (attachment apparatus) and molecularly (internal transcribed spacer region, ITS). A Bayesian phylogenetic tree using ITS sequences established relationships between gyrodactylids collected from goodeid fishes and those from parasites infecting poeciliids.ResultsGyrodactylids were collected from G. atripinnis in six localities on both sides of the watershed where exotic poeciliids occurred sympatrically. Morphological and molecular analyses indicated the presence of four undescribed species of Gyrodactylus infecting this goodeid host. Gyrodactylus tomahuac n. sp., the most abundant and geographically widespread species, is described here. The other three Gyrodactylus spp. are not described, but their ITS sequences are used as molecular data presented here, are the only available for gyrodactylids infecting goodeid fishes. Morphological and molecular data suggest that two distinct groups of gyrodactylids infect goodeids, one of which shares a common ancestor with gyrodactylids parasitizing poeciliids.ConclusionsNo evidence was found of gyrodactylids switching hosts from invasive poeciliids to endemic goodeids, nor vice versa. Moreover, considering that G. atripinnis is known to host both Gyrodactylus lamothei Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009 and Gyrodactylus mexicanus Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009, with the addition of G. tomahuac n. sp. and the three undescribed Gyrodactylus spp. reported, at least six gyrodactylids may infect this host. This would make monogeneans the second most abundant parasite group infecting G. atripinnis, which to date is known to harbour 22 helminth species: nine digeneans, five nematodes, four cestodes, three monogeneans and one acanthocephalan.