Seasonal development and pathological changes associated with the parasitic nematodePhilometroides sanguineusin wild crucian carpCarassius carassius(L.) in England

Abstract

Pathological changes associated with the parasitic nematode Philometroides sanguineus (Rudolphi, 1819) are described for the first time from observations of infections in wild crucian carp Carassius carassius (L.) in England. The damage caused by P. sanguineus was influenced strongly by host size, parasite development and the seasonal migrations of female nematodes within host tissues. Male and unfertilized female nematodes located on the swim-bladder wall caused only minor, localized changes. In contrast, the migration of gravid female nematodes into the fins during autumn provoked an acute inflammatory response comprising neutrophils, eosinophils and lymphocytes. This was accompanied by fin distortion, swelling of the dorsal and caudal tissues, degenerative changes and localized oedema. The encapsulation of female nematodes in connective tissue throughout winter limited additional tissue damage. The emergence of gravid nematodes from the fins in spring to facilitate larval dispersal caused necrosis, hyperplasia and loss of skin integrity. This activity was again accompanied by acute inflammatory reactions. Pathological changes were more severe in crucian carp measuring less than 60 mm in length, with no signs of debilitation in larger fish. These observations suggest that any impact of P. sanguineus is strictly seasonal and may be limited to fry. Lesions caused by this parasite, only recently recorded in Britain, may represent an additional pressure upon wild crucian carp populations already threatened by hybridization, competition and habitat loss.

What are the consequences of infection by the introduced parasite Philometroides sanguineus for threatened crucian carp Carassius carassius populations in England?

“…Our findings indicate that the disease risk assessment for P. sanguineus in England no longer has to rely on precautionary principles. The data presented here, in conjunction with data from histopathology (Williams et al. in press), will enable the development of evidence‐based assessment methods for managing risk to native fishes.…”

“…Whilst the pathology of infection in C . carassius is now being increasingly understood (Williams et al. in press), it is not yet known how this translates into sub‐lethal impacts on ecological parameters such as growth, condition and energetics.…”

Review of the parasitic nematodes of marine fishes from off the American continent

“…One important family is Philometridae, which is highly speciose in marine and freshwater environments and exclusive to fish (Anderson, 2000; Moravec and de Buron, 2013). However, life cycles of these parasites have received attention only recently (Perez et al ., 2009; Chávez and Oliva, 2011; de Buron et al ., 2011; Séguin et al ., 2011; Williams et al ., 2012). Philometrids are tissue-dwelling parasites commonly haematophagous, which may negatively impact their hosts, causing economic losses in economically important fish (Moravec, 2006; Moravec and de Buron, 2013).…”

“…Females of philometrids are ovoviviparous giving birth to first-stage larvae, through bursting their bodies when in contact with water (except Alinema ) (Anderson, 2000; Moravec and de Buron, 2013). Evidence indicates that the development of philometrids can be seasonal, and that the copepod component of the zooplankton and some prey fish may act as intermediate and paratenic hosts, respectively, for these parasites (see Molnár and Fernando, 1975; Perez et al ., 2009; Chávez and Oliva, 2011; de Buron et al ., 2011; Séguin et al ., 2011; Williams et al ., 2012).…”

A new species of Philometra Costa, 1845 (Nematoda: Philometridae) from the freshwater fish (red piranha) Pygocentrus nattereri Kner (Characidae) in Amazonia, Brazil

“…Some of them are highly pathogenic and occur in commercially important wild or cultured fish hosts (e.g. Vasilkov, 1967;Vismanis & Nikulina, 1968;Deardorff & Stanton, 1983;Sakaguchi et al, 1987;Clarke et al, 2006;Moravec et al, 2007a;Santos & Moravec, 2009;Williams et al, 2012). Due to some morphological and biological peculiarities (Moravec, 2004(Moravec, , 2006, most of them are known only by their large females.…”