The differential effects ofLigula intestinalis(L.) plerocercoids on host growth in three natural populations of roach,Rutilus rutilus(L.)

Abstract

The differential effects of Ligula intestinalis (L.) plerocercoids on host growth in three natural populations of roach, Rutilus rutilus (L.) Un resumen en espanÄ ol se incluye detra s del texto principal de este artõ culo.Abstract ± This study reports the differential effect of the pseudophyllidean cestode, Ligula intestinalis, on the growth rates of three fish populations of the roach, Rutilus rutilus, under field conditions. Here, we show that only one host-population is affected by parasite-induced gigantism in the first 2 years of host life. Paradoxically, this increase in fish growth is strongly correlated with the parasitic load in plerocercoid stages, in that only the roach population subjected to the heaviest parasitic pressure shows an enhanced growth of cestodeparasitized individuals. This host gigantism observed in only one locality is associated with parasite-induced fish mortality occurring, on average, one year earlier in this fish population when compared to other populations. We discuss the different reasons for this differential parasite effect on growth enhancement across host-population in natural settings. Whether the growth effects represent an adaptive response by the host or a manipulation by L. intestinalis of the host, remains to be elucidated.

The tapeworm Ligula intestinalis (Cestoda: Pseudophyllidea) inhibits LH expression and puberty in its teleost host, Rutilus rutilus

“…As has been noted previously by Kennedy et al (2001) and Loot et al (2001Loot et al ( , 2002, our data suggest that Ligula may have a small inhibitory effect on body length, weight and condition in young fish (i.e. 2 years old).…”

“…steroid receptors), which are necessary for the process of gametogenesis, may be disrupted, thus preventing brain activation and subsequent initiation of puberty. Furthermore, peripheral stimulators and inhibitors, active at all levels of the brain-pituitary-gonadal (BPG) axis, may be targets of the putative hormonal disruption by Ligula, which results in an inability of the gonads to respond to hormonal signals.As has been noted previously by Kennedy et al (2001) and Loot et al (2001Loot et al ( , 2002, our data suggest that Ligula may have a small inhibitory effect on body length, weight and condition in young fish (i.e. 2 years old).…”

Is the continental life of the European eel Anguilla anguilla affected by the parasitic invader Anguillicoloides crassus ?

“…response to infection (increased energy demand) has been observed in other helminth -fish systems [49,50]. Alternatively, it is possible that larger size results from a beneficial effect of the blood diet of adult worms, which may increase haematopoiesis and blood regeneration, in turn favouring metal elimination or food conversion [51,52].…”

Seasonal dynamics of Posthodiplostomum cuticola (Digenea, Diplostomatidae) metacercariae and parasite-enhanced growth of juvenile host fish

“…On the other hand, there are several studies that detected an increase rather than decrease in the growth of parasitized hosts. A growth-enhancing effect on the fish host has especially been described in cestodes: plerocercoids of the pseudophyllidean Schistocephalus solidus infecting Gasterosteus aculeatus (Milinski 1985;Arnott et al 2000) and Ligula intestinalis infecting Rutilus rutilus (Museth 2001;Loot et al 2002). In fish infected with digenean larvae, increased growth has only been recorded in Phoxinus phoxinus experimentally infected with a low number of Diplostomum phoxini, although the effect appeared to cease with high infections (Ballabeni 1994).…”