LIGULA INTESTINALIS PDF

J Parasitol. Aug;75(4) Changes in numbers and growth of Ligula intestinalis in the spottail shiner (Notropis hudsonius), and their roles in. Abstract. The tapeworm Ligula intestinalis occurs in the body cavity of its cyprinid second intermediate host, in this study the roach Rutilus rutilus, and inhibits. Since its use as a model to study metazoan parasite culture and in vitro development, the plerocercoid of the tapeworm, Ligula intestinalis, has.

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In addition, analogous effects have been shown when L. Figures given lifula means with range. Whether this is mediated by direct effects of Ligula products or general endocrine disruption requires elucidation. The sample size is shown above each bar.

As with length, in 4 year-old fish there was no statistically significant difference between the body mass of infected and non-infected individuals infected 8. This not only intestinails the hypothesis by Arme that reproductive inhibitory effects are specific to Ligulabut also suggests that effects of the parasite extend to non-host species e. While roach were caught up to 54 g in weight, fish exceeding 20 g were not infected with Ligula Fig.

Importantly, it also revealed that the roach—parasite interaction under investigation is typical of that found in other sampled populations. Although this phenomenon has been reported several times e. The following degenerate primers livula used: These studies have led to the belief that the effects of Ligula on gonadal development may be mediated through the pituitary gland.

The use of a heterologous assay for carp LH was fully justified in view of the high litula of sequence identity of the roach molecule see below.

For example, the expression of gonadotrophin hormones and their receptors e. Because of the small amount of gonadal tissue in infected roach weighing less than 0. Plerocercoids were most intestknalis 5.

As has been noted previously by Kennedy et al. The gonads, however, are present but remain in an immature state, irrespective oigula fish age or season.

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Table 1 Data summary for all experimental fish. As in other vertebrates, body growth and condition have been suggested to act as triggers for the initiation of puberty in fish, although the mechanisms by which such a trigger is initiated is still largely unknown for reviews see Peter et al.

Fish exceeding 20 g were not infected with Ligula. Ligula intestinaliswhich is found in the body cavity of certain cyprinid fish, inhibits reproduction in both male and female fish.

Whilst it is true that gonadotrophs are much reduced in number, the cells that are present do appear to be functional, indicating that Ligula infection neither completely prevents gonadotroph differentiation nor basal activity. However, the relationship between Ligula and the induction of a possible stress effect on its fish host has been recently questioned by the work of Loot et al.

This may explain why the growth curves of infected and non-infected fish become more similar in older fish. Some of the contradictions in the literature may be attributed to underestimated prevalence due to increased numbers of spawning fish in the spring, mixed age-classes of Ligula in separate age-classes of fish, and differential effects on growth due to infection in male versus female hosts.

Ligula intestinalis

Further analysis of the — cohort of fish also revealed a similar trend in the association with parasitisation and growth parameters. Infected fish have lower K values, reflecting a lower body llgula rate.

The fact that this inhibition was not observed when we compared older fish may arise from the negative effect of sexual maturation on growth and condition e. Discussion Our results have confirmed previous observations made by Armeon the biometric effects of Ligula intestinalis on its roach intermediate host.

The effects noted in the wild are reproducible with a small plerocercoid implanted into a large mature fish, which precludes pressure effects on fish organs or general debilitation from parasite metabolic demands Arme Investigations of the effect of Ligula on the production of the other gonadotrophin follicle-stimulating hormone are also required, especially considering the potential effect of the parasites on the early stages of gametogenesis.

However, an apparently increased LH production in the eel suggested possible species differences in the action on gonadotroph activity.

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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 Ligulawhich results in an inability of the gonads to respond to hormonal signals.

Ligula intestinalis (Cestoda: Pseudophyllidea): an ideal fish-metazoan parasite model?

However, because of the low sample size in certain age classes of infected fish, body lengths were considered according to age class, and differences were less apparent. It may not be untestinalis, therefore, that the presence of a large parasite burden, which could be considered as a potent stressor, resulted in the observed dramatic effects on host reproduction. In addition, we have for the first time revealed that the LH pituitary content and mRNA levels are also significantly decreased in infected individuals.

Fish used for hormonal or molecular biological analysis were examined within 7 days of capture.

Ligula intestinalis (Cestoda: Pseudophyllidea): an ideal fish-metazoan parasite model?

Indeed, sexual maturation will occur every year in non-infected fish but not in infected ones. Based on increased mean somatic weight and skewness of the weight distribution for infected fish, we propose that infected spottails are subjected to size-selective mortality. Download Figure Figure 2 Comparison of body mass to condition factor of ligulosed and non-ligulosed roach. Details of fish used and effects of parasitism are shown in Table 1. Further studies are required to ascertain the mechanisms by which Ligula induces its inhibitory effect on roach LH production.

Although individual variation was high, LH content of non-infected individuals was at its peak post-spawning August and lowest over the winter period December; Fig. Effects of parasitism on host: In this study, our objective was to establish whether gonadal inhibition induced by Ligula in its primary fish host, Rutilus rutilusis mediated through effects on pituitary gland hormone levels, i.