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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Figure 2 shows the condition factor of fish according to age, showing lower K values in infected fish, reflecting the fact that non-infected individuals are in better condition, irrespective of age, than their infected counterparts.

This abnormal behaviour may also expose roach to different light intensities, a parameter vitally important in the control of the reproductive cycle in fish Bromage et al. 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.

As has been noted previously by Kennedy et al. Previous observations have revealed that two GnRH intestinlais salmon and chicken occurred in the brain of non-infected and infected roach Williams et al.

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

The effects noted in intestinali 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 Whilst it is true that gonadotrophs are much reduced in number, the cells that are present do appear to ligla functional, indicating that Ligula infection neither completely prevents gonadotroph differentiation nor basal activity.

In addition, we have for the first time revealed that the LH pituitary content and mRNA levels are also significantly decreased in infected individuals.

The reproductive system in fish is particularly susceptible to stress and immediate cessation of reproductive function is not uncommon when fish are brought into captivity Wendelaar Bonga Because of the lack of sequence data available intrstinalis roach, fragments of LH and the control gene 18S ribosomal RNA intestinallis amplified and intestinaljs to identify specific primers for use inteztinalis real-time PCR.


Previous studies have indicated effects of infection at the pituitary gland level. Although this effect was dose dependent, significant differences were found between Ligula and a related tapeworm species, Schistocephalus solidus. Analysis of host and parasite growth revealed that the soma of male spottails infected with Ligula weighed more but had a reduced growth rate.

The fragments and nucleotides respectively obtained were cloned and sequenced Genbank accession numbers: Transcript levels were normalised to those of 18S rRNA and data for infected fish presented as a fold change relative to the values obtained for non-infected fish. In the roach, our data also showed that Ligula infection exerts some inhibitory effects on body growth and condition, but these effects are small and would, therefore, not account for the complete blockade of puberty noted in ligulosed fish.

A subset of four non-infected ligulaa fish from each group was used for histological analysis of gonadal development and two categories of oocytes were observed, i. While roach were caught up to 54 g in weight, fish exceeding 20 g were not infected with Ligula Fig.

The distribution, cell number and staining intensity of both these types of neurones, intestianlis are considered to be the first steps in BPG axis activation, were not affected by Ligula Penlington et al.

The majority of non-infected fish achieved sexual maturation by 2 years of age as determined by the presence of yolky oocytes and all non-infected females were mature by 3 years of age. However, seasonal variations in pituitary LH content observed in non-infected fish were absent in infected roach.

The sample size is shown above each bar. 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.

The condition factor assumes that liyula fish of kntestinalis given length are in better condition and eliminates variation attributable to gonadal development over the reproductive season. Further quantification was performed in sections of the ovaries to determine the extent of oocyte development.


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.

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. Figures given are means with range. Table 1 Data summary for all experimental fish. 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.

Our results have confirmed previous observations made by Armeon the biometric effects of Ligula intestinalis on its roach intermediate host. Results Parasite burden Details of fish used and effects of parasitism are shown in Table 1. Natural variations were found within the sampled population, i.

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

I, infected fish; NI, non-infected fish; F, female; M, male. For example, the expression of gonadotrophin hormones and their receptors e.

Based on increased mean somatic weight and skewness of the weight distribution for infected intwstinalis, we propose that infected spottails are subjected to size-selective mortality. Previous studies have revealed that several parasitic infections can affect host reproduction. February leading up to spawning in springAugust post spawning and December mid cycle.

Ligula intestinalis – Wikipedia

Plerocercoids were most prevalent 5. In non-infected females, the ovaries contained large, mature eggs and several smaller, primary oocytes with ligulw immature stages of development occurring post spawning. However, seasonal variations in GnRH cell activity in non-infected fish were not investigated, and it cannot therefore be deduced that GnRH cells or GnRH release are not affected in infected fish. Materials and methods Fish Ligulosed and non-ligulosed roach were collected from the Altami Angling Club, Chester, Cheshire, UK during — at three times during the reproductive year:

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