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, we have for the first time revealed that the LH pituitary content and mRNA levels are also significantly decreased in infected individuals. Given that fish infected with Ligula intestinalis do not exhibit normal behaviour patterns in terms of shoaling e.

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 This may explain why the growth curves of infected and non-infected fish become more similar in older fish.

WoRMS – World Register of Marine Species – Ligula intestinalis (Linnaeus, ) Gmelin,

Young infected roach, 2 and 3 years old, rarely attained the same body weight as their non-infected counterparts mean body mass: Download Figure Figure 2 Comparison of body mass to condition factor of ligulosed and non-ligulosed roach. Importantly, it also revealed that the roach—parasite interaction under investigation is typical of that found in other sampled populations. I, infected fish; NI, non-infected fish; F, female; M, male. February leading up to spawning in springAugust post spawning and December mid cycle.

Results Parasite burden Details intestina,is fish used and effects of parasitism are shown in Table 1. Previous observations have revealed that two GnRH forms 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?

Data were analysed using the Abi Prism sequence detection system Applied Biosystems. 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.

Because of the lack of sequence data available for roach, fragments of LH and the control gene 18S ribosomal RNA were amplified and sequenced to identify specific ligla for use in real-time PCR. As an internal control, 18S rRNA was amplified in an identical manner. This suggested that Ligula infection decreases LH synthesis by inhibiting its expression and indicates that the levels of gonadotrophin-producing cells being affected by parasitisation are critical to normal reproductive function.


Kerr and Arme noted that in ligulosed roach, Rutilus rutilusthe putative gonadotrophs are much reduced in number, compared with non-ligulosed individuals, are intsetinalis lightly granulated, and have an irregular nuclear membrane, no prominent nucleolus and a marked reduction in the cytoplasmic volume. 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.

Figures given are means with range. GSI leading up to spawning February varied between 0. Previous studies have revealed that several parasitic infections can affect host reproduction. In contrast, in liguoa fish, only these immature stages of oogenesis were present throughout and no cyclical variations were recorded see Arme Fish used for hormonal or molecular biological analysis were examined within 7 days of capture.

Although this effect was dose dependent, significant differences were found between Ligula ligu,a a related tapeworm species, Schistocephalus solidus. 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. Plerocercoids were most prevalent 5.

The distribution, cell number and staining intensity of both these types of neurones, which are considered to be the first steps in BPG axis activation, were not affected by Ligula Penlington et al. Analysis of host and parasite growth revealed that the soma of male spottails infected with Ligula weighed more but had a reduced growth rate.

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. However, because of the low sample size in certain age classes of infected fish, body intestinakis were considered according to age class, and differences were less apparent.

Previous studies have indicated effects of infection at the pituitary gland level.

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

Discussion Our results have confirmed previous observations intestinxlis by Armeon the biometric effects of Ligula intestinalis on its roach intermediate host. 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.


As has been noted previously by Kennedy et al. Further studies are required to ascertain the mechanisms by which Ligula induces its inhibitory effect on roach LH production. Reproduction6; However, an apparently increased LH production in the eel suggested possible species differences in the action on gonadotroph activity.

Because of the very small amount of gonadal tissue present in infected fish, and thus the problem of finding and confirming the presence of gonads without histological examination, the condition factor was calculated including the gonadal tissue in parasitised individuals.

The liguoa has been demonstrated in other cyprinids where positive intestinaljs negative responses have been noted for GnRH and dopamine respectively for review see Peter et al. The condition factor intesyinalis that heavier fish of a given length are in better condition and eliminates variation attributable to gonadal development over the reproductive season.

The effects noted in the wild are intesyinalis 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 Because of the small amount of gonadal tissue in infected roach weighing less than 0.

Orrpheromonal stimuli which would normally be received within the group-shoaling situation are absent from infected individuals, which may enhance the delay in puberty Francis et al.

Detailed analysis of the spottail shiner-Ligula ligual system revealed that the number of plerocercoids differed between years and among habitats but there was no statistically significant seasonal pattern; recruitment of new worms was highest in young fish and decreased with age, and ingestinalis spottails had reduced gonad development.

Although this phenomenon has been reported several times e.