The life cycle and seasonal changes in the occurrence ofPomphorhynchus laevis(Palaeacanthocephala, Pomphorhynchidae) in a small isolated lake

Abstract

Summary:In a small isolated lake in Slovakia, the fish acanthocephalan Pomphorhynchus laevis using Gammarus balcanicus and the minnow Phoxinus phoxinus, respectively, as its intermediate and final hosts, represented a dominant helminth species. Its prevalence and intensity of infection in fish showed no significant variation during a year fluctuating above the mean values of 89 % and 6.6 worms per fish. The mean prevalence of P. laevis larvae in Gammarus was 41.4 % with a maximum in the late summer and autumn ; individual crustaceans were infected by 1-9 larvae. There was one generation of P. laevis per year. Following up an annual cycle, an occurrence of new infections of Gammarus culminated in October and in the next May for Phoxinus. The sex ratios of both the adults and larvae of acanthocephalans were near unity but favoured slightly males in spring and autumn. The distribution of P. laevis in minnows and crustaceans was highly aggregated and fitted with the negative binomial model. The spatial distribution analysis of parasites along the fish alimentary tract showed a clear preference of P. laevis for its proximal half, with the maximum numbers in the site of the first intestinal loop. Immature worms of both sexes predominated in the proximal region and moved slightly down the alimentary tract during their growth and maturation.

Variation and covariation in infectivity, virulence and immunodepression in the host–parasite associationGammarus pulex–Pomphorhynchus laevis

“…However, we cannot exclude a seasonality effect in the physiology of hosts and the level of immune defence of hosts (Sandland & Minchella 2003) nor parasite 'qualities' that could explain the higher infectivity and faster development found in winter. Nevertheless, higher prevalence in autumn and winter has been reported in the field for P. laevis infection in Gammarus balcanicus (Dudinak & Spakulova 2003).…”

Fish odour triggers conspecific attraction behaviour in an aquatic invertebrate

“…It is conceivable that parasitization might also influence the gammarids' aggregation behaviour. To avoid this effect, this study was conducted in the late winter when the number of infected individuals is low (Dezfuli et al 1999;Dudinak & Spakulova 2003). Furthermore, only uninfected individuals were used, leaving the question of parasites' influence on gammarids' aggregation behaviour open for future studies.…”

Occurence of Pomphorhynchus laevis (Acanthocephala) in the Marsh Frog (Rana ridibunda Pallas, 1771), from Turkey

“…According to Dudiňák & Špakulová (2003)'s data, the developing worms with body length from 6 to 12 mm with developed gonads. On the basis of these characters, our specimens, are comparable to Dudiňák & Špakulová (2003), the present specimens in this paper, have a short body length (10.10 mm) males with developed testes, females with ovarian balls, and their stage is "developing worm". The intermediate host of P. laevis is Gammarus pulex which were also observed in the Civril Isikli Lake (Denizli Province).…”

“…(410.24 µm -1410.20 µm ) Five developing worms were observed on mesenteries (Figures 1 A -B Dudiňák & Špakulová (2003), were divided to P. laevis according to the sex and maturity, the males and females were categorised into three groups, corresponding with three developmental stages in their study. According to Dudiňák & Špakulová (2003)'s data, the developing worms with body length from 6 to 12 mm with developed gonads. On the basis of these characters, our specimens, are comparable to Dudiňák & Špakulová (2003), the present specimens in this paper, have a short body length (10.10 mm) males with developed testes, females with ovarian balls, and their stage is "developing worm".…”

“…Seventy-three P. laevis (68 cysts, 5 developing worms) were observed in nine R. ridibunda samples, liver, urinary bladder, intestine walls, body cavities, and mesenteries, the mean lenght and width of P. laevis cysts were measured 2856.29 µm (1989.92 µm -3640.88 µm) x 712.92 µm. (410.24 µm -1410.20 µm ) Five developing worms were observed on mesenteries (Figures 1 A -B Dudiňák & Špakulová (2003), were divided to P. laevis according to the sex and maturity, the males and females were categorised into three groups, corresponding with three developmental stages in their study. According to Dudiňák & Špakulová (2003)'s data, the developing worms with body length from 6 to 12 mm with developed gonads.…”