Development In Roach Research Articles

The effect of an alternating electromagnetic field upon early development in roach (Rutilus rutilus: Cyprinidae, cypriniformes)

The effect of an alternating electromagnetic field (EMF) upon three stages of roach’s (Rutilus rutilus) early development was studied. The studies covered the periods before gastrulation; from gastrulation until hatching; and from hatching until yolk sac resorption. It has been shown that the EMF effect is as stronger as earlier in the embryogenesis the roach was subjected to an impact. The following responses to EMF were registered: earlier hatching of prelarvae, increase in the morphological diversity of juvenile fish, decrease in body lengths and weights, and changes in the number of vertebrae in yearlings.

Expression of gonadotropin subunits in roach ( Rutilus rutilus, Cyprinidae) infected with plerocercoids of the tapeworm Ligula intestinalis (Cestoda)

Plerocercoids of the tapeworm Ligula intestinalis (Cestoda: Bothriocephalidea) have been reported to inhibit gametogenesis of their intermediate fish hosts. However, mechanistic studies are rare and the proximate cues leading to impaired reproduction still remain unknown. In the present study we investigated the effects of infection by L. intestinalis on reproductive parameters of roach ( Rutilus rutilus, Cyprinidae), a common fish host of this parasite. Field studies on roach demonstrated that in both genders infection prevented gonad development. As revealed by quantitative PCR, infection was accompanied by essentially lower pituitary expression of follicle-stimulating hormone β-subunit (FSHβ) and luteinizing hormone β-subunit (LHβ) mRNA compared with uninfected roach, providing clear evidence for gonadotropin-insufficiency as the cause of arrested gametogenesis. Under controlled laboratory conditions infected roach showed lower mRNA levels of FSHβ but not of LHβ, despite histology revealing similar gonad stages as in uninfected conspecifics. These findings indicate the involvement of FSH rather than LH in mediating effects of infection early during gonad development in roach. Moreover, the impact of L. intestinalis on reproductive parameters of roach appeared to be independent of the parasite burden. Together, these data provide valuable information on the role of FSH and LH as mediators of parasite-induced sterilization in a vertebrate and implicate the selective inhibition of host reproduction by L. intestinalis as a natural source of endocrine disruption in fish.

Altered Sexual Development in Roach (Rutilus rutilus) Exposed to Environmental Concentrations of the Pharmaceutical 17α-Ethinylestradiol and Associated Expression Dynamics of Aromatases and Estrogen Receptors

Wild roach (Rutilus rutilus) inhabiting UK rivers contaminated with estrogenic effluents from wastewater treatment works show altered sexual development, including intersex, and this can impact negatively on their reproductive capabilities. The molecular events underlying these disruptions in gender assignment, however, are still poorly understood. In this study, two isoforms of aromatase (cyp19a1a and cyp19a1b) were cloned from the roach, and effects of exposure to 17alpha-ethinylestradiol (EE(2)) during early life were determined on the expression of both aromatases and on the estrogen receptors (ERs) (subtypes esr1 and esr2b) and analyzed against effects on the progression of gonadal sex differentiation. Exposure to environmentally relevant concentrations of EE(2) during the critical period of sex differentiation resulted in gonadal feminization and all roach exposed to 4 ng EE(2)/l were females. These effects on gonadal development were associated with alterations in the expression of both esr and cyp19a1 genes in bodies and heads of exposed fish with the most marked effects on the expression of esr1 and cyp19a1b. Our findings show that both aromatase isoforms and both ER subtypes are associated with sexual differentiation in roach, and alterations in their expression can signal for disruptions in sexual development.

Ontogeny of sexual development in the roach (Rutilus rutilus) and its interrelationships with growth and age

The roach (Rutilus rutilus) has become a sentinel species for the study of sexual disruption in wild fish populations as a consequence of exposure to endocrine disrupting chemicals (EDCs). Little is known, however, about the normal ontogeny of sexual development in this species. Here, we analyzed the ontogeny of sexual development in captive-bred roach and assessed how growth rate and fish size affected the timing of both sexual differentiation and sexual development over a 2-year period. Ovarian differentiation was first recorded at 68 days post-fertilization (dpf) and this preceded testicular differentiation (first recorded at 98 dpf). In contrast, sexual maturation occurred at an earlier age in males (300 dpf) compared with females (728 dpf). No differences in body size (length or weight) were recorded between male and female roach until the fish were 415 dpf. Studies on three populations of roach which grew at different rates showed that the timing of sexual differentiation was highly variable and more related to fish size than to fish age. Time to sexual maturation was also variable among populations but, subsequent to their first year of life, gonadal status was less well associated with fish size. Interestingly, the sex ratio of the population was biased towards females in populations that grew more rapidly during early life. The findings presented here provide a valuable foundation of work to support both field- and laboratory-based assessments on the effects of EDCs, and other stressors, on sexual differentiation and development in the roach.

Effect of ultralow concentrations of N-methyl-N′-nitro-N-nitrosoguanidine upon early development in roach (Rutilis rutilus): Intestine carbohydrase activities and kinetic characteristics of carbohydrate hydrolysis in the intestine of underyearlings

The prolonged effects of short-term action of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in low concentrations 3 × 10−7 to 3 × 10−1 mg/l upon roach (Rutilus rutilus) early development have been studied. It was revealed that the treatment resulted in an increase in fish length and weight, in a decrease in total amylolytic and saccharase activities, and in different changes in parameters of di-and polysaccharide hydrolyses. The concentration-effect dependence is nonlinear. Both ultralow and the highest tested MNNG concentrations cause similar changes in carbohydrase activities and kinetic parameters of carbohydrate hydrolysis. The decrease in K m values of sucrose hydrolysis evidencing the increase in the enzyme to substrate affinity may be attributed to adaptive reactions of roach at early developmental stages in response to damaging embryotoxic action of MNNG in ultralow concentrations.

Effect of N-methyl-N-nitro-N-nitrosoguanidine upon early development in roach (Rutilus rutilus): Characteristics of mitoses in germ cells, hatching dynamics and morphology of larvae

Fertilized roach (Rutilus rutilus) eggs were incubated for the first 48 h in 3 × 10−7 to 3 × 10−1 mg/l N-methyl-N-nitro-N-nitrosoguanidine (MNNG) solutions. The incubation resulted in changes in blastomere mitotic indices and an increase in the number of aberrant mitoses. The concentration dependence of the studied parameters is described by a nonlinear curve. Egg incubation in a tested MNNG concentrations range leads to decrease in larvae length and weight.

How parasitism and pollution affect the physiological homeostasis of aquatic hosts

Parasitism poses a serious threat to hosts under certain circumstances, while the well-being of organisms is also negatively affected by environmental pollution. Little information is available on the simultaneous effects of parasites and pollutants on the physiological homeostasis of organisms. The present paper demonstrates that parasites: (i) may influence the metabolism of pollutants in infected hosts, (ii) interact with pollution in synergistic or antagonistic ways, and (iii) may induce physiological reactions in hosts which were thought to be pollutant-induced. Experimental studies on the uptake and accumulation of metals by fish reveal that fish infected with acanthocephalans have lower metal levels than uninfected hosts; e.g. Pomphorhynchus laevis reduces lead levels in fish bile, thereby diminishing or impeding the hepatic intestinal cycling of lead, which may reduce the quantity of metals available for fish. Alterations in pollutant uptake and accumulation in different intermediate and final hosts due to parasites are thus very important in the field of ecotoxicology. In addition to such alterations, there is a close interaction between the effects of pollutants and parasites which seems to be mediated at least partly by the endocrine system, which itself is closely related to the immune system in fish. Laboratory studies on eels experimentally infected with the swimbladder nematode Anguillicola crassus reveal that toxic chemicals such as polychlorinated biphenyls produce immunosuppressive effects which facilitate parasite infection. Similarly, an increase in serum cortisol concentration in eels due to chemical exposure and infection is correlated with decreasing levels of anti-A. crassus antibodies. Furthermore, parasites are able to elicit physiological changes which are attributed to chemicals with endocrine disrupting activity, e.g. the cestode Ligula intestinalis is known to suppress gonad development in roach. The most thoroughly documented examples of endocrine disruption in wild fish are in roach, and it is conceivable that this disruption is not only due to chemical activity but also to parasites such as L. intestinalis or species of the phylum Microspora.

Ontogenetic patterns of relative growth in young roach Rutilus rutilus: within‐river basin comparisons

To address the lack of information on the ecomorphology of young of the year juveniles (0 +) freshwater fishes, despite its importance to understanding geographical variation in life history, we compared the morphology of 0+ juvenile roach Rutilus rutilus from eight sub‐regions of the River Great Ouse basin (U.K.). We tested for variation due to water retention structures, which could act to isolate upstream stocks from the general population. Differences in mensural characters between the eight different regions appeared in ventral fin length and eye diameter only, which both were strongly affected by variable relative growth during early juvenile development; thus the discrepancies between regions were not due to geographical location. Morphological development in roach ≥ 15 mm standard length (SL) consists of two different intervals: during the first (≅ 15–40 mm SL), in contrast to adults, several mensural characters continue to develop allometrically, either positively or negatively, suggesting a continuance of the larval period. Whereas, in the second interval (> ≅ 40 mm SL), all the mensural characters except head length and eye diameter grew close to isometrically with body length, and the rate of variation in relative growth became as strongly limited as that previously reported for adults. In contrast to previous studies, which are based on few specimens, we suggest this second interval to be the true start of the juvenile period.