Adult Carp Research Articles

Otolith microchemistry of koi carp in the Waikato region, New Zealand: a tool for identifying recruitment locations?

We assessed differences in the otolith microchemistry of koi carp, a colour variant of the invasive common carp Cyprinus carpio, at various locations in the Waikato region of New Zealand. Although koi carp are abundant here, little is known about where and in what habitats they breed. We investigated the feasibility of determining the natal habitats of adult koi carp (in the Waikato River, selected tributaries, and riverine lakes in the catchment) using otolith elemental signatures and employing laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Differences in elemental concentrations in water among the sites indicated that variation in otolith microchemistry was likely. Ratios of manganese (Mn), rubidium (Rb), strontium (Sr), and barium (Ba) to calcium (Ca) in otolith edges differed significantly among the sites, and Sr:Ca in the water and otoliths was positively correlated. A discriminant function analysis using Rb, Sr, and Ba accurately classified the otolith edge signatures of koi carp from some locations, but the otolith signatures of koi carp caught from adjacent locations were often indistinguishable. This suggests that our results could have been confounded by either (1) recent movement of koi carp or (2) a lack of differences in water chemistry among sites. Taken together, these results demonstrate that otolith microchemistry can be used to test retrospectively for koi carp migration between sites on a broad scale in theW aikato region, but fine-scale movements may not be detectable

Environmental Water Allocations in regulated lowland rivers may encourage offstream movements and spawning by common carp, Cyprinus carpio: implications for wetland rehabilitation

Environmental Water Allocations (EWAs) are used to enhance native flora and fauna in regulated rivers, but may also benefit alien invasive species like common carp (Cyprinus carpio). We examined the invasion and spawning risk posed by adult common carp during an EWA delivered from the River Murray to a flow-through wetland in South Australia from June to December 2008. Offstream movements of fish and turtles were monitored continuously via the inlet and outlet creeks. Long-necked turtles (Chelodina longicollis, n = 129) dominated at the inlet where few fish were collected (n = 24), whereas much larger numbers of common carp in prime spawning condition (n = 4709), alien goldfish (Carassius auratus, n = 1201) and native bony herring (Nematalosa erebi, n = 93) were attracted to the outlet and displayed distinct movements. Adult common carp movements began in August, in response to increasing water temperatures, peaked in mid-September before spawning, then declined and were close to zero by December. The timing of EWA deliveries potentially could be manipulated to reduce adult carp invasion and spawning potential while providing some advantage to native fish, but the benefits may be short-lived without additional carp management interventions such as wetland drying.

Chloride cell morphometrics of Common carp, Cyprinus carpio, in response to different salinities

Salinity plays an important role in the survival, metabolism, and distribution of fish during development. The successful establishment of species in a given habitat depends upon the ability of each developmental stage to cope with salinity via osmoregulation. The present study was conducted to assess the effect of salinity on number and size of chloride cells or mitochondria rich cells and their relation to osmoregulatory ability in Cyprinus carpio, a freshwater (FW) fish. No mortality occurred when the Common carp was gradually transferred into brackish water. Branchial chloride cell numbers decreased after brackish water exposure, whereas a gradual increase was observed in chloride cell size. Chloride cells exist in both FW and brackish water. The number of chloride cell fish in 9 ppt salinity was greatly significant (p < 0.05) when compared with other treatments, while chloride cells with larger size were observed in 12 ppt salinity (p < 0.05). Hence, our data indicate that in culture conditions, adult Common carp can survive successfully in brackish water with salinity of up to 9 ppt.

IMPORTANCE OF LIGHT IN TEMPORAL ORGANIZATION OF PHOTORECEPTOR PROTEINS AND MELATONIN-PRODUCING SYSTEM IN THE PINEAL OF CARP CATLA CATLA

The importance of light in the temporal organization of photoreceptor proteins and melatonin-producing system has been investigated for the first time in the pineal of a tropical fish. In this study, an identical experimental paradigm was followed during the four distinct phases of an annual cycle in adult carps (Catla catla) maintained either under natural photoperiod (NP) or continuous illumination (LL) or darkness (DD) for 30 days. At the end of each experiment, the pineal from fish in each experimental group was collected either at 06:00, 12:00, 18:00, or 24:00 in a daily cycle and assessed by Western blot analysis for pineal rod-like opsin, α-transducin, and AANAT. The same animals were also used for measurement of serum melatonin levels, and the serum as well as intra-pineal Ca++ levels at each timepoint. The study revealed a daily rhythmicity with a peak at 12:00 h and nadir at 24:00 h in the band intensity of pineal rod-like opsin and α-transducin in NP fish, while the band intensities of these photo-pigment proteins remained high under LL and low under DD, irrespective of clock hour during the 24 h cycle. The band intensity of pineal AANAT, levels of serum melatonin, and both serum Ca++ and intra-pineal Ca++ were maximum at 24:00 h and minimum at 12:00h in NP fish, and they were significantly lower under LL and higher under DD at each point of study. The results showed loss of daily rhythm in each studied variable in both LL and DD carps, suggesting that their circadian organization is dependent on the external light-dark conditions, rather than an endogenous circadian oscillator in the pineal. (Author correspondence: dgp_skmaitra@yahoo.co.in)

EFFECT OF SUPPLEMENTAL VE ON MEAT QUALITY AND ANTI-OXIDANT CAPACITY OF ADULT GRASS CARP

A Study was conducted to investigate the effects of supplemental vitamin E(VE) in practical diet on growth,meat quality and anti-oxidant capacity of adult grass carp(Ctenopharyngodon idellus).Basal diet,added with VE 0(control group),25,50,100 or 200 mg/kg,were fed to adult grass carp for 60 days.The basal diet contained 28.05% crude protein,3.25% crude fat and 24.1 mg/kg VE.Adult grass carp,with body weight of(614.9±60.5) g,were divided into five treatments with triplicate groups,and raised in 15 cement pools(3.0m×2.5m×1.2m).Fishes were fed twice per day(8:00 and 17:00) with the feed intake of 2% of the body weight.Growth rate,feed conversion rate(FCR),muscle composition,drip loss of fresh meat,exudative loss of freezing meat,VE and maleic dialdehyde(MDA) in liver and muscle,serum SOD,total antioxidant capacity(T-AOC) were measured.Results showed that growth rates of the five groups were 51.6%,53.5%,53.4%,53.5%,54.8%,and FCR were 2.28,2.17,2.20,2.19,and 2.15,respectively.There was no significantly effect of supplemental VE in diets on growth and FCR of adult grass carp,but growth rate tended to be increased and FCR tended to be decreased by supplemental 200mg/kg VE in diet(P0.10).With supplemental VE increased,the drip loss of fresh meat and exudative loss of freezing meat decreased,but the moisture,crude protein,crude fat of meat kept constant among all groups.The VE concentration of muscle and liver were significantly increased,whereas MDA was decreased by supplemental VE(P0.05).Compared with control group,VE of meat and liver were increased by 431.0%,353.7%,and MDA were decreased by 67.2%,61.3% by supplemental 200mg/kg VE in diet(P0.01).Compared with control group,when supplemental VE was higher than 50 mg/kg,serum SOD activities significantly increased(P0.05),and T-AOC was significantly higher when supplemental VE was 200mg/kg(P0.05).No significant difference in serum T-AOC was observed among groups of 0,50,100 mg/kg VE addition group.Results above showed that growth performance,meat quality and serum anti-oxidant capacity of adult grass carp could be improved by supplemental VE in diets.For adult grass carp,the VE supplement in practical diet(containing VE 24.1 mg/kg) was estimated to be 25 mg/kg according to the growth performance,or 200 mg/kg according to meat quality and anti-oxidant capacity.

A novel push trap element to manage carp (Cyprinus carpio L.): a laboratory trial

Common carp (Cyprinus carpio L.) cause detrimental changes to aquatic ecosystems and are a declared pest fish in several countries. Despite existing management options, the development of new technologies is desirable as the range of the common carp is predicted to expand and their eventual control will rely on an integrated approach. The present paper describes a laboratory trial of a novel ‘finger style’ push trap element designed to catch carp ≥250 mm total length (TL). Forty-five adult carp (mean length: 603.0 ± 74.9 mm s.d. TL) were placed into the downstream section of a 7.25-m flume and exposed to three stimuli (water level manipulation, flow and light) to encourage upstream movement towards the push trap element. Forty-one carp (91.1%) pushed through the trap element over 16 h and none escaped. Only an average of ~5% of carp’s known pushing capacity was needed to push through the ‘fingers’ and enter the trap, and modelling suggested that a 250-mm TL carp would need to exert ~22% of its pushing capacity. The results confirm that the push trap element design is matched to the morphology and ecology of carp and, pending field validation trials, promises success as a novel management option.

Recruitment and abundance of an invasive fish, the common carp, is driven by its propensity to invade and reproduce in basins that experience winter-time hypoxia in interconnected lakes

Although the common carp is globally distributed, it only reaches extreme densities in certain regions. We hypothesized that this phenomenon might be linked to recruitment bottlenecks which carp overcome where environmental conditions create unstable peripheral areas that it can access for spawning and nursery habitat. To test this hypothesis, the abundance, movement and reproductive success of carp was determined in two systems of inter-connected lakes in the North American Midwest whose shallow basins frequently experience winter-hypoxia (‘winterkill’). Radio-tracking demonstrated that while adult carp overwinter in deep lakes that do not winterkill, they aggressively move into winterkill-prone shallow regions in the spring to spawn. The significance of this behavior was demonstrated by ageing analyses which found that carp recruit only in interconnected shallow lakes and then only in years following severe winter hypoxia. Presumably this strategy allows carp to exploit nursery habitat that is relatively free of predators. It likely evolved in response to seasonally variable conditions in the carp’s native habitat in the Ponto-Caspian region. This life history may also explain the carp’s abundance in other unstable regions such as southern Australia and could potentially be exploited to control this damaging invasive.

Structural differences in the motor domain of temperature-associated myosin heavy chain isoforms from grass carp fast skeletal muscle

We determined coding sequences for three types of grass carp myosin subfragment-1 (S1) heavy chain by extending 5'-regions of the three known genes encoding light meromyosin isoforms (10 degrees C, intermediate and 30 degrees C types). The primary structures of these three S1 heavy chain isoforms showed 81.4%, 81.2%, and 97.8% identities between the 10 degrees C and intermediate types, between the 10 degrees C and 30 degrees C types, and between the intermediate and 30 degrees C types, respectively. Isoform-specific differences were clearly observed between the 10 degrees C type and the other two types in 97 amino acid residues. Furthermore, among these amino acid mutations, 51 mutations occurred at the conserved residue sites of S1 heavy chain from fish and homoiotherm. Additionally, the 10 degrees C type showed striking differences compared with the other two types in the two surface loops, loop 1 located near the ATP-binding pocket and loop 2, which is one of the actin-binding sites, suggesting that such structural differences possibly affect their motor functions. Interestingly, this 10 degrees C-type myosin heavy chain isolated from adult grass carp skeletal muscle was surprisingly similar to the embryonic fast-type myosin heavy chain from juvenile silver carp in the structure of S1 heavy chain, indicating that it may also function as embryonic fast-type myosin heavy chain in juvenile stage.

Acoustic and radio-transmitter retention in common carp (Cyprinus carpio) in New Zealand

Common carp (Cyprinus carpio) are notoriously difficult to monitor in water temperatures above 20°C using telemetry owing to transmitter expulsion. To reduce transmitter loss, radio transmitters were anchored to the pelvic girdle and a polymer coating was applied to acoustic transmitters to reduce tissue irritation in two tank trials. Ten dummy transmitters were surgically implanted in each of four groups of adult koi carp, a highly coloured strain of C. carpio. Water temperatures ranged between 7 and 24°C. After 365 days, the control and test groups of each trial had similar expulsion rates (P ≥ 0.30; two-tailed Fisher’s exact probability test). Expulsion rates for uncoated acoustic transmitters were 60% (n = 6), coated acoustic transmitters 50% (n = 5), unanchored radio transmitters 60% (n = 6) and anchored radio transmitters 90% (n = 9). Expulsions occurred 15–362 days after implantation as a result of ulcers at or near the surgical wound. Bacterial infection of the wound appears to be the primary mechanism for transmitter expulsion.

Application of micelles extraction in the purification of protamine from adult carp sperm

Application of micelles extraction in the purification of protamine from adult carp sperm

Liver cyp1A protein expression and pigmented macrophage aggregates as indicators of polychlorinated biphenyl exposure in carp Cyprinus carpio L. from the Kalamazoo River Superfund site, Michigan

Cytochrome p450 1A (cyp1A), pigmented macrophage aggregate (PMA) variables and fish descriptive characteristics were measured in field‐caught adult carp Cyprinus carpio from two upstream reference sites and two downstream Superfund sites contaminated with polychlorinated biphenyls (PCBs) in the Kalamazoo River, MI, U.S.A. Liver PCB content in fish differed among sites, and immunocytochemical cyp1A protein expression was significantly elevated in fish liver at contaminated sites and with liver PCBs. PMA number (number per mm2), mean size [mean size (area) per mm2] and percentage area occupied (total area of PMAs per total field area evaluated) were significantly greater in fish livers from the contaminated sites. PMA number was significantly greater at one contaminated site, Lake Allegan, than at the Trowbridge Dam impoundment, the other contaminated site. The level of cyp1A protein was significantly correlated with PMA mean size and PMA per cent area but not with PMA number. These results suggest that carp are responding to PCB contamination and point to complex site dynamics related to fish condition in the Kalamazoo River.

Species-specific responses of aquatic macrophytes to fish exclusion in a prairie marsh: A manipulative experiment

An exclosure experiment was carried out at two sites in Delta Marsh, Manitoba, Canada to investigate the role of fish in limiting the growth of submersed macrophytes. The experiment consisted of three treatments: (1) fine-mesh exclosures designed to exclude both planktivorous fish and carp, (2) coarsemesh exclosures designed to exclude adult carp but admit smaller fish, and (3) reference plots marked with corner stakes but without sides. Treatments were established in mid-May, and macrophyte biomass was sampled from within the exclosures in late August to assess treatment effects. Exclosure treatments had strong effects on the macroalgae Chara, with biomass 11.9-fold greater in full-exclosure plots than in reference plots, and 3-fold greater in carp exclosures than in reference plots. Exclosure treatments had no effect on above-ground or below-ground biomass of Stuckenia pectinata, the most widespread and abundant macrophyte in Delta Marsh. Thus, fish appear to limit macrophyte growth in Delta Marsh, but the effect of fish exclusion was dependent on species composition of the macrophyte assemblage.

Molecular cloning and mRNA expression analysis of carp embryonic, slow and cardiac myosin heavy chain isoforms

Three embryonic class II myosin heavy chains (MYHs) were cloned from the common carp (Cyprinus carpio L.), MYHemb1, MYHemb2 and MYHemb3. MYH DNA clones were also isolated from the slow muscle of adult carp acclimated to 10 degrees C (MYHS10) and 30 degrees C (MYHS30). Phylogenetic analysis demonstrated that MYHemb1 and MYHemb2 belonged to the fast skeletal muscle MYH clade. By contrast, the sequence of MYHemb3 was similar to the adult slow muscle isoforms, MYHS10 and MYHS30. MYHemb1 and MYHemb2 transcripts were first detected by northern blot analysis in embryos 61 h post-fertilization (h.p.f.) at the heartbeat stage, with peak expression occurring in 1-month-old juveniles. MYHemb1 continued to be expressed at low levels in 7-month-old juveniles when MYHemb2 was not detectable. MYHemb3 transcripts appeared at almost the same stage as MYHemb1 transcripts did (61 h.p.f.), and these genes showed a similar pattern of expression. Whole mount in situ hybridization analysis revealed that the transcripts of MYHemb1 and MYHemb2 were expressed in the inner part of myotome, whereas MYHemb3 was expressed in the superficial compartment. MYHS10 and MYHS30 mRNAs were first detected at hatching. In adult stages, the expression of slow muscle MYH mRNAs was dependent on acclimation temperature. MYHS10 mRNA was expressed at an acclimation temperature of 10 and 20 degrees C, but not at 30 degrees C. In contrast, MYHS30 mRNA was strongly expressed at all acclimation temperatures. The predominant MYH transcripts found in adult slow muscle and in embryos at hatching were expressed in adult fast muscle at some acclimation temperatures but not others. A MYH DNA clone was isolated from the cardiac muscle of 10 degrees C-acclimated adult fish (MYHcard). MYHcard mRNA was first detected at 61 h.p.f., but strong signals were only observed in the adult myocardium. The present study has therefore revealed a complex pattern of expression of MYH genes in relation to developmental stage, muscle type and acclimation temperature. None of the skeletal muscle MYHs identified so far was strongly expressed during the late juvenile stage, indicating further developmentally regulated members of the MYH II gene family remain to be discovered.

Common carp insulin-like growth factor-I gene: complete nucleotide sequence and functional characterization of the 5′-flanking region

Insulin-like growth factor-I (IGF-I) plays an important role in the growth and development of fish. To understand the molecular mechanism which controls the transcription of the IGF-I gene in common carp, we have cloned and completely sequenced the IGF-I gene and the 5′-flanking region from a local tropical fish, the common carp ( Cyprinus carpio), and characterized its promoter activity by transfection into human embryonic kidney (293GHR) cells which express the human growth hormone (GH) receptor. The common carp gene is the smallest IGF-I gene known so far, spanning approximately 13 kb, and is consisted of five exons and four introns. The sequence of the gene is consistent with the single type of IGF-I cDNA that we have isolated previously from a common carp liver cDNA library. The expression pattern of IGF-I is similar between juvenile carp and adult carp. While liver was found to be the major site of IGF-I gene expression in common carp, the expression levels in other tissues are relatively low. Like many other IGF-I gene promoters, there are no apparent TATA box and CCAAT box upstream of the transcription initiation site. However, sequence analysis of the common carp IGF-I promoter region identified several consensus liver-enriched transcription factor binding sites, including HNF-1α, HNF-3β, C/EBP, and one STAT5. We have analyzed the promoter activity of the 5′-flanking region of the common carp IGF-I gene by performing luciferase reporter assays in transfected 293GHR cells. Addition of human GH to the transfected cells led to an increased expression of the reporter gene, indicating that the cloned genomic fragment possessed promoter activity. This was confirmed by the lack of promoter activity of a construct in which the putative promoter was cloned in a reverse orientation upstream of the reporter gene. The liver-specific transcription factor, hepatic nuclear factor (HNF)-1α, was also found to be involved in the regulation of the common carp IGF-I transcription. Transfection results from a set of deletion mutants helped to map the locations of the responsive elements on the promoter responsible for the GH effect and for the interaction with HNF-1α. These observations provide information for delineating the transcriptional regulation of IGF-I gene expression in common carp.

Morphometric and Histopathological Parameters of Gonadal Development in Adult Common Carp from Contaminated and Reference Sites in Lake Mead, Nevada

Abstract This study examined the hypothesis that exposure to sublethal concentrations of contaminants alters the gonadal condition of feral common carp Cyprinus carpio. Adult common carp in Lake Mead, Nevada, were collected from a contaminated site (Las Vegas Bay) that receives municipal and industrial effluent and from a reference site (Overton Arm) with a relatively low level of contamination. Fish were sampled seven times over a 1-year period extending over two separate spawning seasons. Morphometric and histopathological parameters of gonadal and germ cell development were determined. In males, the pattern of seasonal changes in the gonadosomatic index (GSI) was similar between the sites and showed no clear association with site-specific seasonal temperature profiles. However, Las Vegas Bay males had consistently lower GSI values and, on one of the sampling dates, a lower proportion of sperm relative to other germ cell stages (determined histologically). Further, Las Vegas Bay males had a higher incid...

Autoradiographic distribution of neuropeptide Y binding sites in the brain of the carp Cyprinus carpio L. (Cyprinidae, Teleostei)

The present study reports the distribution of neuropeptide Y (NPY)-binding sites in the brain of the adult carp Cyprinus carpio L. Radioiodinated NPY was used as tracer in the autoradiographic procedure. The NPY-binding sites (NPY-bs) were widely distributed in the carp brain. Generally, a good match was observed between the distribution of NPY-bs and the distribution of NPY-immunoreactive (NPY-ir) elements previously reported in the forebrain of the carp. Low to moderate concentration of NPY-bs were found in the telencephalon, this finding indicates that NPY may play a role in the processing of olfactory inputs and in more complex behaviours like spatial learning acquisition and retention, whose importance could correlated with similar results obtained in mammals. Moreover, in the rhombencephalon, the presence of NPY-bs at level of lobus vagus and the lobus facialis suggests that NPY may be implicated in food-seeking behaviour and swallowing reflex.

PCR-cloning and gene expression studies in common carp ( Cyprinuscarpio) insulin-like growth factor-II

Insulin-like growth factor-II (IGF-II) is a member of a growth factor family related to fetal growth in mammals but its physiological role has not been clearly identified in fish. In teleosts, the basic mechanism of the growth hormone (GH)–IGF axis is known to be operative but in a different manner. For instance, IGF-I exhibits GH dependence whereas for IGF-II, its GH dependence varies in different fish species. In this study, we used polymerase chain reaction (PCR) to obtain a common carp IGF-II (ccIGF-II) cDNA fragment and methods of rapid amplification of cDNA ends (RACEs) to obtain a full-length ccIGF-II sequence. The ccIGF-II encodes for a predicted amino acid sequence showing identities of 70.6%, 68.7%, 63.4% and 35% in comparison with salmon, barramundi, tilapia and human IGF-II, respectively. The nucleotide identity between the open reading frame (ORF) of the ccIGF-II and ccIGF-I cDNA sequence is only 36.2%. Distribution of ccIGF-II mRNA levels in common carp tissues was also studied; ccIGF-II expressed in hepatopancreas, heart, and many other tissues in adult carps are similar to the levels of ccIGF-I except in gills and testis. ccIGF-II levels were significantly higher than that of ccIGF-I in most juvenile tissues except in hepatopancreas, where ccIGF-I was higher (threefold) than that of ccIGF-II. The levels of ccIGF-I were also higher than ccIGF-II in carp larvae, from pre-hatched stage to day 30 post-hatching. Injection of porcine GH (pGH) increased the IGF-I and IGF-II mRNA levels in the hepatopancreas and brain of juvenile carps. However, hepatic IGF-I mRNA levels were induced more than IGF-II by pGH, whereas ccIGF-II levels gave a higher response than IGF-I in the brain in response to GH induction.

The nuclear export signal (NES) found in the amino-terminal region of carp MEK1 and MKK6 is lacking in carp MKK4

Carp MKK4 (cMKK4) cDNA was isolated from an ovary cDNA library. cMKK4 mRNA was ubiquitously distributed in various tissues of adult carp. Sequence analysis revealed that cMKK4 lacks a nuclear export signal sequence, unlike mammalian and frog MEKs (ERK activator) and cMKK6 (carp p38 activator), where it plays an important role in anchoring these MAP kinase activators to the cytoplasm. cMKK4 protein was found to be diffused throughout the cell, whereas cMEK1 and cMKK6 proteins were seen exclusively in the cytoplasm.

Response of fish membranes to environmental temperature

The effect of temperature on fluidity, fatty acid and molecular species composition of liver and brain phospholipids in fish adapted or exposed to extreme temperatures was investigated. Membranes from cold-adapted fish were more fluid than those from warm-adapted fish. Ability to control membrane fluidity according to temperature appears in early ontogenesis and is first evident in swim-up fry of carp. Red blood cells as well as neurons of adult carp can continuously adjust the fluidity of their external membranes to changing temperatures. Segregation of choline and ethanolamine phosphoglycerides from livers of fish adapted to a cold/warm environment showed an accumulation of molecular species containing a monoenic fatty acid in position sn-1 and a polyenic fatty acid in position sn-2 of the molecule in cold conditions. Model experiments using mixtures of synthetic 18:1/22:6 phoshatidylethanolamines and 16:0/18:1 phosphatidylcholines demonstrated the involvement of these molecular species in rendering the membranes less packed (more fluid) during adaptation to reduced temperatures.

Fine structure of the skin cells of a stenohaline freshwater fish Cyprinus carpio exposed to diluted seawater

Seawater diluted to half (1.750% salinity) is lethal for adult carps after 3h and 15min. At lower salinities (0.350%–0.875%), the fish survived for longer periods, but only 0.175% salinity was innocuous. In carps, adapted to 0.175% salinity, the secretory activity of pavement cells was very high and their external ridges flattened or even disappeared. Mucus secretion was conspicuous, characterized by holocriny of old cells and apparition of young ones in large numbers. The intracellular mucus droplets often coalesced. Pavement cells and mucus cells were disconnected from their neighboring tissue fabric and were sloughing off. Mitotic figures of filament cells were frequent, suggesting high turnover. Club cells appeared near the epidermal surface. The number of pinocytotic vesicles of the basal cell layer markedly decreased, indicating a possible decrease in dermis-epidermis molecular transfers. Leucocytes, mainly lymphocytes penetrated into the epidermis, where also rodlet cells appeared. The low salinity tolerance of the carp might be related among other possible factors to the absence of chloride cells in the skin.