Minute tubercles on the skin surface of larvae in the Korean endemic bitterling, Rhodeus pseudosericeus (Pisces, Cyprinidae)

The morphology and distribution of the minute tubercles on the skin surface of larvae in Korean bitterling, Rhodeus pseudosericeus, were observed during larval development. Just after hatching, the epidermis of the larvae consists of a thin single cell layer having smaller basophilic flat or round‐flattened basal cells. As the larvae grow, the epidermis contains more small flat cells and large epidermal cells that are round or hemisphere‐shaped. These large unicellular epidermal cells, called minute tubercles, consist of more or less homogeneous cytoplasm that is PAS (Periodic acid‐Schiff method) positive. They are more densely distributed in the wing‐like yolk sac projection. Vestigial minute tubercles occur in the body region and the caudal fin‐fold region. These minute tubercles grow in number and height from 6 to 8 days after hatching onward. However, they become reduced in height and number as the larvae develop. At day 31 after hatching (i.e. free‐swimming stage), minute tubercles no longer exist on the larval skin. The sequence of occurrence and gradual disappearance of these cell structures are described and histologically documented for comparative purposes of beta, taxnomomic and environmental studies.     

Development of the bitterling,Paracheilognathus himantegus (Cyprinidae), with a note on minute tubercles on the skin surface

The development of the eggs and larvae and minute tubercles on the skin surface ofParacheilognathus himantegus larvae were observed. The egg began to hatch approximately 68 hours after insemination and the larvae reached the free-swimming stage 23 days after hatching at water temperature of 22±1°C. The larval development and minute tubercles on the skin surface of this species were similar to those ofAcheilognathus lanceolata, A. limbata, A. signifer andTanakia tanago. However, the shape of the ripe eggs ofP. himantegus differed from those of the four species. As regards the shape of eggs, there was a common characteristic amongP. himantegus, Rhodeus uyekii andA. limbata from Korea. As regards larval development,P. himantegus had two characters also found inRhodeus. These facts seem to suggest thatP. himantegus is closely related toA. lanceolata, A. limbata, A. signifer andT. tanago but is more specialized than these four species, except forA. limbata from Korea.     

Minute tubercles in bitterling larvae: Developmental dynamic structures to prevent premature ejection by host mussels

1. Bitterlings are small freshwater fish that use long ovipositors to lay eggs in host mussels, and they have morphological adaptations to increase larval survival. The most well‐known adaptation is the minute tubercles on the skin surface of larvae; they are developed in early‐stage larvae with weak swimming ability and disappear in free‐swimming larvae before they leave the host mussel.
2. In the present study, I comprehensively analyzed the developmental stages of Rhodeus pseudosericeus larvae, their morphological and physiological characteristics, their migration inside mussels, and the development of minute tubercle in order to elucidate the morphological function of the minute tubercles. These tubercles began to develop 1 day after hatching (formation stage), grew for 2–5 days (growth stage), reached the peak height after 6–7 days (peak stage), abruptly reduced in height after 8–10 days (abrupt reduction stage), and gradually reduced in height (reduction stage) until completely disappearing 27 days after hatching (disappearance stage).
3. The larvae remained in the mussels’ interlamellar space of the gill demibranchs until 10 days after hatching and began to migrate to the suprabranchial cavity 11 days after hatching. At this time, the larvae had a heart rate and the caudal fin began to develop. At 24 days after hatching, the minute tubercles had almost disappeared, and some individuals were observed swimming out of the mussels.
4. The results presented herein elucidate that the minute tubercles are the developmental dynamic structures that the bitterling larvae have morphologically adapted to prevent premature ejection from the mussel.

     

Breeding tubercles of Phoxinus (Teleostei: Cyprinidae): Morphology,distribution, and phylogenetic implications

Studies of the skin with scanning electron microscopy (SEM) reveal a diverse morphology in breeding tubercles among species of Phoxinus. Based mainly on the fine structure of the surface of tubercles, nine morphotypes, coded as letters A-I, occur in Phoxinus. Most of the morphotypes are common to all Phoxinus species, but type E is present only on the dorsum of the head of P. phoxinus, type H on the breast scale of female P. phoxinus, and type I on the pectoral fin in P. erythrogaster. Multicellular breeding tubercles bearing unicellular projections, identified as unculiferous tubercles are found in type H and probably types F and G. The distribution of tubercles on head, body, and fins is described and compared among Phoxinus species. Breeding tubercles in Phoxinus and other minnow genera are compared in order to interpret the phylogenetic implication of the tuberculation in Phoxinus. The deeply embedded breast scales and the breeding tubercles on their apical margins, and a series of tubercles on the apical margins of lateral scales of the caudal peduncle in breeding males of Phoxinus species, are the characters supporting the monophyly of the genus. © 1996 Wiley-Liss, Inc.     

Development of the bitterling,Tanakia tanago (cyprinidae), with a note on minute tubercles on the skin surface

The development of eggs and larvae and minute tubercles on the skin surface in larvae ofTanakia tanago were observed. The eggs began to hatch approximately 52 hours after insemination and the larvae reached free-swimming stage 19 days after hatching at water temperature of 22±1°C. The egg and larval development and minute tubercles on the skin surface in larvae of this species were similar to those ofAcheilognathus lanceolata andA. limbata. However,T. tanago was distinguishable in egg and larval development fromA. lanceolata andA. limbata by the following characters: the perivitelline space was narrower, embryonic and larval development was faster, and minute tubercles on the skin surface of the anteriormost parts of the yolk sac, and of the body and head were hemispheric in shape. From these characters,T. tanago is considered to be more specialized thanA. lanceolata andA. limbata.     

Ammonia excretion by the skin of zebrafish (Danio rerio) larvae

The mechanism of ammonia excretion in freshwater teleosts is not well understood. In this study, scanning ion-selective electrode technique was applied to measure H(+) and NH(4)(+) fluxes in specific cells on the skin of zebrafish larvae. NH(4)(+) extrusion was relatively high in H(+) pump-rich cells, which were identified as the H(+)-secreting ionocyte in zebrafish. Minor NH(4)(+) extrusion was also detected in keratinocytes and other types of ionocytes in larval skin. NH(4)(+) extrusion from the skin was tightly linked to acid secretion. Increases in the external pH and buffer concentration (5 mM MOPS) diminished H(+) and NH(4)(+) gradients at the larval surface. Moreover, coupled decreases in NH(4)(+) and H(+) extrusion were found in larvae treated with an H(+)-pump inhibitor (bafilomycin A1) or H(+)-pump gene (atp6v1a) knockdown. Knockdown of Rhcg1 with morpholino-oligonucleotides also decreased NH(4)(+) excretion. This study demonstrates ammonia excretion in epithelial cells of larval skin through an acid-trapping mechanism, and it provides direct evidence for the involvement of the H(+) pump and an Rh glycoprotein (Rhcg1) in ammonia excretion.     

Diet-shifts and food-dependent survival in Engraulicypris sardella (Cyprinidae) larvae from Lake Malawi, Africa

The diet of Engraulicypris sardella (Cyprinidae) larvae wasdeterinmed from the open waters of Lake Malawi, Africa. Theguts of first-feeding larvae of 2–3 mm total length (TL)usually contained many cells of 5–9 µm diametertentatively identified as a non-colonial green alga (Chlorophyta).The number of these cells in the guts of larvae declined aslarvae increased in size, and were not found in larvae greaterthan 9 mm TL. Other types of phytoplankton were rarely seenin the guts of larvae. Copepod nauplii were eaten by larvaegreater than 4 mm TL, and copepodite copepods and cladoceansby larvae greater than 5 mm TL. The biomass of open water crustaceanzooplankton and E.sardella larvae were determined over a 2-yearsampling programme. The mortality rate of E. sardella was negativelycorrelated with zooplankton biomass, but was not significantlycorrelated with the amount of zooplankton food in the guts oflarvae.     

Structural peculiarities of the tubercles in the skin of the turbot,Scophthalmus maximus (L., 1758) (Osteichthyes,Pleuronectiformes, Scophthalmidae)

The structure of the bony tubercles of the turbot, Scophthalmus maximus (L., 1758), was examined using ground sections, microradiography, SEM, and TEM. The tubercles are small, isolated, mineralized conical plates randomly distributed in the eyed side of the body. They are composed of three layers: the outer limiting layer, the external layer, and the basal plate, which make up the thin and flat elasmoid scales of Teleostei. The main difference between regular elasmoid scales and bony tubercles lies in the organization and the growth of the basal plate. Indeed, the conical shape of the tubercle is the result of a prominent thickening of the central part of the basal plate where the collagen matrix is organized in a complicated three-dimensional network. Densely packed thick collagen fibrils form superimposed plies organized in a plywood-like structure that resembles that of the elasmoid scales but it is criss-crossed by numerous vertical sheets of thin collagen fibrils. The tubercles originate from thin and flat plates located in the skin of larvae and juveniles, whose structure is that of regular-developing elasmoid scales. Thus, the tubercles of Scophthalmus maximus could be considered as modified elasmoid scales rather than bony structures. They might be the result of specific arrangements related to the general trend of reduction of the dermal skeleton in the teleostean lineage.     

Metabolic responses of fish larvae [Rutilus vutilus (L.)] to forced activity (Cyprinidae, Teleostei)

Larvae of Rutilus rutilus (L.) weighing approx. 40 mg were exercised for 5 min by mechanical stimulation. Individual larvae were taken before and immediately after stimulation, and during 2 h of recovery. The concentrations of glucose, glucose-6-phosphate, pyruvate, lactate, 2-oxoglutarate, and ascorbic acid were determined in individual larvae. The larvae recovered faster from forced activity than juvenile roach, recovery being complete after 1 h. Larvae also differed from juveniles in that metabolite levels increased less during activity. It is suggested that the combination of low glycolytic, and high oxidative capacity was responsible for the specific metabolic responses of the larvae.     

Profiles of enzyme activity in larvae of two cyprinid species with contrasting life styles (Cyprinidae; Teleostei)

Growth and the development of gills, muscle fibres and 10 enzymes serving different metabolic functions were studied in larvae of Rutilus rutilus (L.) and Chalcalburnus chalcoides (Agassiz, 1832). R. rutilus starts swimming and feeding one to three days after hatching, whereas in C. chalcoides this process is delayed by about 10 days. This difference in behaviour is reflected in the time-course of growth, the differentiation of the red muscle fibres and the activity of the enzymes of aerobic energy metabolism. On the other hand, the activity of the enzymes of anaerobic energy metabolism increases steadily throughout the period of observation (up to 60 days post-hatch), this trend being more pronounced in C. chalcoides than in R. rutilus . A weight-independent and a weight-dependent phase of development can be distinguished in the enzymes of aerobic energy metabolism. It is suggested that, in accord with previous findings, the early phase of locomotor activity of cyprinid larvae is fuelled mainly by aerobic processes, and that the central muscle mass of the larvae is more aerobic than the white muscle fibres of the adults. The delayed development of aerobic enzyme activity in C. chalcoides is compensated by the accelerated development of anaerobic enzyme activity, particularly of creatine kinase and lactate dehydrogenase. This difference between the two species studied suggests differences in the metabolic basis of burst activity.     

Interactions between developmental processes,growth, and food selection in the larvae and juveniles of Rutilus rutilus (L.) (Cyprinidae)

Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988).     

The dermal tubercles of Cranchia scabra (Mollusca, Cephalopoda); surface structure and development

The cartilaginous tubercles of the mantle of the squid Cranchia scabra have been examined with the scanning electron microscope. Some tubercles are small, simple nodules whereas others are large with a complex Maltese cross form. The varying shapes and sizes probably represent a developmental sequence. The possible role of the tubercles is discussed.     

Flexibility on the karyotype evolution in bitterlings (Pisces, Cyprinidae)

In bitterlings (Acheilognathinae) C- and Ag-banding karyotypes of 6 species-subspecies collected in China and South Korea were analyzed. The chromosomal constitution of 2n=46 (4SM+42ST) in Rhodeus atremius fangi was quite different from that of 2n=48 (8M+20SM+20ST) in other species-subspecies in Rhodeus. It was concluded from the analysis of banded chromosomes that the increase in number of ST during the karyotype change from 2n=48 to 2n=46 was achieved by a series of pericentric inversions from 24 M-SM to 24 ST, and the decrease in the diploid number was caused by an additional tandem fusion of 4 ST chromosomes, forming a new ST pair in the 2n=46 karyotype. The karyotype of Tanakia koreensis, T. signifer, and Acheilognathus macropterus is 2n=48 (8M+20SM+20ST), 2n=48 (8M+20SM+14–16ST+4–6 A), 2n=44 (14M+16SM+14ST), respectively. In R. ocellatus ocellatus, T. koreensis, T. signifer and A. macropterus, karyotype changes from 2n=48 to 2n=44 due to centric fusion and inversion have also been estimated. It was suggested that C-banding heterochromatin was greatly concerned with the karyotype evolution in bitterlings.     

六种鲤科鱼类核仁组织者区的研究

采用银染及荧光染色技术,对6种鲤科鱼的NORs进行了研究。结果表明：这6种鲤科鱼中瓦氏雅罗鱼、花 、麦穗鱼、白甲鱼具有2个NORs,长春鳊、墨头鱼具有4个NORs。根据实验研究结果对鲤科鱼类NORs多态性及演化等进行了讨论。 The NORs were examined in 6 species of Cyprinidae by both silver nitrate and chromomycin A3,which led to the detections of 2 NORs in 4 species(Leuciscus waleckii,Hemibarbus maculates,Pseudorasbora parva,and Varicorhinus simus)and of 4 NORs in 2 species (Parabramis pekinensis,and Garra pingi pingi).Based on our results,the variation and evolution of fish NORs were discussed.     

Sound Production in Codoma ornata (Girard) (Cyprinidae)

Male Codoma ornata produce sounds associated with aggression and spawning activities during the breeding season. Females do not produce sounds. Males most often produced sounds associated with escalated displays of aggression, courtship and the spawning act. C. ornata spawn in crevices, but previously were reported to spawn as egg-clusterers in cavities. Structurally, sounds are low frequency, vary in duration according to context and are not harmonic. The mechanism of sound production is unknown.     

Phylogenetic analysis of the genus Rasbora (Teleostei: Cyprinidae)

Liao, T. Y., Kullander, S. O. & Fang, F. (2009). Phylogenetic analysis of the genus Rasbora (Teleostei: Cyprinidae).—Zoologica Scripta, 39, 155–176. A phylogenetic analysis was conducted based on 35 cyprinid taxa, including 29 species of Rasbora, and 41 morphological characters. A strict consensus tree from four equally parsimonious trees recovered rasborins as a monophyletic group characterized by (i) presence of dark supra‐anal pigment and subpeduncular streak, (ii) 5–6 branched anal‐fin rays, (iii) dorsal‐fin insertion 1–3 scales behind pelvic‐fin insertion, (iv) lateral process of second vertebra more or less straight, (v) 1–5 more abdominal than caudal vertebrae, (vi) absence of foramen in anterior wall of horizontal limb of the cleithrum, (vii) presence of rasborin process on epibranchial 4, and (viii) interhyal well ossified. Rasbora sensu stricto can be distinguished from all other rasborin genera by the presence of an opercular canal. Four new genera, viz. Brevibora, n. gen., Kottelatia, n, gen., Rasbosoma, n. gen. and Trigonopoma, n. gen., are recognized and described.     

Phylogeny of the gudgeons (Teleostei: Cyprinidae: Gobioninae)

The members of the cyprinid subfamily Gobioninae, commonly called gudgeons, form one of the most well-established assemblages in the family Cyprinidae. The subfamily is a species-rich group of fishes, these fishes display diverse life histories, appearances, and behavior. The phylogenetic relationships of Gobioninae are examined using sequence data from four loci: cytochrome b, cytochrome c oxidase I, opsin, and recombination activating gene 1. This investigation produced a data matrix of 4114 bp for 162 taxa that was analyzed using parsimony, maximum likelihood, and Bayesian inference methods. The phylogenies our analyses recovered corroborate recent studies on the group. The subfamily Gobioninae is monophyletic and composed of three major lineages. We find evidence for a Hemibarbus-Squalidus group, and the tribes Gobionini and Sarcocheilichthyini, with the Hemibarbus-Squalidus group sister to a clade of Gobionini-Sarcocheilichthyini. The Hemibarbus-Squalidus group includes those two genera; the tribe Sarcocheilichthyini includes Coreius, Coreoleuciscus, Gnathopogon, Gobiocypris, Ladislavia, Paracanthobrama, Pseudorasbora, Pseudopungtungia, Pungtungia, Rhinogobio, and Sarcocheilichthys; the tribe Gobionini includes Abbottina, Biwia, Gobio, Gobiobotia, Huigobio, Microphysogobio, Platysmacheilus, Pseudogobio, Romanogobio, Saurogobio, and Xenophysogobio. The monotypic Acanthogobio is placed into the synonymy of Gobio. We tentatively assign Belligobio to the Hemibarbus-Squalidus group and Mesogobio to Gobionini; Paraleucogobio and Parasqualidus remain incertae sedis. Based on the topologies presented, the evolution of swim bladder specializations, a distinctive feature among cyprinids, has occurred more than once within the subfamily.     

Loss of surface coat by Strongyloides ratti infective larvae during skin penetration: evidence using larvae radiolabelled with 67gallium

The optimal conditions for labelling infective larvae of Strongyloides ratti with 67gallium citrate were determined. Radiolabelled larvae were injected s.c. into normal and previously infected rats. The distribution of radioactivity in these animals was compared with that in rats infected subcutaneously with a similar dose of free 67Ga by using a gamma camera linked to a computer system. Whereas free 67Ga was distributed throughout the body and excreted via the hepatobiliary system, the bulk of radioactivity in rats injected with radiolabelled larvae remained at the injection sites. Direct microscopical examination of these sites, however, revealed only minimal numbers of worms. When rats were infected percutaneously with radiolabelled larvae, it was found that most radioactivity remained at the surface, despite penetration of worms. When infective larvae were exposed to CO2 in vitro and examined carefully by light microscopy, loss of an outer coat was observed. It was concluded that infective larvae lose an outer coat on skin penetration.     

Morphology and microanatomy of harbor porpoise (Phocoena phocoena) dorsal fin tubercles

The unique pattern of small tubercles on the leading edge of the dorsal fins of harbor porpoises (Phocoena phocoena) has been widely noted in the literature, though their structure or function has never been conclusively identified. We examined external morphology and microanatomy of the tubercles for further understanding of the nature of the tubercles. Measurements were taken of height and peak‐to‐peak distance of the tubercles using scaled photographs. Mean tubercle height was standardized as a percentage of the dorsal fin height and ranged from 0.63 to 0.87%. Mean peak‐to‐peak distance ranged from 4.2 ± 2.0 to 5.6 ± 2.0 mm. The microstructure analysis of the dorsal fin leading edge, trailing edge and tubercles revealed an epidermal thickness of 0.7–2.7 mm with the thickest epidermis at the tubercular apex. The epidermis contained three distinct strata (=layers), including the stratum corneum, spinosum, and basale. The stratum corneum was significantly thickened in tubercles, over four times thicker than in the leading or trailing edge of the fin. The stratum spinosum, composed of lipokeratinocytes and lamellar oil bodies, was significantly thinner in the trailing edge than in the other two sites. There was no significant difference in the stratum basale among the three sites. Volume fraction of lipokeratinocytes was significantly higher at the sides of the leading edge and the apex of the tubercles, while volume fraction of lamellar oil bodies was significantly lower at the apex of the tubercles. Though the function of the tubercles is unknown, their position, hardened structure and increased epidermal stratum corneum suggest that they may have hydrodynamic importance. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.