Black Tetra Gymnocorymbus Ternetzi Research Articles

Tetra disseminated microsporidiosis: a novel disease in ornamental fish caused by Fusasporis stethaprioni n. gen. n. sp.

A novel microsporidial disease was documented in two ornamental fish species, black tetra Gymnocorymbus ternetzi Boulenger 1895 and cardinal tetra Paracheirodon axelrodi Schultz 1956. The non-xenoma-forming microsporidium occurred diffusely in most internal organs and the gill, thus referring to the condition as tetra disseminated microsporidiosis (TDM). The occurrence of TDM in black tetra was associated with chronic mortality in a domestic farmed population, while the case in cardinal tetra occurred in moribund fish while in quarantine at a public aquarium. Histology showed that coelomic visceral organs were frequently necrotic and severely disrupted by extensive infiltrates of macrophages. Infected macrophages were presumed responsible for the dissemination of spores throughout the body. Ultrastructural characteristics of the parasite developmental cycle included uninucleate meronts directly in the host cell cytoplasm. Sporonts were bi-nucleated as a result of karyokinesis and a parasite-produced sporophorous vesicle (SPV) became apparent at this stage. Cytokinesis resulted in two spores forming within each SPV. Spores were uniform in size, measuring about 3.9 ± 0.33 long by 2.0 ± 0.2μm wide. Ultrastructure demonstrated two spore types, one with 9-12 polar filament coils and a double-layered exospore and a second type with 4-7 polar filament coils and a homogenously electron-dense exospore, with differences perhaps related to parasite transmission mechanisms. The 16S rDNA sequences showed closest identity to the genus Glugea (≈ 92%), though the developmental cycle, specifically being a non-xenoma-forming species and having two spores forming within a SPV, did not fit within the genus. Based on combined phylogenetic and ultrastructural characteristics, a new genus (Fusasporis) is proposed, with F. stethaprioni n. gen. n. sp. as the type species.

Histological, histochemical and biochemical characterization of larval digestive system ontogeny in black tetra Gymnocorymbus ternetzi to inform aquaculture weaning protocols

Identifying an appropriate larval diet is a significant challenge in aquaculture. To overcome this bottleneck, characterization of larval fish digestive system ontogeny is critical for optimizing nutritional protocols. Intensive culture of characids for ornamental trade is highly dependent on live Artemia nauplii through the larval stage. Live feeds have unique challenges relative to prepared microparticulate diets (MDs), specifically pertaining to availability, labor, and cost. In this study, a feeding trial was conducted to compare three commercially available MDs in larval Black Tetra Gymnocorymbus ternetzi. Larvae exhibited poor survival and growth for MDs relative to Artemia. Digestive system ontogeny was characterized using histology, histochemistry, and digestive enzyme activity assays from the onset of exogenous feeding through the larval stage. G. terntzi exhibited an agastric larval stage, as well as low digestive enzyme activity at the onset of exogenous feeding, followed by increases in trypsin, lipase, and pepsin activity. Histological differentiation of the stomach, including gastric gland formation and production of periodic acid Schiff positive neutral mucopolysaccharides, as well as the onset of pepsin activity, occurred at 22 days post hatch (dph). This shift from agastric to gastric digestion indicated elevated digestive capacity and increased ability to consume a diversity of prey.Based on these data, experiments were conducted to evaluate different weaning times from Artemia to a MD. Larvae were fed Artemia exclusively from hatch through the end of the trial, a MD exclusively, or were transitioned from Artemia to a MD at three different time points. For G. ternetzi fed until 33 dph, weaning beginning at 13 dph exhibited higher survival (20.6 ± 1.8%) than live Artemia and weaning beginning at 18 dph and 23 dph (mean: 13.6 ± 1.5%), while the MD resulted in the lowest survival (0.8 ± 0.2%). These results indicate that weaning is possible prior to gastric differentiation, suggesting that it is possible to rely less on Artemia as a larval feed in this characid species.

Assessment of the Risks of Transgenic Fluorescent Ornamental Fishes to the United States Using the Fish Invasiveness Screening Kit (FISK)

AbstractThree species of transgenic fluorescent ornamental fish are commercially available to the public in the United States—Zebra Danio Danio rerio, Black Tetra Gymnocorymbus ternetzi, and Tiger Barb Systomus tetrazona. Despite qualitative assessments of the risks of these transgenic fishes by the U.S. Food and Drug Administration and two state agencies, critics argue that the risk assessment and approval processes were not transparent and that the results were never published or otherwise open to scientific scrutiny. We used an internationally recognized risk screening tool, the Fish Invasiveness Screening Kit (FISK), to provide a transparent, peer‐reviewed assessment for the conterminous United States. We found that the three transgenic fluorescent ornamental fishes in question represent a low risk of invasiveness. Any risk is limited to the warmer regions of the country. No potential for hybridization with native species, little history of invasiveness elsewhere, a lack of traits associated with persistence, and small body size coupled with predation‐enhancing fluorescence all indicate that the ability of these species to become established and have impacts is limited even in warm regions. Our finding of low risk is consistent with the results of unpublished, qualitative agency assessments using expert panels or in‐house expertise. The risk screens identified few data gaps, areas of important uncertainty, or potentially elevated risk levels, thus suggesting that there would be limited gain to committing resources to a full risk assessment. A low‐risk result further indicates little need for risk management actions in addition to those already being taken. Risk screens such as FISK can have high value for managers because they capture important elements of risk, providing vital information for assessment and management decisions with relatively small investments in time and funding.

Pheromones: Fish Fear Factor

Fish, like many other animals, panic when another individual is injured. Now, the chemical nature of a substance that mediates this reaction has been uncovered.

Descriptive osteology of Gymnocorymbus ternetzi (Teleostei: Characiformes: Characidae)

The purpose of this paper is giving an extensive overview of the cranial skeleton of Gymnocorymbus ternetzi (Boulenger, 1895) in a form of a formalized scheme that reflect its Bauplan (German for building plan, blueprint; plural: baupläne or bauplaene), a term in biology referring to the common new and original [homologous] properties of the members of a systematic group [taxon]). Each element of the Bauplan can be described by a set of parameters, i.e., size, shape, structure, material composition and position. Though Bauplan is undoubtedly an abstraction, it is a necessary abstraction to be used in phylogenetic analysis with preference to "ingroup" and "outgroup" comparisons.The cranial osteology of black tetra Gymnocorymbus ternetzi (Boulenger, 1895) is described based on the study of larvae, juvenile and adult specimens. Provided are Latin terms and some English equivalents as well remarks on origin, homology and terminology for each cranial bone discussed.

Endocytosis of horse-spleen ferritin in the black tetra, Gymnocorymbus ternetzi (Characidae: Teleostei)

The capability and capacity of various tissues in black tetra Gymnocorymbus ternetzi (Boulenger), family Characidae, to take up horse-spleen ferritin from the blood stream are described. In the head kidney from specimens injected intraperitoneally with horse-spleen ferritin, numerous large cells were tightly packed by yellow-brown granules when the period of time between injection and sacrifice was over 2 h. These cellular granules were tightly packed with Prussian blue precipitation in tissues treated with an acid ferrocyanide solution, i.e., they displayed a deep blue colour. Similarly, smaller cells were also observed in the trunk kidney, gills and peripheral connective tissue of the pancreas and spleen at this stage after ferritin injection, but they were always few in number. Yellow-brown granules or Prussian blue granules were not found in endothelial cell layers of heart and liver. We suggest that practically all clearance of the blood from foreign and scavenger macromolecules is performed by macrophages in the head kidney of the black tetra, whereas the spleen seems to function mainly as a reservoir for red blood cells in this species.

Larval feeding behaviour of blind fish Astyanax fasciatus (Characidae), black tetra Gymnocorymbus ternetzi (Characidae) and angel fish Pterophyllum scalare (Cichlidae) fed zooplankton

We studied the feeding behaviour during the larval stages (from hatching until 8 weeks) of the Mexican blind fish Astyanax fasciatus, black tetra Gymnocorymbus ternetzi and angel fish Pterophyllum scalare using four zooplankton species (two rotifers: Brachionus calyciflorus and B. patulus and two cladocerans: Daphnia pulex and Moina macrocopa). Components of feeding behaviour (numbers of encounters, attacks, captures, ingestions, rejections and escapes) were quantified for 10 min observation periods per larvae. Data on the increase of the body length and mouth size of the three fish species during this period were also collected. When B. calyciflorus was used as prey, P. scalare showed higher capture and ingestion rates than A. fasciatus or G. ternetzi. With reference to age, B. calyciflorus was more frequently attacked, captured and ingested by G. ternetzi and P. scalare than A. fasciatus from the first to the 8th week. When offered B. patulus as prey, larvae of the three fish species showed increased consumption of B. patulus with time. A. fasciatus sometimes rejected B. patulus which could also escape after being captured. A. fasciatus began to attack and ingest Daphnia pulex and Moina macrocopa from the first week onwards while, G. ternetzi could neither capture nor ingest cladocerans until the fifth week. P. scalare began to ingest M. macrocopa and D. pulex from the third week onwards. These results are discussed with reference to the non-functional eyes of larval A. fasciatus.

Tolerance of Yolk Sac and Free-Swimming Fry of the Zebra DanioBrachydanio rerio, Black TetraGymnocorymbus ternetzi, Buenos Aires TetraHemigrammus caudovittatus, and Blue GouramiTrichogaster trichopterusto Therapeutic Doses of Formalin and Sodium Chloride

Abstract The purpose of this study was to determine the tolerance of larval fish in the families Characidae, Cyprinidae, and Belontiidae to therapeutic doses of sodium chloride and formalin. Four species of fish were included in this study: zebra danio Brachydanio rerio (also known as Danio rerio), black tetra Gymnocorymbus ternetzi, Buenos Aires tetra Hemigrammus caudovittatus, and blue gourami (also known as threespot gourami) Trichogaster trichopterus. Representative species from each family for both yolk sac fry (2–3 d old) and free-swimming fry (5–7 d old) were tested. The treatments consisted of 1 or 3 g/L sodium chloride or 12.5 or 25 mg/L formalin. Mortalities at 24 and 48 h were compared. Although 12.5–25 mg/L of formalin appears to be safe for very young zebra danio fry, therapeutic doses of salt are not recommended. Yolk sac and free-swimming fry of the blue gourami are tolerant of therapeutic doses of salt (1–3 g/L) but very sensitive to formalin. Because there are significant differences in t...

Effect of hypoxanthine-3(N)-oxide and hypoxanthine-1(N)-oxide on central nervous excitation of the black tetraGymnocorymbus ternetzi (Characidae, Ostariophysi, Pisces) indicated by dorsal light response

The change of state in the central nervous system ofGymnocorymbus ternetzi after detection of hypoxanthine-l(N)-oxide, hypoxanthine-3(N)-oxide, and of the alarm substance from conspecifics was measured quantitatively by means of the fishes' equilibrium behavior. The fish swam freely in a tiny cage, illuminated horizontally from one side. The change of the angle of inclination of the dorsoventral axis of the fish was registered by means of a videorecorder. The recordings were later measured on the monitor in single frames at 0.2-sec intervals where the equilibrium position of the fish could be accurately determined ± 1 °. Various substances were presented to the fish, and their effects upon equilibrium position were recorded. An enhanced optical alertness shown by an increase in the fishes' inclination was generally produced with alarm substance. Without any additional stimulation, the factorU, representing quantitatively the degree of the change of central state, varied slightly within the experimental period of 1 min; however, this factor never exceededU= 1.0 ± 0.15 in control fish. The increase ofU usually exceeded considerably the value 1.15 when skin extract from conspecifics or 7-8 μg of hypoxanthine-3(N)-oxide were given. However, when hypoxanthine-l (N)-oxide was presented,U generally did not exceed 1.15. The difference between hypoxanthine-3(N)-oxide and hypoxanthine-l(N)-oxide was highly significant. This result is in accordance with the findings on fish schools ofDanio malabaricus, where hypoxanthine-3(N)-oxide elicited the fright reaction, but hypoxanthine-1(N)-oxide was ineffective. The results support the hypothesis that the alarm substance from the skin ofPhoxinus phoxinus is identical with hypoxanthine-3(N)-oxide. The results with alarm substance or hypoxanthine-3(N)-oxide did not show any adaptation. This was also true in fish that were stimulated repeatedly at intervals of a couple of minutes only. InGymnocorymbus, which has compensated for removal of the otolith of one utriculus, conspecific skin extract triggers the typical postoperative phenomenon, i.e., rotation around the fishes' long axis towards the operated side. Whereas such a decompensation could be elicited by hypoxanthine-3(N)-oxide as well, hypoxanthine-l(N)-oxide had no effect. This finding is interpreted as an effect of the alarm substance and of hypoxanthine-3(N)-oxide on the centers of equilibrium.

The effect of the alarm substance on the central nervous excitation of the black tetraGymnocorymbus ternetzi (Characidae, Ostariophysi, Pisces) indicated by dorsal light response

The effect of the alarm substance on the central nervous excitation was measured quantitatively in the black tetra (Gymnocorymbus ternetzi) using the dorsal light response. The tetra swam freely in a tiny cage, illuminated unilaterally; its inclination towards the light was registrated by means of a videorecorder (Fig. 1). Later its angle of inclination was measured on the monitor in steps of 0.2 s with an exactness of ±1°. Various substances—one group which had previously elicited the fright reaction in experiments with schools of fish, whereas the other had not—were presented to the fish, and their effects upon equilibrium position were recorded. An enhanced optical alertness shown by an increase in the fishes' inclination was generally produced with skin-extract from the European minnow (Phoxinus phoxinus) (Figs. 2, 3a–v), whereas skin-extract from red swordtail (Xiphophorus helleri) was ineffective (Figs. 2, 4r–t). Without any additional stimulation the factorU, representing quantitatively the degree of the change of central state varied slightly within the experimental period of 1 min; however, this factor never exceededU=1.0±0.15. The increase ofU was greater with minnow skin-extract, and smaller with swordtail extract. The difference was highly significant. The three individuals tested responded uniformly. Curves from various individuals did not differ more than curves from one fish registrated at different times (Fig. 3a–v). The increase ofU usually exceeded considerably the value of 1.15 when 7–8 μg of pure substances, which in the experiments with schools had been active, were given (Figs. 3 w, x; 4a–n). However, when substances were presented that had been inactive in the experiments with schools,U generally did not exceed 1.15 (Fig. 4u–z). The differences between the highly effective substances (i.e. isoxanthopterin, 6-acetonylisoxanthopterin, and isolated pure alarm substance) and the ineffective substances (i.e. xanthopterin, 7-acetonylxanthopterin, and hypoxanthine) were highly significant (Fig. 5). A positive correlation generally existed between size and duration of the change of central state (Fig. 6). The results did not indicate the existence of any adaptation. This was also true in fishes that were stimulated repeatedly with one effective substance at intervals of a couple of minutes only.