South American Catfish Research Articles

Nests and Nest Habitats of the Invasive Catfish Hoplosternum littorale in Lake Tohopekaliga, Florida: A Novel Association with Non-native Hydrilla verticillata

Hoplosternum littorale is a South American catfish (Family Callichthyidae) first discovered in the United States in 1995 in Florida. The presence of H. littorale was documented from early 2002 to late 2003 in Lake Tohopekaliga (Kissimmee River Basin) in central Florida. In this paper, 22 H. littorale nests and nest sites are described. The characteristic bubble nests were present from late May to early September, with number of nests peaking in August when water stage and temperature were both high. Nest habitats (shallow, open marshes) and timing of nest construction (rainy season) were similar to what has been reported for H. littorale in its native range. Most nests (n = 14) were in areas dominated by Hydrilla verticillata and constructed largely from parts of this Asian aquatic plant, representing a unique association between two non-native species. Nevertheless, during August, as water levels increased, nesting shifted from H. verticillata-dominated communities to use of inshore grass zones dominated by Luziola fluitans. Knowledge of H. littorale nesting seasonality and habitat preferences may be useful for any efforts to control or manage this invasive fish.

Cestodes of cestodes of Peruvian freshwater stingrays.

Adult tetraphyllidean tapeworms (Platyhelminthes: Eucestoda) from the spiral intestines of 3 species of potamotrygonid stingrays (Paratrygon aiereba, Potamotrygon castexi, and Portamotrygon motoro) in the Madre de Dios river in Peru were found to host numerous cysts embedded in their parenchymal tissues. Histological sections of the cysts revealed the presence of a scolex bearing 4 suckers and an unarmed apical organ consistent with larval stages of both Cyclophyllidea and Proteocephalidea. To further elucidate their identities, partial 28S ribosomal DNA (rDNA) sequences were characterized from 3 cysts and 4 adult Rhinebothrium spp. 'host' worms and screened against all available cestode 28S rDNA data. Initial BLAST screening and subsequent alignment ruled out the possibility that the cysts were cyclophyllidean, and the cyst and adult sequences were thus aligned together with all available lecanicephalidean, litobothriidean, proteocephalidean, and tetraphyllidean sequences. Sequences from all 3 cysts were identical, and phylogenetic analysis clearly placed them among derived members of the Proteocephalidea, although no exact match was found. Sequences from the adult host worms formed 2 identical pairs and grouped together with other tetraphyllidean species from rays. These results are compared with records of hyperparasites of South American catfish cestodes. This is the first confirmed record of a proteocephalidean cestode parasitizing a tetraphyllidean cestode.

Effects of surgically implanted dummy transmitters on the South American catfish Jundiá (Rhamdia quelen)

High water temperatures and low water quality may negatively influence wound healing, growth and transmitter retention in radio-tagged fish of tropical and subtropical water bodies which in turn may hamper radio tracking studies. For a period of 90 days, we compared growth of an experimental group of ten Rhamdia quelen, which were submitted to intraperitoneal dummy transmitter implantation, with that of a control group. Additionally, wound healing and transmitter expulsion were observed in the experimental group. Water temperature varied between 24 degrees C and 30 degrees C during the study. Experimental group and control fish decreased in body weight during the investigation period, but the differences between the mean individual weight loss in both groups were not significant (Student t-test, p = 0.64). Wound healing in experiment group fish was advanced after 14 days, while after 70 days eight out of ten incision wounds were closed and cicatrized. One fish had its dummy transmitter expulsed through the ventral body wall. After 90 days two more fish had the dummies expulsed, one through the ventral body wall and the other through the antenna exit. One experimental group fish died with visible signs of infection. The results encourage the use of surgically implanted radio transmitters for long-term tagging studies at high water temperatures.

Farelo de soja na alimentação de alevinos de jundiá (Rhamdia quelen)

O trabalho foi conduzido com o objetivo de testar diferentes fontes protéicas em dietas práticas para alevinos de jundiá (Rhamdia quelen). Foram realizados dois experimentos com duração individual de 42 dias utilizando-se 320 animais com peso médio inicial de 1,18 <FONT FACE=Symbol>±</font> 0,28 gramas e 4,00 ± 0,18 gramas, respectivamente, distribuídos em 16 unidades experimentais de um sistema com recirculação de água, testando-se quatro dietas com quatro repetições em cada experimento. No primeiro experimento, testaram-se quatro dietas isoprotéicas (34% proteína bruta) e isocalóricas (3.500 Kca<img src="http:/img/fbpe/cr/v32n3/a21img01.gif" align="absmiddle"> /kg de energia digestível) sendo que a dieta A1 continha levedura de cana, farelo de soja e farinha de carne e ossos, e nas demais (A2, A3 e A4) suprimiu-se uma das fontes. Alevinos alimentados com a dieta A2 (levedura de cana e farelo de soja) mostraram desempenho superior (P<0,01). No segundo experimento, utilizaram-se as fontes proteicas da dieta que proporcionou o melhor desempenho no experimento I (A2), e avaliou-se o efeito da substituição da levedura de cana pelo farelo de soja em níveis crescentes (75%, 87,5% e 100%) a partir de uma dieta (B1) contendo os mesmos níveis de inclusão (36,4%) das duas fontes. A dieta B1 proporcionou um melhor crescimento e ganho de peso dos alevinos de jundiá (P<0,01).

Sperm and Spermatozeugma Ultrastructure in the Inseminating Catfish, Trachelyopterus lucenai (Ostariophysi: Siluriformes: Auchenipteridae)

This study presents details of the ultrastructure of the spermatozeugmata and spermatozoa of the South American catfish, Trachelyopterus lucenai, an inseminating species. Spermatozoa are tightly packaged into unencapsulated bundles, spermatozeugmata, with as many as 130 cells comprising a single packet. Within an individual spermatozeugma, cells are aligned side by side such that the anterior region of the bundle is comprised of nuclei, the middle region midpieces, and the posterior region flagella. Integrity of the packet appears to be maintained by specialized junctions between adjacent cells along their entire lengths. Each spermatozoon is characterized by an elongate nucleus containing condensed chromatin and a fossa at the posterior end. The elongate midpiece contains multiple mitochondria, abundant glycogen deposits, and accessory microtubules that run along the length of the midpiece. The ultrastructural modifications of the spermatozoa are discussed as possible adaptations associated with the reproductive mode of insemination.

Substituição parcial ou total de óleo de canola por lecitina de soja em rações para larvas de jundiá (Rhamdia quelen), pisces, Pimelodidae

O trabalho foi realizado no Setor de Piscicultura do Departamento de Zootecnia da Universidade Federal de Santa Maria, em um sistema para criação de larvas com recirculação de água termoregulada. O objetivo foi avaliar a substituição de óleo de canola por lecitina de soja na alimentação de larvas de jundiá durante os primeiros 21 dias de vida. No experimento, testaram-se sete tratamentos com três repetições, usando-se diferentes proporções de óleo de canola (0 a 5%) e lecitina de soja (0 a 4%), incorporadas em uma ração preparada com fígado bovino e levedura de cana. Os melhores resultados foram obtidos no tratamento com 2% de lecitina de soja. Com ele, as larvas de jundiá apresentaram 80,25% de sobrevivência, peso médio individual de 184,89mg e 28,03mm de comprimento total, diferindo significativamente dos demais tratamentos. De acordo com os resultados obtidos no experimento, conclui-se que a lecitina de soja em nível de 2% é mais eficiente que a lecitina usada em combinação com óleo de canola na nutrição de larvas de jundiá.

The evolution of electroreception and bioelectrogenesis in teleost fish: a phylogenetic perspective

According to current phylogenetic theory, both electroreceptors and electric organs evolved multiple times throughout the evolution of teleosts. Two basic types of electroreceptors have been described: ampullary and tuberous electroreceptors. Ampullary‐type electroreceptors appeared once in the common ancestor of the Siluriformes+Gymnotiformes (within the superorder Ostariophysi), and on two other occasions within the superorder Osteoglossomorpha: in the African Mormyriformes and in the African Notopteriformes. Tuberous receptors are assumed to have evolved three times; all within groups that already possessed ampullary receptors. With the exception of a single catfish species, for which studies are still lacking, all fish with tuberous electroreceptors also have an electric organ. Tuberous electroreceptors are found in the two unrelated electrogenic teleost lineages (orders Gymnotiformes and Mormyriformes) and in one non‐electrogenic South American catfish species (order Siluriformes). Electric organs evolved eight times independently among teleosts: five of them among the ostariophysans (once in the gymnotiform ancestor and in four siluriform lineages), once in the common ancestor of Mormyriformes, and in two uranoscopids. With the exception of two uranoscopid genera, for which no electroreceptive capabilities have been discovered so far, all electric organs evolved as an extension of a pre‐existing electroreceptive (ampullary) condition. It is suggested that plesiomorphic electric organ discharges (EODs) possessed a frequency spectrum that fully transgressed the tuning curve of ampullary receptors, i.e. a signal such as a long lasting monophasic pulse. Complex EOD waveforms appeared as a derived condition among electric fish. EODs are under constant evolutionary pressure to develop an ideal compromise between a function that enhances electrolocation and electrocommunication capabilities, and thereby ensures species identity through sexual and behavioural segregation, and minimizes the risk of predation.

Plasma levels of cortisol and glucose in response to capture and tank transference in Rhamdia quelen (Quoy & Gaimard), a South American catfish

Males and females of Rhamdia quelen (Quoy & Gaimard) were subjected to capture and tank transference in order to evaluate the stress response. This process provoked a characteristic stress response in both sexes, with cortisol values reaching a peak in one hour after stress. High levels of cortisol found in females were explained by the increase of energy demand and the mobilization in the vitellogenic phase. Several previous studies have shown that cortisol is strongly correlated to these periods in another catfish.

Ação do tempo e da forma de suplementação alimentar com Artemia franciscana sobre a sobrevivência e o crescimento de larvas de jundiá

O presente trabalho foi realizado com o objetivo de verificar o efeito da suplementação alimentar com Artemia franciscana no desempenho de larvas de jundiá (Rhamdia quelen). Os tratamentos foram: T1 - Suplementação com náuplios de Artemia durante 7 dias; T2 - Suplementação com cistos de Artemia durante 7 dias; T3 - Suplementação com náuplios de Artemia durante 3 dias; T4 - Suplementação com cistos de Artemia durante 3 dias; T5 - Sem suplementação. Cada tratamento possuía 4 repetições. O experimento, realizado em sistema com recirculação de água, teve duração de 20 dias. Em todos os tratamentos, as larvas receberam ração ad libitum com 41% de PB e 4293Kcal EB/kg. Os resultados demonstraram que o fornecimento de náuplios proporcionou melhor crescimento que o de cistos ou somente ração. Com relação ao peso e produto peso x sobrevivência, constataram-se diferenças significativas dos tratamentos 1 e 3 (náuplios) para os tratamentos 2 e 4 (cistos). A baixa sobrevivência do T5 foi responsável pelo pior resultado deste tratamento com relação ao produto peso x sobrevivência, porém sem diferenças de peso em relação ao T2 e T4. Não se constataram diferenças significativas com relação à sobrevivência entre os tratamentos que receberam cistos e náuplios de Artemia. Somente o T5 apresentou menores taxas de sobrevivência que os demais. As melhores taxas de crescimento específico (TCE) foram de 25,6 e 25,4%/dia, respectivamente para o T1 e T3 durante os 20 dias de experimento.

Comparative morphology of cotylephores in Platystacus and Solenostomus: modifications of the integument for egg attachment in skin-brooding fishes

External skin brooding evolved independently in several groups of fishes. Cotylephores, sites for the attachment of developing embryos, occur within the fused pelvic fins of the ghost pipefishes, Solenostomus, on the ventral surface of the South American catfish, Platystacus, and on other aspredinid cattfishes of the tribe Aspredini. Cotylephores are transient outgrowths of tissue that occur only on brooding fish. They consist of a pedicle that extends from the abdomen or fin and terminates in an apical calyx. The calyx supports and adheres to the egg envelope that encloses the developing embryo. The pedicle of the catfish cotylephore is a single, large structure (1615 ± 23.25 µm), while those of ghost pipefishes are small and branched (687 ± 3.89 µm; number of branches: 26 ± 0.63). In both instances, a simple cuboidal epithelium, whose cells bear microplicae, encloses an extensive connective tissue core that contains large blood vessels that ramify into a capillary plexus in the calyx. Cotylephores of Platystacus are more heavily vascularized than those of Solenostomus and contain 34.77% more blood vessel surface area at the calyx, to which the egg envelope adheres. In addition to their role in attachment, cotylephores may function in embryonic maintenance through the exchange of gas across the egg envelope, mediated by female circulatory vessels within the cotylephore calyx. Comparisons of morphology and development suggest that cotylephores are the result of convergent evolution of a reproductive adaptation.

Adaptations for reproduction and development in the skin-brooding ghost pipefishes,Solenostomus

Ghost pipefishes comprise a small family (Solenostomidae) of skin-brooding fishes related to true pipefishes and seahorses (Syngnathidae).Solenostomus embryos develop within the fused pelvic fins of the female, unlike syngnathids in which males brood the eggs. Embryos, enclosed in egg envelopes, are attached to epidermal stalks, termed cotylephores, that occur only in brooding females. Cotylephores are cellular outgrowths of the epithelium on the inside surface of the pelvic fins. They attain a mean length of 687 ± 3.89 μm and diameter of 105 ± 3.38 μm. Cotylephores originate on the epithelial surface that lies over the lepidotrichia and they develop into multi-headed cylindrical branches approximately 125 ± 3.65 μm in length and 78 ± 2.19 μm in diameter. A mean of 26 ± 0.63 lateral branches are found on fully developed cotylephores. Each branch terminates in a wide apical calyx, approximately 112 ± 4.16 μm in diameter, to which the egg envelope adheres. Adjacent calyces of the same cotylephore establish attachments with the envelope of a single egg. Cotylephores are composed of a surface epithelium that is continuous with the skin and a fibrous connective tissue core that contains blood vessels that ramify into an apical capillary plexus. The plexus may function in maternal-embryonic metabolic exchange. The cotylephores ofSolenostomus closely resemble the epidermal stalks (cotylephores) that are the sites of egg attachment in the skin-brooding South American catfish,Platystacus cotylephorus. Based on similarity in structure and probable function, cotylephores in the two groups of fishes are an example of evolutionary convergence.

B-chromosome polymorphism in the South American catfish, Rhamdia sapo

The karyological characteristics of a South American catfish ( Rhamdia sapo) were examined. Twelve specimens were collected from three lakes in the province of Buenos Aires (Argentina). Three different karyotypes are presented with two chromosome numbers, 2n=58 (44 metacentric-submetracentric and 14 subtelocentric-acrocentric chromosomes, with an FN=102) and 2n=59. The latter exhibited two different kinds of supernumeraries or B-chromosomes. One of them was acrocentric and smaller than the other, stained deeper, and showed positive heteropycnosis. The other was metacentric and also showed positive heteropycnosis. Heteromorphic sex chromosomes were not observed.

Comparative study of the male reproductive tract in seven families of South-American catfishes

Specimens belonging to 20 species (7 families) of catfishes have been collected in French Guyana. The anatomy and histology of the male reproductive tracts have been studied. In the most primitive species (Helogeneidae, Ariidae) no seminal vesicle is present in the males. In the Pimelodidae, Loricariidae and Callichthyidae (and also in an african Bagridae), there is a progressive transition, going from anterior to posterior in the male tract, from testicular tissue towards round germ cell-free tubules and finally to seminal vesicular tissue. All these families produce round-headed spermatozoa and have external fertilization. The Auchenipteridae and Ageneiosidae are characterized by elongated sperm nuclei, internal fertilization with the aid of a gonopodium and sperm storage in the ovaries. In the Auchenipteridae there is a clear-cut distinction between testes and seminal vesicles. In the Ageneiosidae there is no seminal vesicle, but the dilated deferent duct displays a high secretory activity. Depending on the family and species, the seminal vesicles may carry out either one or both of the two main functions: secretion and sperm storage. In addition, in some species, sperm is also stored in one or two accessory pouches until fertilization. The trends that we have observed in the changes in the organization of the reproductive tracts are in agreement with the hypotheses proposed for catfish evolution from comparative anatomical data.

Rearing fry of South American catfish ( Rhamdia sapo) on natural zooplankton populations

Two experiments were performed on rearing South American catfish ( Rhamdia sapo) fry in 8-m 2 concrete tanks. Live zooplankton was found to be an adequate food for Rhamdia fry. However, fry showed a natural preference for benthic organisms when they were available. No differences in selectivity due to fry age were observed. Differences in selectivity between small and large fry were only detected for Daphnia parvula, the largest zooplanktonic item. This suggested that food partitioning may occur only when large prey items are available.

Evolutionary Allometry and Variation in Body Form in the South American Catfish Genus Corydoras (Callichthyidae)

The systematic relationships within the speciose genus Corydoras have been very difficult to elucidate due to similar body forms among species, lack of discrete morphological features, and uncertain homologies of pigmentation patterns. Most taxa have been described on the basis of pigmentation and of proportional differences in body measurements, which often are variable within and among conspecific populations. Multivariate comparisons of body form among species indicate that both meristic and mensural attributes are highly correlated with body size, thus displaying strong evolutionary allometry. Most ratios of measurements, including those often considered diagnostic among taxa, are as strongly dependent on body size as are untransformed measurements; however, some bivariate ratios reflect multivariate patterns of shape variation and, thus, may be useful in descriptive taxonomic studies. Size-independent variation in form seems to be continuous among species, with no apparent morphological gaps with which to distinguish “natural” species groups. Thus, changes in morphology in these fishes are highly conservative and result from subtle, perhaps heterochronic changes in relative growth rates among body structures.

Evolutionary Allometry and Variation in Body form in the South American Catfish Genus Corydoras (Callichthyidae)

Evolutionary Allometry and Variation in Body form in the South American Catfish Genus Corydoras (Callichthyidae)

Pond Culture Experiments of South American Catfish, Rhamdia sapo, Fingerlings

Pond Culture Experiments of South American Catfish, Rhamdia sapo, Fingerlings

Preliminary dataon larval survival of South American catfish, Rhamdia sapo

Larvae of Rhamdia sapo were fed four test diets of Artemia nauplii; a balanced diet formula; boiled egg yolk, coagulated blood and liver homogenate; and live zooplankton. The homogenized mixture was the most effective for growth. Highest survival was recorded with the Artemia diet. Larger trials performed in indoor raceways, using the homogenate diet for 10 days followed by a balanced ration, were successful before transfer to grow-out ponds.

Induced breeding of the South American catfish, Rhamdia sapo (C. & V.)

Pituitary suspensions from the characin, Prochilodus platensis, were injected intraperitoneally into male and female Rhamdia sapo at doses between 0.37 and 6 mg dry weight per kg of body weight. Doses from 0.75 to 6.0 mg/kg effectively induced ovulation. The latent period between injection and ovulation for females held at different temperatures (17 to 27°C) decreased with increasing temperature. Stripping of gametes from both sexes, and dry method fertilization were successful and produced viable eggs. The period between ovulation and stripping for the highest hatching rates decreased from about 9 h at 20°C, to 5 h at 24°C. No viable eggs remained in samples obtained after 15 h at 20°C, or 8 h at 24°C. Hatching percentage and the fraction of deformed fry were negatively correlated ( r = −0.75; P < 0.001).

The caudal skeleton of ostariophysan fishes (Teleostei): Intraspecific variation in trichomycteridae (Siluriformes).

The different elements of the caudal skeleton of the South American catfish genera Nematogenys (Nematogenyinae) and Trichomycterus, Hatcheria, and Bullockia (Pygidiinae) (Siluriformes, Trichomycteridae) show Ontogenetic transformation of the second ural centrum in Trichomycteridae separates the subfamilies Nematogenyinae and Pygidiinae. In the former, the second ural centrum is aligned with the first ural centrum in early stages of ontogeny; it is not fused with the bases of hypurals 3 and 4 in any stage of development. In the Pygidiinae, in contrast, the second ural centrum is connected with the base of hypural 3 from an early stage of development on. One of the most noteworthy features of the Pygidiinae is the epural, a polymorphic element with three or four morphotypes that are species specific. The primitive catfish Nematogenys shows intraspecific variation in the ural centra, segmentation of procurrent caudal rays, and principal caudal ray formulae. Species of Trichomycterus, Hatcheria, and Bullockia are characterized by great intraspecific variability that involves ural centra, the epural, hypurapophyses, and the neural arches of the compound centrum. There is intraspecific variation in the fusion of the hypurals in some species of Trichomycterus. Intraspecific variation of the caudal skeleton of fishes of the family Trichomycteridae involves the presence and frequency of different morphotypes of the epural, neural arch of the compound centrum, fusion of hypurals, and principal caudal ray formulae. Ontogenetic changes of the first and second ural centra, hypurapophyses (with the exception of Nematogenys), and segmentation of procurrent caudal rays (in Nematogenys) are involved also.