Sound production and reproductive behaviour of the armoured catfish Corydoras paleatus (Callichthyidae)

Sound production during reproductive behaviour, dyadic encounters and distress situations was investigated in the callichthyid catfish Corydoras paleatus. Sounds were broad-band, pulsed, acoustic signals produced during abduction of the pectoral spines. Only males emitted trains of sounds during courting and trains of sounds of shorter duration during dyadic encounters. Several males, which are usually smaller than females, courted one gravid female without obvious cooperation or competition between them. During mating, one previously vocalizing male clasped the female's barbels with one pectoral spine and inseminated the eggs. The number of successful spawnings, days until spawning, and number of eggs laid was not related to the number of males (one, two or three) combined with one female. Males did not behave aggressively towards each other during courting or in dyadic encounters. In distress situations, when fish were hand held, both sexes and juveniles produced single sounds. The dominant frequency was negatively correlated with body size and the sound duration was positively correlated with relative length of pectoral spines (standardized to body length). This acoustical behaviour in C. paleatus differs considerably from Hoplosternum thoracatum, a representative of the callichthyine subfamily, in which vocalization was observed during territorial behaviour in males and aggressive behaviour in both sexes. This is the first report of a major difference in vocalizing behaviour within one teleost family.     

Gill morphology and morphometry of the facultative air-breathing armoured catfish,Corydoras paleatus,in relation on aquatic respiration

The Neotropical armoured catfish Corydoras paleatus is a facultative air-breathing teleost commonly exported as ornamental fish. In this species, air breathing enables it to survive and inhabit freshwater environments with low oxygen levels. Therefore, it is important to analyse the gills from a morphological aspect and its dimensions in relation to body mass with reference to aquatic respiration. For that, the gills were analysed using a stereoscopic microscope for morphometric studies, and structural and ultrastructural studies were carried out to compare the four branchial arches. Furthermore, two immunohistochemical techniques were used to locate and identify the presence of a Na⁺/K⁺ pump. The characterization of the potential for cell proliferation of this organ was assessed using an anti-PCNA antibody. The results show that gills of C. paleatus present some characteristics related to its diet and lifestyle, such as the limited development of gill rakers and the abundance of taste buds. In addition, other special features associated with the environment and bimodal breathing were observed: scarce and absent mucous cells (MCs) in the gill filaments and branchial lamellae, respectively, and the localization of mitochondria-rich cells (MRCs) covering the basal third of the branchial lamellae, which reduces the gill respiratory area. A peculiar finding in the gill epithelium of this armoured catfish was the presence of mononuclear cells with sarcomeres similar to myoid cells, whose functional importance should be determined in future studies. Finally, in C. paleatus, the interlamellar space of gill filaments is an important site for cell turnover and ionoregulation; the latter function is also performed by the branchial lamellae.     

Modulation of antioxidant and detoxification responses mediated by lipoic acid in the fish Corydoras paleatus (Callychthyidae)

Lipoic acid (LA) has been reported as a potential therapeutic agent due its antioxidants proprieties. It was considered its effect in different organs (gills, brain, muscle and liver) of the fish Corydoras paleatus (Callychthyidae). LA (70 mg/kg of body mass) was added to a commercial fish diet, organisms being fed daily (1% body weight). Sixty animals (mean mass: 2.37+/-0.09 g) were placed randomly in aquariums and received (+LA) or not (-LA) lipoic acid enriched diet during four weeks. After, fish were killed and the brain, muscle, gills and liver were dissected. LA treatment reduced significantly (p<0.05) reactive oxygen species concentration in brain and increased (p<0.05) glutamate-cysteine ligase activity in brain and liver of the same experimental group. LA fed organisms showed higher (p<0.05) brain glutathione-S-transferase activity, indicating that LA improves the detoxification and antioxidant capacity face components that waste glutathione in phase II reactions. A conspicuous reduction of protein oxidation was observed in muscle and liver of +LA organisms, indicating that the treatment was also effective in reducing oxidative stress parameters.     

Postotic laterosensory canal and pterotic branch homology in catfishes

Morphology of the postotic laterosensory canal was surveyed across loricarioid and outgroup catfishes in order to resolve conflicting statements regarding homology and phylogenetic significance of intrinsic character variation. A pterotic branch is widespread among catfishes and has been identified as a synapomorphy for siluriforms, but its presence in loricarioid catfishes has been disputed. In contrast to previous statements that absence of a pterotic branch is synapomorphic for loricarioids, we confirm the presence of a pterotic branch in Nematogenys inermis and other trichomycterids, callichthyids, and loricariids. The pterotic branch is secondarily absent in scoloplacids and astroblepids. We present criteria for establishing homology of the pterotic branch and review character state optimization schemes on the currently accepted phylogeny. The postotic region of loricariids is further specialized in having an expanded swimbladder capsule that incorporates the trunk lateral line canal and has a lateral opening covered by a greatly expanded pterotic complex. The trunk lateral line enters the swimbladder capsule mesial to the pterotic lateral wall and passes anteromedially as a fleshy tube before forming the postotic canal in the pterotic, a morphology reported previously for a single loricariid representative. Variation in the relative extent and topographic position of postotic canal branches and other morphologies is diagnostic of certain loricariid taxa, suggesting a rich character complex of potential utility in phylogeny reconstruction.     

Trade-off between digestion and respiration in two airbreathingcallichthyid catfishes Holposternum littorale (Hancock) and Corydoras aeneus (Gill)

In callichthyid catfishes, the posterior intestine is modified to function as an air breathing organ by being air-filled, thin-walled and highly vascularized. These modifications make it unsuitable for digestive functions and digesta has to be transported quickly through this region to minimize disruption of vital respiratory functions. However, the weak muscles of the wall of the respiratory intestine make this problematic. It is hypothesized that the unidirectional ventilatory air current within the respiratory intestine is responsible for the quick transport of digesta through the respiratory intestine. To verify this, movement of digesta through the alimentary tract was examined in Hoplosternum littorale and Corydoras aeneus that were either allowed to breathe air or prevented from air breathing. When air breathing was prevented, digesta was not transported to the rectum in H. littorale and there was a 94% reduction in the amount of digesta in the rectum of C. aeneus. This study suggests that the anterior digestive intestine facilitates the passage of air although it is filled with digesta. The anterior digestive intestine packages digesta into a string of slightly compressed boluses, creating an air channel in the digestive intestine thus allowing air to pass unimpeded.     

On the ontogeny of alar cells in Drepanocladus aduncus,D. exannulatus and some other species

Abstract

The development of alar cells in Drepanocladus aduncus and D. exannulatus follows quite different paths. The type of development found in D. aduncus is also found in D. sendtneri, D. capillifolius and, in a somewhat modified form, in D. uncinatus, D. lycopodioides, D. brevifolius, Scorpidium turgescens and Calliergon trifarium. The Drepanocladus exannulatus type was found in the N. European Calliergon species (except C. trifarium), in Drepanocladus tundrae, D. fluitans (incl. D. h-schulzei), D. exannulatus var. procerus, D. trichophyllus and D. badius. Outside the Calliergon-Scorpidium-Drepanocladus-complex of species types of development like that in Drepanocladus aduncus seem to be the most frequent though other quite different kinds do occur.     

Extensive chromosomal rearrangements and nuclear DNA content changes in the evolution of the armoured catfishes genus Corydoras (Pisces, Siluriformes, Callichthyidae)

Karyotypes and nuclear DNA content were studied in 11 species of the genus Corydoras from rivers in South America: C . sp. from Caripi river 2 n =60, C . cf. simulatus 2 n =62, C . simulatus 2 n =62, C . reticulatus 2 n =74, C . sp. from Galheiro river 2 n =84, C . aff. punctatus from Negro river 2 n =102, C . flaveolus 2 n =58, C . arcuatus 2 n =46, C . trilineatus 2 n =46, C . schwartzi 2 n =46, and C . metae 2 n =92. Extensive chromosome diversity and differences in DNA content were detected among species. The high variability in chromosome counts was not exclusively related to chromosomal structural rearrangements, but also to large changes in DNA content. Species could be grouped using their shared cytogenetic characteristics, suggesting that within the genus Corydoras different groups of species followed distinct evolutionary trends. Chromosomal rearrangements in Corydoras are, apparently, more frequent that morphological modifications, so cytogenetic data may be very useful for species delimitation and for the understanding of interrelationships among species.     

Postembryonic ontogeny and functional anatomy of the ligamentum mandibulo-hyoideum and the ligamentum interoperculo-mandibulare,with notes on the opercular bones and some other cranial elements in Salmo gairdneri Richardson, 1836 (Teleostei: Salmonidae)

This study deals with the development of the opercular bones the ligamentum mandibulo-hyoideum, the ligamentum interoperculo-mandibulare and with some aspects of the development of the ceratohyale and the cartilago meckeli during postembryonic ontogeny of Salmo gairdneri (rainbow trout). It is stated that the ligamentum mandibulo-hyoideum is present from hatching onward, while the development of the ligamentum interoperculo-mandibulare appears during the period of active feeding. Some functional reasons are proposed to explain these facts. It is further suggested that the opercular bones develop under influence of the opercular muscles.     

串果藤属(Sinofranchetia)叶的个体发育研究

对串果藤属(Sinofranchetia)叶的个体发育过程进行了观察,结果表明,其叶原基在发生时为不分裂的,其后叶原基两侧产生两个突起,形成两个侧生小叶原基,而中央部分形成中央小叶的原基。同时对串果藤属植物叶原基发生的类型等问题进行了讨论。     

Haematological parameters in a neotropical fish, Corydoras paleatus (Jenyns, 1842) (Pisces, Callichthyidae), captured from pristine and polluted water

We report normal ranges of haematological indices in healthy Corydoras paleatus from an unpolluted area. Haematological parameters studied include: erythrocyte counts (Er), haematocrit (Ht), haemoglobin concentration (Hb), mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC). Normal red blood parameters did not change according to maturation stages, sex or seasons. Then, we compared them with those coming from fish captured in a site polluted by sewage. Fish exposed to pollution presented significantly higher values of Er, Ht, Hb, MCH and MCHC than those captured in an unpolluted area. Discriminant analysis showed that Hb is a key parameter to point out differences between populations exposed to different environmental conditions. We suggest that haematological values of C. paleatus, registered during this study, could be used as biomarkers in future works evaluating the incidence of environmental stress on fish as well as pointing out changes in the water quality.