Corydoras Aeneus Research Articles

Developmental Social Experience Changes Behavior in a Threatening Environment in Corydoras Catfish

ABSTRACTCoordinated responses to threats are important for predator evasion in many species. This study examines the effect of developmental social experience on antipredator behavior and group cohesion in a highly gregarious catfish that communicates via tactile interaction, Corydoras aeneus. We reared fish either in a mixed‐age group of age‐matched peers and adult C. aeneus (mixed‐age condition, or MAC), or with age‐matched peers only (same‐age condition, or SAC). A startle test was conducted with small groups of subadults from either social rearing condition. Prior to any startle events, SAC subadults had increased tactile communication compared to MAC subadults, but SAC individuals were overall less active. SAC fish exhibited a stronger antipredator response to startles, and were more likely to freeze or take refuge in cover in response to a startle than MAC fish. MAC fish tended to respond to startle events by maintaining or decreasing their cohesion, whereas SAC fish tended to maintain or increase their cohesion. These behavioral differences are attributed to MAC fish developing with group protection as a result of shoaling with adults, resulting in reduced antipredator responses when reared with adults. This study underscores how social context during development can be critical in shaping how individuals perceive and respond to potential threats in their environment.

Kinematic analysis of swimming ontogeny in seabass (Dicentrarchus labrax)

Swimming has been investigated in multiple species, but few studies consider the establishment of swimming through ontogeny. This study describes the establishment of cyclical swimming in Dicentrachus labrax, a marine fish from cold, temperate waters. The data were compared with results from previous studies on two subtropical freshwater catfish species (Clarias gariepinus and Corydoras aeneus). The three species have different modes of locomotion each during their adult stage (anguilliform, subacarangiform and carangiform). The swimming of Dicentrarchus labrax was recorded with a high-speed video camera (500 fps) from 0 to 288 hours and from 960 to 2496 hours post-hatching. Three indices, i.e. coefficient of determination (r²), coefficient of variation (CV), and Strouhal number (St), were used to investigate the establishment and efficiency of swimming. Important differences in the timing of swimming establishment were observed between the seabass and the two catfish species. The two catfish species display a sine-shaped swimming mode immediately or soon after hatching, and the efficiency of movement substantially improves during the first days of life. For seabass, however, establishment of swimming is slower during the same developmental period. These differences may be related to a faster developmental rate in the catfishes that allows them to swim rapidly in an intermediate regime flow and to develop the required morphology to establish efficient movements earlier.

Pigment matters: Behavior and lateralization of albino and pigmented fish (Bronze Corydoras) in aquaculture

Animal welfare science recognizes fish as sentient beings capable of experiencing pain, stress, and various emotions. As social interactions and mutual relationships are essential for fish welfare, the social environment in aquacultures is important for fish welfare. Pigmentation influences fish social behavior, e.g., communication and/or shoaling behavior. We investigated how pigmentation and shoal phenotypic composition affect locomotor activity in relation to feeding, exploratory behavior, sheltering and lateralization in holding tanks and Y-mazes in pigmented and albino Bronze Corydoras (Corydoras aeneus). The fish were divided into three treatment groups: pigm only, alb only, and mix groups. Each group comprised 12 shoals, with a total of 288 fish distributed across 36 shoals, each containing eight individuals. The study revealed behavioral differences between fish with pigmented and albino phenotypes, both within and among shoals. For both phenotypes, an increase in locomotor activity before feeding was followed by a decrease in activity after food consumption, indicating an anticipatory response and a shift from foraging to postfeeding behavior. In the mixed shoals, pigmented fish exhibited greater activity and sheltering behavior than albino fish. Both albino and pigmented fish showed lateralization toward the right arm of the Y-maze; however, in the mixed shoals, the preference for the right arm was not significant. Albino fish reached the shelter at the end of the Y-maze more often; however, in the mixed shoals, albino fish maintained their success rate in exploring the maze, while pigmented fish showed an increased success rate. We emphasize the significance of considering phenotypic variation and shoal composition when evaluating fish behavior and welfare. Such insights can inform the management of practices in aquaculture and ornamental breeding to ensure optimal fish welfare and enhance their overall quality of life.

The armored catfish Corydoras aeneus shapes the meiofaunal community due to predation and disturbance-induced water column dispersal

Bottom-feeding fish can exert strong top-down pressure on benthic invertebrates while also causing mechanical disturbance of the sediment. In our laboratory study, we investigated the influence of predation and disturbance-induced water column emigration on meiofauna, triggered by the armored catfish Corydoras aeneus. We hypothesized that both factors would significantly reduce the abundance of meiofauna, depending on their body size. Accordingly, we also expected a change in the nematode community structure. After 24 h, the abundances of nematodes, tardigrades, hydracarina, copepods and oligochaetes were significantly lower than in control aquariums without fish, in the latter two groups primarily due to predation. All other taxa were equally affected by predation and emigration. Within the nematodes, mainly large individuals (≥ 1 mm) were consumed, while smaller worms (< 1 mm) were increasingly dispersed. This, though it did not reduce species numbers, resulted in altered size and species composition. Our results show that the real top-down effects can quickly be overestimated as emigration of prey is overlooked and, on the other hand, that fish may also influence adjacent, undisturbed areas due to subsequent immigration of meiofauna.

Ichthyofauna of the Água das Araras stream, Paranapanema River basin, upper Paraná River system, Southern Brazil

ABSTRACT This study comprises the first fish inventory of the Água das Araras stream, a small tributary of the Laranjinha River, in the upper Paraná River basin. Four samplings were carried out seasonally between June 2010 and July 2011, in 12 collecting sites distributed from the headwater to the mouth of Água das Araras stream and its tributaries, using seines and gill nets to capture specimens. A total of 5,328 specimens were collected, distributed in six orders, 15 families, 33 genera, and 41 species. The most representative orders, in terms of species richness, were Siluriformes and Characiformes. Among the families, Characidae (eight species) and Loricariidae (seven species) presented higher richness contributing together with approximately 36.6% of all collected species. The most frequent species captured in ≥75% of the sampled sites were Astyanax lacustris, Characidium aff. zebra, Corydoras aeneus, and Imparfinis schubarti. The classification of species with the Kendeigh Index highlighted the following ranking of the more abundant species: Phalloceros harpagos, C. aeneus, A. lacustris, and I. schubarti. Finally, our results emphasize the importance of sampling small aquatic bodies, revealing their potential for maintaining a significant portion of fish diversity in Neotropical freshwater environments.

Preliminary Investigations into Use of Metomidate for Euthanasia of Ornamental Fishes

The goals of this study were to investigate the potential use of metomidate for one-step euthanasia of ornamental fish species representing commonly sold families in the ornamental fish trade and to determine a baseline euthanasia dose for most species tested. Metomidate hydrochloride, a rapid-acting, water-soluble, nonbarbiturate hypnotic related to etomidate, was tested at various concentrations and durations for euthanasia of species representing the following freshwater and marine aquarium fish families: Apogonidae, Ariidae, Blenniidae, Callichthyidae, Characidae, Cichlidae, Cyprinidae, Gobiidae, Gyrinocheilidae, Loricariidae, Melanotaeniidae, Osphronemidae, Pimelodidae, Poeciliidae, Pomacentridae, and Pseudochromidae. Fish in each trial were euthanized as a group (n=1). Most groups contained 10-12 fish. Some higher doses required buffering. Euthanasia was considered successful if all fish in each group did not recover after 6h in unmedicated water. All species immediately lost buoyancy and equilibrium, dropping to the tank bottom within 1min and ceasing ventilation typically within minutes. However, reactivity to vibration, sound, or touch was noticeable for varying time periods afterward (8-66min), so an additional 30min of exposure after cessation of reactivity was included as part of the protocol. Although some species (Neon Tetras Paracheirodon innesi and Australian Rainbowfish Melanotaenia australis) were euthanized at a concentration of 40mg/L metomidate for a total exposure time of 38min, most species tested were successfully euthanized with metomidate at a concentration of 100mg/L, with total exposure times ranging from 35-96min. A few catfish species (Otocinclus sp. and Bronze Corydoras Corydoras aeneus) were refractory and recovered after 100mg/L. However, Otocinclus sp. were successfully euthanized at 250mg/L, and Bronze Corydoras were euthanized at 1,000mg/L. Further studies are needed to provide additional data for these and other species and families, for different water chemistry conditions, and for various biological factors to fine-tune dosing regimens.

The Life Cycle of Heterophyes yacyretana n. sp. (Digenea, Heterophyidae), Parasitic in the Endemic Snail Aylacostoma chloroticum (Caenogastropoda, Thiaridae) in Argentina.

Here we describe a new heterophyid species, Heterophyes yacyretana n. sp., and resolve its life cycle experimentally. We found the prosobranch snail Aylacostoma chloroticum in Candelaria, Province of Misiones, Argentina (a sector of the High Paraná River affected by the Yacyretá Dam), naturally infected with opisthorchioid cercariae. These cercariae lacked pigmented eyespots as well as body pigment and possessed 7 pairs of penetration glands arranged in 2 lateral bands, together with 18 pairs of flame cells and a V-shaped excretory vesicle. We exposed specimens of 21 fish species to emerging cercariae and obtained metacercariae from the muscles of the caudal peduncle of 3 species of siluriform fish, and adults from chicks infected with experimentally obtained metacercariae from the albino variety of the bronce corydoras, Corydoras aeneus. The new species differs from other species in the genus by the number of sclerites on the genital sac, the distribution of the vitelline follicles, and the combination of the size relationship of the suckers and the genital sac with respect to the posterior extent of intestinal ceca. Heterophyes yacyretana is the first species of the genus reported from the Americas.

The development of tactile social interactions in Corydoras aeneus larvae

Abstract Many social animals acquire social behaviours during development, and social experience during development can be vital for acquiring necessary social behaviours in adulthood. We investigated the development of a distinctive tactile interaction behaviour in Bronze Cory catfish, in which adults interact with one another tactilely during foraging and during group responses to threats. We found that larvae respond to applied tactile stimulation with a flight response significantly less often as larvae matured. This habituation to tactile stimulation is consistent with developing appropriate adult social behaviour. We also found that social exposure affects the larval response to tactile interactions with conspecifics, and that isolation in early life leads to a greater likelihood of responding to tactile interactions with conspecifics with a flight response. This suggests that social exposure is important for developing social tactile interaction behaviour and underscores the particular importance of early experience in social development.

Larval growth, survival, and partial budget analysis related to replacing Artemia in larval culture of six freshwater ornamental fishes

AbstractCultured freshwater ornamental fish are primarily fed Artemia at early life stages. Development of alternative feeding strategies could decrease the Artemia reliance of ornamental producers, reduce labor costs, and improve industry resilience by diversifying larval feeding options. In this study, Corydoras aeneus, Synodontis eupterus, Synodontis nigriventris, Epalzeorhynchos bicolor, Pterophyllum scalare, and Trichogaster lalius larvae were offered one of four diets at first feeding: newly hatched Artemia or one of three microparticulate diets (MDs). After 14 days of feeding, survival and standard length (SL) were evaluated, and partial budget analyses (PBA) were conducted to evaluate the economic feasibility of replacing Artemia with MDs. For all species except E. bicolor, at least one MD performed as well as or better than Artemia with regard to the parameters in question. E. bicolor exhibited reduced survival when fed MDs compared to Artemia, although SL did not vary significantly among treatments. PBAs indicated that replacing Artemia with MDs at first feeding resulted in an average net benefit of $0.043 ± 0.004 for all species except E. bicolor, which resulted in a net cost of $0.048. These results indicate that MDs represent a physiologically and economically feasible alternative to Artemia for larval culture of many freshwater ornamental fishes.

Social dynamics obscure the effect of temperature on air breathing in Corydoras catfish.

ABSTRACTIn some fishes, the ability to breathe air has evolved to overcome constraints in hypoxic environments but comes at a cost of increased predation. To reduce this risk, some species perform group air breathing. Temperature may also affect the frequency of air breathing in fishes, but this topic has received relatively little research attention. This study examined how acclimation temperature and acute exposure to hypoxia affected the air-breathing behaviour of a social catfish, the bronze corydoras Corydoras aeneus, and aimed to determine whether individual oxygen demand influenced the behaviour of entire groups. Groups of seven fish were observed in an arena to measure air-breathing frequency of individuals and consequent group air-breathing behaviour, under three oxygen concentrations (100%, 60% and 20% air saturation) and two acclimation temperatures (25 and 30°C). Intermittent flow respirometry was used to estimate oxygen demand of individuals. Increasingly severe hypoxia increased air breathing at the individual and group levels. Although there were minimal differences in air-breathing frequency among individuals in response to an increase in temperature, the effect of temperature that did exist manifested as an increase in group air-breathing frequency at 30°C. Groups that were more socially cohesive during routine activity took more breaths but, in most cases, air breathing among individuals was not temporally clustered. There was no association between an individual's oxygen demand and its air-breathing frequency in a group. For C. aeneus, although air-breathing frequency is influenced by hypoxia, behavioural variation among groups could explain the small overall effect of temperature on group air-breathing frequency.

Coping with strangers: how familiarity and active interactions shape group coordination in Corydoras aeneus.

Social groups composed of familiar individuals exhibit better coordination than unfamiliar groups; however, the ways familiarity contributes to coordination are poorly understood. Prior social experience probably allows individuals to learn the tendencies of familiar group-mates and respond accordingly. Without prior experience, individuals would benefit from strategies for enhancing coordination with unfamiliar others. We used a social catfish, Corydoras aeneus, that uses discrete, observable tactile interactions to assess whether active interactions could facilitate coordination, and how their role might be mediated by familiarity. We describe this previously understudied physical interaction, ‘nudges’, and show it to be associated with group coordination and cohesion. Furthermore, we investigated nudging and coordination in familiar/unfamiliar pairs. In all pairs, we found that nudging rates were higher during coordinated movements than when fish were together but not coordinating. We observed no familiarity-based difference in coordination or cohesion. Instead, unfamiliar pairs exhibited significantly higher nudging rates, suggesting that unfamiliar pairs may be able to compensate for unfamiliarity through increased nudging. By contrast, familiar individuals coordinated with comparatively little nudging. Second, we analysed nudging and cohesion within triplets of two familiar and one unfamiliar individual (where familiar individuals had a choice of partner). Although all individuals nudged at similar rates, the unfamiliar group-mate was less cohesive than its familiar group-mates and spent more time alone. Unfamiliar individuals that nudged their group-mates more frequently exhibited higher cohesion, indicating that nudging may facilitate cohesion for the unfamiliar group-mate. Overall, our results suggest that nudges can mitigate unfamiliarity, but that their usage is reduced in the case of familiar individuals, implying a cost is associated with the behaviour.

The role of tactile interactions in flight responses in the Bronze Cory catfish (Corydoras aeneus)

AbstractOne of the primary functions of animal aggregations is defence against predators. Many social animals enjoy reduced predation risk as a result of grouping, and individuals within groups can benefit from information transferred by their group‐mates about a potential predator. We present evidence that a tactile interaction behaviour we term “nudging” substantially modified group responses to a potential threat in a highly social catfish, Corydoras aeneus. These catfish deployed nudges during flight responses, and these nudges were associated with a greater likelihood of group cohesion following a threat event. Increased nudging behaviour also resulted in longer flight responses, a potentially costly outcome in natural contexts. In addition, individuals that perceived the threat first were more likely to initiate nudges, implying that nudges could be used to alert group‐mates to the presence of a threat. Taken together, our results suggest that tactile communication plays an important role in mediating anti‐predator benefits from sociality in these fish.

Biofloc technology on the intensive aquaculture of bronze corydoras ornamental fish Corydoras aeneus with different stocking densities

ABSTRACT Ornamental fish is non consumption fish which is an important source of Indonesian foreign exchange. The objective of this study is to analyze the productivity of bronze corydoras Corydoras aeneus ornamental fish through increased stocking density with biofloc technology. The average weight of the experimental corydoras was 0.61 ‒0.72 g with 2.32‒2.40 cm standard length. This study used a randomized design method with biofloc technology treatment in 3000, 4500, and 6000 fish/m2 stocking densities. The results showed that the daily length and weight-growth rate among treatments were not significantly different (P&gt;0.05), while survival rate and the number of fish production on all treatments were significantly different (P&lt;0.05). The water quality during the rearing period, such as temperature, pH, alkalinity, ammonia, nitrite, and nitrate, were in a tolerable range for corydoras culture. The total suspended solids tended to be higher due to higher stocking density. The best productivity using biofloc technology obtained from 6000 fish/m2 stocking density. Keywords: Biofloc technology, Corydoras aeneus, growth rate, stocking density, survival rate. ABSTRAK Ikan hias merupakan produk perikanan non konsumsi yang menjadi sumber devisa Indonesia yang cukup penting. Penelitian ini bertujuan untuk menganalisis produktivitas ikan hias koridoras melalui peningkatan padat tebar dengan teknologi bioflok. Ikan yang digunakan adalah ikan hias koridoras (Corydoras aeneus) berbobot 0,61‒0,72 g dan panjang baku 2,32‒2,40 cm. Penelitian ini menggunakan rancangan acak lengkap dengan perlakuan teknologi bioflok pada padat tebar 3000, 4500, dan 6000 ekor/m2. Hasil penelitian menunjukkan bahwa laju pertumbuhan harian panjang dan bobot antar perlakuan tidak berbeda nyata (P&gt;0,05), sedangkan kelangsungan hidup dan jumlah produksi ikan pada semua perlakuan berbeda nyata (P&lt;0,05). Nilai kualitas air selama pemeliharaan yakni suhu, pH, alkalinitas, amonia, nitrit, dan nitrat yang berada pada kisaran yang cukup baik untuk budidaya ikan. Total padatan tersuspensi cenderung tinggi akibat dari semakin tinggi padat tebar. Produktivitas terbaik pada budidaya ikan koridoras dengan teknologi bioflok adalah pada padat tebar 6000 ekor/m2. Kata kunci: Corydoras aeneus, kelangsungan hidup, padat tebar, pertumbuhan, teknologi bioflok

Adipose fin development and its relation to the evolutionary origins of median fins

The dorsal, anal and caudal fins of vertebrates are proposed to have originated by the partitioning and transformation of the continuous median fin fold that is plesiomorphic to chordates. Evaluating this hypothesis has been challenging, because it is unclear how the median fin fold relates to the adult median fins of vertebrates. To understand how new median fins originate, here we study the development and diversity of adipose fins. Phylogenetic mapping shows that in all lineages except Characoidei (Characiformes) adipose fins develop from a domain of the larval median fin fold. To inform how the larva’s median fin fold contributes to the adipose fin, we study Corydoras aeneus (Siluriformes). As the fin fold reduces around the prospective site of the adipose fin, a fin spine develops in the fold, growing both proximally and distally, and sensory innervation, which appears to originate from the recurrent ramus of the facial nerve and from dorsal rami of the spinal cord, develops in the adipose fin membrane. Collectively, these data show how a plesiomorphic median fin fold can serve as scaffolding for the evolution and development of novel, individuated median fins, consistent with the median fin fold hypothesis.

The presence and expression of the HIF-1α in the respiratory intestine of the bronze Corydoras Corydoras aeneus (Callichthyidae Teleostei).

Bronze corydoras (Corydoras aeneus) is a small diurnal activity fish from South America. Under hypoxia conditions, it uses the posterior part of the intestine as an accessory respiratory organ. The present PCR studies demonstrated higher expression of HIF-1α (hypoxia-inducible factor) gene in the respiratory than that in digestive part of bronze corydoras intestine. Further, immunolocalization studies using antibodies specific to HIF-1α and transmission electron microscopy (TEM) revealed the presence of HIF-1α epitopes in the intestine of Corydoras aeneus. In the respiratory intestine, the numerous clusters of gold particles visualizing HIF-1α antibody were observed within fibroblasts, whereas in the digestive tract of this species, single gold grains in the epithelial cells were noted. On the other hand, the presence of HIF-1α and the cytoplasmic domain of the epidermal growth factor receptor (EGFR) in the respiratory intestine of bronze corydoras assumes their interactions in the system where these factors appeared for the first time. The non-obligatory air-breathing fishes using their digestive tract as an accessory respiratory organ during hypoxia conditions are very interesting for the studies of the processes that control HIF-1α expression and squamous cell proliferation.

The early catfish catches the worm: predation of Corydoras aeneus (Siluriformes, Callichthyidae) on freshwater nematodes

In this study, we measured the daily consumption of four different nematode species by a small freshwater catfish species, Corydoras aeneus (Gill, 1858). Consumption of nematodes by fishes was significant with a single C. aeneus individual being able to consume in 24 h between 40 581 and 75 849 adult nematodes depending on the nematode species offered. This represented the ingestion of up to 238 mg wet weight when considering the largest nematode species: Panagrellus redivivus. Our results strengthen the growing evidence of a significant trophic channel existing between meiobenthic invertebrates like nematodes and small bottom-feeding fishes like C. aeneus. We also discuss the relevance of using P. redivivus as live food for rearing C. aeneus which is a popular ornamental fish.

Confirmation of the immunoreactivity of monoclonal anti-human C-terminal EGFR antibodies in bronze Corydoras Corydoras aeneus (Callichthyidae Teleostei) by Western Blot method

Bronze corydoras (Corydoras aeneus) uses the distal part of the intestine as accessory respiratory organ. Our previous study showed the presence of epidermal growth factor receptor (EGFR) cytoplasmic domain in the digestive tract of the bronze corydoras. In this study, using Western Blot method, we validated the results presented in the previous research. In detail, results of Western Blot analysis on digestive and respiratory part of bronze corydoras intestine homogenates confirmed the immunoreactivity of anti-cytoplasmic domain (C-terminal) human EGFR antibodies with protein band of approximately 180kDa (EGFR molecular weight). This indicates a high homology of EGFR domain between these species and the possibility of such antibody use in bronze corydoras. Statistically significantly higher EGFR expression was observed in the respiratory part of intestine when compared to the digestive part. This implies higher proliferation activity and angiogenesis of epithelium in this part of intestine, creating conditions for air respiration. Therefore, Corydoras aeneus may be considered as a model organism for the molecular studies of the mechanisms of epithelial proliferation initiation and inhibition depending on hypoxia and normoxia.

Squamous epithelium formation in the respiratory intestine of the bronze Corydoras Corydoras aeneus (Callichthyidae Teleostei)

Accessory respiratory organs in fish exhibit great diversity but share the presence of numerous capillaries covered by a simple squamous epithelium. The adoption of the intestine for respiratory function needs certain special modifications. In this study, we explored immunohistochemical and metabolic fingerprint features that could underlay this adaptation in bronze corydoras Corydoras aeneus. Immunohistochemical localization of the cytoplasmic domain of epidermal growth factor receptor (EGFR) in the respiratory part of intestine demonstrated a strong positive immunoreaction in epithelial cells and connective tissue. Fourier Transfer Infrared (FTIR) spectroscopy coupled with chemometrics discriminated between anterior and posterior region of intestine in terms of secondary structure of proteins and the abundance of p-cresol and other phenolics. The latter were reduced in the posterior part of intestine, indicating the cessation of digestive function in this region. It has been suggested that aquatic hypoxia via endocrine cells (hypoxia-sensitive) activate EGFR, which induce proliferation of squamous epithelial cells, thereby enabling gas diffusion in the posterior part of intestine. It seems that hypoxia and normoxia are opposed conditions adjusting the production of squamous epithelial cells in this intestine. The physiological role of EGFR in the respiratory intestine of bronze corydoras is of interest not only from an evolutionary aspect but also in terms of a potential model for observations process proliferation squamous epithelial cells. Future investigations on the molecular responses to different water oxygen levels in air-breathing bronze corydoras fish are required to clarify the mechanism responsible for squamous cell proliferation.

Estrutura populacional e aspectos reprodutivos de Corydoras aeneus (Siluriformes, Callichthyidae) em riachos da bacia do rio Ivinhema, Alto rio Paraná

RESUMO Apesar do crescente número de estudos sobre biologia de espécies de peixes de pequeno porte, o conhecimento dos aspectos básicos da biologia da maioria das espécies ainda é incipiente. Com isso, o objetivo desse estudo foi descrever alguns aspectos populacionais e reprodutivos de Corydoras aeneus (Gill, 1858) em riachos da bacia do rio Ivinhema, Alto rio Paraná. As amostragens foram realizadas entre 2008 e 2011 em 57 riachos distribuídos na bacia. Foram analisados 684 indivíduos, sendo 213 fêmeas e 190 machos, além de 281 exemplares analisados apenas quanto aos dados de comprimento padrão. O comprimento padrão máximo da população analisada foi de 50,19 mm para as fêmeas e de 45,24 mm para machos; Desta forma, as fêmeas foram maiores que os machos. A proporção sexual foi de 52,7% para fêmeas e de 47,1% para os machos, sem variação significativa entre os sexos (Χ2= 1,313; p = 0,252). Quanto à relação peso/comprimento ambos os sexos apresentaram a crescimento isométrico. As maiores frequências de fêmeas maduras foram observadas nos meses de outubro a dezembro, embora tenham sido observadas fêmeas maduras em outros meses do ano. Estimou-se que 50% das fêmeas estão sexualmente maduras com 33,54 mm de comprimento padrão. A fecundidade média foi estimada em 359,47 oócitos, sendo que a população apresenta desova total. O padrão de recrutamento não apresentou um padrão unimodal, embora a maior intensidade tenha sido observada nos meses de outubro a dezembro. O comprimento assintótico foi estimado em 54,59 mm e a taxa de crescimento de 1,1 ano-1. O índice de performance de crescimento foi estimado em 3,51; a longevidade de 2,72 anos e a mortalidade de 1,48 ano-1.

Philocorydoras longus sp. n. (Monogenea, Dactylogyridae) from the gills of Hoplosternum littorale (Siluriformes, Callichthyidae) in Southeastern Brazil and the reassignment of two species from the genus Urocleidoides to Philocorydoras

Summary Philocorydoras longus sp. n. (Dactylogryridae) is described from the gills of the freshwater fish Hoplosternum littorale (Hancock, 1828) (Callichthyidae) from Jurumirim reservoir, Upper Paranapanema River, São Paulo State, Brazil. This new species belongs to the genus Philocorydoras mainly by possessing a curved cirrus accompanied by an accessory piece attached by a conspicuous filament. Philocorydoras longus sp. n. most resembles P. platensis, but differs by having delicate and smaller hooks, grooves in ventral and dorsal anchors, larger cirrus and accessory piece, and ventral bar with a long postero-medial process. Two species of the genus Urocleidoides (U. corydori Molnar, Hanek et Fernando, 1974 and U. margolisi Molnar, Hanek et Fernando, 1974) originally described from the gills of Corydoras aeneus (Gill, 1858) from Talparo River, Trinidad (near Brazil), were transferred to the genus Philocorydoras mostly by the absence of a sinistral vaginal sclerite (i. e., the primary characters of Urocleidoides) and counterclockwise cirral rings (i.e., curved tube, and tapered anteriorly in Philocorydoras). The new species is the fourth species assigned to the genus and the first recorded for Brazil.