Neotropical Characid Research Articles

Integrating geometric morphometrics to biotechnology: a multivariate approach to discriminating, males, females, gynogenetic, and diploid and triploid juveniles in an important Neotropical characid

Integrating geometric morphometrics to biotechnology: a multivariate approach to discriminating, males, females, gynogenetic, and diploid and triploid juveniles in an important Neotropical characid

Henneguya (Cnidaria: Myxobolidae) species infecting Oligosarcus jenynsii (Characiformes: Characidae) in a Neotropical shallow lake from Argentina: morphological and molecular characterisation.

Two previously undescribed myxozoan species, Henneguya sardellae sp. n. and H. margaritae sp. n., found infecting connective tissues of the Neotropical characid fish Oligosarcus jenynsii (Günther) from Argentina are morphologically and molecularly characterised. Mature spores of H. sardellae sp. n. are ellipsoid, with two, straight and visibly fused caudal appendages cleaved at its blunt terminal end; measuring 33.5 ± 1.2 (30.9-35.5) μm in total length, spore body 17.5 ± 0.6 (16.3-18.6) µm, 7.8 ± 0.4 (7.0-8.8) µm wide and 6.9 ± 0.2 (6.6-7.2) µm thick, with two elongated, unequally-sized polar capsules situated at anterior end, and 11-13 turns of polar tubules. Mature spores of H. margaritae sp. n. are pyriform, with two caudal appendages visible fused together and much longer than spore body, with unequal endings; measuring 35.9 ± 2.8 (29.2-40.7) µm in total length, spore body 11.5 ± 0.9 (9.2-13.0) µm long, 5.8 ± 0.4 (5.1-6.7) µm wide and 5.5 ± 0.2 (5.1-5.8) µm thick, with two polar capsules similar in size, pyriform polar capsules containing polar tubules with 4-5 coils. Both species showed a membraneous sheath surrounding the spore body and caudal appendages; in H. sardellae sp. n. this feature can deploy laterally. Phylogenetic analyses based on SSU rDNA sequences showed that H. sardellae sp. n. and H. margaritae sp. n. clustered with other myxobolids parasitising Characiformes in Brazil, Cichliformes in Mexico and Cyprinodontiformes in Mexico and the United States. The description of these two new species of Henneguya as the first described species of the genus that parasitise freshwater fish in Argentina highlights the importance of further research on the diversity and distribution of myxozoans in this region.

Two new species of miniature tetras of the fish genus Priocharax from the Rio Juruá drainage, Acre, Brazil (Teleostei: Characiformes: Characidae)

Two new miniature tetra species of the Neotropical characid genus Priocharax Weitzman and Vari, 1987 are described, raising the known species diversity to seven. Both species occur in the Rio Juruá system, Cruzeiro do Sul municipality, Acre State, Brazil. Priocharax toledopizae sp. nov. occurs in streams flowing to the lower Rio Moa, a tributary of Rio Juruá, and is distinguished from congeners by a combination of presence of claustrum and infraorbitals 1 and 2, absence of infraorbital 3, and presence of five branched pelvic-fin rays. Priocharax marupiara sp. nov. is known from Igarapé Canela Fina, tributary of Rio Juruá, and is diagnosed by a combination of fewer maxillary teeth (21–27 vs. 27–58 in remaining species), fewer branched anal-fin rays (18–23 vs. 22–27 in two species) and colour pattern. Both species differ from each other in the general body shape: Priocharax toledopizae is more robust with deep body and Priocharax marupiara more elongate. DNA barcode data support the specific distinctness of the two new species and that of the other five species in the genus. We describe a remarkable sexual dimorphism of the pelvic girdle of Priocharax toledopizae in which the pelvic musculature is enlarged forming a pedicel for the fin in mature males. Most localities where these species were found suffer from significant degradation mainly due to litter accumulation and suppression of the riparian forest, raising concerns about their conservation status.

Expression patterns and immunolocalisation of IGF-I and IGF-II in male and female gonads of the Neotropical characid fish Astyanax fasciatus.

The insulin-like growth factor (IGF) system plays important roles in fish reproduction, but the expression pattern and cellular location of IGF-I and IGF-II during gonadal maturation are uncertain. The present study reports a stage-specific assessment of gonadal expression levels and immunolocalisation of IGF-I and IGF-II in Astyanax fasciatus, a characid fish from South America. Adult fish in different maturity stages were caught in the Furnas Reservoir, Grande River, Brazil. Gonad samples were processed for histology, immunohistochemistry, and ELISA for IGF-I and IGF-II. Ovarian levels of IGF-I were low during ripening and ripe stages, higher in totally spent, and then decreased in resting. Levels of IGF-II increased during ovarian maturation, reaching significantly higher values at stage totally spent. In males, IGF-I levels followed gonadal maturation, with higher values in ripening and ripe stages, whereas IGF-II levels showed higher values in stage ripening and partially spent. A positive correlation was found between IGF-I and gonadosomatic index (GSI) for males (r = 0.59), while females showed a negative correlation (r = - 0.43), but IGF-II showed no correlation to GSI. IGF-I was expressed mainly in oogonia nests whereas IGF-II stained the follicular cells in the perinucleolar follicles, cortical vesicles in the previtellogenic follicles, and oogonia nests. In males, IGF-I was evident in spermatogonia and spermatocytes while IGF-II stained Sertoli cells surrounding spermatids cysts and spermatogonia in late stages. Together, these findings support a hypothesis that the balance between IGF-I and IGF-II levels is important in the regulation of gonad maturation in Astyanax fasciatus.

Dietary differentiation in relation to mouth and tooth morphology of a neotropical characid fish community

The relationship between diet and mouth and tooth morphology among eleven characid species is evaluated herein. Specifically, we tested for: (1) significant differences among the diets and (2) corresponding variation of mouth and tooth morphology. Fishes were collected bimonthly during 2012 and 2013 using electrofishing techniques in the Alto Jacuí sub-basin. A total of 1525 stomachs were analyzed representing eleven species of characid fishes. A Permutational Multivariate Analysis of Variance (PERMANOVA) analysis showed significant interspecific differences among the diets, and Similarity Percentage (SIMPER) analysis indicated that the main food items that contributed to this differentiation were variation in the relative consumption of terrestrial and aquatic plants, terrestrial and unidentified aquatic insect, and adult Hymenoptera. Lastly, Constrained Principal Analysis on Coordinates (CAP) analyses showed that several morphological features were associated with dietary patterns. For example, sub-terminal mouth positions were correlated with the ingestion of benthic items (i.e., aquatic insects and organic matter). Large mouths were associated with species that consume large items such as Decapoda (e.g., Aegla) and fish. Species that showed a minor variation in tooth morphology along the outer row of the premaxilla, as well as those that have fewer teeth on the maxilla, consumed high proportions of plants and terrestrial insects. Species with intermediate and high numbers of cusps in the maxilla teeth tended to consume aquatic insects. Here, we demonstrated that eleven species of characid fishes had different diets and that those diets were correlated to a specific mouth and tooth morphology. Therefore, diet and oral morphology likely co-evolved such that divergence in trophic-related morphology likely facilitated dietary differentiation among characid fishes.

Comparative morphology of bony hooks of the anal and pelvic fin in six neotropical characid fishes (Ostariophysi: Characiformes)

The morphology of bony hooks on anal-fin and pelvic-fin rays in six neotropical characid fish (Astyanax fasciatus, A. lacustris, Hyphessobrycon bifasciatus, H. itaparicensis, Compsura heterura and Serrapinnus heterodon) representing different reproductive modes (inseminating and externally fertilizing) was analysed with a particular focus on the form, distribution, development and orientation of bony hooks of the male anal-fin and pelvic-fin rays.When present bony hooks of the anal-fin and pelvic-fin rays in adult males represented a permanent structure and its development is likely closely related to the reproductive phase. Bony hooks were found on anal-fin and pelvic-fin rays in A. lacustris, C. heterura, H. itaparicensis and S. heterodon whereas A. fasciatus and H. bifasciatus showed bony hooks only on the anal-fin rays. The absence of pelvic-fin rays may be related to hormonal factors and linked to the courtship behavior. Despite their reproductive mode, the bony hooks on anal-fin and pelvic-fin rays were positioned along the posterolateral border. On pelvic-fin rays, the distal tips of the bony hooks were directed towards the anterior fin ray border in inseminating or non-inseminating species. On the anal-fin rays, the distal tips of the hooks were morphologically different in inseminating and externally fertilizing species. Inseminating characids such as C. heterura exhibited a distinct morphological arrangement of hooks exclusively present on pelvic-fin rays similar to the structures found in inseminating species. The number of bony hooks on anal-fin rays was higher only among the Cheirodontinae such as C. heterura and S. heterodon regardless of their reproductive mode. Apparently the presence and morphology of bony hooks on fin rays represent an important data source for phylogenetic, reproductive and behavioral studies of characid fish.

TROPHIC AND REPRODUCTIVE ECOLOGY OF A NEOTROPICAL CHARACID FISH HEMIBRYCON BREVISPINI (TELEOSTEI: CHARACIFORMES)

Hemibrycon brevispini is a Neotropical characid fish endemic in La Venada Creek, a headwater tributary of the Quindio River of Colombia (Cauca River drainage). It is mainly a diurnal insectivore with a diet dominated by benthic dipterans (Chironomidae, Simuliidae, Psychodidae, Culicidae, Calliphoridae, Dixidae and Muscidae), hymenopterans (Formicidae and Vespidae) and ephemeropterans (Baetidae), as well as allochthonous prey and items eaten accidentally. Microhabitats of mountain streams with lower water velocity tend to have more riparian vegetation and the associated terrestrial arthropods that are consumed by H. brevispini. It has three peaks in reproduction: December, April and August. Average fecundity was 776 mature oocytes per female.

Reproductive biology of the characid dourado Salminus franciscanus from the São Francisco River, Brasil

The neotropical characid Salminus franciscanus is an economically valuable migratory fish whose populations have been drastically reduced in recent decades due to industrial and economic development in Brasil. To study its reproduction, a total of 283 adult specimens were captured in the Upper São Francisco River, downstream from the Três Marias dam, Minas Gerais, south-eastern Brasil, from August 2009 to July 2010. The gonadal maturity stages were determined from histological features of the gonads and gonadosomatic index (GSI). Gametogenesis was assessed by light and electron microscopy. For analysis of the oocyte's surface and fecundity, mature females were subjected to hormonal induction and oocyte stripping. Fish in resting (Stage 1) were common in all samplings, ripening/ripe and spawning (Stages 2 and 3) were predominant in October–November and December–January and post-spawning (Stage 4) occurred from December–January extending until April–May. The GSI followed the morphological changes of gonadal maturation, with a peak in October–November, when maximum GSI (7.08 in females and 3.46 in males) was achieved. From scanning electron microscopy, stripped oocytes showed a funnel-shaped micropyle and a simple oocyte surface arrangement, which is typical for non-adhesive eggs. Fecundity ranged from 160 to 440×103 oocytes per female and 129 to 175×103oocytes/kg. The results of this study indicate that S. franciscanus reproduces in the Upper São Francisco River from October to January, exhibiting a total spawning pattern, non-adhesive eggs and high fecundity, providing support for aquaculture and conservation biology of this important neotropical characid fish.

Could native predators help to control invasive fishes? Microcosm experiments with the Neotropical characid, Brycon orbignyanus

Abstract – The potential of the native characid, Brycon orbignyanus, to help to control some invasive fish species currently present in the Paraná River basin was addressed through microcosm experiments. Juveniles of three invasive (Cichla piquiti, Oreochromis niloticus and Ictalurus punctatus) and two native (Astyanax altiparanae and Prochilodus lineatus) fish species were offered as prey to B. orbignyanus in 300‐l aquarium trials with three habitat complexity treatments (0%, 50% and 100% structure). Prey survival was much more variable among species (I. punctatus < C. piquiti < O. niloticus∼P. lineatus∼A. altiparanae) than through time, and B. orbignyanus predation was clearly mediated by habitat complexity, with lower prey survival in low‐complexity treatments. The lower survival observed for C. piquiti could be partially explained by its less active behaviour and its preference for a surface microhabitat and less structured areas. Prey size also affected predation rates, as for the three less consumed species the largest individuals were significantly preyed on. Our results suggest that preserving and restoring the populations of B. orbignyanus might help to control some fish species introduced to the Paraná River basin, particularly I. punctatus and C. piquiti.

Preliminary field study of hepatic porphyrin profiles of Astyanax fasciatus (Teleostei, Characiformes) to define anthropogenic pollution

The implementation of eco-toxicological assessment in South America is presently limited due to significant scientific information gaps concerning native species and their potential use as biomarkers. Recently, a common southern hemisphere fish species, Astyanax fasciatus, has been pointed out as a potential bio-indicator to anthropogenic pollution. This is a small, abundant, Neotropical characid, which is widely distributed from Central America south, to the Rio de la Plata Basin of western Uruguay. Our study found a statistically significant increase of coproporphyrin, uroporphyrin and protoporphyrin concentrations in hepatic tissues of A. fasciatus collected from a stream segment with high anthropogenic disturbance (due mainly to agricultural derivatives and motor vehicle transportation activities). Although the area studied showed differences in up and downstream limno-chemical parameters, these differences were not related to the increase of hepatic porphyrin concentrations. Based on the results of our study, we conclude that A. fasciatus is a good bio-indicator of exposure to environmental contaminants, and we propose that this abundant fish species be considered as a sentinel organism for monitoring potential disturbances to freshwater ecosystems.

Insectivore to frugivore: ontogenetic changes in gut morphology and digestive enzyme activity in the characid fish Brycon guatemalensis from Costa Rican rain forest streams

Brycon guatemalensis, a Neotropical characid fish, consumes an entirely terrestrial diet, shifting from eating insects as juveniles to fruits and leaves as adults. Juvenile and larger‐sized fish collected in the Rio Puerto Viejo at the La Selva Biological Station in Costa Rica were studied to test the hypotheses that, with ontogeny, (1) relative gut length increases, (2) pyloric caeca arrangement and number remain unchanged and (3) pepsin, trypsin and lipase activities decrease, while α‐amylase activity increases. These hypotheses were mainly supported in that larger fish had longer guts, unchanged pyloric caeca arrangement but fewer caeca, and, at both environmental and standard temperatures for the enzyme assays, lower pepsin and trypsin activities but higher α‐amylase activities than the juveniles. Only lipase, among the digestive enzymes, exhibited the unexpected outcome of either not differing significantly in activity (per g of tissue) between juveniles and larger fish or being significantly higher (per mg of protein) in larger fish. The overall results support the view that B. guatemalensis is specialized morphologically and biochemically to function first as a carnivore and then as a herbivore during its life history.

Taxonomic revision of the South American fish genus Chalceus Cuvier (Teleostei: Ostariophysi: Characiformes) with the description of three new species

The Neotropical characid fishes of the genus Chalceus Cuvier, 1817, are reviewed. In total, five species are recognized (including three new species). Chalceus epakros sp. nov. is the most widespread geographically, occurring in many rivers of the Amazon basin, the Rio Orinoco and in the Essequibo River drainage in Guyana. Chalceus guaporensis sp. nov. is restricted to the upper Rio Madeira, Rio Guapore and Rio Madre de Dios, of Brazil, Bolivia and Peru, respectively. Chalceus spilogyros sp. nov. occurs only in the Rio Trombetas, lower Rio Tapajos and lower Rio Madeira drainages. Chalceus macrolepidotus Cuvier occurs in the Rio Negro drainage, middle and lower Rio Orinoco basin and in the rivers of the Atlantic slopes of the Guianas, and Chalceus erythrurus Cope in the Rio Amazonas and Rio Solimoes to Rio Ucayali drainage in Peru. Chalceus ararapeera Cuvier & Valenciennes and Creagrutus pellegrini Puyo are considered synonyms of C. macrolepidotus, and Pellegrinina heterolepis Fowler is placed into the synonymy of C. erythrurus. Characters pertaining to the monophyly of Chalceus are discussed and a key to species is presented. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140, 103−135.

Gill‐derived glands in glandulocaudine fishes (teleostei: Characidae: Glandulocaudinae)

The Glandulocaudinae is a subfamily of neotropical characid fishes from Central and South America. A unifying feature of the subfamily is the caudal gland, found almost exclusively in males. The gland consists of tissue on the base of the caudal fin covered in part by hypertrophied scales. Scale movement as the caudal fin is flexed appears to facilitate the release of chemical compounds from the glandular tissue. We describe here a different structure, found in the gill cavity of mature males in 12 of 17 glandulocaudine genera examined. Termed a gill gland, it develops as a male secondary sex character and appears morphologically suited to release chemical signals. The gland forms by the growth of tissue over and around 4-13 anterior gill filaments on the first gill arch, forming chambers with ventral openings. Within the gland chambers, gill secondary lamellae usually shorten and may disappear. When secondary lamellae persist, simple columnar epithelial cells develop between them. In the absence of secondary lamellae, the gland chambers are lined with a simple cuboidal or columnar epithelium. Gland size and the degree of gill modification vary among species. Gill glands appear absent in five glandulocaudine genera, suggesting character reversals based on current phylogenetic hypotheses and systematic classification. Gill gland morphology suggests that this structure releases chemical compounds into the gill current. The presence of gill glands only in mature males suggests a function in reproduction and/or male aggression. Together with studies of the caudal gland, this research suggests that chemical signals may play important roles in glandulocaudine reproduction.

Ontogenic diet shifts and scale-eating in Roeboides dayi, a Neotropical characid

Scale feeding (lepidophagy) has been documented for a variety of Neotropical fish taxa, including the characid genus Roeboides. Ontogenetic differentiation of jaws and snout teeth allow larger Roeboides to remove scales, however, the less specialized tooth/jaw structure in Roeboides dayi, indicates that it may be a facultative scale feeder. Population dynamics and diets of R. dayi in a Venezuelan lowland swamp/creek and a piedmont stream were compared over an annual cycle. Juvenile R. dayi consumed aquatic insect larvae and microcrustacea, and although spawning was year-round at both sites, most reproduction occurred during the wet season when the availability of these resources was greatest for juveniles. At both sites, larger R. dayi fed on a combination of invertebrate prey and fish scales, the former being more important at the piedmont site, and the latter being especially important during initial low water conditions at both sites. In the lowland stream, the reduction of aquatic habitat during the early dry season created higher fish densities and a more profitable environment for scale-feeders. Insectivory probably was less profitable during this early low water period due to interspecific competition for reduced aquatic insect stocks.