Explore the vast range of titles available.

The bristlenose pleco (Ancistrus cirrhosus) is a species of Loricariidae armored catfish that breathes air using its highly vascularized stomach when faced with hypoxic aquatic environments. The main goals of this study were to determine the developmental onset of air breathing and air-breathing behavior in A. cirrhosus from juveniles to adults. Developing juveniles reach functional maturity within 4 to 6 months of hatching, growing to an adult length of 8 to 10 cm. To examine the timing of the developmental onset of air breathing, we tested for air-breathing behavior in juveniles beginning at 1 cm in length up through adults at 8 cm in length by exposing each fish to an acute gradual decrease in aquatic oxygen content from 100% air saturation down to 8% air saturation over a 50-min period. Juvenile fish first began to breathe air at body lengths between 2.1 and 3 cm and masses of 1.1 and 2 g. Fish with body lengths above 3 cm all breathed air when hypoxia challenged. In fish that breathed air, there was a weak negative correlation between fish length and % air saturation at which air breathing began. Fish were also exposed to an acute bout of 15% air saturation for 60 min, and breathing behavior was observed. Fish exposed to 60 min acute 15% air saturation exhibited a negative correlation between the frequency of air breathing and fish length. The developing A. cirrhosus can take advantage of the aerial environment once they reach 3 cm in length and 2 g when exposed to aquatic hypoxia. Prior to this size, these animals would potentially succumb to severe aquatic hypoxia without the ability to breathe air.

The catfish Ancistrus triradiatus belongs to the species-rich family Loricariidae. Loricariids display remarkable traits such as herbivory, a benthic lifestyle, the absence of scales but the presence of dermal bony plates. They are exported as ornamental fish worldwide, with escaped fishes becoming a threat locally. Although genetic and phylogenetic studies are continuously increasing and developmental genetic investigations are underway, no genome assembly has been formally proposed for Loricariidae yet. We report a high-quality genome assembly of Ancistrus triradiatus using long and short reads, and a newly assembled transcriptome. The genome assembly is composed of 9530 scaffolds, including 85.6% of ray-finned fish BUSCOs, and 26,885 predicted protein-coding genes. The genomic GC content is higher than in other catfishes, reflecting the higher metabolism associated with herbivory. The examination of the SCPP gene family indicates that the genes presumably triggering scale loss when absent, are present in the scaleless A. triradiatus, questioning their explanatory role. The analysis of the opsin gene repertoire revealed that gene losses associated to the nocturnal lifestyle of catfishes were not entirely found in A. triradiatus, as the UV-sensitive opsin 5 is present. Finally, most gene family expansions were related to immunity except the gamma crystallin gene family which controls pupil shape and sub-aquatic vision. Thus, the genome of A. triradiatus reveals that fish herbivory may be related to the photic zone habitat, conditions metabolism, photoreception and visual functions. This genome is the first for the catfish suborder Loricarioidei and will serve as backbone for future genetic, developmental and conservation studies.

Ancistrus Kner, 1854, is the most diverse genus among the Ancistrini (Loricariidae) with 70 valid species showing a wide geographic distribution and great taxonomic and systematic complexity. To date, about 40 Ancistrus taxa have been karyotyped, all from Brazil and Argentina, but the statistic is uncertain because 30 of these reports deal with samples that have not yet been identified at the species level. This study provides the first cytogenetic description of the bristlenose catfish, Ancistrus clementinae Rendahl, 1937, a species endemic to Ecuador, aiming to verify whether a sex chromosome system is identifiable in the species and, if so, which, and if its differentiation is associated with the presence of repetitive sequences reported for other species of the family. We associated the karyotype analysis with the COI molecular identification of the specimens. Karyotype analysis suggested the presence of a ♂ZZ/♀ZW1W2 sex chromosome system, never detected before in Ancistrus, with both W1W2 chromosomes enriched with heterochromatic blocks and 18S rDNA, in addition to GC-rich repeats (W2). No differences were observed between males and females in the distribution of 5S rDNA or telomeric repeats. Cytogenetic data here obtained confirm the huge karyotype diversity of Ancistrus, both in chromosome number and sex-determination systems.

The evolutionary process of adaptation to the cave environment leads to extreme genetic, morphological, and physiological modifications commonly known as stygomorphism. The cave-dwelling armored catfish Ancistrus cryptophthalmus is a good model to understand the evolutionary processes of stygomorphism in the Neotropics as its ecology and morphology have been studied in detail. Interestingly, it has been found a non-stygomorphic epigean population named Ancistrus sp. This population is morphologically distinct to the hypogean population of A. cryptophthalmus as they present better-developed ocular structures and intense pigmentation. Here we used Illumina sequencing technology to produce partial genome sequences for specimens of Ancistrus sp. and A. cryptophthalmus; we also genotyped molecular markers from individuals of both species. Based on the high level of mitogenome similarity and metapopulation connectivity between the surface and cave populations, we suggest that the evolution of stygomorphisms observed in A. cryptophthalmus may be the result of morphologic modification, by natural selection, of Ancistrus sp. surface population to colonize the harsh cave environment.

In order to fully comprehend the evolution and kinship of fishes in the family of Loricariidae, the complete mitochondrial genome of the Loricariidae fish Ancistrus temmincki was firstly characterized in the present study. The whole mitogenome was 16,657 bp in size and consisted of 13 protein-coding genes, 22 tRNAs, 2 rRNAs genes, a control region and origin of light-strand replication. The proportion of coding sequences with a total length of 11,473 bp was 68.88%, which encoded 3,813 amino acids. The genome composition was highly A + T biased (56.29%), and exhibited AT-skew (0.0661) and a negative GC-skew (-0.2740). All protein-coding genes were started with ATG except for GTG in CO1, while stopped with the standard TAN codons or a single T. The control region (D-loop) ranging from 15,635 bp to 16,657 bp was 1023 bp in size. Until now, there is hardly any studies on the complete mitochondrial sequence in the genus of Ancistrus, phylogenetic analysis showed that A. temmincki was most closely related to Ancistrus cryptophthalmus in the genus of Ancistrus. The complete mitochondrial genome sequence has provided a new insight into the taxonomic classification, and a more complex picture of the species diversity within the family of Loricariidae.

Summary We hypothesized that the use of habitat by two armored catfish species, Ancistrus aff. cirrhosus and Hypostomus ancistroides, which share the same stream reach, is temporally segregated. To test this, fish residence time within a culvert and fish movements through the culvert were analyzed in relation to the daily hours, lunar cycle and discharge using Passive Integrated Transponder telemetry. The residence time for A. aff. cirrhosus conducting upstream movements was longer than H. ancistroides. Both species exhibited high nocturnal activity, although at different periods: A. aff. cirrhosus was most active at dawn (00:00–05:59 hr), while H. ancistroides exhibited intense activity at night (18:00–23:59 hr), indicating temporal segregation of movement behavior between species. In addition, A. aff. cirrhosus was most active in the new moon phase and when there was high water discharge, while H. ancistroides was most active only when there was high water discharge. This study elucidates the patterns of daily movement behavior and temporal habitat use of these fish species.

The relationships among the morphology, trophic ecology, and use of food resources by fish fauna in a pristine stream in Iguaçu National Park (INP), Brazil were evaluated. We expected that the trophic patterns would be explained by ecomorphological variations among fishes and the availability of food resources. Sampling was conducted quarterly from May 2015 to April 2016 using electrofishing. The stomach contents of 599 individuals belonging to nine species were analyzed using the volumetric method. Thirty-two morphological measures related to trophic ecology and body morphology were then converted into 10 ecomorphological indices. The fish assemblage consumed aquatic (Diptera, Ephemeroptera) and terrestrial (Hymenoptera) insects, other aquatic invertebrates, plants, and detritus/sediment. Therefore, the consumption frequencies of these food items were considered representative of their environmental availability. Furthermore, the fish fauna presented wide trophic niche breadths and little diet overlap. Principal component analysis (PCA) was used to classify the fishes’ ecomorphological variations into three ecomorphotypes. The benthonic ecomorphotype comprised species with more depressed bodies that eat detritus/algae and dipteran larvae (Ancistrus mullerae and Corydoras carlae). The nektobenthic ecomorphotype included species with elongated bodies and wider heads and mouths that eat aquatic insects and Aeglidae (Trichomycterus stawiarski and Rhamdia spp.). The nektonic ecomorphotype contained species with more compressed bodies and terminal mouths, which are generalist consumers of allochthonous and autochthonous resources. Morphology was significantly correlated with diet, which suggests that ecomorphological variations together with the availability of food in the environment are the main mechanisms underlying trophic segregation and coexistence among species.

In ecosystems where excretion by fish is a major flux of nutrients, the nitrogen (N) to phosphorus (P) ratio released by fish can be important in shaping patterns of algal biomass, community composition, primary production, and nutrient limitation. Demand for N and P as well as energy influences N/P excretion ratios and has broad implications in ecosystems where nutrient recycling by fishes is substantial. Bioenergetics and stoichiometric models predict that natural fish populations are generally energy-limited and therefore N/P recycling by fishes is relatively invariant. Yet, the potential for P limitation of growth has not been examined in herbivorous fishes, which are common in many aquatic habitats. We examined N/P excretion ratios and P demand in two P-rich herbivorous catfishes of the family Loricariidae, Ancistrus triradiatus (hereafter Ancistrus) and Chaetostoma milesi (hereafter Chaetostoma). Both fishes are common grazers in the Andean piedmont region of Venezuela where we conducted this study. Mass balance (MB) models indicate that these fishes have a high P demand. In fact, our Ancistrus P MB model predicted negative P excretion rates, indicating that Ancistrus did not consume enough P to meet its P demand for growth. Direct measurement of excretion rates showed positive, but very low P excretion rates and high N/P excretion ratios for both taxa. To obtain measured P excretion rates of Ancistrus from the MB model, gross growth efficiency must be reduced by 90%. Our results suggest that growth rates of both of these herbivorous and P-rich fish are likely P-limited. If P limitation of growth is common among herbivorous fish populations, herbivorous fishes recycle likely at high N/P ratios and act to diminish the quality of their food.

Background The capture of ornamental fish is one of the main economic activities of riverine families in the Amazon. However, studies regarding the local ecological knowledge of workers in this activity are still incipient. In view of this, we have studied and explored the local ecological knowledge of artisanal fishers who specialize in the capture of fish for the aquarium trade in the middle part of the Negro River basin and investigated issues related to the ecological aspects of the fish species that are targeted by this trade in the region. Methods Therefore, we conducted semi-structured interviews and applied questionnaires to artisanal fishers of ornamental fish ( N = 89), from the municipality of Barcelos, from January to April 2016. Results In total, 41 popular names were cited, which correspond to four ethnocategories and 10 families. The main species were Paracheirodon axelrodi (12.5%), Hemigrammus bleheri (8.3%), Ancistrus dolichopterus (6.4%), Symphysodon discus (5.3%), and Potamotrygon motoro (3.8%). According to the fishers, the species of fish known in the region as “piabas” have a preference for living in clusters (28.9%) and carry out migratory movements (26.1%). The diet of local fish species reported by fisheries is diverse, though mainly based on periphyton (42.2%), and the reproductive cycle directly influenced by the period of flooding of rivers in the region (37.6%) Conclusion Our study revealed that the fishers possess information on the ecological aspects of local ornamental fish species, many of which are consistent with scientific literature. The information presented may assist in the decision-making process for the management of local fishery resources and contribute to the resumption of growth and sustainability in the capture of ornamental fish.

The reproductive traits of two loricariid catfishes, Ancistrus multispinis and Pareiorhaphis hypselurus, from tributaries of the Mampituba river basin, southern Brazil, were analyzed and tested for relationships with biotic and abiotic parameters. Samples were taken monthly from July 2008 to December 2009 and data were grouped by season. Traits include population structure, reproductive period, size at first maturation, fecundity, spawning type, and possible influences of biotic and abiotic factors on reproduction. Results found the sex ratio to be 1:1 for both species. Males of A. multispinis and both sexes of P. hypselurus presented isometric growth, while females of A. multispinis had positive allometric growth. The reproductive activity of both species started during winter and reached its highest intensity in spring and summer. Both species had low fecundity with large oocytes and multiple spawning. Size at first maturation for A. multispinis was 58.3 mm for males and 49.2 mm for females, while for P. hypselurus, it was 40.5 for males and 34.1 for females. Day length seems to be the most influential abiotic factor for increasing the gonadosomatic index (GSI) for both species. Other abiotic factors, such as water depth and velocity, rainfall, and temperature, may also play a role in the reproductive cycle. The hepatosomatic index (HSI) also influenced reproduction, especially for A. multispinis. The reproductive traits presented by both species, such as an extended reproductive period, large oocytes, low fecundity, multiple spawning, and the occurrence of parental care, place these species within the equilibrium reproductive strategy.