Occurrence of Sex Chromosomes in Fish of the Genus Ancistrus with a New Description of Multiple Sex Chromosomes in the Ecuadorian Endemic Ancistrus clementinae (Loricariidae).

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.

First record of the invasive dwarf surf clam Mulinia lateralis (Say 1822) in the eastern Pacific Ocean

Mulinia lateralis is a native bivalve from the Western Atlantic Ocean, distributed from the Gulf of Saint Lawrence in Canada to Yucatan in Mexico. Based on morphological and genetic data of specimens collected in shrimp farms, in this work, we confirm the presence of M. lateralis in the Gulf of Guayaquil, Ecuador. Presence and its consequences of this invasive bivalve in the region is discussed.

Mulinia lateralis es un bivalvo nativo de las aguas del Océano Atlántico Occidental, distribuido desde el Golfo de Saint Lawrence en Canadá hasta Yucatán en México. En este trabajo, la presencia de M. lateralis es confirmada en el Golfo de Guayaquil, Ecuador, con base en datos morfológicos y genéticos de ejemplares colectados en camaroneras. Se presenta una discusión sobre la presencia y consecuencias de este bivalvo invasor en la región.

Tracking the evolutionary pathways among Brazilian Lebiasina species (Teleostei: Lebiasinidae): a chromosomal and genomic comparative investigation

Despite several difficulties in chromosomal analyses of small-sized fishes, the cytogenetics of the Lebiasinidae was largely improved in the last years, showing differential patterns in the chromosomal evolution inside the family. In this context, it has been shown that genus Lebiasina preserves its karyotypic macrostructure, composed of 2n = 36 chromosomes, whereas the other genera generally present higher 2n. This study focused on the comparative cytogenetics of three Lebiasina species, one of them analyzed here for the first time, using conventional and molecular procedures. The results reinforced the differentiated evolutionary path of the genus Lebiasina while, at the same time, highlighted the genomic particularities that have accompanied the evolution of each species. In this sense, the repetitive components of the genome played a significant role in the differentiation of each species. It is also notable that L. minuta and L. melanoguttata, the two species that occur exclusively in the Brazilian territory, show greater chromosomal similarities to each other than to the trans-Andean sister species, L. bimaculata.(AU)

Apesar das dificuldades encontradas em se realizar análises cromossômicas em peixes de pequeno porte, os estudos citogenéticos em Lebiasinidae vêm crescendo nos últimos anos e demonstrando padrões diferenciados na evolução cromossômica entre os membros da família. Nesse contexto, o gênero Lebiasina tem mostrado preservar sua macroestrutura cariotípica, composta por 2n = 36 cromossomos, enquanto os demais gêneros geralmente apresentam 2n maiores. Este estudo tem como foco a citogenética comparativa de três espécies de Lebiasina, sendo uma delas analisada pela primeira vez aqui, através do emprego de técnicas convencionais e moleculares. Os resultados obtidos reforçam a trajetória evolutiva diferenciada do gênero Lebiasina, ao mesmo tempo em que evidenciam as particularidades genômicas que acompanham a evolução de cada uma das espécies. Neste contexto, os componentes repetitivos do genoma tiveram um papel importante na caracterização particular de cada uma das espécies. Também, é notável que L. minuta e L. melanoguttata, duas espécies que ocorrem exclusivamente no território brasileiro, apresentam maior proximidade citogenética entre elas do que com a espécie irmã transandina, L. bimaculata.(AU)

Chromosome analysis in Saccodon wagneri (Characiformes) and insights into the karyotype evolution of Parodontidae

Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.(AU)

Parodontidae é um grupo relativamente pequeno de peixes caraciformes neotropicais que consiste em três gêneros (Apareiodon, Parodon e Saccodon) com 32 espécies válidas. Uma vasta literatura citogenética está disponível sobre Apareiodon e Parodon, mas até o momento não há dados citogenéticos sobre Saccodon, um gênero que contém apenas três espécies com distribuição transandina. No presente estudo foi descrito o cariótipo de S. wagneri, baseado em métodos convencionais (coloração de Giemsa, Ag-NOR, bandas C) e moleculares (mapeamento de DNA repetitivo por hibridização fluorescente in situ). Um número cromossômico diplóide de 2n = 54 foi observado, e a presença de cromossomos sexuais heteromórficos do tipo ZZ/ZW foi revelada. O cromossomo W possui uma banda terminal heterocromática que ocupa aproximadamente metade do braço longo, sendo esta banda aproximadamente a metade do tamanho do cromossomo Z. O ensaio FISH mostrou uma sintenia dos genes 18S-rDNA e 5S-rDNA no par de cromossomos 14, e a ausência de sítios teloméricos intersticiais. Nossos dados reforçam a hipótese de uma estrutura cariotípica conservadora em Parodontidae e sugerem uma origem ancestral dos cromossomos sexuais nos peixes desta família.(AU)

Sex Chromosomes and Internal Telomeric Sequences in Dormitator latifrons (Richardson 1844) (Eleotridae: Eleotrinae): An Insight into their Origin in the Genus.

The freshwater fish species Dormitator latifrons, commonly named the Pacific fat sleeper, is an important food resource in CentralSouth America, yet almost no genetic information on it is available. A cytogenetic analysis of this species was undertaken by standard and molecular techniques (chromosomal mapping of 18S rDNA, 5S rDNA, and telomeric repeats), aiming to describe the karyotype features, verify the presence of sex chromosomes described in congeneric species, and make inferences on chromosome evolution in the genus. The karyotype (2n = 46) is mainly composed of metacentric and submetacentic chromosomes, with nucleolar organizer regions (NORs) localized on the short arms of submetacentric pair 10. The presence of XX/XY sex chromosomes was observed, with the X chromosome carrying the 5S rDNA sequences. These heterochromosomes likely appeared before 1 million years ago, since they are shared with another derived Dormitator species (Dormitator maculatus) distributed in the Western Atlantic. Telomeric repeats hybridize to the terminal portions of almost all chromosomes; additional interstitial sites are present in the centromeric region, suggesting pericentromeric inversions as the main rearrangement mechanisms that has driven karyotypic evolution in the genus. The data provided here contribute to improving the cytogenetics knowledge of D. latifrons, offering basic information that could be useful in aquaculture farming of this neotropical fish.

An Insight into the Chromosomal Evolution of Lebiasinidae (Teleostei, Characiformes).

Lebiasinidae fishes have been historically neglected by cytogenetical studies. Here we present a genomic comparison in eleven Lebiasinidae species, in addition to a review of the ribosomal DNA sequences distribution in this family. With that, we develop ten sets of experiments in order to hybridize the genomic DNA of representative species from the genus Copeina, Copella, Nannostomus, and Pyrrhulina in metaphase plates of Lebiasina melanoguttata. Two major pathways on the chromosomal evolution of these species can be recognized: (i) conservation of 2n = 36 bi-armed chromosomes in Lebiasininae, as a basal condition, and (ii) high numeric and structural chromosomal rearrangements in Pyrrhulininae, with a notable tendency towards acrocentrization. The ribosomal DNA (rDNA) distribution also revealed a marked differentiation during the chromosomal evolution of Lebiasinidae, since both single and multiple sites, in addition to a wide range of chromosomal locations can be found. With some few exceptions, the terminal position of 18S rDNA appears as a common feature in Lebiasinidae-analyzed species. Altogether with Ctenoluciidae, this pattern can be considered a symplesiomorphism for both families. In addition to the specific repetitive DNA content that characterizes the genome of each particular species, Lebiasina also keeps inter-specific repetitive sequences, thus reinforcing its proposed basal condition in Lebiasinidae.

Molecular Analysis and Chromosome Mapping of Repetitive DNAs in the Green Terror Andinoacara rivulatus (Cichlidae: Cichlasomatini).

Neotropical cichlids include hundreds of species whose taxonomy has benefited of molecular phylogeny and whose karyotype evolution has been related to the amount and distribution of different classes of repetitive sequences. This study provides the first integrative molecular (cytochrome c oxidase subunit 1 and 16S sequences) and cytogenetic analyses of wild samples of the green terror Andinoacara rivulatus, a cichlid naturally distributed in Ecuador and spread throughout the world as an aquarium pet. Molecular data revealed that sequences of green terror constitute a single monophyletic clade within the genus and allowed species attribution of uncertain samples previously cytogenetically analyzed. Chromosome number (2n = 48) conforms to the general trend observed within neotropical cichlids. However, mapping of different classes of repeated sequences (18S rDNA, 5S rDNA, U1 snDNA and telomeric) revealed the presence of features uncommon among representatives of these fishes, like multiple major rDNA sites, and suggested a recent occurrence of rearrangements (fusion/inversion) in two chromosome pairs.

Redescription of Mugil setosus Gilbert 1892 with comments on the occurrence of Mugil curema Valenciennes 1836 in the Pacific Ocean (Teleostei: Perciformes: Mugilidae).

Mugil setosus Gilbert 1892 was originally described by Gilbert based on specimens from Clarion Island, in the western and most remote of the Revillagigedo Islands, about 1,000 km off the western Pacific coast of Mexico. Examination of the type of material and recently collected specimens from Ecuador and Peru, resulted in the redescription provided herein. Diagnostic characters of the species were mainly: tip of the pelvic fin reaching beyond the vertical through the base of the third dorsal-fin spine, the pectoral-fin rays with ii+13-14 rays, the anterodorsal tip of second (soft) dorsal fin uniformly dark, and an external row of larger teeth, and more internally a patch of scattered smaller teeth, visible mainly in adults 150 mm SL. The expansion of geographic distribution of Mugil setosus and occurrence of Mugil curema Valenciennes 1836 in the Pacific Ocean are discussed.

Tilapia en Ecuador: paradoja entre la producción acuícola y la protección de la biodiversidad ecuatoriana / Tilapia in Ecuador: paradox between aquaculture production and the protection of Ecuadorian biodiversity

La tilapia es un pez dulceacuícola originario del África que posee muchas características que la convierten en un excelente pez para acuicultura, pero también es considerada como una de las especies exóticas invasoras más peligrosas del mundo debido a su adaptabilidad y potencial reproductivo. En este ensayo se analiza el dilema entre las bondades de estos peces como alternativa para contribuir con la seguridad agroalimentaria y la amenaza que representa para la biodiversidad acuática de Ecuador. La ausencia de información oficial hace necesario investigar el efecto de las invasiones por tilapia en los ríos, lagunas y esteros colonizados por esta especie. El nivel de acción para prevenir, erradicar o controlar la tilapia en Ecuador ha sido muy limitado y por lo tanto se impone la necesidad de establecer estrategias para evitar su propagación hacia áreas aún no invadidas. Aunque el gobierno de Ecuador posee regulaciones que restringen la introducción de especies exóticas, la realidad es que, en el caso de la tilapia, lejos de establecer controles adecuados, el cultivo de estos peces es impulsado sin mayores objeciones. Se discute la posibilidad de adoptar estrategias de control biológico para erradicar y/o mitigar las consecuencias de la invasión por tilapias en el país y la necesidad de fomentar campañas educativas para crear un nuevo comportamiento ambiental, conciencia y responsabilidad en la sociedad.

Tilapia is a freshwater fish native to Africa that has many characteristics that make it an excellent fish for aquaculture, but it is also considered one of the most dangerous invasive exotic species in the world due to its adaptability and reproductive potential. This essay analyzes the dilemma between the benefits of these fish as an alternative to contribute to agrifood security and the threat it poses to Ecuador's aquatic biodiversity. The absence of official information makes it necessary to investigate the effect of the invasions by tilapia in the rivers, lagoons and estuaries colonized by this species. The level of action to prevent, eradicate or control the tilapia in Ecuador has been very limited and therefore the need to establish strategies to prevent its spread to areas not yet invaded is imposed. Although the government of Ecuador has regulations that restrict the introduction of exotic species, the reality is that, in the case of the tilapia, far from establishing adequate controls, the culture of these fish is promoted without major objections. The possibility of adopting biocontrol strategies to eradicate and / or mitigate the consequences of the invasion by tilapia in the country and the need to promote educational campaigns to create a new environmental behavior, conscience and responsibility in society is discussed.

Genotoxic effects of mercury chloride on the Neotropical fish Andinoacara rivulatus (Cichlidae: Cichlasomatini)

Understanding the effects of heavy metals in aquatic ecosystems is of significant importance due to their potential to bioaccumulate at various trophic levels and induce damage in DNA. Mercury is considered one of the most dangerous heavy metals, causing chromosomal breakage (clastogenic event) or spindle dysfunction (aneugenic event), that can lead to the formation of encapsulated chromatin into a separate smaller nucleus, generally referred to as a micronucleus. We evaluated the sensitivity of the micronucleus test in the neotropical cichlid Andinoacara rivulatus (Günther 1860). The fish were divided into four groups of 16 individuals, and each group was placed in separate aquaria (140 L) provided with filtered water and constant aeration. Fish were exposed to mercury chloride (HgCl2) at doses 0.1, 0.25, and 0.50 mg/kg body weight, administered by intraperitoneal (IP) injection. Fish from the control group were injected with a physiologic solution. The following erythrocyte anomalies were identified: erythrocytes with micronuclei varying to some extent in size and position in the cytoplasm, blebbed nucleus, binucleated cell, nuclei showing a deep invagination toward the center (notched nuclei). Examination of blood smears demonstrated a higher level of micronucleus and notched erythrocytes in fish injected with HgCl2 than in the controls. There were significant differences in the frequency of micronucleated and notched erythrocytes among the groups exposed to mercury. Linear regression analysis revealed a positive relationship between the frequency of micronucleated and notched erythrocytes (P< 0.0001), with a moderately strong correlation coefficient (R= 0.737). We propose that, in addition to the two so far known mechanisms of micronucleus formation (spindle apparatus damage and chromosomal ruptures), chromatin fragmentation in notched nuclei resulting from a combination of the cytotoxic effects of mercury and mechanical stress, may be a third mechanism of micronuclei genesis.

Comprender los efectos de los metales pesados en los ecosistemas acuáticos es de gran importancia debido a su potencial de bioacumulación en los diversos niveles tróficos y de inducir daños en el ADN. El mercurio, considerado uno de los metales pesados más peligrosos, causa fracturas cromosómicas (evento clastogénico) o disfunción del huso mitótico (evento aneugénico), y puede conducir a la formación de fragmentos de cromatina encapsulada en un núcleo separado más pequeño, generalmente denominado micronúcleo. En este trabajo se evalúa la sensibilidad del test de micronúcleos en el cíclido neotropical Andinoacara rivulatus (Günther 1860). Los peces fueron divididos en cuatro grupos de 16 individuos, y cada grupo se colocó en acuarios separados (140 L) provistos de agua filtrada y aireación constante. Los peces fueron expuestos al cloruro de mercurio (HgCl2) en dosis de 0.1, 0.25 y 0.50 mg/kg de peso corporal, administrada por inyección intraperitoneal (IP). Los peces del grupo control fueron inyectados con solución fisiológica. Se identificaron las siguientes anomalías en los eritrocitos: micronúcleos que varían en tamaño y posición en el citoplasma, núcleo con evaginaciones, células binucleadas núcleos con muesca (núcleos con una profunda invaginación hacia el centro). El examen de los frotis de sangre demostró un mayor nivel de eritrocitos micronucleados y con muesca en peces inyectados con HgCl2 que en los controles. Fueron detectadas diferencias significativas en la frecuencia de eritrocitos micronucleados y células con núcleos con muescas entre los grupos expuestos al mercurio. El análisis de regresión lineal reveló una relación positiva entre la frecuencia de eritrocitos micronucleados y con muescas (P< 0.0001), con un coeficiente de correlación moderadamente fuerte (R= 0.737). Se propone que, además de los dos mecanismos hasta ahora conocidos de formación de micronúcleos (daño del huso mitótico y rupturas cromosómicas), la fragmentación de la cromatina en núcleos con muesca probablemente a causa de la combinación de los efectos citotóxicos del mercurio y el estrés mecánico, podría ser un tercer mecanismo de génesis de micronúcleos.

Chromosomal Evolution and Evolutionary Relationships of Lebiasina Species (Characiformes, Lebiasinidae).

We present the first cytogenetic data for Lebiasina bimaculata and L. melanoguttata with the aim of (1) investigating evolutionary events within Lebiasina and their relationships with other Lebiasinidae genera and (2) checking the evolutionary relationships between Lebiasinidae and Ctenoluciidae. Both species have a diploid number 2n = 36 with similar karyotypes and microsatellite distribution patterns but present contrasting C-positive heterochromatin and CMA3+ banding patterns. The remarkable interstitial series of C-positive heterochromatin occurring in L. melanoguttata is absent in L. bimaculata. Accordingly, L. bimaculata shows the ribosomal DNA sites as the only GC-rich (CMA3+) regions, while L. melanoguttata shows evidence of a clear intercalated CMA3+ banding pattern. In addition, the multiple 5S and 18S rDNA sites in L. melanogutatta contrast with single sites present in L. bimaculata. Comparative genomic hybridization (CGH) experiments also revealed a high level of genomic differentiation between both species. A polymorphic state of a conspicuous C-positive, CMA3+, and (CGG)n band was found only to occur in L. bimaculata females, and its possible relationship with a nascent sex chromosome system is discussed. Whole chromosome painting (WCP) and CGH experiments indicate that the Lebiasina species examined and Boulengerella maculata share similar chromosomal sequences, thus supporting the relatedness between them and the evolutionary relationships between the Lebiasinidae and Ctenoluciidae families.

Chromosomal polymorphism and molecular variability in the pearly razorfish Xyrichtys novacula (Labriformes, Labridae): taxonomic and biogeographic implications.

The pearly razorfish Xyrichtys novacula (Linnaeus, 1758) is a sedentary benthic species distributed in both sides of the Atlantic Ocean and in the Mediterranean Sea. Previous cytogenetic analysis reported different diploid numbers in samples from Italy, Venezuela and Brazil. This research aims to test the hypothesis that samples from American Atlantic coast and Mediterranean Sea belong to the same single evolutionary lineage, characterized by intra-specific chromosome polymorphism. To this purpose a cytogenetic and molecular (mitochondrial COI sequences) survey was undertaken. Results revealed the existence of three different pearly razorfish molecular lineages: one present in Mediterranean Sea and two in the central and south American area, which are characterized by different karyotypes. One of these lineages shows substantial intra-population chromosomal polymorphism (2n = 45-48) determined by Robertsonian fusions that produce large metacentric chromosomes. On the whole data suggest that specimens morphologically identified as X. novacula correspond to three cryptic species.

Identification of a New Mullet Species Complex Based on an Integrative Molecular and Cytogenetic Investigation of Mugil hospes (Mugilidae: Mugiliformes).

Mullets are very common fishes included in the family Mugilidae, (Mugiliformes), which are characterized by both a remarkably uniform external morphology and internal anatomy. Recently, within this family, different species complexes were molecularly identified within Mugil, a genus which is characterized by lineages that sometimes show very different karyotypes. Here we report the results of cytogenetic and molecular analyses conducted on Mugil hospes, commonly known as the hospe mullet, from Ecuador. The study aims to verify whether the original described species from the Pacific Ocean corresponds to that identified in the Atlantic Ocean, and to identify species-specific chromosome markers that can add new comparative data about Mugilidae karyotype evolution. The karyotype of M. hospes from Ecuador is composed of 48 acrocentric chromosomes and shows two active nucleolar organizer regions (NORs). In situ hybridization, using different types of repetitive sequences (rDNAs, U1 snDNA, telomeric repeats) as probes, identified species-specific chromosome markers that have been compared with those of other species of the genus Mugil. Cytochrome c oxidase subunit I (COI) sequence analysis shows only 92-93% similarity with sequences previously deposited under this species name in GenBank, all of which were from the Atlantic Ocean. Phylogenetic reconstructions indicate the presence of three well-supported hospe mullet lineages whose molecular divergence is compatible with the presence of distinct species. Indeed, the first lineage includes samples from Ecuador, whereas the other two lineages include the Atlantic samples and correspond to M. brevirostris from Brazil and Mugil sp. R from Belize/Venezuela. Results here provided reiterate the pivotal importance of an integrative molecular and cytogenetic approach in the reconstruction of the relationships within Mugilidae.

The Mugil curema species complex (Pisces, Mugilidae): a new karyotype for the Pacific white mullet mitochondrial lineage.

Recent molecular phylogenetic analyses have shown that the Mugil curema Valenciennes, 1836 species complex includes M. incilis Hancock, 1830, M. thoburni (Jordan & Starks, 1896) and at least four "M. curema" mitochondrial lineages, considered as cryptic species. The cytogenetic data on some representatives of the species complex have shown a high cytogenetic diversity. This research reports the results of cytogenetic and molecular analyses of white mullet collected in Ecuador. The analyzed specimens were molecularly assigned to the Mugil sp. O, the putative cryptic species present in the Pacific Ocean and showed a 2n = 46 karyotype, which is composed of 2 metacentric and 44 subtelocentric/acrocentric chromosomes. This karyotype is different from the one described for M. incilis (2n = 48) and from those of the two western Atlantic lineages Mugil curema (2n = 28), and Mugil margaritae (2n = 24). Data suggest the need for a morphological analysis to assign a species name to this Pacific lineage.

First description of the karyotype and localization of major and minor ribosomal genes in Rhoadsiaaltipinna Fowler, 1911 (Characiformes, Characidae) from Ecuador.

Karyotypic features of Rhoadsiaaltipinna Fowler, 1911 from Ecuador were investigated by examining metaphase chromosomes through Giemsa staining, C-banding, Ag-NOR, and two-color-fluorescence in situ hybridization (FISH) for mapping of 18S and 5S ribosomal genes. The species exhibit a karyotype with 2n = 50, composed of 10 metacentric, 26 submetacentric and 14 subtelocentric elements, with a fundamental number FN=86 and is characterized by the presence of a larger metacentric pair (number 1), which is about 2/3 longer than the average length of the rest of the metacentric series. Sex chromosomes were not observed. Heterochromatin is identifiable on 44 chromosomes, distributed in paracentromeric position near the centromere. The first metacentric pair presents two well-defined heterochromatic blocks in paracentromeric position, near the centromere. Impregnation with silver nitrate showed a single pair of Ag-positive NORs localized at terminal regions of the short arms of the subtelocentric chromosome pair number 12. FISH assay confirmed these localization of NORs and revealed that minor rDNA clusters occur interstitially on the larger metacentric pair number 1. Comparison of results here reported with those available on other Characidae permit to hypothesize that the presence of a very large metacentric pair might represent a unique and derived condition that characterize one of four major lineages molecularly identified in this family.

Taxonomic review of the species of Mugil (Teleostei: Perciformes: Mugilidae) from the Atlantic South Caribbean and South America, with integration of morphological, cytogenetic and molecular data.

Analysis of morphological, molecular and cytological data helped to define and more precisely characterize the species of Mugil from the Atlantic coasts of South Caribbean and South America, allowing a correction of prior misidentifications and distributional ranges. A new species from Venezuela is described and all the species from the area are redescribed. It is demonstrated that the apparent similarity in morphological traits, which contradicted the results from recent molecular studies, is the result of the misuse of traditional morphological characters, and thus both the molecular and cytological data instead are congruent with the morphological differences that are found among mullet species. The presence of Mugil hospes Jordan & Culver in the western south Atlantic is refuted based on the comparison of type material of this species with specimens from this area that also indicated a very significant morphological difference, what on the other hand justifies the recognition of these specimens as Mugil brevirostris (Ribeiro). The distribution of Mugil incilis Hancock is restricted and the similarities among the species formerly depicted in a prior dendrogram is modified following the inclusion of recently obtained molecular data for Mugil curvidens Valenciennes.

Karyotype of the invasive species Pterois volitans (Scorpaeniformes: Scorpaenidae) from Margarita Island, Venezuela / Cariotipo de la especie invasora Pterois volitans (Scorpaeniformes: Scorpaenidae) de Isla Margarita Island, Venezuela

The genus Pterois includes nine valid species, native to the Red Sea and Indian Ocean throughout the Western Pacific. P. volitans and P. miles are native to the Indo-Pacific, and were introduced into Florida waters as a result of aquarium releases, and have been recently recognized as invaders of the Western Atlantic and Caribbean Sea (Costa Rica to Venezuela). Thus far, cytogenetic studies of the genus Pterois only cover basic aspects of three species, including P. volitans from Indo-Pacific Ocean. Considering the lack of more detailed information about cytogenetic characteristics of this invasive species, the objective of the present study was to investigate the basic and molecular cytogenetic characteristics of P. volitans in Venezuela, and compare the results with those from the original distribution area. For this, the karyotypic characteristics of four lionfish caught in Margarita Island, Venezuela, were investigated by examining metaphase chromosomes by Giemsa staining, C-banding, Ag-NOR, and two-colour-Fluorescent in situ hybridization (FISH) for mapping of 18S and 5S ribosomal genes. Comparing the sequences of the 16S gene of the specimens analyzed, with sequences already included in the Genbank, we corroborated that our specimens identified as P. volitans are in fact this species, and hence exclude the possibility of a misidentification of P. miles. The diploid number was 2n=48 (2m+10sm+36a) with FN=60. Chromosomes uniformly decreased in size, making it difficult to clearly identify the homologues except for the only metacentric pair, and the pairs number two, the largest of the submetacentric series. C-banding revealed only three pairs of chromosomes negative for C-band, whereas all remaining chromosomes presented telomeric and some interstitial C-positive blocks. Only two chromosomes were C-banding positive at the pericentromeric regions. Sequential staining revealed Ag-NOR on the tips of the short arms of chromosome pair number two and the FISH assay revealed that 18S rDNA and 5S rDNA genes are co-located on this chromosome pair. The co-localization of 5S rDNA and 45S rDNA is discussed. Both constitutive heterochromatin and NOR location detected in samples examined in this study, differ from those reported for P. volitans in previous analysis of specimens collected in Indian Ocean (Java), suggesting the occurrence of chromosome microrearrangements involving heterochromatin during the spread of P. volitans.Rev. Biol. Trop. 62 (4): 1365-1373. Epub 2014 December 01.

El género Pterois contiene nueve especies válidas, nativas del Mar Rojo y el Océano Índico en el Pacífico occidental. P. volitans y P. miles son nativas del Indo-Pacífico, y fueron introducidas en las aguas de Florida como resultado de la liberación de peces confinados en acuario y han sido reconocidas recientemente como invasoras en el Atlántico Occidental y Mar Caribe (Costa Rica hasta Venezuela). Los estudios citogenéticos realizados hasta ahora en el género Pterois cubren solamente aspectos básicos de tres especies que incluyen a P. volitans del océano Indo-Pacífico. Debido a la ausencia de información detallada sobre las características cromosómicas de esta especie invasora, el objetivo del presente estudio fue investigar las características citogenéticas en ejemplares de Venezuela mediante técnicas convencionales y moleculares y comparar los resultados con los reportados para el área de distribución original. Para ello, se investigaron las características cariotípicas mediante tinción con Giemsa, bandeo-C, impregnación con Nitrato de Plata (Ag-NOR) e hibridación fluorescente in situ (FISH) dual para localizar los genes ribosomales 18S rDNA y 5S rDNA en cuatro ejemplares de pez león capturados en la Isla Margarita, Venezuela. La comparación de secuencias del gen 16S de los especímenes analizados con secuencias ya incluidas en el Genbank permitieron corroborar la identificación de P. volitans excluyendo así la posibilidad de una identificación errónea de P. miles. El número diploide fue 2n=48 (2m+10sm+36a) con un FN=60. Los cromosomas presentaron tamaños que disminuyen de manera uniforme dificultando la identificación de homólogos, excepto el único par metacéntrico y el par cromosómico número 2. El bandeo-C reveló tres pares de cromosomas bandas-C negativos, mientras que los restantes presentaron bloques bandas-C positivos en posición telomérica y, en algunos casos, intersticial. Sólo dos cromosomas mostraron bandas-C pericentroméricas. La tinción secuencial reveló las Ag-NOR localizadas en los extremos de los brazos cortos del par número dos y el ensayo FISH demostró que los genes 18S rDNA y 5S rDNA se localizan en ese mismo par. Se discute la co-localización de los genes 5S rDNA y 18S rDNA. La distribución de la heterocromatina constitutiva y localización de las NORs en los peces examinados difirió de la reportada para ejemplares de P. volitans del Océano Índico (Java), sugiriendo que durante la propagación de P. volitans han ocurrido reorganizaciones cromosómicas que involucran la heterocromatina.

Chromosome evolution in fishes: a new challenging proposal from Neotropical species

We present a database containing cytogenetic data of Neotropical actinopterygian fishes from Venezuela obtained in a single laboratory for the first time. The results of this study include 103 species belonging to 74 genera assigned to 45 families and 17 out of the 40 teleost orders. In the group of marine fishes, the modal diploid number was 2n=48 represented in 60% of the studied species, while in the freshwater fish group the modal diploid complement was 2n=54, represented in 21.21 % of the studied species. The average number of chromosomes and the mean FN were statistically higher in freshwater fish than in marine fish. The degree of diversification and karyotype variation was also higher in freshwater fish in contrast to a more conserved cytogenetic pattern in marine fish. In contrast to the assumption according to which 48 acrocentric chromosomes was basal chromosome number in fish, data here presented show that there is an obvious trend towards the reduction of the diploid number of chromosomes from values near 2n=60 with high number of biarmed chromosomes in more basal species to 2n=48 acrocentric elements in more derived Actinopterygii.

Se presenta una base de datos que contiene los datos citogenéticos de peces Actinopterigios Neotropicales de Venezuela obtenidos por primera vez en un solo laboratorio. Los resultados de este estudio incluyen 103 especies pertenecientes a 74 géneros de 45 familias contenidas en 17 de los 40 órdenes de teleósteos. En el grupo de peces marinos, el número diploide modal fue 2n=48 representado en 60% de las especies estudiadas, mientras que en el grupo de peces de agua dulce el complemento diploide modal fue 2n=54, representado en el 21,21% de las especies estudiadas. El número de cromosomas y FN promedio fueron estadísticamente superiores en peces dulceacuícolas. El grado de diversificación y variación en el cariotipo también fue mayor en peces de agua dulce en contraste con un patrón citogenético más conservado en peces marinos. En contraposición a la suposición según la cual 48 cromosomas acrocentricos era el número cromosómico basal en los peces, los datos aquí presentados muestran que existe una evidente tendencia hacia la reducción del número de cromosomas desde valores cercanos a 2n=60 con alto número de cromosomas birrámeos en las especies más basales a 2n=48 elementos acrocéntricos en los actinopterigios más derivados.

Efecto de la congelación y cocción sobre la textura y patrón electroforético de las proteínas de brazos de pulpo (Octopus vulgaris) / Effect of freezing and cooking on the texture and electrophoretic pattern of the proteins of octopus arms (Octopus vulgaris)

La textura es la característica más valorada en los cefalópodos. Los factores que principalmente afectan la textura del pulpo son congelación, escaldado y cocción. El objetivo de esta investigación fue evaluar el efecto de la congelación, escaldado y diferentes tiempos de cocción sobre la textura y perfil electroforético de las proteínas de brazos de pulpo (Octopus vulgaris). Los ejemplares fueron capturados con nasa en las cercanías de la Isla de Margarita y transportados al laboratorio, donde fueron empacados y sometidos a: a) congelación a -27°C ó a -20 °C b) escaldado o no escaldado c) cocción por 25, 35 ó 45 min. Se determinó la fuerza de corte sobre tiras de brazo de pulpo mediante celda de Kramer. Extractos de proteínas fueron sometidos a electroforesis en gel de poliacrilamida-dodecil sulfato de sodio (SDS-PAGE) al 12 % según método Laemmli. Fue realizada evaluación sensorial de la preferencia de la textura empleando escala hedónica de 7 puntos y panel no entrenado. La textura del pulpo no resultó afectada ni por la temperatura de congelación ni el escaldado. El pulpo congelado, al cocerlo, fue más blando que el fresco. En la medida que aumentó el tiempo de cocción, el pulpo se ablandó más. La cocción no afectó significativamente la cadena pesada de miosina (MHC) (205 kD); sin embargo, causó aparición de agregados proteínicos más pesados, nuevas bandas y pérdida de definición de bandas. Las fracciones de miosina y de paramiosina resultaron más afectadas cuando el pulpo fue congelado previo a la cocción.

Texture is the most valuable feature in cephalopods. Factors that mainly affect the texture of octopus are: freezing, scalding and cooking. The aim of this study was to assess the effect of freezing, scalding and length of cooking time on the texture and electrophoretic pattern of proteins of octopus arms. Octopuses were trapped near Margarita Island and carried with ice to the laboratory where they were packed and subjected to: a) freezing at -27°C or at -20 °C b) scalding c) cooking for 25 min, 35 min or 45 min. Shear force was determined by Kramer cell on strips of octopus arms. SDS-PAGE was done according to the Laemmli method with 12% polyacrilamide gels. A sensory evaluation of the preference of texture was carried out using a hedonic scale of 7-points and a non-trained panel. Octopus texture was not affected by freezing temperature or scalding. Frozen octopus was softer after cooking than fresh. The longer the cooking time was, the softer the octopus was. Myosin heavy chain (MHC) was not significantly affected by scalding or cooking; however large aggregates heavier than MHC, new bands and loss of resolution of the bands appeared. Myosin and paramyosin bands were more affected by freezing prior to cooking.