Molecular phylogenetic analyses of mullets (Mugilidae, Mugiliformes) based on two mitochondrial genes

Molecular phylogenetic studies are very scarce for the Mugilidae family; the present analysis using DNA sequences of the mitochondrial 16S rRNA and cytochrome b genes is the first study involving Brazilian mugilids. The results corroborate the monophyly of Mugil and are elucidative for the taxonomy of Brazilian mugilids. Mugil curema is clearly divided into two genetically distinct taxa, M. curema type I being closer related to Mugil hospes and the true M. curema (type II) grouping significantly with M. incilis. The results also suggest that Mugil liza and Mugil platanus should be treated as a single species or even populations of Mugil cephalus.     

Case study: Comparing the use of nonlinear discriminating analysis and Artificial Neural Networks in the classification of three fish species: acaras (Geophagus brasiliensis), tilapias (Tilapia rendalli) and mullets (Mugil liza)

This study used the Discriminant Analysis statistical technique and Artificial Neural Networks, multilayer perceptron, in the classification of three fish species sampled in the state of Rio de Janeiro, Brazil: Geophagus brasiliensis (acaras), Tilapia rendall (tilapias) and Mugil liza (mullets). These fish were sexed when possible, weighed, measured, and had their Gonadosomatic and Hepatosomatic Indices calculated, as well as their Condition Factor. The use of an Artificial Neural Network (ANN) presented satisfactory results, even though the groups were composed of very diverse-sized animals. Without the need for non-violation assumptions and other considerations, the Artificial Neural Network was found to be the excellent alternative to classification problems of unbalanced data, such as the one presented in this study.     

Migration and reproductive biology of Mugil liza (Teleostei: Mugilidae) in south Brazil

The mullet Mugil liza occurs along the Atlantic coast of South America from Venezuela to Argentina, but 95% of the commercial catch is collected from south Brazil between São Paulo and Argentina. Mugil liza is a single spawner with oocyte development occurring synchronously in two groups. Spawning happens in marine areas and occurs after migration. The reproductive migration occurs from Argentina (38° S) to the southern Brazilian states (24–26° S) from April to July, with peak spawning in June between northern Santa Catarina and Paraná. The presence of hyaline oocytes was associated with high salinity and sea surface temperatures of 19–21° C, and followed the seasonal northward displacement of these oceanographic conditions. The average size at first maturity (L_m) for both sexes was 408·3 mm total length, L_T. Males (L_m = 400·1) matured earlier than females (L_m = 421·9 mm). Fecundity ranged from 818 992 to 2 869 767 oocytes (mean = 1 624 551) in fish that were between 426 and 660 mm L_T.     

Ultrastructure of the tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955 (Monogenea, Microcotylidae).

The ultrastructure of the body tegument of Metamicrocotyla macracantha (Alexander, 1954) Koratha, 1955, parasite of Mugil liza from Brazil, was studied by transmission electron microscopy. The body tegument is composed of an external syncytial layer, musculature, and an inner layer containing tegumental cells. The syncytium consists of a matrix containing three types of body inclusions and mitochondria. The musculature is constituted of several layers of longitudinal and circular muscle fibers. The tegumental cells present a well-developed nucleus, cytoplasm filled with ribosomes, rough endoplasmatic reticulum and mitochondria, and characteristic organelles of tegumental cells.     

Coastal zone use and migratory behaviour of the southern population of Mugil liza in Brazil

We analysed the ratios Sr:Ca and Ba:Ca in the otoliths of 55 adults of the southern population of Mugil liza in Brazil (Paraná to Rio Grande do Sul) to investigate its coastal zone use and migratory behaviour. All individual M. liza analysed had Sr:Ca and Ba:Ca values indicating that their birth was in the marine environment, which is consistent with the southern population migration to spawn in the ocean,. Juveniles exhibited at least three coastal use and recruitment strategies (contingents): the majority (89%) of M. liza juveniles migrated toward brackish water. They entered the estuary before completing the first year of life (64%) or after (25%) their first year of life. The remaining 11% did not appear to enter brackish or freshwater water as a nursery or at any point in their life cycle. Some adults returned to the estuary after spawning in the ocean but others (of both sexes) never returned to the estuary after spawning, remaining in the marine environment. The pattern of juvenile habitat use in the Brazilian southern population of M. liza seems to be recurrent throughout the extent of its distribution as a consequence of the reproductive spawning aggregation behaviour, which mixes all contingents (with marine or estuarine preferences).     

Morphological and morphometric changes of sagittae otoliths related to fish growth in three Mugilidae species

The aim of this study was to analyze morphologic and morphometric changes of sagittae otoliths throughout the growth of three mullets: Mugil liza, Mugil cephalus and Liza ramada. Fish were collected seasonally between October 2011 and April 2014, and three methods were used: regression analysis of traditional biometric characters; morphological analysis for group identification; and morphometrical analysis of shape indices among groups (circularity, rectangularity, aspect ratio and percentage occupied by the sulcus). In all species, dependence of standard length on otolith length and height were best described as power functions. Two morphological groups were identified for M. liza and M. cephalus, while three for L. ramada. Morphological changes were supported by morphometry differences only for the first two species. Smaller size specimens of M. liza had more rectangular otoliths with more percentage covered by the sulcus while bigger fish tended to have a more circular shape. For M. cephalus smaller size fish had a more elliptical shape. The observed changes may be reflecting life history changes, related to habitat or dietary shifting.     

Seasonal growth of Mugil liza Valenciennes, 1836 in a tropical estuarine system

Seasonal changes in the abiotic factors and cyclical events – with the reproduction diagnosed by the gonadosomatic index and the energy status diagnosed by the condition index – were estimators of seasonal growth for juvenile and adult lebranche mullets, Mugil liza, during the rainy and dry seasons in a tropical estuarine system of the western south Atlantic. Fish were collected monthly by gillnets of different mesh sizes. Salinity, water temperature (°C) and dissolved oxygen (%) were measured using a multiparameter. Daily rainfall data (mm) were obtained from the National Institute of Meteorology. Seasonal rings were identified and counted in the sagittae otoliths. Relative Marginal Increment (RMI) was calculated to determine the seasonal growth rate. Gonadosomatic Index (GSI) and Condition Index (CI) were assessed separately for juveniles and adults by anova , with time (month) M. liza growth is controlled by annual cycles of biological and abiotic processes. Using general linear models, the seasonal growth rate of M. liza was well predicted by body condition and rainfall for juveniles, and by salinity for adults. Seasonal variation was observed in the Mundaú Lagoon, with rainfall directly or indirectly being the main seasonal factor influencing the cyclical biological fish processes of M. liza.     

Comparative Molecular Cytogenetic Analysis of Two Congeneric Species, <Emphasis Type="Italic">Mugil Curema</Emphasis> and <Emphasis Type="Italic">M. Liza</Emphasis> (Pisces,Mugiliformes), Characterized by Significant Karyotype Diversity

Two congeneric mullet species, Mugil liza and M. curema, respectively with an all-uniarmed and an all-biarmed karyotype, were cytogenetically studied by base-specific fluorochrome staining and FISH-mapping of 45S and 5S ribosomal RNA genes (rDNA) and the (TTAGGG)_n telomeric repeats. Whereas 45S rDNA sites might be homeologus in the two species, 5S rDNA sites are not, as they are localized on chromosome arms of different size. In both species, the (TTAGGG)_n telomeric probe hybridized to natural telomeres and was found scattered along the NORs. In metacentric chromosomes of M. curema, no pericentromeric signals of the telomeric probe were detected. Data are discussed in relation to the karyotype evolution in Mugilidae and to the mechanisms and the evolutionary implications of Robertsonian rearrangements in M. curema.     

Length–weight relationships of two mugilid species from tropical estuarine systems in Alagoas,northeastern coast of Brazil

Length‐weight relationships were estimated for two mugilid species from estuarine systems in Alagoas, northeastern Brazil. Fish were sampled monthly using nylon monofilament gillnets with different mesh sizes during two fishery surveys. The first LWR reference for Mugil curvidens and new maximum lengths for both M. rubioculus and M. curvidens are provided.     

Mitochondrial DNA divergence and phylogenetic relationships in mullets (Pisces: Mugilidae) of the Sea of Japan and the Sea of Azov revealed by PCR-RFLP-analysis

Three Mugilid species: Mugil cephalus (Linnaeus, 1758) and Liza haematocheila (Temminck et Schlegel, 1845; syn. Mugil soiuy, M. haematocheilus, L. soiuy, Chelon haematocheilus) from the Sea of Japan, as well as M. cephalus and Liza aurata (Risso, 1810) from the Sea of Azov were investigated on the basis of PCR-RFLP analysis of mitochondrial DNA (mtDNA) fragments, which included 12S/16S rRNA, and ND3/ND4L/ND4 genes. Among 61 individuals of three Mugilid species thirteen different haplotypes were detected. Eight and thirteen restriction endonucleases were found to be species-specific in 12S/16SrRNA and ND3/ND4L/ND4 respectively. This method may be useful for species identification. M. cephalus showed the largest genetic divergence while L. haematocheila and L. aurata were closely related and clustered together. The level of mtDNA differentiation between the two M. cephalus samples from the Sea of Japan and the Sea of Azov, i.e., nucleotide substitutions of approximately 3%, appeared to be relatively high.     

Strengthening Myriostoma (Geastraceae,Basidiomycota) diversity: Myriostoma australianum sp. nov

A new species in the genus Myriostoma (Geastraceae, Basidiomycota) is described from Australia. Phylogenetic analyses of the internal transcribed spacer (ITS) and large subunit (LSU) of nuclear ribosomal DNA, as well as morphological data are evidence that the new species, Myriostoma australianum, is closely related to M. capillisporum from South Africa. Additional collections under M. coliforme from Brazil and USA (New Mexico) were analyzed and confirmed as belonging to M. calongei.     

Molecular phylogeny of Mugilidae fishes revised

Systematics derived from morphological characters often does not correspond with the evolutionary processes underlying the divergence within a group of organisms. In the family Mugilidae (Teleostei) morphological similarities have resulted in inconsistencies between taxonomy and phylogeny among its species, and particularly for the genera Mugil, Liza and Chelon where both intrageneric and intergeneric phylogenetic clarifications are needed. To address these issues, the direct sequencing of the mitochondrial region that encodes Phenylalanine (69 bp), 12S rRNA (842 bp), cytochrome c oxidase subunit I (651 bp) and cytochrome b (702 bp) was carried out. The data reveal that Mugil platanus and Mugil liza represent a continuum of a single species, closely related to but distinct from Mugil cephalus which itself appears to comprise a grouping of multiple and closely related species. This species complex was genetically distinct from Mugil curema, which, based on three clearly diverged species identified in this study along the Atlantic coast of the Americas, requires extensive taxonomic revision throughout its world-wide distribution. Unlike the monophyly supported within Mugil, relationships within Liza are paraphyletic, and a taxonomic revision of the genera Liza, Chelon and Oedalechilus is needed.     

Elemental turnover rates and trophic discrimination in juvenile Lebranche mullet Mugil liza under experimental conditions

The aim of this study was to determine the isotopic‐turnover rate (R_IT) and trophic‐discrimination factor (F_TD) in muscle tissues of Lebranche mullet Mugil liza fed an experimental diet (δ¹³C = ?27·1‰; δ¹⁵N = 1·0‰). Juvenile M. liza exhibited a relatively fast R_IT, with a half‐life (t₅₀) of only 16 and 14 days for δ¹³C and δ¹⁵N respectively and a nearly complete isotopic turnover (t₉₅) of 68 and 60 days for δ¹³C and δ¹⁵N.     

Effect of dietary dextrin levels on the growth performance,blood chemistry,body composition,hepatic triglicerides and glycogen of Lebranche mullet juveniles (Mugil liza Valenciennes 1836, Mugilidae)

The effects of increasing levels of dietary dextrin on growth performance, body composition, blood chemistry and hepatic triglycerides and glycogen levels were evaluated for juvenile Lebranche mullet, Mugil liza Valenciennes 1836, Mugilidae). Five diets were formulated to be isonitrogenous (350 g kg^?1) and isolipidic (6 g kg^?1) with increasing dextrin levels (D150: 150 g kg^?1; D200: 200 g kg^?1; D250: 250 g kg^?1; D300: 300 g kg^?1; D350: 350 g kg^?1). The experimental diets were offered to the fish for 34 days, four times per day, until apparent satiation. Each treatment was tested in triplicate, with nine fish per tank (mean weight 4.69 ± 0.31 g). Fish were reared in a recirculating aquatic system of 15 fibreglass tanks each containing 50 L of saltwater. Growth parameters and body composition of the mullets were not significantly affected (P > 0.05) by the dietary treatments. Plasma glucose concentration declined (P < 0.05) when dietary dextrin increased from D250 to D300, but recovered to the previous values (in reference to D150 and D200) when fish were fed with D350. Glycated haemoglobin, plasma proteins, triglycerides and cholesterol showed no significant differences among these treatments. Hepatic glycogen reached a maximum in treatment D250, followed by D350, D200 and D300, with the lowest concentration of liver glycogen found in D150 (P < 0.05). The concentration of liver triglycerides showed an increase (P < 0.05) in treatments D300 and D350 compared with D200. In conclusion, Mugil liza juveniles can be fed diets with high levels of dietary dextrin with no deleterious effects to their growth or plasma biochemistry, hepatic glycogen or triglycerides.     

Morphologic and Genetic Evidence for Mixed Infection with Two Myxobolus Species (Myxozoa: Myxobolidae) in Gray Mullets,Mugil cephalus,from Korean Waters

The present study was performed to trace the decisive evidence for mixed infection of 2 Myxobolus species, M. episquamalis and Myxobolus sp., in the gray mullet, Mugil cephalus, from Korean waters. Mullets with whitish cyst-like plasmodia on their scales were collected near a sewage plant in Yeosu, southern part of Korea, in 2009. The cysts were mainly located on scales and also found in the intestine. The spores from scales were oval in a frontal view, tapering anteriorly to a blunt apex, and measured 7.2 µm (5.8-8.0) in length and 5.3 µm (4.7-6.1) in width. Two polar capsules were pyriform and extended over the anterior half of the spore, measuring 3.5 µm (2.3-4.8) in length and 2.0 µm (1.5-2.2) in width. In contrast, the spores from the intestine were ellipsoidal, 10.4 µm (9.0-11.9) in length and 8.4 µm (7.3-10.1) in width. The polar capsules were pyriform but did not extend over the anterior half of the spore, 3.7 µm (2.5-4.5) in length and 2.2 µm (1.8-2.9) in width. The nucleotide sequences of the 18S rDNA gene of the 2 myxosporean spores from scales and intestine showed 88.1% identity to each other and 100% identity with M. episquamalis and 94.5% identity with M. spinacurvatura from mullet, respectively. By the above findings, it is first confirmed that mullets from the Korean water are infected with 2 myxosporean species, M. episquamalis and Myxobolus sp.     

Understanding the early ontogenetic stages of Mugil liza (Mugilidae): Morphological traits and digestive/metabolic profile of pre-juveniles after recruitment

The family Mugilidae consists mainly of diadromous species, whose reproduction occurs in offshore waters. Pre-juveniles shift their diet in the surf zone (zooplanktophagous to iliophagous). Later, during their recruitment into estuaries, huge changes take place in their digestive system. However, digestive and metabolic characteristics and some morphological traits at recruitment are unknown for Mugilidae. We performed comparative studies on early and late pre-juveniles of Mugil liza recruited in Mar Chiquita Coastal Lagoon (37°32′–37°45′S, 57°19′–57°26′W, Argentina). We determined digestive enzyme activities (intestine), energy reserves (liver/muscle), total/standard length, total weight, intestinal coefficient, hepatosomatic index and retroperitoneal fat. Pre-juveniles exhibited amylase, maltase, sucrase, lipase, trypsin and aminopeptidase-N (APN) activities, which were maintained over a wide range of pH and temperature, and exhibited Michaelis–Menten kinetics. In late pre-juveniles, amylase (422 ± 131 μmol maltose min⁻¹ mgprot⁻¹), sucrase (86 ± 14 mg glucose min⁻¹ mgprot⁻¹), trypsin (84 ± 9 μmoles min⁻¹ mgprot⁻¹) and APN (0.58 ± 0.08 μmoles min⁻¹ mgprot⁻¹) activities were higher (42%, 28%, 35% and 28%, respectively) than in the early stage. Also, the intestinal coefficient was higher in late (3.04) compared to early (2.06) pre-juveniles. Moreover, the liver appeared to be a main site of glycogen and triglyceride storage in late pre-juveniles, muscle being the site of storage in early pre-juveniles, exhibiting higher glycogen, free glucose and protein concentrations (92%, 82%, 32%, respectively). The results suggest that pre-juveniles of M. liza exhibit an adequate digestive battery to perform complete hydrolysis of various dietary substrates, availability of energy reserves and morphological characteristics to support their feeding habit and growth after recruitment. Our results represent an important contribution to knowledge of the ecology and digestive physiology of pre-juveniles of Mugilidae in the wild.     

Distributional Patterns of Chacoan Water Bugs (Heteroptera: Belostomatidae,Corixidae, Micronectidae and Gerridae)

Distributional patterns of South American species of aquatic and semiaquatic Heteroptera from the Chaco biogeographic province were analyzed. Based on a track analysis of 60 species of Belostomatidae, Corixidae, Micronectidae, and Gerridae, five generalized tracks were found:(1) Bolivia, and northwestern and central Argentina (Belostoma dallasi, Ectemnostega montana, E. quechua, E. stridulata, E. venturii, Sigara tucma, S. yala, Tenagobia pulchra, Eurygerris fuscinervis, and Trepobates taylori); (2) southern Brazil, eastern Bolivia, Paraguay, and northeastern Argentina (Belostoma bosqi, Heterocorixa brasiliensis, Tenagobia selecta tarahui, and T. schadei); (3) southeastern Brazil and northeastern Argentina, determined by Belostoma candidulum, B. testaceopallidum, Heterocorixa nigra, Sigara hungerfordi, Brachymetra furva,Halobatopsis spiniventris, Metrobates plaumanni plaumanni, and M. vigilis; (4) southeastern Brazil, Uruguay, and central western Argentina (Belostoma cummingsi, B. martini, Sigara argentiniensis, Tenagobia fuscata, and T. carapachay); and (5) southern (Trichocorixa milicorum, Sigara santiagiensis, and S. forciceps). Three panbiogeographic nodes have been determined:(1) northeastern Argentina, in the intersection of generalized tracks 2 and 3; (2) central Argentina, in the intersection of generalized tracks 1 and 4; and (3) central Argentina, in the intersection of generalized tracks 4 and 5. In spite of these complex patterns, these results show that the Chaco province appears to be a natural biogeographic area.