Scielo RSS <![CDATA[Latin american journal of aquatic research]]> vol. 50 num. 5 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Reproductive dynamics of <em>Peprilus medius</em> captured in the Ecuadorian Pacific]]> ABSTRACT. In Ecuador, Peprilus medius is an important fishery resource whose destination is for local consumption and export. There are few local studies on its reproductive biology, and its capture is not regulated. Therefore, this study evaluates the most relevant aspects of its reproductive activity. Samples were obtained monthly from January to December 2017 from the capture of the purse seine fleet and the artisanal gillnet fleet landing near Manta. The morphometric analysis included the length-weight relationship, estimated using the allometry equation. The size at sexual maturity is based on the L50 criterion; the reproductive cycle was determined according to the monthly analyses of the gonadosomatic index (GSI), hepatosomatic index (HSI), and relative condition factor (Kn). A total of 334 specimens were analyzed, with average sizes of 22.0, 21.87, and 21.91 cm of total length (TL), for males, females, and combined sexes, respectively. Sex ratio was 1.17M: 1F (P &gt; 0.05), while the length-weight relationship showed negative allometric growth for both males and females (b = 2.58; CI95% 2.48-2.72). Size at sexual maturity L50 was estimated at 21.84 and 21.23 cm TL for males and females, respectively. The GSI and HSI values and Kn showed significant differences among months (P &lt; 0.05), with a marked seasonality during the single reproductive period. Mean size at first capture of 21 cm TL is recommended. <![CDATA[New records of elasmobranchs (Vertebrata: Elasmobranchii) from the southwestern Gulf of Mexico]]> ABSTRACT. We present information about new records of 11 species of chondrichthyans in the southern Gulf of Mexico, adding information about new specimens and occurrence of the species in Mexican waters. The second record of the Bathytoshia centroura, Mustelus sinusmexicanus, Mobula hypostoma and Squalus clarkae species for Mexico is presented, as well as new records in marine areas and the Lagoon Alvarado system corresponding to Hexanchus vitulus, Heptranchrias perlo, Scyliorhinus retifer and Squalus cubensis. In this paper increase the number of records for species of elasmobranchs to the southwestern region of the Gulf of Mexico, increase the distribution range and knowledge about the chondrichthyofauna of Mexico. <![CDATA[Effects of temperature, pH, and photoperiod on the performance of a freshwater cladoceran <em>Moina micrura</em> culture enriched with <em>Lysinibacillus fusiformis</em> and <em>Bacillus pocheonensis</em>]]> ABSTRACT. The freshwater cladoceran Moina micrura has tremendous potential for mass culture as a live feed for larviculture. This study aimed to evaluate the efficacy of probiotics Lysinibacillus fusiformis A1 and Bacillus pocheonensis S2 in enhancing the population density, growth rate, and production of M. micrura under different environmental conditions. Four different temperatures (15, 20, 25, and 30°C), pH levels (4, 6, 8, and 10), and photoperiods (4L:20D, 6L:18D, 8L:16D, and 12L:12D) were set up. The daily number of individuals incubated under each environmental parameter was monitored for 12 days to determine the population density and growth rate of M. micrura. Meanwhile, the daily number of neonates from five females kept under respective environmental parameters was monitored until they died naturally. Probiotics were added individually at 5×104 CFU mL-1 twice during the first and sixth days of the experiment. M. micrura enriched with B. pocheonensis S2 at 30°C had the highest maximum population density (10 ± 0.2 ind mL-1) and the number of neonates produced (132 ± 6.43 ind), whereas treatment at 20°C had the best growth rate (0.1863 ± 0.006 d-1). M. micrura incubated with B. pocheonensis S2 at a normal photoperiod of 12L:12D had the highest maximum population density (10 ± 0.3 ind mL-1) and the number of neonates produced (129 ± 4.58 ind) while incubation at 8L:16D had the best growth rate (0.2879 ± 0.0007 d-1). M. micrura enriched with L. fusiformis A1 at pH 8 had the highest maximum population density (11 ± 0.8 ind mL-1), growth rate (0.5508 ± 0.04 d-1), and the number of neonates produced (129 ± 4.36 ind). Results recommend that a warmer temperature of 30°C, alkaline pH from 8 to 10, and a normal photoperiod of 12L:12D can be adopted for M. micrura enrichment with B. pocheonensis S2 to maximize its productivity for aquaculture use. <![CDATA[New records of nematodes from three aquatic mammals in Mexico with notes about the nematode fauna recorded in Mexican waters]]> ABSTRACT. Nematodes are among the most common parasites in aquatic mammals. Because of their cuticular covering, these worms are frequently collected from the examination of feces or stranded hosts. This work provides new records of three nematode taxa infecting three different aquatic mammal species (Lontra longicaudis annectens, Trichechus manatus, and Zalophus californianus) in Mexico. Additionally, it brings together all available published records about this country's nematode fauna parasitizing aquatic mammals. The aim is to describe the current state of the art, which sets the basis for the strategic design of future research. Given the diversity of printed sources recording nematode fauna, we gathered literature, including theses and articles in journals profiled in the Journal Citation Reports or similar academic databases. The compiled information shows that 24 nominal nematode taxa have been reported from 11 species of aquatic mammals in Mexico. Our study exhibits irregular patterns of geographic distribution and host spectrum, existing entire marine ecoregions, and numerous host species lacking records. <![CDATA[Two-year monitoring of enterovirus and rotavirus A in recreational freshwater from an island region, Pará State, northern Brazil]]> ABSTRACT. Enteric viruses are major causes of waterborne diseases and are present in large quantities in the stools of infected individuals. Its viability in the environment lasts for months, favoring the contamination of water used for consumption and recreation. The study aimed to monitor monthly the circulation of enterovirus (EV) and group A rotavirus (RVA) in recreational freshwater from an island region used as a bathhouse in northern Brazil, from January 2012 to December 2013. The viral RNA was obtained using guanidine isothiocyanate/silica after viral concentration by adsorption-elution method. The molecular detection was carried out by semi (EV) and nested-PCR (RVA) and the amplicons were sequenced on automated sequencer. At least one of these viruses was detected on 40.4% (42/104) of the samples. RVA was the most frequent (n = 32; 30.8%) when compared to EV (n = 20; 19.2%). Co-circulation between both was identified in 9.6% (n = 10). The highest viral positivity was found in SP02 (46.1%). The highest viral positivity was observed during high tides (57.7%; 60/104). Most EV samples were characterized as coxsackievirus (CV) A5 (85.7%, 12/14) and others as Sabin 1 poliovirus (14.2%, 2/14). The RVA positive samples were genotyped as G2, G3, G9, G12, P[8], P[4], and P[6]. These viruses were detected in 35.6% (37/104) of the samples with an acceptable concentration of fecal coliform bacteria. These results demonstrate the contamination of surface water intended for recreation by enteric viruses of Public Health concern even when bacterial indicators are within the tolerated limit, a factor that confirms the need for public policies aimed the sewage treatment before its release into water bodies. <![CDATA[<em>Leocrates ernstehlersi</em> n. sp. (Polychaeta: Hesionidae), a new species from Juan Fernández Archipelago, Chile]]> ABSTRACT. The genus Leocrates is currently made up of 11 nominal species, of which Leocrates chinensisKinberg, 1866 is the type species. Kinberg's original description is brief, and the diagnostic morphological characters are poorly defined. Therefore, numerous subsequent records in different world regions have been considered doubtful. Numerous specimens of Leocrates collected by SCUBA diving in various locations of Robinson Crusoe Island (33°37′S, 78°51′W) in the Juan Fernández Archipelago, between 4 and 10 m depth were examined and determined as a new species herein named Leocrates ernstehlersi n. sp. It is characterized by the size of anterior and posterior eyes, the median chaetigers with scarce notochaetae and neurochaetae per bundle; neurochaetal blades are 4-14 times longer than wide and neuracicular lobes slightly longer than wide. A key to identifying species of Leocrates having large anterior eyes and anterior eyes/prostomial width ratio between 1/4 to 1/8 is also included. <![CDATA[The cohabitation of Chinook salmon (<em>Oncorhynchus tshawytscha</em>) with trout populations in two important recreational fishing rivers in southern Chile]]> ABSTRACT. A study was carried out on two important recreational fishing rivers in southern Chile, the Petrohué and the Puelo, to assess the population structure of the salmonid species inhabiting both rivers. Five river sectors were surveyed on four dates between April 2016 and February 2017. In the Petrohué River, 2400 fish were sampled (42.9% rainbow trout Oncorhynchus mykiss; 23.8% brown trout Salmo trutta, and 33.3% Chinook salmon Oncorhynchus tshawytscha), while in the Puelo River, 1972 fish were examined (51.6% rainbow trout; 30.4% brown trout and 18% Chinook salmon). Fry and fingerling stages accounted for the highest proportion of fish collected by electrofishing. In the Petrohué and Puelo rivers, rainbow trout fry and fingerlings represented 96.3 and 99.2% of the fish sampled, respectively; 96.8 and 97.1% in the case of brown trout, while for Chinook salmon, parr and pre-smolts represented 97% of the fish examined in the Petrohué River and 98.3% in the Puelo River. Rainbow and brown trout shared the same habitats and food items in both rivers, and the two oldest trout recorded 5+ and 6+years. Parr and pre-smolt Chinook salmon were present mainly in the winter and spring seasons and were aged 1+ and 2+, respectively. There were no differences in the food items recorded from the juvenile fish sampled in both rivers. The mature, returning adult Chinook salmon aged between 1.5+ and 1.6+ years were devoid of food and were recorded over the autumn season with the highest abundance in the Petrohué River. The study did not identify any adverse competition or negative interactions among the three main salmonid species sharing the same habitat. <![CDATA[Yeast <em>Rhodoturula glutinis</em> as a modulator of innate immune and oxidative stress-related genes in <em>Oreochromis niloticus</em> cultured in a Biofloc system]]> ABSTRACT. The effect of live yeast Rhodoturula glutinis was evaluated on juvenile Oreochromis niloticus cultivated in a Biofloc system. Growth performance and the expression of innate response and relevant oxidative stress genes were evaluated after a 12-week feeding trial. Three experimental treatments were evaluated in a conventional tilapia culture (control), Biofloc culture (BFT), and Biofloc with the addition of the live yeast R. glutinis 1×106 CFU g-1 (BFT+Rg), with four replicates per treatment. In all cases, commercial food was supplied to the organisms (32% protein and 5% lipids). O. niloticus juveniles (7.02 ± 0.04 g) were randomly distributed in 12 tanks, each with 15 animals. BFT+Rg treatment showed a significant increase in weight gain compared with the other treatments. Significant improvements were found in Fulton's condition factor, feed conversion rate, and hepatosomatic index under Biofloc conditions, BFT, and BFT+Rg treatments. No significant differences were observed in survival. R. glutinis directly influenced gene expression in the liver and intestine. The expression of tnfa, tgfb, hsp70, and gpx, genes in the liver significantly increased in the BFT+Rg treatment compared with the other treatments. Similarly, a significant increase was found in intestinal il1b, tnfa, tgfb, trf, hsp70 gpx, and cat expression patterns in the BFT+Rg treatment. Based on the performance and immune response, the present study suggests the use of R. glutinis as a strategy to increase the productivity of tilapia in Biofloc culture. <![CDATA[Toxicity of secondary treated sewage disinfected with chlorine gas and hypochlorite to zebrafish <em>Danio rerio</em>]]> ABSTRACT. The sewage contains toxic chemical compounds that secondary treatment plants do not eliminate, and chlorine is usually added for disinfection before discharge. Chlorine reacts with sewage compounds forming other toxic compounds. The objective of this study was to evaluate the toxicity of treated sewage from a secondary treatment plant using Danio rerio embryos. Three types of treated sewage were tested, one disinfected with chlorine gas (dCl2), another with sodium hypochlorite (dClO), and the plant discharge, which is a mixture of the two sewage disinfection methods (mCl) with a proportion of 70% of dCl2 and 30% of dClO. To estimate the median lethal dilution treated sewage was diluted with dechlorinated tap water at 20, 40, 60, and 80%. Two additional points were made with pure treated sewage and pure dechlorinated tap water. Embryos were exposed 1 h after fertilization (hpf) to 144 hpf. The dCl2 and the mCl were lethal at 60 and 72 hpf, respectively, while the dClO did not show lethality. The embryos exposed to the mCl showed heart failure and slower blood circulation. Those exposed to dCl2 showed teratogenic effects such as pericardial edema and spinal curvature, while those exposed to dClO presented malformations such as incomplete eye development and otolith formation absence. <![CDATA[First report of synophthalmia and leucism in a bull shark (<em>Carcharhinus leucas</em>) embryo from the southeastern Gulf of Mexico]]> ABSTRACT. An abnormal embryo (male of 465 mm total length) and 13 other embryos were removed from a pregnant female bull shark (Carcharhinus leucas) caught in coastal waters between the Grijalva River and Terminos Lagoon in the southwestern Gulf of Mexico. The first record of synophthalmia and leucism in the bull shark is presented. The shark cyclopia case is reviewed. <![CDATA[Geomorphology and sedimentary features of the Simpson Submarine Canyon (44°S), southern Chilean margin]]> ABSTRACT. This note analyzes for the first time the geomorphology and sedimentary features of the Simpson Submarine Canyon (SSC), located between Chiloé Island and the Taitao Peninsula. For that purpose, multibeam bathymetric data were obtained in 2018. The SSC has a unique orientation compared to most canyons on the Chilean margin. Slope escarpments, topographic irregularities, and sinuosity of the canyon could be associated with regional tectonics. Sediment transport and deposition along the axis define the transversal morphology. On the canyon walls, erosion and transport processes dominate, evidenced by gullies, channels, and mass removals, which leave debris on the axis. We report a large landslide from a canyon wall, which could be due to a high-energy event such as an earthquake; and the generation of a large sediment wave field outside the canyon mouth, indicating a great activity by sedimentary processes. All the above could indicate that the canyon is continuously evolving. <![CDATA[First report of sea cucumber species (Holothuroidea: Holothuriidae) in Matanchén Bay, México]]> ABSTRACT. Sea cucumbers (holothuroids) play a major role in coastal environments; their detritivore conduct favors oxygen penetration in the sediments and the disposal of pathogens on the sea floor. This study determined holothuroid diversity in the rocky intertidal zone of Matanchén Bay, Mexico. Sampling campaigns were carried out in January, March, May, and July 2018. Linear transects (10 m length and 1 m width) perpendicular to the coastline in rocky areas (0-3 m depth) were established, where the density (ind m-2) and proportion (%) of sea cucumbers were estimated. Organisms were photographed, examined live, and preserved in 70% alcohol for subsequent identification utilizing ossicle characterization. Our results show the presence of four sea cucumber species: Holothuria (Halodeima) inornataSemper, 1868, Holothuria (Selenkothuria) lubricaSelenka, 1867, Holothuria (Selenkothuria) portovallartensisCaso, 1954, and Holothuria (Mertensiothuria) viridiaurantiaBorrero-Pérez &amp; Vanegas-González, 2019. The average density per species was 0.208, 0.108, 0.017, and 0.025 ind m-2, respectively; each species' proportion was 58.1, 30.2, 4.7, and 7.0%, respectively. Due to the above values, we found that the number and spatial distribution of sea cucumber species vary in Matanchén Bay. <![CDATA[Assessing the influence of Humboldt penguin (<em>Spheniscus humboldti</em>) by excrements on the levels of trace and rare earth elements in the soil]]> ABSTRACT. Rare earth elements (REE) and some transition metals (e.g. Nb) are a group of chemicals that have recently been widely used in industrial processes due to the increasing demand for new technologies. As a result, these chemicals are increasingly being released into the environment, which could mean that these pollutants could modify marine and terrestrial ecosystems. Seabirds, such as penguins, can biotransport pollutants and nutrients from the sea to land through excreta. However, there is no information about the role of the Humboldt penguin (Spheniscus humboldti) in bio-transporting emerging contaminants such as REE. This study aimed to assess any possible contribution of Humboldt penguins to the geochemical composition of some terrestrial areas. Excreta samples were collected from Chañaral Island, one of the most important sites in Chile for the conservation of Humboldt penguins. The results showed that this species tends to contribute to soil enrichment with REE (Ce, La, Nd, and Pr) and Nb through excreta, as well as with carbon. More studies are needed to see the potential impacts on the soil. <![CDATA[On the identity of "<em>Dendrilla membranosa</em>" (Porifera, Dendroceratida) <em>sensu</em> Burton, and the specimens collected in Argentina, SW Atlantic Ocean]]> ABSTRACT. There has been confusion regarding the specimens identified as "Dendrilla membranosa (Pallas, 1766)" in Antarctic and subantarctic waters, considering that the original description corresponded to specimens from the Indian Ocean. In this study, we clarified the identification of the specimens collected in Argentinian waters, SW Atlantic Ocean, that should be identified as Dendrilla antarcticaTopsent, 1905, updating its distributional range and considering the new records reported in the present study.