Ignacio Leyva-Valencia

Instituto Politécnico Nacional | IPN · Departamento de Plancton y Ecología Marina

Allelopathy refers to biochemical interactions among competing microalgae, it involves a donor species that produces metabolites which can cause inhibitory effects on susceptible species. This phenomenon can participate in the regulation of harmful algal blooms. The dinoflagellate Gymnodinium catenatum is negatively affected by allelopathic interac...

This study provides the first baseline information on the trophic interactions of the endemic shark Cephalurus cephalus through a multidisciplinary approach analyzing its diet, parasite component community, parasite diversity, and infection rates. Preys and parasites of 132 sharks caught off Magdalena Bay, Mexico, during June and July 2015 were ide...

Background: Mexican studies on marine benthic dinoflagellates (MBD) began in 1942 from the offshore region of Oaxaca, based on water column samples. Subsequently, in ten Mexican maritime states, both epibenthos and plankton samples have been collected, species have been cultured, and field and laboratory studies have been carried out. Goals: The o...

RESUMEN. Coolia es un género que actualmente incluye ocho especies de dinoflagelados epibentónicos, siendo un grupo de interés debido a las toxinas que producen algunas especies del género (por ejemplo, cooliatoxina) y por las asociaciones que presentan con otros géneros de dinoflagelados epibentónicos toxigénicos (Ostreopsis, Amphi-dinium, Proroce...

Allelopathy between phytoplankton organisms is promoted by substances released into the marine environment that limit the presence of the dominating species. We evaluated the allelopathic effects and response of cell-free media of Chattonella marina var. marina and Gymnodinium impudicum in the toxic dinoflagellate Gymnodinium catenatum. Additionall...

The main element to assess the potential risks associated with toxic cyanobacterial blooms is the precise identification of the species. As part of a water quality monitoring during 2015 in Santa María del Oro crater lake, Nayarit, a cyanobacterial bloom was detected. Thus, this work aimed to identify the bloom-forming cyanobacteria species using a...

The main element to assess the potential risks associated with toxic cyanobacterial blooms is the precise identification of the species. As part of a water quality monitoring during 2015 in Santa María del Oro crater lake, Nayarit, a cyanobacterial bloom was detected. Thus, this work aimed to identify the bloom-forming cyanobacteria species using a...

Allelopathy between phytoplankton species can promote cellular stress and programmed cell death (PCD). The raphidophyte Chattonella marina var. marina, and the dinoflagellates Margalefidinium polykrikoides and Gymnodinium impudicum have allelopathic effects on Gymnodinium catenatum; however, the physiological mechanisms are unknown. We evaluated wh...

Paralytic shellfish toxin (PST) content in the dinoflagellate Gymnodinium catenatum changes with culture age, with a higher toxin concentration in the logarithmic phase that decreases when the culture ages. The gene copy number (GCN) of domains sxtA1 and sxtA4 was higher in the lag and stationary phase, and lag phase, respectively. No relationship...

Cherax quadricarinatus is a decapod crustacean of interest to the aquaculture industry. In Mexico, a significant effort has been made to improve biological requirements, but the genetic characteristics are unknown. We examined the genetic diversity and differentiation in four populations in Mexico (three commercial farms and one feral population),...

Most of the shellfish fisheries of Mexico occur in the Gulf of California. In this region, known for its high primary productivity, blooms of diatoms and dinoflagellates are common, occurring mainly during upwelling events. Dinoflagellates that produce lipophilic toxins are present, where some outbreaks related to okadaic acid and dinophisystoxins...

Harmful algae blooms (HABs) are characterized for the coexistence of phytoplankton species with dynamic and complex biotic interactions (e.g., competition, symbiosis, predation, parasitism, allelopathy), that occur at fine temporal and spatial scales, and are relevant to understand the role that different species of phytoplankton play in the regula...

The marine dinoflagellate Margalefidinium polykrikoides is a harmful species that has affected aquaculture, fisheries and tourism activities. It produces reactive oxygen species (ROS) as well as hemolytic and neurotoxic-like substances that have been associated with mass mortalities of marine organisms. It has a tropical and subtropical distributio...

In this review we summarize the current state of knowledge regarding taxonomy, bloom dynamics, toxicity, autoecology, and trophic interactions, of saxitoxin producing dinoflagellates in this region. The dinoflagellates Gymnodinium catenatum, Pyrodinium bahamense and several species of Alexandrium are saxitoxin producers, and have been responsible o...

Evaluating the spatial scale of biological variation in marine species aids understanding of the ways in which environmental selection pressures can shape life histories, population demography, and morphological traits. The Pacific geoduck Panopea generosa is an ideal candidate to investigate patterns of life history variation and morphological pla...

The Cortes geoduck Panopea globosa is a large bivalve with a high commercial value distributed from the southern Pacific coast of the Baja California Peninsula to the northern Gulf of California, inhabiting a wide range of subtropical temperatures. A new record of this species in shallower waters suggests that it can tolerate a warmer environment t...

Saxitoxin (STX) and its analogs are a broad group of natural neurotoxic alkaloids, commonly known as paralytic shellfish toxins. SxtA is the initial gene in the biosynthesis of saxitoxin. It has been proposed that the genes for STX biosynthesis had a bacterial origin and were acquired in the dinoflagellates by a horizontal gene transfer (HGT). In G...

The effect of cells and cell-filtrates of microalgae belonging to different taxonomic groups were tested on the growth and toxin content of Gymnodinium catenatum cultures. Cultures of a raphidophyte (Chattonella marina var. marina), a dinoflagellate (Margalefidinium polykrikoides), and a bacterial community isolated from G. catenatum were used. All...

La Red Temática sobre Florecimientos Algales Nocivos (RedFAN) fue creada bajo el marco de la convocatoria 2014 del Consejo Nacional de Ciencia y Tecnología (CONACYT). La RedFAN agrupa a investigadores que realizan estudios sobre los florecimientos algales nocivos (FAN) en México y estudiantes con proyectos de investigación en el área. Asimismo, inc...

The geoduck Panopea globosa is found on the Pacific coast of Baja California south of Bahia Magdalena Bay and throughout the Gulf of California, and sustains a vibrant and growing fishery. Despite morphometric analyses that suggest populations fromthe Pacific are distinct fromthose inside theGulf of California, it is unclear whether populations are...

Geoducks (Panopea spp.) are recognized as one of the longest-lived and largest burrowing bivalves. Five extant species support commercial fisheries in different countries, yet their phylogenetic relationships are unclear. Phylogenetic analyses using cytochrome oxidase c subunit I, 28S, and 18S partial sequences on five Panopea spp. were performed t...

The geoduck clam Panopea globosa is found on the Pacific coast of Baja California south of Bahia Magdalena Bay and throughout the Gulf of California, and sustains a vibrant and growing fishery. Despite morphometric analyses that suggest populations from the Pacific are distinct from those inside the Gulf of California, it is unclear whether populat...

Panopea globosa is a marine bivalve mollusk important for small-scale fisheries from Northwest Mexico. Twenty-four tetra-nucleotide microsatellite markers were characterized by 454 XL+ Titanium pyrosequencing. High average levels of allelic diversity and heterozygosity were observed (N A = 16.68; Ne = 9.77; H O = 0.643; H E = 0.858). Significant...

Two species of geoduck clams, Panopea, are known from the Pacific coast of Mexico: P. generosa, also present in the temperate areas along the western coast of North America, and P. globosa, originally considered endemic to the Gulf of California. Often regarded as a temperate and a tropical species, their respective distributions were assumed to be...

Most previous studies identifying Panopea generosa and P. globose have used non-rigorous visual methods as well as older shell measurement techniques. Newer mathematical methods based on shell shape variation allow for more accurate identification of clam species, as well as modeling of phenotypic differences due to environmental effects in populat...

Halotolerance, upper thermotolerance and optimum temperature for growth was investigated in juvenile penshell (Atrina maura). Halotolerance and thermotolerance were determined measuring LD50-96h within the salinity and temperature ranges of 15-50‰ and 19-35°C. Optimum temperature for growth was measured estimating scope for activity, ingestion, and...