Development of compound microsatellite markers in the harmful dinoflagellate Cochlodinium polykrikoides (Dinophyceae)

We isolated 15 polymorphic microsatellites from Cochlodinium polykrikoides. These loci provide a class of highly variable genetic markers, as the number of alleles ranged from two to 15, and the estimate of gene diversity was from 0.083 to 0.880 across the 15 microsatellites. We consider that these loci have a potential to reveal the genetic structure and gene flow among C. polykrikoides populations.     

Deep-water polychaetes (Annelida) from the southeastern Gulf of California, Mexico

Polychaetes inhabiting deep-sea soft bottoms from the southeastern Gulf of California were collected during four oceanographic cruises during 2000 and 2001. Sampling of benthic organisms was performed with a benthic sledge to collect epifauna and a Karling dredge for epifauna and infauna, in a depth range from 732 to 2 250 m. A list of the polychaetes that were collected and their distribution are presented here. A total of 73 species (distributed among 33 families) were identified. Moreover, 11 species were identified only to genus level and 20 species only to family level. With the exception of Ancistrosyllis hartmanae and Melinnampharete eoa, all identified species have been previously reported in soft bottoms of the Gulf of California or in adjacent areas. Additional previously unreported information is provided herein regarding depth ranges, geographical distribution, morphology and tubes inhabited by the organisms. The morphology of the ampharetids Amage sp. and Samytha sp. does not coincide with that of other species in these genera reported for the Gulf of California, which suggests that they are probably undescribed species.     

Feeding habits of dolphinfish (Coryphaena hippurus) in the southeastern Gulf of California,Mexico

The objective of the study was to identify key elements of the feeding ecology of the dolphinfish, which is a high tropic predator important for sport and artisanal fishing in the Mexican Pacific. Feeding habits were investigated during the years 2000–2003. This species is seasonal in the southern Gulf of California and probably remains there because of the abundant prey. The contents of 232 dolphinfish stomachs were analyzed, identifying 98 prey species, although only eight of these were well‐represented in the diet. The most important prey by weight was the fish Hemiramphus saltator, however by number and frequency of occurrence was the crustacean Hemisquilla californiensis. No differences in the diet were found between males and females, although there was an ontogenic diet shift between seasons. There was no relationship between dolphinfish size and prey size, because dolphinfish fed preferentially on prey with an average size of 4.7 cm.     

Optimization of total RNA isolation from Cochlodinium polykrikoides

Dinoflagellates are eukaryotic microorganisms that represent a group of single-celled algae composed of a highly diversified phylum that is well known for displaying an amazing range of ecological adaptation. Cochlodinium polykrikoides is an unarmored dinoflagellate species belonging to the Family Gymnodiniaceae. It is one of the causative agents for harmful algal blooms occurring in the west coast of Sabah, which result in massive economic damages to the aquaculture and mariculture industries. The limited availability of information pertaining to the genetics of C. polykrikoides raises the need for an in-depth study into the expression mechanisms and regulation of the genes of this microorganism. However, isolation of good quality and intact RNA samples from C. polykrikoides seems to be quite a challenge for molecular biologists. Rapid degradation of freshly isolated RNA samples is a bottleneck for researchers to conduct studies on the gene expression and regulation patterns, which requires intact and high-quality RNA samples. In this study, an attempt to establish the best protocol for isolation of good quality and intact RNA from C. polykrikoides was carried out by testing four different total RNA isolation protocols. We conclude that the RNA isolation protocol using the TRIzol reagent produced the best results among the methods tried. The information from this study will allow further research pertaining to the molecular aspects of C. polykrikoides to be conducted with much ease in the future.     

Sea star (Asteroidea) association structures on the rocky reef in the Gulf of California, Mexico

Sea stars are invertebrates that play relevant roles in rocky and coral reefs: they occupy different levels in food webs and may act as top predators. There are numerous studies on taxonomy and biogeography of the class in the eastern tropical Pacific, but information about the attributes and composition of its assemblages is scant. The objectives of this study were the examination and comparison of asteroid community structure from four regions of the Gulf of California, Mexico, characterized by the presence of rocky reefs, and the search for possible associations between pairs of species. In August 2004 we visited four locations in the western gulf: Bahia de Los Angeles (29 degrees N), Santa Rosalia (27 degrees N), Loreto (26 degrees N) and La Paz (24 degrees N), and censuses sea stars using 50 m2 belt transects (N=93). Abundance and species richness was estimated, as well as diversity (H'), evenness (J') and taxonomic distinctness (delta*); then, all variables were compared among regions with analysis of variance. In addition, an ordination analysis was run looking for groups of locations with similar faunistic composition. Our results showed that Loreto Bay had the highest richness and abundance of asteroids, probably because it presents a large number of habitats and multiple food sources; these conditions seem to favor the occurrence of rare species and of detritivores. However, there were no significant interregional differences among ecological indices, nor we detected groups of locations singled out because of its species composition. Thus, community structure of sea stars in rocky areas of the Gulf of California is quite homogeneous and do not change with latitude. This is a consequence of the fact that all regions under analysis had the species Phataria unifascialis and Pharia pyramidatus as dominant in number. There were significant positive associations between three pairs of species: apparently competition is not particularly relevant to control sea star community structure in the Gulf.     

Optimum fishing strategies for Isostichopusfuscus (Echinodermata: Holothuroidea) in the Gulf Of California, Mexico

The Isostichopus fuscus fishery in Mexico was heavily exploited until 1994, when it was closed due to overfishing. However, no information existed on the status of the populations. The fishery was evaluated through an age structured simulation model, and according to our analysis of the stock, the fishery can be feasible and sustainable as long as fishing mortality and age of first catch are optimized. In order to evaluate exploitation strategies, several scenarios were simulated considering different combinations of fishing intensities and ages of first catch. Input data for the model included population parameters, commercial catch and costs and benefits of the fishing operations. Yield production was strongly influenced by the fishing pressure and by the age of first capture. When the first one increased, significant decreases in yield and profits occurred. The best exploitation strategy was these parameters: fishing mortality level F = 0.15, age at first capture t(c) = 4 years, and yielding of approximately 430 tons. However, since the species reproduces for the first time at 5 years, extracting younger specimens would collapse the population. The critical value of fishing mortality was detected at Fc = 0.25. If exceeded, the population tends to exhaustion and the fishery is no longer profitable. In conclusion, I. fuscus fishery is highly vulnerable to overfishing and age of catch. It must be taken into account that the management policies should be considered as pilot and used on a regional basis. Continuous monitoring of the stock, control of the number of fishing licenses and extracting only specimens 5 yeasr-old and older (around 20 cm and >400 g), will allow the populations to recover from fishing activities. Rev. Biol. Trop.     

Grazers and vitamins shape chain formation in a bloom-forming dinoflagellate, Cochlodinium polykrikoides

Predators influence the phenotype of prey through both natural selection and induction. We investigated the effects of grazers and nutrients on chain formation in a dinoflagellate, Cochlodinium polykrikoides, which forms dense blooms and has deleterious effects on marine ecosystems around the world. Field populations of C. polykrikoides formed longer chains than laboratory cultures without grazers. In the field, chain length of C. polykrikoides was positively correlated with the abundance of the copepod Acartia tonsa. Chain length of C. polykrikoides increased when exposed to live females of A. tonsa or its fresh (<24 h post-isolation) exudates for 48 h. These results suggest that dissolved chemical cues released by A. tonsa induce chain formation in C. polykrikoides. Ingestion rate of A. tonsa on four-cell chains of C. polykrikoides was lower than on single cells, suggesting that chain formation may be an effective anti-grazing defense. Finally, nutrient amendment experiments demonstrated that vitamins (B₁, B₇, and B₁₂) increased the chain length of C. polykrikoides both singly and collectively, while trace metals and inorganic nutrients did not, showing that vitamins may also influence chain formation in this species.     

Bergmann ecogeographic trends among triplefin blennies (Teleostei: Tripterygiidae) in the Gulf of California,Mexico

Synopsis Bergmann-type ecogeographic patterns are common among small resident rocky-shore fishes in the Gulf of California where triplefin blennies (Tripterygiidae) represent a significant component of the community. Using estimates of adult body size from samples throughout the Gulf, four triplefin species, three more than previously reported, showed significant correlations of body size with latitude. The intensity and form of the relationships are given. Measuring the length of the largest individual in samples rather than using average body weight per individuals in samples offers a better estimate of adult body size.     

Conservation strategies for coastal wetlands in the Gulf of California,Mexico

Wetlands worldwide, the fisheries they support, and the communities that depend on them are threatened by habitat modification. We describe strategies being used for wetland conservation in the Gulf of California, Mexico, their effectiveness, and challenges for implementation. We base our analysis on the authors’ experience working for local environmental non-governmental organizations and available literature. The strategies discussed include public and private policy instruments such as Environmental Impact Evaluations, environmental land easements, concessions and transfer agreements, Natural Protected Areas, and international agreements such as the Ramsar convention and the North American Wetlands Conservation Act. We present examples from the Gulf of California that highlight some of the challenges to wetland conservation. These challenges range from governmental failure to enforce existing environmental legislation, lack of verification of requirements for development projects, to low economic penalties for wetland modification or destruction. We found that in the Gulf of California successful conservation of coastal wetlands required a combination of policy instruments and relied on integrating science, management, and public participation through partnerships between non-governmental institutions, academic institutions, community stakeholders, and government agencies.     

Possible factors responsible for the toxicity of Cochlodinium polykrikoides,a red tide phytoplankton

Cochlodinium polykrikoides, a harmful red tide dinoflagellate, is highly toxic to fish, but the toxic mechanism is still unknown. Recent study has suggested that C. polykrikoides generates reactive oxygen species (ROS) such as superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)), and the ROS-mediated ichthyotoxicity has been proposed. In this study, we found that the levels of O(2)(-) and H(2)O(2) detected in C. polykrikoides were trace levels as compared with those of Chattonella marina which is well-known to produce ROS. Furthermore, no significant increase in O(2)(-) generation by C. polykrikoides was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus prepared from skin and gill of yellowtail, whereas C. marina generated increased level of O(2)(-) responding to these stimuli. Interestingly, the cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on the HeLa cells, but the extract of C. marina had no significant effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the growth of C. polykrikoides, and the medium gradually became viscous, but no such changes were observed in the medium of C. marina. These results suggest that multiple factors may be responsible for the toxic mechanism of C. polykrikoides.     

Differential responses of the dinoflagellate Cochlodinium polykrikoides bloom to episodic typhoon events

To better understand the effect of typhoons on the harmful alga Cochlodinium polykrikoides, we investigated cell population dynamics in relation to hydrographic conditions in Korean coastal waters before and after the passage of typhoons. After typhoon Lingling passed through the Yellow Sea, significant accumulation of C. polykrikoides on the southern coast of Namhae Island was associated with southerly winds on September 8, 2019. Similar to field observations of red tide, a particle transport model simulation showed that the virtual particles were greatly influenced by wind-driven currents associated with typhoons, particularly when diel vertical migration was included in the model. However, a bloom of C. polykrikoides disappeared immediately after the passage of typhoon Tapah on September 23, 2019. Because of the different patterns of bloom behavior after the passage of these typhoons, characteristics of other typhoons that affected the Korean peninsula during previous C. polykrikoides blooms were investigated. Analysis of typhoon properties including wind direction, precipitation, and wave height and energy suggested that high wave energy during the passage of a typhoon plays a critical role in the termination of C. polykrikoides blooms, because of its generation of high turbulence relative to other factors. In our study, the wave energy associated with typhoon Tapah (753.6 kJ m^?2 over 48 h) was much higher than that associated with typhoon Lingling (441.7 kJ m^?2 over 48 h). The results indicate that typhoons have an important role in determining the accumulation and termination of C. polykrikoides blooms through the physical effects of wind direction and wave energy.

     

Annual distribution and abundance of Ceratium dens (Peridinales: Ceratiaceae) in the Gulf of California, Mexico

Ceratium dens distribution in the Gulf of California was studied based on three oceanographic campaigns, monthly abundance (1995-96) and during three red tide events in Mazatlán Bay. 52 phytoplankton samples with a Bongo net and 64 microns mesh light, during the year 120 water samples with a van Dorn bottle were collected in two sampling stations and from three red tide events. All samples were counted by the inverted-microscope method. The results showed that C. dens was present in the upper Gulf of California and surroundings of Cabo San Lucas. Two peaks were observed during spring and autumn in Mazatlán Bay during 1995-1996. The highest densities (20-360 cells.-l-1) were observed in coastal areas, whereas the lowest densities (1-14 cells.-l-1) were recorded in the open sea. During red tide events in 1985, 1989 and 1997, 144,000-256,000 cells.-l-1, 100,000-400,000 cells.-l-1, and 189,000-592,000 cells.ul-l was observed, respectively. During the red tide events C. dens varied, although sometimes was replaced by Skeletonema costatum or Pseudonitzchia spp and Ceratium furca. C. dens, seems to prefer areas with high productivity.     

Biochemical responses of fish exposed to a harmful dinoflagellate Cochlodinium polykrikoides

To elucidate the ichthyotoxic mechanisms of a harmful dinoflagellate Cochlodinium polykrikoides, biochemical responses of fish exposed to blooms were investigated. Particularly, based on our finding that oxidative damages of gill were associated with fish mortality (J. Plankton Res. 21 (1999) 2105-2115), dysfunction of ion-transporting enzymes and secretion of gill mucus of fish exposed to this bloom species were examined. The susceptibilities of several fishes to C. polykrikoides were different; the active pelagic fishes such as black scraper Thamnaconus septentrionalis, red sea bream Pagrus major, beakperch Oplegnathus fasciatus and seaperch Malakichthys wakiyae, were more vulnerable than the benthic fishes, flounder Paralichthys olivaceus and rockfish Sebastes inermis. In addition, the higher the algal cell density, the higher the fish mortality. When the test fishes were exposed to C. polykrikoides of 5000 cells ml(-1), the transport-related enzymes, carbonic anhydrase and Na(+)/K(+)-ATPase activities were significantly decreased. The activity of carbonic anhydrase was decreased with increasing algal cell density and exposure time. The quantity of total polysaccharide in gill mucus is higher in the fish exposed to C. polykrikoides than in the control fish; the magnitudes were higher in the pelagic fishes than that of benthic fishes. Moreover, a drop of blood pH and oxygen partial pressure (pO(2)) was also observed in red sea bream and flounder subjected to C. polykrikoides. These results suggest that the inactivation of gill transport-related enzymes activities, the fall in blood pO(2) and abnormal secretion of gill mucus by the C. polykrikoides may be one of the principal causes of fish kill.     

Marine resources subsidize insular rodent populations in the Gulf of California,Mexico

Inputs of energy and nutrients from one ecosystem may subsidize consumers in adjacent ones, with significant consequences for local communities and food webs. We used stable isotope and faecal pellet analysis to quantify use of ocean-derived resources by small mammals on islands in the Gulf of California, Mexico. Rodents were live-trapped on grids originating near shore and extending 125-200 m inland to evaluate the extent to which rodents transport marine nutrients inland, and to determine whether marine foods subsidize island populations, permitting higher densities than would be possible based on terrestrial resources alone. Both faeces and stable carbon and nitrogen isotopes revealed that omnivorous mice (Peromyscus maniculatus) consume ocean-derived prey, including littoral and supralittoral invertebrates, and that their diets differed markedly from those of granivorous rodents (Chaetodipus rudinoris). On a small, seabird roosting island, marine prey were important in the diet of mice regardless of their proximity to shore, underscoring the pervasive influence of the ocean on small islands with relatively large coastline area. On a large island, however, consumption of marine foods declined sharply > or =50 m from shore, which suggests that mice are poor conduits of inland movement of energy and nutrients from the sea. Marine resources seemed to act as subsidies for omnivorous rodents: more P. maniculatus were captured near shore than farther inland and there was an inverse relationship between island area and rodent abundance, suggesting that small islands with large amounts of marine inputs support the highest population densities. Patterns of local and island-wide abundance of P. maniculatus are likely the result of several interacting factors, including frustrated dispersal, competition with C. rudinoris, and the absence of predators. We speculate, however, that the availability of marine resources allows P. maniculatus to reach high densities and to persist on small islands in the Gulf despite low and unpredictable terrestrial productivity. Spatial trophic subsidies thus provide a possible mechanistic explanation for the widely reported inverse relationship between population density and island or habitat area.     

Effects of temperature, salinity and irradiance on the growth of the harmful red tide dinoflagellate Cochlodinium polykrikoides Margalef (Dinophyceae)

The effects of temperature, salinity and irradiance on the growthof the harmful red tide dinoflagellate Cochlodinium polykrikoideswere examined in the laboratory. From 60 different combinationsof temperature (10–30°C) and salinity (10–40)under saturated irradiance, C. polykrikoides exhibited its maximumspecific growth rate of 0.41 day^-1 at a combination of 25°Cand salinity of 34. Optimum growth rates of >0.3 day^-1 wereobserved at temperatures ranging from 21 to 26°C and atsalinities from 30 to 36. The organism did not grow at temperatures10°C and only grew at salinities >30 if the temperaturewas >15°C. It was able to grow in temperatures rangingfrom 15 to 30°C and at salinities from 20 to 36. These valuesclosely resembled those observed for this species in situ. Itappears as if C. polykrikoides is a stenohaline organism thatprefers high salinities, indicative of offshore waters. Temperaturehad the greatest influence on the growth rate, followed by salinity,and then the interaction between temperature and salinity. Theoptimum irradiance for growth was >90 µmol m^-2 s^-1.Photoinhibition did not occur at 230 µmol m^-2 s^-1, whichwas the maximum irradiance used in this study.     

Comparative feeding ecology of two herbivorous damselfishes (Pomacentridae: Teleostei) from the Gulf of California,Mexico

Two species of benthic damselfishes from the Gulf of California, Mexico, use contrasting behaviors when feeding on benthic algal communities. The small (±70 g) Cortez damselfish, Eupomacentrus rectifraenum (Gill, 1862), feeds selectively from a multi-species algal mat, eats fleshy red and green algae and ignores brown and calcareous algae. The giant blue damselfish, Microspathodon dorsalis (Gill, 1862), is a large (±450 g), lethargic, nonselective feeder which grazes on a near monoculture of a fleshy red alga, Polysiphonia sp. Feeding activity for both species is low in the morning peaks during late afternoon, and drops sharply as night approaches. Based on feeding rates, gut-filling times, and weights of gut contents, Cortez damselfish process six to eight full guts of food and giant blue damselfish three full guts of food per day. The algal mat exhibits high standing crops (291–618 g dry wt · m^?2) and low productivity, but the preferred food of the Cortez damselfish (Ulva) appears to colonize the mat frequently and grow rapidly. The Polysiphonia dominated community on giant blue damselfish territories exhibits low standing crops (23 g · m^?2) and high productivity (34–47 times that of the mat per gram algae). Even though the feeding behaviors and resources used by the two damselfishes differ, both species eat similar food (delicate red and green fleshy algae, and depend on rapid colonization and/or high productivity to maintain their primary foods in the grazed algal community.     

Reproductive activity and condition index of Holacanthus passer (Teleostei: Pomacanthidae) in the Gulf of California,Mexico

Annual variation and relationship between the gonadosomatic index (IG) and the condition index (K) of Holacanthus passer were evaluated in 194 specimens from Cueva de León, Gulf of California (24 degrees 02' N, 110 degrees 24' W). There was a significant negative correlation between IG and K in both sexes: indices exhibit an opposite seasonal pattern. The reproductive activity of both sexes is inversely related with nutritional status. There was a significant difference in IG but not in K values between males and females. The condition index may be used to determine reproduction time of the species in other localities without sacrificing the organisms. This could be a valuable tool to develop monitoring programs for fisheries and culture of this species.     

Ultrastructure of the Harmful Unarmored Dinoflagellate Cochlodinium polykrikoides (Dinophyceae) with Reference to the Apical Groove and Flagellar Apparatus

ABSTRACT. The external and internal ultrastructure of the harmful unarmored dinoflagellate Cochlodinium polykrikoides Margalef has been examined with special reference to the apical groove and three‐dimensional structure of the flagellar apparatus. The apical groove is U‐shaped and connected to the anterior sulcal extension on the dorsal side of the epicone. The eyespot is located dorsally and composed of two layers of globules situated within the chloroplast. A narrow invagination of the plasma membrane is associated with the eyespot. The nuclear envelope has normal nuclear pores similar to other eukaryotes but different from the Gymnodinium group with diagnostic nuclear chambers. The longitudinal and transverse basal bodies are separated by approximately 0.5–1.0 μm and interconnected directly by a striated basal body connective and indirectly by microtubular and fibrous structures. Characteristic features of the flagellar apparatus are as follows: (1) a nuclear extension projects to the R1 (longitudinal microtubular root) and is connected to the root by thin fibrous material; (2) fibrillar structures are associated with the longitudinal and transverse flagellar canal; and (3) a striated ventral connective extends toward the posterior end of the cell along the longitudinal flagellar canal. We conclude, based on both morphological and molecular evidence, that Cochlodinium is only distantly related to Gymnodinium.