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.     

Photosynthetic and respiratory responses of Gracilaria vermiculophylla (Ohmi) Papenfuss collected from Kumamoto, Shizuoka and Iwate, Japan

The photosynthetic and respiratory responses to irradiance, salinity and temperature of the red alga, Gracilaria vermiculophylla, collected from Kumamoto, Shizuoka and Iwate in Japan were studied using an electronic Dissolved Oxygen sensor. The parameters derived from the photosynthesis versus irradiance relationship indicated the potential to acclimate to broad irradiance variations in all of the populations of G. vermiculophylla collected from these three sites. In addition, the light-saturated photosynthesis rate (P _max) and the dark respiration rate of all populations increased with increasing temperature up to 20–30°C, while the P _max decreased at 35°C. All populations also showed a broad variation of photosynthetic responses to salinity changes in the range from 10 to 30 psu. On the other hand, the population from Iwate showed high photosynthetic efficiency, especially in the temperature range of 5–10°C, and showed low values of saturation irradiance compared to the populations from Shizuoka and Kumamoto. These results suggest that there is greater potential to acclimate to low irradiance and low temperature in the population from Iwate compared to those from the Shizuoka and Kumamoto populations. However, the P _max of the populations from Iwate and Shizuoka was reached at 20°C and 25°C, respectively, while the Kumamoto population reached P _max at 30°C. This implies that the latter population has greater potential to tolerate higher temperatures than the former. Such characteristics in photosynthesis and respiration of G. vermiculophylla collected from the three locations probably indicate an acclimation to prevailing environmental conditions in their respective habitats.     

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.     

Evidence of Leptospira interrogans infection in California sea lion pups from the Gulf of California

Forty-two urine and 96 blood and serum samples were obtained from California sea lion (Zalophus californianus) pups from the Gulf of California during the 2000 reproductive season. Antibody prevalence to 13 serovars of Leptospira interrogans was determined by microagglutination tests (MAT); presence of pathogenic leptospires was detected by polymerase chain reaction (PCR). Samples with antibody titers > or = 1:25 or 115 bp fragments on ethidium bromidestained 1.5% agarose gels were considered positive. Antibody prevalence was 54% overall with highest prevalence against serovar cynopteri (50% of all positive reactions). Highest antibody titers (1:50) were detected against serovars cynopteri and pomona. Polymerase chain reaction products were observed in two of 42 urine samples, six of 96 blood samples, and one of 96 serum samples. Presence of PCR products in blood and serum was demonstrated in pups that were seronegative. Kruskall-Wallis tests and corresponding post hoc Tukey tests (alpha = 0.05) showed that prevalence of leptospirosis was significantly different among all rookeries. The high seroprevalence (54%), low antibody titers (maximum 1:50), absence of pups showing clinical signs indicative of the disease, and lack of recent reports of increased mortality of sea lions in the Gulf of California are suggestive of the presence of enzootic host-adapted serovars. Crowding in rookeries as well as the presence of bats and rodents on some of the islands may explain infection by L. interrogans (sensu lato) and some of the differences in seroprevalence among reproductive rookeries.     

Antibodies against Leptospira interrogans in California sea lion pups from Gulf of California

One hundred and twenty-five serum samples from California sea lion (Zalophus californianus californianus) pups, and one from an adult female from eight reproductive rookeries located in seven islands in the Gulf of California (Mexico), were collected during the 1994-96 reproductive seasons. These were tested for antibodies to 19 serovars of Leptospira interrogans using a Microscopic Agglutination Test (MAT). Forty-one samples (32%) had antibody levels from 1:20 to 1:320 to one or more serovars. The most frequently detected serotypes were Leptospira interrogans hardjo (n = 13), cynopteri (8), ballum (6), and szwajizak (5). Serovars with the highest prevalence were Leptospira interrogans hardjo and serjoe (1:320), ballum (1:160), and cynopteri, girppotyphosa, and tarassovi (1:80). Based on these results, exposure of sea lions to L. interrogans serovar hardjo seems to be relatively common among colonies located in the islands of the Gulf of California in contrast with those located on the Pacific coast, where the most frequently detected serovar is L. interrogans serovar pomona.     

Echinoderms (Echinodermata) from the Gulf of California, Mexico

A systematic list of the echinoderms of the Gulf of California, based on museum specimens of the Colección Nacional de Equinodermos, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autónoma de México and the National Museum of Natural History, Smithsonian Institution, Washington, D.C. is presented. A total of 193 echinoderm species is recorded, distributed in 108 genera, 51 families and 19 orders. 12 new records for the Gulf of California are presented: Asteroidea (four), Ophiuroidea (three) and Holothuroidea (five).     

Growth rate, age and size of bonefish from the Gulf of California

Growth rates of cultured first-year bonefish Albula sp. averaged 0·32 mm day⁻¹. Maximum theoretical growth (±95% CI) was 278 (±11·2) mm L _S (sexes combined), confirming that Albula sp. from the Gulf of California grow less than other species in the' vulpes 'complex.     

Hepatic carcinoma with spleen metastasis in a California sea lion from the Gulf of California.

A primary hepatic carcinoma with a neuroendocrine pattern was detected in an adult female California sea lion (Zalophus californianus) found dead on Granito Island in the Gulf of California (Mexico) in January 1996. At necropsy, several light yellow nodules of different sizes were observed on the entire surface of the liver and spleen. Microscopic examination of these nodules using routine haematoxylin-eosin stain, revealed cubic, polyhedral and pleomorphic cells with three to four bizarre mitotic figures per field (40X). An immunohistochemistry test revealed a positive reaction of indirect immunoperoxide to cytokeratin (CK2). This is the first known case of a primary hepatic carcinoma in free-ranging California sea lions from Mexican waters.     

Partial inclusion of Ulva lactuca and Gracilaria parvispora meal in balanced diets for white leg shrimp (Litopenaeus vannamei)

The algae Ulva lactuca and Gracilaria parvispora are abundant in the Gulf of California, rich in nutrients, and may be used as a source of protein in balanced diets for shrimp. This study tests whether their meal, as a partial inclusion in diets for juvenile Litopenaeus vannamei, is feasible. Percentages of inclusion were 5, 10, and 15 %. Results showed that final weight, weight gain, and specific growth rate varied significantly among diets (P?U. lactuca (P?G. parvispora (P?>?0.05). In general, better results were obtained when using G. parvispora compared with U. lactuca. When compared to the control diet (without inclusion), diets that included 10 and 15 % U. lactuca meal yielded a significantly lower growth (P?U. lactuca 5 % meal (P?>?0.05), suggesting the feasibility of inclusion to this limited percentage. No significant differences were detected between the control and the three treatments with G. parvispora, suggesting the possibility of using higher percentages of inclusion. We conclude that both seaweeds may be used as a component in preparing feed for juvenile L. vannamei.     

Photosynthetic and respiratory responses of <Emphasis Type="Italic">Gracilaria salicornia</Emphasis> (C. Ag.) Dawson (Gracilariales,Rhodophyta) from Thailand and Japan

The photosynthetic and respiratory responses of Gracilaria salicornia in the subtropical waters of Japan (in Okinawa) and in the tropical waters of Thailand (in Rayong and Phuket Provinces), were studied under various conditions of irradiance, salinity and temperature. This alga showed adaptability in its photosynthetic and respiratory responses to oceanic salinity as well as to subtropical to tropical temperature. Significant differences in the photosynthetic and respiratory rates among the G. salicornia populations collected from the above sites were observed. The Phuket population showed adaptability to high irradiance and temperature, characteristic of its natural sun-exposed environment, as it exhibited the highest I _k and I _c, and lowest α and higher P _max at 30–35°C. On the other hand, the Okinawa population demonstrated adaptability to low submarine irradiance as it had a lower I _k and I _c than either population from Thailand. Its P _max at 20–25°C was also higher than that of the Phuket population. The Rayong population, however, showed the highest P _max, R_d, α, I _k and I _c, suggesting its adaptability to both sun and shade light conditions in its natural environment. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines     

Photosynthetic and respiratory responses to temperature and light of three Alaskan tundra growth forms

Photosynthetic and respiratory response of four Alaskan tundra species comprising three growth forms were investigated in the laboratory using an infrared gas analysis system. Vaccinium vitis-idaea , a dwarf evergreen shrub, demonstrated a low photosynthetic capacity: P_max= 1 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt < 10°C. Betula nana , a deciduous shrub, had a high relatively photosynthetic capacity: P_max= 14 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt 17°C. Two graminoid (sedge) species, Carex aquatilis and Eriophorum vaginalum , showed different responses. Carex showed a high photosynthetic capacity: P_max= 20 mg CO₂ g dry wt⁻¹ h⁻¹; T_opt 22°C. Eriophorum vaginatum demonstrated an intermediate photosynthetic capacity of 4 mg CO₂ g dry wt⁻¹ h⁻¹ at saturated light levels. Leaf dark respiration, up to 20°C, was approximately the same for all species. The patterns of root respiration among species was opposite to the trend in photosynthesis. Vaccinium vitis-idaea had the highest rate of root respiration and B. nana the lowest ( C aquatilis was not measured). Correlation between leaf nitrogen content (%) and photosynthetic capacity was high. Hypothesized growth form relationships explained differences in photosynthetic capacity between the deciduous shrub and evergreen shrub, but did little to account for differences between the two sedges. Differences in rooting patterns between species may affect tissue nutrient content, carbon flux rates, and carbon balance.     

Length‐weight relationship for sea catfishes (Siluriformes: Ariidae) from the southeastern Gulf of California with new records on maximum length

The parameters of length‐weight relationship (LWR) are presented for seven species of catfish from the southeastern Gulf of California. Samples were obtained every three months, in Bahia de Matanchen (using bottom trawl nets consistent of 72 hauls, with mesh sizes of 3.2 cm in the wings and 2.54 cm in the cod‐end) from February to November, 2016 and in the San Blas estuarine system (using gill nets consistent of 32 hauls, with mesh sizes of 5 cm) from August, 2015 to May, 2016 respectively. The allometric coefficient (b) of LWR varied from 2.797 for the Cominate Sea Catfish (Occidentarius platypogon (Günther, 1864)) to 3.373 for the Tete Sea Catfish (Ariopsis gilberti (Jordan & Williams, 1895)). Four species reached new records on maximum total length (Tete Sea Catfish, A. gilberti; Widehead Sea Catfish, A. guatemalensis (Günther, 1864); Conguito Sea Catfish, Cathorops liropus (Bristol, 1897); and Curator Sea Catfish, C. raredonae Marceniuk, Betancur‐R, & Acero, 2009). For six of these species this accounts for the first report on estimations of LWR parameters.     

Distribution of silicoflagellates in plankton and core top samples from the Gulf of California

Plankton and surface sediment samples from the Gulf of California were examined to determine the present geographic distribution of silicoflagellate species in this area. Variations in the species composition of the silicoflagellate assemblage were found to be related to water mass distributions. Eight species were identified in these samples. Octactis pulchra is associated with high levels of primary productivity in the surface waters and is found in greatest abundance in the central Gulf of California. Dictyocha messanensis dominates the silicoflagellate assemblage in stations outside the Gulf of California and increases in relative abundance with decreasing amounts of Octactis pulchra. Dictyocha calida, Dictyocha sp. A, and Dictyocha sp. B are associated with equatorial waters and have the highest relative abundance near the mouth of the Gulf. Dictyocha epiodon and Distephanus speculum are associated with cold California Current Water, and Dictyocha epiodon is present in minor abundance in Gulf samples. Dictyocha sp. 2 has a patchy distribution with low relative abundance.     

Seasonal variation of the agar quality and chemical composition of Gracilaria veleroae and Gracilaria vermiculophylla (Rhodophyceae,Gracilariaceae) from Baja California Sur,Mexico

Yield and physico‐chemical properties of agar from Gracilaria veleroae E.Y. Dawson and Gracilaria vermiculophylla (Ohmi) Papenfuss were studied and the chemical composition of the two seaweeds was determined. Samples were collected seasonally from summer 2003 to spring 2005. The agar yield did not vary significantly between seasons for both species. The lowest agar gel strength was obtained from G. veleroae (207.5 g cm^–2) in summer 2003 and the highest from G. vermiculophylla (793.1 g cm^–2) in winter 2004. Melting temperatures and hysteresis were higher in G. vermiculophylla, whereas gelling temperatures and 3,6‐anhydrogalactose content were higher for G. veleroae. Moisture, ash, crude fiber, and ether extract showed no significant seasonal variation for G. veleroae. The chemical composition of G. vermiculophylla showed significant seasonal variation. G. vermiculophylla possesses a better agar quality than G. veleroae and is a species that could be considered as a source of agar for commercial use.     

Ecological effects of seaweed harvesting in the Gulf of California and Pacific Ocean off Baja California and California

The ecological effects of harvesting were investigated for two species, the giant kelp Macrocystis pyrifera and Eucheuma uncinatum, by using harvest records and aerial surveys that show yield changes and by using studies of recruitment, survivorship and community interactions. There were no ecological effects found for M. pyrifera harvested with contemporary methods, and there are no recommendations for changing current management practices for this species. It is recommended that E. uncinatum, which on occasion produces commercially significant standing crops, not be harvested unless special precautions are taken to leave some plants for regeneration of the harvested populations.     

Major and Trace Elements in Zooplankton from the Northern Gulf of California During Summer

We report the distribution of major and trace element concentrations in epipelagic zooplankton collected in the Northern Gulf of California in August 2003. The Bray–Curtis index defined three element assemblages in zooplankton: (1) major metals, which included only two elements, Na (3.6–17.0%) and Ca (1.0–4.8%). Na had its highest concentrations in the shallow tidally mixed Upper Gulf, where high salinity, temperature, and zooplankton biomass (dominated by copepods) prevailed. Ca showed its highest concentrations south of Ballenas Channel, characterized by tidal mixing and convergence-induced upwelling, indicated by low sea-surface temperature, salinity, and zooplankton biomass; (2) Six biological essential elements, like Fe (80–9,100 mg kg⁻¹) and Zn (20–2,570 mg kg⁻¹), were detected in high concentrations in zooplankton collected near Guaymas Basin, which had high surface temperature and chlorophyll a concentrations. (3) Metals of terrigenous origin, such as Sc (0.01–1.4 mg kg⁻¹) and Th (0.03–2.3 mg kg⁻¹), and redox-sensitive metals, like Co (3–23.8 mg kg⁻¹); this was the assemblage with the largest number of elements (15). Both types of elements of assemblage 3 had maximum concentrations in the cyclonic eddy that dominates the summer circulation in the Northern region. We concluded that sediment resuspension by tidal mixing in the Upper Gulf, upwelling south of Ballenas Channel, and the cyclonic eddy were key oceanographic features that affected the element concentrations of epipelagic zooplankton in the Northern Gulf of California. Oceanographic mechanisms such as these may contribute to element incorporation in marine organisms in other seas.     

Fish larvae assemblages in the Gulf of California

The distributional diversity and assemblages of fish larvae in the Gulf of California indicated two main seasonal stages and two transitional periods: in winter, the tropical water mass is confined to the south‐east portion of the mouth of the Gulf and larval fish assemblages are dominated by subtropical and temperate‐subarctic species; in summer; tropical water invades the Gulf and assemblages are dominated by tropical species. Both seasonal stages are separated by transitional periods coinciding with strong latitudinal temperature gradients. During the autumn and spring transitional periods, the Gulf of California splits into three regions: a northern region where temperate and subarctic species spawn from autumn to spring, a southern region dominated by tropical and subtropical species year round and a central region where tropical and temperate assemblages merge. Seasonal changes in the location of the regions, as well as the borders between them, show expansion and contraction of the northern and southern faunas related to the general oceanic circulation patterns during the year.     

Agar Analysis,nuclear genome quantification and characterization of four agarophytes (Gracilaria) from the Mexican Gulf Coast

DNA reassociation kinetics were used to determine nuclear genome organization and complexity in four species of Gracilaria (Gracilariales, Rhodophyta). In Gracilaria tikvahiae, G. caudata, G. cervicornis and G. divaricata, results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–46% and unique DNA ranged from 45–78%, Thermal denaturation (T _m) indicated guanine + cytosine (G + C) levels of 41.9–46.0 mol % G + C. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA content. Comparisons of mean nuclear DNA (I _f) values to chicken erythrocytes (RBC) resulted in an estimate of 0.37–0.40 pg/2C genomes for the four Gracilaria species. Total agar content following alkaline pretreatment ranged from 7–15% dry weight. Gel strengths were generally below commercial levels, ranging from 40–260 g cm⁻² Nuclear genome profiles developed from information for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity as previously speculated.