Coccolithophorids from the west coast of Baja California, Mexico

Studies on coccolithophorids in Mexico are rather scarce, probably due to the use of traditional methods for studying marine phytoplankton (e.g. collection, preservation and analysis). This is the first study of the coccolithophorid flora from west coast of Baja California, Mexico. Bottle samples (4 l) were taken at various depths (5, 25 and 50 m), at fixed stations located on perpendicular transects along the west coast of Baja California, considering three different zones: North, Central and South. A total of 32 samples were studied by optical and scanning electron microscopy, yielding 24 taxa identified (17 species and 5 nominal varieties, plus 2 different varieties). The coccolithophorid assemblages are considered subtropical and coastal (with many cosmopolitan taxa). Emiliania huxleyi and Gephyrocapsa oceanica were the most abundant (relative abundance) and widespread species in the study area. We report 15 new records for the Mexican Pacific. The zonal and vertical distribution of some taxa are briefly discussed, as well as the taxonomy of Rhabdosphaera claviger, Helicosphaera carteri, H. hyalina and related taxa.     

The length–weight relationship parameters of demersal fish species off the western coast of Baja California Sur, Mexico

The length–weight relationship parameters were recorded for 24 families, 34 genera and 46 species of 10 963 specimens sampled off the western coast of Baja California Sur, Mexico, many for the first time. New maximum length records were obtained for seven of these species. The b values ranged from 2.62 for Sebastes rubrivinctus to 3.80 for Peprilus simillimus .     

A toxic Pseudo-nitzschia bloom in Todos Santos Bay,northwestern Baja California,Mexico

A toxic Pseudo-nitzschia spp. bloom in the Todos Santos Bay area (31.8°N), Mexico, is described. This is the southernmost report of the presence of domoic acid (DA) in the California Current System and it is also the first report of the distribution of toxic Pseudo-nitzschia species and DA on the Baja California west coast. The maximum cell abundance of Pseudo-nitzschia was 3.02 × 10⁵ cells L^?1 and the maximum concentration of DA in particulate matter (pDA) was 0.86 μg L^?1. P. australis constituted the major proportion of cells identified as Pseudo-nitzschia. The environmental conditions associated with wind-driven upwelling were the cause for the accumulation of toxic cells. Maximum pDA and cell concentration were detected around 14 °C. The ratio of the concentration of macronutrients seemed to be the important factor for the accumulation of P. australis. The highest cell abundance was detected in areas with a high Si(OH)₄ to N ratio in the entire water column. Therefore, the relative increase of silicate concentration related to upwelling conditions was the probable cause for the accumulation of P. australis. Maximum photosystem II (PSII) quantum efficiency of charge separation (F_v/F_m) was negatively correlated to the pDA to fucoxanthin ratio. This ratio was used in this work as an index of cellular DA content. Therefore, the photosynthetic competence of the cells might be an important factor that affected their DA cellular content.     

Diel vertical and offshore-inshore movements of anchovies off the central Baja California coast

During the night anchovies were observed in the deep offshore oceanic and intermediate slope zones off the Baja California coast, Mexico, in high abundance. Anchovies moved towards the shallow inshore neritic zone in low density groups, returning at dawn to deeper depth strata. During the day, abundances were reduced drastically and those observed were forming compact and discrete schools at deeper depth strata. Anchovy and euphausiid abundance, as recorded by the echosounder, Were positively correlated.     

Deep-water bivalves from the oxygen minimum zone area off the western Peninsula of Baja California,Mexico

ABSTRACT

Eighteen species of deep-sea bivalves were collected below the Oxygen Minimum Zone (OMZ) core off western Mexico. This material was obtained during the research cruises XVI, XVIB (off the northwestern Peninsula of Baja California), and VIII (Gulf of California) of the TALUD project aboard the R/V El Puma. The samples were taken with an epibenthic sledge (710–2077?m deep) and with a box corer (750–2600?m). The species belong to 10 families: Solemyidae, Nuculanidae, Malletiidae, Tindariidae, Limopsidae, Propeamussiidae, Tellinidae, Periplomatidae, Poromyidae and Lyonsiellidae. Environmental parameters (oxygen, salinity, sediments composition and temperature) are given for each sampling station. Tolerance to oxygen depletion is analysed for all deep-water species collected by the TALUD survey off the Baja California Peninsula. The additional file includes shell characteristics and distributional information for each species.     

Food habits of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) off the western coast of Baja California Sur,Mexico

The objective of this study was to establish the trophic niche of the silky shark and to determine the ecological role of this predator in the ecosystem close to Baja California. The trophic spectrum was analyzed from samples taken during summer and autumn (2000–2002) from the fishing camps of Punta Lobos and Punta Belcher on the western coast of Baja California Sur. A total of 263 stomach contents were analyzed (143 with food; 120 empty). The index of relative importance (IRI) showed that at Punta Lobos, silky sharks fed mainly on red crabs Pleuroncodes planipes (%IRI = 83%), whereas at Punta Belcher the main food item was the jumbo squid Dosidicus gigas (%IRI = 41%), followed by chub mackerel Scomber japonicus (%IRI = 33%). According to the Levin Index (Bi), the trophic niche breadth in silky sharks is low (Bi = <0.6), which means that silky sharks are specialist predators because they mainly consume three prey types: red crab, chub mackerel, and jumbo squid. The Shannon‐Wiener Index indicated that all trophic categories at Punta Belcher (0.85–1.22) had lower diversity than at Punta Lobos (0.50–1.6), because the silky shark feeds more on tropical prey found close to Punta Lobos. The Morisita‐Horn Index (Cλ) showed an overlap in the diet between the two areas analyzed and between sexes (Cλ = >0.6). The juveniles and adult females did not show any overlap. In the caloric analysis of the main prey, the jumbo squid (D. gigas) contributed the most calories to the silky shark diet (76%).     

Infrared analysis of eleven carrageenophytes from Baja California,Mexico

Infrared analyses of the carrageenan in ten species (representing four genera) of Gigartinaceae and one species of Hypneaceae in different reproductive phases from the northwestern coast of Baja California were studied. Cystocarpic samples of the Gigartinaceae presented varying degrees of a / hybrid. The degree of hybridization was determined based on the ratio between the peak absorbances at 805/845 cm^–1. A high correlation was observed between the 805/845 cm^–1 and 805/970 cm^–1 ratios. Tetrasporic samples of Gigartina leptorhynchos, Iridaea splendens, Rhodoglossum affine and R. roseum, presented a -carrageenan profile, whereas Gigartina tepida, G. exasperata, G. harveyana, G. canaliculata and G. spinosa presented a -carrageenan. The tetrasporic sample of Hypnea valentiae showed a -carrageenan with a very low degree of hybridization.     

Eriogonum (Polygonaceae) novelties from Baja California,Mexico

Five new entities ofEriogonum are described from Baja California and Baja California Sur, Mexico, including one species,E. preclarum, and four varieties of other species:E. fasciculatum var.emphereium,E. wrightii var.oresbium,E. elongatum var.areorivum, andE. grande var.testudinum. Three combinations are proposed:E. wrightii var.dentatum,E. elongatum var.vollmeri, andE. repens.     

The lambeosaurine dinosaur Magnapaulia laticaudus from the late cretaceous of Baja California, Northwestern Mexico

The taxonomy, osteology, phylogenetic position, and historical biogeography of the lambeosaurine hadrosaurid Magnapaulia laticaudus (new combination) are revised. The diagnosis of this species is amended on the basis on two autapomorphies (i.e., longest haemal arches of proximal caudal vertebrae being at least four times longer than the height of their respective centra; base of prezygapophyses in caudal vertebrae merging to form a bowl-shaped surface) and a unique combination of characters (i.e., downturned cranioventral process of the maxilla; tear-shaped external naris with length/width ratio between 1.85 and 2.85; neural spines of dorsal, sacral, and proximal caudal vertebrae being at least four times the height of their respective centra). A maximum parsimony analysis supports a sister taxon relationship between M. laticaudus and Velafrons coahuilensis. Both taxa constitute a clade of southern North American lambeosaurines, which forms a sister relationship with the diverse clade of helmet-crested lambeosaurines from northern North America that includes well-known genera like Corythosaurus, Lambeosaurus, and Hypacrosaurus. According to the results of a Dispersal-Vicariance analysis, southern North American lambeosaurines split from the northern forms via vicariance from a common ancestor that lived in both the northern and southern regions of the continent.     

Daily vertical migration of dense deep scattering layers related to the shelf-break area along the northwest coast of Baja California, Mexico

Echo signals were collected with a Simrad 200 kHz transduceracross the shelf-break features off the northwest coast of BajaCalifornia (30°05'–30°42'N, 115°50'–116°26'W)during two diel cycles (July 1995) with the objective of describingvertical migrations of two dense deep scattering layers (DSL)found near the shelf break. DSL records were made within anarea ±50 m in the neritic zone, ±200 m at theshelf break and ±1000 m depth in the offshore station.Using an Isaacs-Kidd midwater net and Bongo nets, we inferredthat the DSL were composed mainly of juveniles and adults ofthe euphausiids Nyctiphanes simplex Hansen and Euphausia pacificaHansen. These aggregations have a close interaction with theocean bottom during the daytime and display a vertical migration,rising near to the surface at night where a progressive horizontaldispersion then occurs. The DSL measured 3.5–6.0 km horizontallyduring the night. The ascent and descent migrations of the DSLwere significantly fitted to a polynomial function of the secondorder, suggesting different swimming behavior during these twoprocesses. Vertical migrations of the DSL were between 60 and90 m. During the descent migration, maximum instantaneous speedsreached 0.7 cm s¹, and during the ascent, maximum instantaneousspeeds were 0.3 cm s¹. These coastal euphausiid species, alongwith other macrozooplankton and nektonic organisms, have a dailyclose interaction with the ocean bottom and also with the pelagicenvironment, suggesting that they play an important role providingfood for demersal and pelagic organisms on the slope and shelfbreak in the upwelling region off the northwest coast of BajaCalifornia.     

Carterella (Rubiaceae), new genus from Baja California,Mexico

Carterella is described as a new genus based on Bouvardia alexanderae, endemic to Baja California Sur, Mexico. Closest relationships are to the Houstonia mucronata group, but qualitative differences in seed characters and striking quantitative differences in floral characters provide evidence for recognition of a new monotypic genus.     

Seasonal and interannual variation of sterols in macrophytes from the Pacific coast of Baja California Peninsula (Mexico)

The seasonal and interannual proximate and sterol composition were assessed in two red (Gelidium robustum, Gelidiaceae and Gracilariopsis sjoestedtii, Gracilariaceae), two brown (Ecklonia arborea, Lessoniaceae and Macrocystis pyrifera, Laminariaceae), and two green (Ulva lactuca and Ulva clathrata, Ulvaceae) macroalgae species and the seagrass Phyllospadix torreyi (Zosteraceae) sampled over 3 years in a subtropical climate in Baja California Sur, Mexico. Each macroalga had a particular sterol composition that was typical of their taxonomic group. The red algae had cholesterol as the major sterol; 92% on average in G. robustum and 90% in G. sjoestedtii, followed by t‐dehydrosterol and brassicasterol. In the brown algae the major sterol was fucosterol, which accounted for approx. 90% and 92% of total sterols for M. pyrifera and E. arborea, respectively, followed by campesterol (7% and 5%) and isofucosterol (1.5% and 1.3%). The green algae had isofucosterol as the major sterol, with 92% on average for U. lactuca and 87% for U. clathrata, followed by cholesterol, fucosterol, and brassicasterol or norcholesterol. The seagrass P. torreyi had β‐sitosterol as the major sterol (39 to 89%, depending on the season), followed by campesterol (4 to 7%), stigmasterol (3 to 6%), and isofucosterol (1.7 to 3.5%). Four (cholesterol, campesterol, fucosterol, and isofucosterol) of the 14 sterols identified in macroalgae and the seagrass could be used to differentiate between classes (Florideophyceae – red, Phaeophyceae – brown, Ulvophyceae – green, and Monocots – seagrass) both seasonally and interannually. The seasonal and interannual sterol composition of macroalgae and seagrass was quite stable, with the exception of red G. sjoestedtii sampled in August and green macroalga U. lactuca and seagrass P. torreyi both sampled in May 2002. Seasonal and interannual variations of proximate and sterol composition are discussed in relation to their reproductive state and environmental parameters.     

The biology of Vaejovis littoralis Williams, an intertidal scorpion from Baja California, Mexico

Vaejovis littoralis Williams is an intertidal scorpion inhabiting chiefly the drift zone in the high intertidal of beaches in Baja California, Mexico. Density within the drift zone averages approximately 2–4/m² (island sites) to 12/m² (mainland sites). Populations are aggregated into patches. Primarily, juveniles exhibit diurnal activity. Nocturnally active juveniles tend to be spatially segregated from nocturnally active adults within the drift zone.
Diet of V. littoralis includes the isopod Ligia, V. littoralis , spiders, pseudoscorpions, centipedes and beetles. Prey size is not a function of predator size. Centruroides exilicauda, V. littoralis and Ligia were observed as predators on V. littoralis .
The adult sex ratio is skewed toward females (1 male : 2.1 females). Adult females are usually larger than adult males. Litter size ranges from 1–8. Limited data suggest that offspring size and litter size increase with maternal size.
Vaejovis littoralis exhibits cryptic coloration, small size and lithophilic tarsal claws, all of which favour intertidal existence. Although V. littoralis is able to withstand up to 12 hours of submergence, it does not survive submergence significantly better than a comparable desert species. Field data suggest that V. littoralis does not exhibit an endogenous tidal rhythm.     

Endemic regions of the vascular flora of the peninsula of Baja California,Mexico

Question: Can we recognize areas of high endemism and high endemic richness, using data from collections, and what are the ecological variables that best explain these areas? Location: Peninsula of Baja California, Mexico. Methods: We analysed the distribution of 723 endemic vascular plants species along the peninsula of Baja California and neighbouring islands distributed in 218 cartographic cells 15’ x 20’ in size. By means of a residual analysis, we identified areas of significantly high endemic species richness, and we calculated the degree of endemicity (or rarity) in each cell by giving to each species a weight factor inversely proportional to the land area it covers. Results: Nine regions of high‐endemicity and/or high endemic species richness were found. Discussion and conclusions: The analyses of rarity and endemic species richness showed two contrasting scenarios: High endemicity values in oceanic and sky islands accounts for a high number of species with a restricted distribution, promoted most likely by genetic isolation and high environmental heterogeneity. High endemic richness along the peninsular coast is related to ecotonal transition along vegetation types. After correcting for collection effort (i.e. the number of specimens collected within a cell), we found the phytogeographic region and altitudinal heterogeneity to be the variables that best predicted endemic richness. Both high endemism and high endemic richness have distinct geographic patterns within our study region. The nine endemic regions provide elements for priority definitions in future conservation programs.     

Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula,Mexico

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.     

Characterization of halophiles isolated from solar salterns in Baja California, Mexico

Solar salterns are extreme hypersaline environments that are five to ten times saltier than seawater (150–300 g L⁻¹ salt concentration) and typically contain high numbers of halophiles adapted to tolerate such extreme hypersalinity. Thirty-five halophile cultures of both Bacteria and Archaea were isolated from the Exportadora de Sal saltworks in Guerrero Negro, Baja California, Mexico. 16S rRNA sequence analysis showed that these cultured isolates included members belonging to the Halorubrum, Haloarcula, Halomonas, Halovibrio, Salicola, and Salinibacter genera and what may represent a new archaeal genus. For the first time, metabolic substrate usage of halophile isolates was evaluated using the non-colorimetric BIOLOG Phenotype MicroArray™ plates. Unique carbon substrate usage profiles were observed, even for closely related Halorubrum species, with bacterial isolates using more substrates than archaeal cultures. Characterization of these isolates also included morphology and pigmentation analyses, as well as salinity tolerance over a range of 50–300 g L⁻¹ salt concentration. Salinity optima varied between 50 and 250 g L⁻¹ and doubling times varied between 1 and 12 h. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.