Resección transoral endoscópica de tiroides lingual / Endoscopic transoral resection of lingual thyroid

La presencia de tejido tiroideo ectópico en la base de la lengua es muy infrecuente, y la mayoría de los pacientes tienen hipotiroidismo. La indicación de tratamiento depende de la presencia o no de síntomas; la cirugía es la primera elección. Diversas técnicas quirúrgicas han sido descriptas, pero para nosotros el abordaje transoral con endoscopios constituye la mejor opción, por la buena exposición y la mínima morbilidad que produce. Se describe el caso clínico de una mujer que consultó por odinofagia, con diagnóstico de tiroides lingual y que fue tratada con éxito mediante un abordaje transoral con asistencia de endoscopios. (AU)

The presence of ectopic thyroid tissue at the base of the tongue is very rare, and most patients have hypothyroidism. The indication of treatment depends on the presence or not of symptoms, surgery being the first choice. Various surgical techniques have been described, being for us the transoral approach with endoscopes the best option, due to the good exposure, and minimum morbidity that it produces. The clinical case of a woman who consulted for odynophagia, with a diagnosis of lingual thyroid and who was successfully treated by a transoral approach with endoscopic assistance is described. (AU)

Reproductive biology of Ferocactus recurvus (Mill.) Borg subsp. recurvus (Cactaceae) in the Tehuacán-Cuicatlán Valley, Mexico.

Mexico has one of the highest diversities of barrel cacti species worldwide; however, all are threatened and require conservation policies. Information on their reproductive biology is crucial, but few studies are available. Ferocactus recurvus subsp. recurvus is a barrel cactus endemic to the Tehuacán-Cuicatlán Valley. Our research aimed to characterise its floral and pollination biology. We hypothesised bee pollination, as suggested by its floral morphology and behaviour, and self-incompatibility, like most barrel cacti studied. Three study sites were selected in the semiarid Zapotitlán Valley, Mexico. We examined 190 flowers from 180 plants to determine: morphometry and behaviour of flowers, flower visitors and probable pollinators, and breeding system. Flowers showed diurnal anthesis, lasting 2-5 days, the stigma being receptive on day 2 or 3 after the start of anthesis. Flowers produced scarce/no nectar and main visitors were bees (Apidae), followed by flies (Muscidae), ants (Formicidae), thrips (Thripidae) and hummingbirds (Throchilidae); however, only native bees and occasionally wasps contacted the stigma and anthers. Pollination experiments revealed that this species is self-incompatible and xenogamous. In natural conditions, fruit set was 60% and cross-pollination fruit set was 100%. Percentage seed germination resulting from cross-pollination was higher than in the control treatment. Our results provide ecological information for conservation programmes to ensure a high probability of breeding and seed production in natural populations of F. recurvus.

Limits to the host range of the highly polyphagous tephritid fruit fly Anastrepha ludens in its natural habitat.

Anastepha ludens (Diptera: Tephritidae) is a highly polyphagous fruit fly that is able to develop in a wide range of hosts. Understanding the limits of this pest's host range could provide valuable information for pest management and plant breeding for pest resistance. Previous studies have shown that guavas (Psidium guajava (Myrtaceae) L.), are not attacked under natural conditions by A. ludens. To understand this phenomenon, guavas were exposed to natural infestation by A. ludens and to other fruit fly species that infest guavas in nature (Anastrepha striata Schiner, Anastepha fraterculus (Wiedemann), Anastepha obliqua (Macquart)). Once the susceptible phenological stage of guavas was determined, fruit infestation levels were compared between A. ludens and A. striata. Choice and non-choice tests were performed under field-cage conditions. Under field conditions, guavas were susceptible to A. striata and A. fraterculus attack all the way from when fruit was undeveloped to when fruit began to ripen. No infestation by A. ludens was recorded under natural conditions. Similar results were obtained when forced exposures were performed, indicating that unripe guavas were preferred by A. striata over ripe fruit, and that infestation rates were higher at early fruit maturity stages. Under forced oviposition conditions, A. ludens larvae were unable to develop in unripe guavas but did so in fully ripe fruit. However, A. ludens fitness parameters were dramatically affected, exhibiting reduced survival and reduced pupal weight compared to conspecifics that developed in a natural host, grapefruit. We confirm that P. guajava should not be treated as a natural host of this pestiferous species, and suggest that both behavioral aspects and the fact that larvae are unable to adequately develop in this fruit, indeed represent clear limits to A. ludens's broad host range.

Phenotype-genotype correlations in hemophilia A carriers are consistent with the binary role of the phase between F8 and X-chromosome inactivation.

BACKGROUND: The recessive X-linked disorder hemophilia A (HA) is rarely expressed in female carriers, most of whom express about half of normal factor VIII activity ( FVIII: C). OBJECTIVE: To propose an integrative assessment model for the binary role of the phase between the mutated F8 and the active X-chromosome (Xa) in FVIII: C in HA carriers. METHODS: We studied 67 females at risk of severe HA, comprising five symptomatic females ( FVIII: C < 1.5 IU dL(-1) ) and 14 controls. A correlation study between FVIII: C (observed vs. expected) and X-chromosome inactivation (XCI) patterns (XIPs; androgen receptor gene [AR] system) in blood leukocyte DNA was performed in carriers, by comparison of a model correlating FVIII: C and XIP with arbitrary models devoid of biological significance, and with FVIII: C levels in non-carriers (mean model) as a proxy from background data dispersion not influenced by XIP. RESULTS: We provide proof-of-concept example from a family presenting with extremely skewed XIPs in which the severe HA phenotype appeared in a heterozygous carrier of a crossover between AR and F8 loci that phased the mutated F8 with the maternally inherited Xa. Furthermore, four cases of severe HA affected women who had a combination of a heterozygous F8 mutation and extremely skewed XIPs in leukocytes or oral mucosa are presented. Correlation analyses between FVIII: C levels and XIPs in carriers (n = 38) but not in non-carriers (n = 20) showed highly significant differences between the proposed correlation model and models without biological significance. The data support a binary influence of XCI, either increasing or decreasing the FVIII: C, subject to the underlying phase set between the F8 mutation and XCI. CONCLUSIONS: Our evidence suggests that the phase between XCI and mutated F8 acts as a molecular switch conditioning FVIII: C levels and HA expression in carriers.

Influenza vaccine: development of a novel intranasal and subcutaneous recombinant adjuvant.

The synthetic peptide GK-1, derived from Taenia crassiceps, enhances the protection induced by human influenza vaccine in both young and aged mice. Herein, the adjuvant properties of GK-1 fused to the pVIII protein of a heat-inactivated phagemid vector (FGK1) when co-administered with the influenza vaccine were assessed, to evaluate its feasibility as a low-cost adjuvant. In mice, FGK1 significantly increased the expected IgG and IgA anti-influenza antibody levels both in sera and in bronchoalveolar fluids when intranasally or subcutaneously co-administered with influenza vaccine. Single-dose pig co-immunization with FGK1 and influenza vaccine induced serum levels of IgG anti-influenza antibodies similar to those elicited by a two-dose immunization with the influenza vaccine alone. Preclinical evaluation of FGK1 with the influenza vaccine is currently in progress, in order to recommend its use for veterinary purposes.

Allergy and acute leukaemia in children with Down syndrome: a population study. Report from the Mexican inter-institutional group for the identification of the causes of childhood leukaemia.

BACKGROUND: Allergies have been described as protective factors against the development of childhood acute leukaemia (AL). Our objective was to investigate the associations between allergy history and the development of AL and acute lymphoblastic leukaemia (ALL) in children with Down syndrome (DS). METHODS: A case-control study was performed in Mexico City. The cases (n=97) were diagnosed at nine public hospitals, and the controls (n=222) were recruited at institutions for children with DS. Odds ratios (OR) were calculated. RESULTS: Asthma was positively associated with AL development (OR=4.18; 95% confidence interval (CI): 1.47-11.87), whereas skin allergies were negatively associated (OR=0.42; 95% CI: 0.20-0.91). CONCLUSION: Our findings suggest that allergies and AL in children with DS share biological and immune mechanisms. To our knowledge, this is the first study reporting associations between allergies and AL in children with DS.

The treatment with an anti-glycosaminoglycan antibody reduces aortic oxidative stress in a rabbit model of atherosclerosis.

Retained low-density lipoproteins (LDL) by arterial glycosaminoglycans (GAG) are more susceptible to reactive oxygen species-mediated oxidation, contributing to oxidative stress and atherosclerosis. Recently, we reported the properties of the chimeric mouse/human monoclonal antibody chP3R99-LALA to bind sulfated GAG, to inhibit LDL-chondroitin sulfate binding, and to avoid LDL oxidation in vitro. Here, we hypothesized that chP3R99-LALA treatment might reduce aortic oxidative stress in a therapeutic setting. Redox biomarkers and serum lipids were determined by spectrophotometric methods. Subcutaneous administration of five doses (100 µg) of chP3R99-LALA, after Lipofundin administration (2 mL/kg/day, i.v.) during 8 days, reduced atherosclerotic lesion development, which was not associated with a serum lipid modulation. In contrast, the treatment with chP3R99-LALA reduced (p < 0.05) malondialdehyde and protein oxidation, induced a restoration of reduced glutathione level, of the superoxide dismutase and catalase activities and of endothelial nitric oxide level. Thus, the antiatherogenic effect of chP3R99-LALA treatment seems to be associated with a reduction of aortic oxidative stress. These results contribute in understanding the molecular mechanisms associated with chP3R99-LALA atheroprotection and support the use of anti-GAG antibody-based immunotherapy as a potential tool to treat the atherosclerosis.

Vascular density, hypoxia inducible factor, vascular endothelial growth factor, and its receptor expression in the chorioallantois of relatively normoxic and hypoxic chicken embryos, at 6 and 7 days of incubation, and corresponding weight values.

The weight of 6- and 7-d-old chicken embryos and their chorioallantoic membrane (CAM), vascular density, protein immunoexpression, and mRNA of hypoxia inducible factor 2 (HIF-2α), vascular endothelial growth factor (VEGF-A), and its type receptor 2 (FLK-1) in the CAM were compared in subjects incubated at 2 different altitudes: 355 and 1,378 m above sea level (masl) in Colombia. A difference was not found when comparing the weight of CAM and embryos incubated at 355 masl with those incubated at 1,378 masl on d 6 and 7 of incubation (P > 0.05). Higher vascular density in CAM (P < 0.05), percentage of cells immunoexpressing HIF-2α and FLK-1 in the CAM (P < 0.05), and relative expression of HIF-2α and FLK-1 mRNA in the CAM (P < 0.05 and P < 0.01, respectively) were encountered in embryos incubated at 1,378 masl compared with those incubated at 355 masl, but only on d 6. Percentages of cells immunoexpressing VEGF-A and relative expression of VEGF-A mRNA in the CAM values were not different when considering altitude and age (P > 0.05). Relative hypoxia (1,378 masl) appears to affect HIF-2α and FLK-1 expression in CAM of 6-d-old chicken embryos, and this change in expression results in increased vascular development in CAM on this day. At hatching, chickens between treatments differed in their BW (P < 0.0001). The lack of differences in findings on d 7 could be due to morphological, physiological, and molecular events occurring at this time.

[Retroperitoneal cystic lymphangioma in an adult: case report]. / Linfangioma quístico retroperitoneal en un adulto: informe de caso.

Retroperitoneal cystic lymphangyoma is a benign lesion, extremely rare in adults. In most cases is asymptomatic. The objective of this report is to present the case of an 82 year old woman who presented abdominal pain, food intolerance and a palpable abdominal mass located toward the upper right quadrant. The abdominal CT scan showed a cystic lesion below the liver which extended to the retroperitoneum. The patient underwent laparotomy achieving complete resection of the lesion and she was discharged soon after. After six months of follow up, she has not presented recurrence. The presentation of this lesion is very rare, generally as a consequence of congenital malformations of the lymphatic vessels. These lesions must be considered as part of the differential diagnosis of the cystic type tumors. The ultrasound and abdominal CT scan are useful for diagnosis. Surgical resection is the only therapeutic option.

Informativeness of a novel multiallelic marker-set comprising an F8 intron 21 and three tightly linked loci for haemophilia A carriership analysis.

The extraordinary heterogeneous nature of the deleterious mutations in the F8 gene that lead to functional deficiency of clotting factor VIII in haemophilia A makes routine direct mutation profiling difficult. When direct mutation analysis cannot be performed or a causative/candidate mutation is not found, a second-line approach to track the defective F8 gene within at-risk families is linkage genetic analysis with, tried-and-tested, F8-intragenic and/or extragenic non-recombining multiallelic short tandem repeats (STR). Although several typing STR loci within and around F8 have been described, there is need for improving assessment, because the combined informativeness of available assays rarely reaches 100%. Here, we characterized a newly identified 0.28 cM-resolution marker-set, consisting of a dinucleotide STR located on F8 intron 21 (F8Int21; [AC](n)) and three extragenic tetranucleotide STR located on GAB3 intron 1 (GAB3Int1; [TAAA](n)) and TMLHE intron 1 (TMLHEInt1.1; [GAAA](n) and TMLHEInt1.3; [ATTC](n)). Heterozygosity rates determined in 100 unrelated females ranged from 0.25 (GAB3Int1) to 0.63 (F8Int21). The set rendered a combined informativeness of 0.91 for at least one marker and 0.60 for a minimum of two loci, with at least one F8-intragenic. Multiallelic interlocus non-random association analysis revealed that GAB3Int1 is not in significant gametic disequilibrium (GD) with F8Int21, F8Int9.2, TMLHEInt1.3 or TMLHEInt1.1. Gametic disequilibrium breakdown attests historical recombination between GAB3Int1 and the F8 gene. Through computational analysis of reference assembly sequence data, we note in the GD breakdown region and in the F8 gene a higher than average density of the 13-mer CCNCCNTNNCCNC consensus motif, commonly associated with recombination hotspots.

BCG-itis in two antiretroviral-treated HIV-infected infants.

Although vaccination with Bacille Calmette-Guérin (BCG) is considered safe, adverse regional (BCG-itis) and disseminated (BCG-osis) diseases preferentially occur in the immunocompromised host. The infection with human immunodeficiency virus (HIV) by mother-to-child transmission leads to impaired cellular immune responses, a situation that poses a great challenge regarding the universal use of BCG vaccine. World Health Organization recommends that children who are known to be HIV-infected, even if asymptomatic, should no longer be immunized with BCG. Many of the complications of BCG vaccination occur in severely immunosuppressed HIV-infected children and are related to late institution of antiretroviral and antimycobacterial therapy. We report two cases of BCG-itis in HIV-infected infants, who fulfilled clinical criteria of immune reconstitution inflammatory syndrome: axillary adenitis, one with suppuration, and both temporally associated with precocious restoration of immunity elicited by the use of antiretroviral therapy. Isoniazid (10 mg/kg/day) was offered until regression of adenopathies, and lesions were not handled.

Interlocus non-random association of multiallelic polymorphisms spanning the coagulation factor VIII gene on human chromosome distalmost Xq28.

The most common severe hereditary bleeding disorder phenotype in humans, the coagulation factor VIII (F8) deficiency haemophilia A (HEMA), maps on Xq28 band, a region that comprises 11.7% of genes and 14.2% of phenotypes on X chromosome. Information about the distribution and extent of gametic disequilibrium (GD) covering the F8 gene is scarce, despite its relevance for linkage and association studies. The aim of this study was to determine the patterns, by frequency and strength, of non-random multiallelic interallelic associations between two-locus combinations of seven microsatellite loci (REN90833, F8Int25.2, F8Int22, F8Int13.2, HEMA154311.3, TMLHEInt5 and HEMA154507.3, in that physical order) spanning 0.813 Mb on distalmost Xq28. We measured sign-based interallelic D' coefficients in 106 men and in 100 women drawn from a single unrelated Brazilian population. Significance and patterns of GD using haploid and phased diploid sample probabilities were close to conformity. Only 9.18% of the variance of D' could be accounted for by changes in length, indicating that GD is not a monotonically decreasing function of length. We defined two regions of overlapping long-range GD extending 698 735 base pairs (bp) (REN90833/TMLHEInt5 block) and 689 900 bp (F8Int13.2/HEMA154507.3 block) The extent of GD overlap is 575 637 bp (F8Int13.2/TMLHEInt5 interstice). Extended haplotype homozygosity analysis centred at the F8 intronic loci revealed that the most frequent core haplotypes decay the least in the flanking GD. The F8 intronic loci attend distinct non-random association forces; F8Int13.2 serves at maintenance of the long-range overlapping pattern of GD, whereas F8Int25.2 and F8Int22 serve at lessening it in force or effect.

Using a floating-gate MOS transistor as a transducer in a MEMS gas sensing system.

Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe(2)O(3) layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane.

Double aneuploidy (48,XXY,+21) of maternal origin in a child born to a 13-year-old mother: evaluation of the maternal folate metabolism.

The occurrence of non-mosaic double trisomy is exceptional in newborns. In this paper, a 48,XXY,+21 child, the parental origin of the extra chromosomes and the evaluation of the maternal folate metabolism are presented. The infant was born to a 13-year-old mother and presented with the typical clinical features of Down syndrome (DS). The origin of the additional chromosomes was maternal and most likely resulted from errors during the first meiotic division. Molecular analysis of 12 genetic polymorphisms involved in the folate metabolism revealed that the mother is heterozygous for the MTHFR C677T and TC2 A67G polymorphisms, and homozygous for the mutant MTRR A66G polymorphism. The maternal homocysteine concentration was 4.7 miromol/L, a value close to the one considered as a risk factor for DS in our previous study. Plasma methylmalonic acid and serum folate concentrations were 0.17 micromol/L and 18.4 ng/mL, respectively. It is possible that the presence of allelic variants for the folate metabolism and Hey concentration might have favored errors in chromosomal disjunction during gametogenesis in this young mother. To our knowledge, this is the first patient with non-mosaic Down-Klinefelter born to a teenage mother, resulting from a rare fertilization event combining an abnormal 25,XX,+21 oocyte and a 23,Y spermatozoon.

Improved criterion-referenced assessment in indirect tracking of haemophilia A using a 0.23 cM-resolution dense polymorphic marker set.

In haemophilia A, linkage analysis with coagulation factor VIII (F8) intragenic and/or neighbouring extragenic short tandem repeats (STRs) enables indirect tracking F8 pathogenic allelic variant-carriers. Even where DNA sequencing is available, linkage analysis still has a role if no causative or candidate mutation is unveiled. The cumulative heterozygosity rate of the available multiplexed STRs haplotyping assays rarely reaches 100%. This means that in a proportion of women these loci are uninformative. The norm-referenced assessment is based on at least one informative marker criterion. We reasoned that by typing a dense market set, spanning a small fraction of recombination, we should be able to improve assessment. The aim of this study was to improve criterion-referenced assessment in polymorphism segregation analyses using a low-recombination fraction and dense informative STRs set. The multiplex quantitative fluorescence PCR assay comprises four novel tetranucleotide and pentanucleotide STRs distant < or = 0.15 cM from the F8 gene, and three F8 intragenic dinucleotide STRs, mapped to a 0.23 cM interval spanning the F8 on human chromosome band Xq28. We determined heterozygosity rates and allele frequencies from 100 unrelated healthy females. To investigate about segregation stability, we typed 50 true trios (mother, daughter and father) and 50 true mother-and-son duos from the general population. The heterozygosity rates for the extragenic markers ranged 0.49-0.76. The 0.23 cM-resolution heptaplex rendered a cumulative heterozygosity of 0.89 for a minimum of two informative markers, with at least one F8 intragenic. The heptaplex assay enabled improving the criterion-referenced assessment in indirect carrier-detection.

High-resolution combined linkage physical map of short tandem repeat loci on human chromosome band Xq28 for indirect haemophilia A carrier detection.

Haemophilia A, the most common severe hereditary bleeding disorder in humans, is chiefly caused by mutations in the coagulation factor VIII F8 gene, which maps on chromosome band Xq28. Linkage analysis with F8 intragenic and/or closely located extragenic short tandem repeat (STR) elements is an effective method for indirect tracing of F8 pathogenic allelic variants in at-risk families. STR profiling is currently limited to 14 markers, 11 of which are dinucleotide elements. The aim of this study was to define novel polymorphic STR loci for haemophilia A carrier screening. The combined linkage physical map was restricted to a 2.4-Mb region on Xq28 that hosts 81 annotated genes, F8 inclusive. The inventory was in silico through comparative analyses with three X chromosome reference sequences, using microsatellite mining and validation computer software. Genetic distances for unmapped markers were interpolated on the Rutgers map of the human genome. The effort yielded 94 STR loci: 53 extragenic and 41 intragenic (14 STR elements map on the F8 gene; the other 27 on 19 further genes). The distribution per repeat period size was 61.7% di-, 5.3% tri-, 26.6% tetra- and 6.4% pentanucleotide loci. The success rate of validation of polymorphism for the new STR loci was 56.3%. For STR elements 0.78 Mb equidistant of the F8 gene, the interpolated downstream genetic length is 3.27 times the upstream genetic length. The inventory represents a 5.7-fold increase in polymorphic STR loci useful in carrier detection. Genotyping with the upstream extragenic tetra- and pentanucleotide markers is thus apprized.

Caracterización espacial y biogeográfica de las asociaciones de macroalgas de Bahía del Rincón, Baja California Sur, México / Spatial and biogeographic characterization of macroalgal assemblages from Bahía del Rincón, Baja California Sur, Mexico

Macroalgal studies in Baja California Sur have dealt mainly with occurrence and seasonality, but some areas are poorly known even for these basic data. Bahía del Rincón-La Rivera is an important high-productivity fisheries area where coastal infrastructure development is under way. A spatial characterization of the marine flora from Bahía del Rincón-La Rivera was done by intensive sampling at different depths and localities with skin and SCUBA diving. At least 500m2 were surveyed in each site. Additionally, quantitative sampling was done in ten random 25 cm2 quadrates per site. In the intertidal section, density and cover estimates were used. We also investigated the historical records and geographical affinities. A total of 72 species were identified (most were red algae: 62%). We found no general trend in the biogeographical affinities, which varied with each taxonomic group. Most brown algae species were tropical-endemic; red algae temperate- cosmopolite and green algae tropical-cosmopolite. In the spatial assemblage structure we found a high similarity between the intertidal areas, but a low similarity in shallow or deeper areas (3-5 m). This pattern was the same when we compared the abundance of the main species. We suggest that there are significant spatial differences in recruitment and development of the assemblages in relation to vertical distribution (depth)and position along the shore. There is a clear-cut Gelidium-Jania belt in the intertidal zone and a Padina-Dictyota belt below the low tide. Sporadic and year-round species occur in the intertidal zone, annual and perennial species below the low tide line. Sites differ in recruitment and this affects the abundance of other species (such as coraline and Caulerpa species). Temperature and sedimentation affect seasonality, but community structure is relatively constant throughout the year

Se caracterizó la flora marina de la zona de Bahía del Rincón -La Rivera por medio de prospecciones intensivas en diferentes localidades a varias profundidades. Además, se realizó un análisis intenso de la literatura y por este mismo medio la determinación de las afinidades geográficas de las especies. En total se encontraron 72 especies, donde la mayor proporción (62%) correspondió a las algas rojas. En el caso de las afinidades biogeográficas se observó que la mayor proporción varió en función de la división, donde para algas cafés las predominantes fueron de naturaleza tropical/ endémica y para las algas rojas fueron las templadas/ cosmopolitas. Espacialmente se encontró una alta similitud entre las zonas someras estudiadas más no así entre las someras y profundas donde existen diferencias significativas. En el caso de la zona intermareal se determinaron diferencias significativas con áreas submareales y entre sitios de la zona somera y profunda basados en las abundancias de los principales taxa. Con base en los resultados se sugiere que existen diferencias verticales en reclutamiento y desarrollo de las poblaciones en relación a su distribución

[Spatial and biogeographic characterization of macroalgal assemblages from Bahía del Rincón, Baja California Sur, Mexico]. / Caracterización espacial y biogeográfica de las asociaciones de macroalgas de Bahía del Rincón, Baja California Sur, México.

Macroalgal studies in Baja California Sur have dealt mainly with occurrence and seasonality, but some areas are poorly known even for these basic data. Bahia del Rincón-La Rivera is an important high-productivity fisheries area where coastal infrastructure development is under way. A spatial characterization of the marine flora from Bahia del Rincón-La Rivera was done by intensive sampling at different depths and localities with skin and SCUBA diving. At least 500 m2 were surveyed in each site. Additionally. quantitative sampling was done in ten random 25 cm2 quadrates per site. In the intertidal section, density and cover estimates were used. We also investigated the historical records and geographical affinities. A total of 72 species were identified (most were red algae: 62%). We found no general trend in the biogeographical affinities, which varied with each taxonomic group. Most brown algae species were tropical-endemic; red algae temperate-cosmopolite and green algae tropical-cosmopolite. In the spatial assemblage structure we found a high similarity between the intertidal areas, but a low similarity in shallow or deeper areas (3-5 m). This pattern was the same when we compared the abundance of the main species. We suggest that there are significant spatial differences in recruitment and development of the assemblages in relation to vertical distribution (depth) and position along the shore. There is a clear-cut Gelidium-Jania belt in the intertidal zone and a Padina-Dictyota belt below the low tide. Sporadic and year-round species occur in the intertidal zone, annual and perennial species below the low tide line. Sites differ in recruitment and this affects the abundance of other species (such as coraline and Caulerpa species). Temperature and sedimentation affect seasonality, but community structure is relatively constant throughout the year.