The ultrastructural features of the spermatogenic development and mature spermatozoa morphology of Atrina maura were investigated through transmission electron microscopy. The testis displays a ...diffuse tubular structure in which gametes develop within a concentric arrangement according to the degree of development. Within the tubules also appear Sertoli cells, which contain a large amount of lipid droplets and glycogen granules in the cytoplasm, suggesting a nutritive role in the first spermatogenesis stage (spermatogonia). Four gamete maturation stages co-occurred in the same individual: spermatogonia (4–8 μm), spermatocytes (3–4 μm) (including primary and secondary), spermatids (2.5 μm) and spermatozoa (∼ 2 μm head length). The proacrosomal vesicle and flagellum occur only until the first stages of spermiogenesis, contrasting with the early formation of both structures in spermatogonia and spermatocytes in other bivalves. In A. maura, the material in the acrosomal vesicle of mature spermatozoa shows a characteristic electron density pattern, which seems to be an exclusive taxonomic feature of the family Pinnidae. However, A. maura displayed only four mitochondria in the midpiece, contrasting with five in all other species in this family.
The lion-paw scallop Nodipecten subnodosus is a commercially important resource in the northwest of Mexico; however few studies evaluate its growth. Length of shell was used to estimate individual ...growth parameters of the lion-paw scallop from a wild population. Monthly samplings were performed from January to December 2006 in Bahia de Los Angeles on the western coast of the Gulf of California, Mexico. Morphometric relationships between total length, height, total weight, and mass weight were estimated. The number of cohorts was determined monthly using the multinomial technique based on a likelihood function. The cohort that was best represented over time was used to fit the stationary growth model of von Bertalanffy. The results indicated that this species presents negative allometric growth and showed high correlation among different morphometric measures (R2> 0.88). Length frequency distributions showed two cohorts in each sample, except from August to November when there were up to three cohorts, with greater variance in those of intermediate sizes. The growth parameters were: L=8734; = 19.06 cm, k = 0.47 year-1, t0 = -0.19 years, C = 0.38, ts = 0.37. Due to fluctuations in the growth of the species, assessments should be performed based on age-structured models to support fishery management measures for this species.
The sailfish Istiophorus platypterus is one of the most common billfish species in the Mexican Pacific. Information about its feeding habits in the coastal region of Acapulco, Guerrero is extremely ...limited. In the present study we quantified the diet of sailfish, based on captures made from March 2008 to December 2009 by the sport fishing fleet of Acapulco. We analysed a total of 561 stomachs, of which 254 contained food (45%). The size interval of examined specimens was between 101 and 212 cm postorbital length and between 15 and 47 kg total weight. In general, teleosts were the most important prey, followed by cephalopods. According to index of relative importance, the most important species in the diet were the fish Auxis thazard (63.04%) and Fistularia commersonii (6.62%), followed by the cephalopod Octopus spp. (4.58%). There were no significant differences in the diet by sex (males and females), sexual maturity (immature and mature), or by season (warm and cold seasons). In all cases the most important prey species was A. thazard. We conclude that the sailfish I. platypterus off Acapulco behaves as a specialist predator because, despite the consumption of a high number of prey items, it feeds preferentially on a reduced number of prey species that form schools, and are available and abundant in the ocean.
Spondylus limbatus es una especie bajo protección especial en México, de la que existe poca información biológica y nada sobre estudios histológicos o de ultraestructura del ovario. El objetivo de ...esta investigación fue caracterizar la morfología ultraestructural de los gametos femeninos maduros y en degeneración. La gónada femenina de S. limbatus en estado de madurez presentó ovocitos postvitelogénicos de 60-70 microm de diámetro, que presentan el aspecto característico de células metabólicamente activas y altamente sintetizadoras. La membrana citoplasmática posee especializaciones destinadas a aumentar la superficie de absorción de la célula, las microvellosidades; el citoplasma presenta numerosos sistemas membranosos relacionados con la síntesis de material de reserva y secreción; y el patrón de organización nuclear altamente lobulado, y por consiguiente con una gran superficie que asegura el intercambio núcleo-citoplasma, se incorpora de forma estructural al proceso de vitelogénesis. Finalmente, se describen los cambios ultraestructurales resultantes de la lisis de los ovocitos: colapso de las membranas nuclear y citoplásmica, y presencia de células hemocíticas macrófagas. PALABRAS CLAVE: Reproducción; Gónada; Microscopía electrónica;Vitelo.
This paper describes the oogenesis of Chiton virgulatus, based on histological observations under transmission and scanning electron microscopy. Three oocyte types were identified: i) previtellogenic ...oocytes with a mean diameter of 50±20.5 µm, surrounded by elongated follicular cells of approximately 5 µm, ii) immature vitellogenic oocytes with a mean diameter of 113±15.3 µm and small cytoplasmic projections denoting the onset of the oocyte hull development; adjacent to each projection are pores approximately 0.7 µm in diameter, and iii) mature vitellogenic oocytes with a mean diameter of 146±24.8 µm; the oocyte cytoplasmic projections grow and its apical zone becomes trident-shaped; follicular cells adopt a bulbous shape due to the growth of the elongation and can reach up to 20 µm in length. The morphology and ultrastructure of the projections of the mature vitellogenic oocyte, as well as the size of pores at their base, are specific to C. virgulatus; therefore, these features could be used in taxonomic or fertilization studies.
Anisotremus interruptus is a widely distributed and commercially important species in the Eastern Pacific. A multi-year research on the reproduction of this species was carried out in coastal waters ...of Jalisco, Mexico. For this purpose, monthly samples were gathered with gillnets of different mesh sizes from 1998-2008. A total of 1090 individuals were collected with a total length range between 15.6-61.0cm. Significant differences from expected 1:1 ratio were found for sex ratios in the total sample and for each size class, but not when comparisons among months and years were done. Temporal variations of the gonadosomatic index and proportions of maturation stages suggest that the main reproductive period is from February to May, although some less intensive spawning events were observed in other months. Seven stages of oocytes development were identified. Oocytes in different stages of development were identified in ovaries classified as mature, suggesting an asynchronic type of gonad development. Mean maturation length (L50) was 31.0 for females and 29.7cm for males. The internal organization of testes is of lobular type.
Se estableció el ciclo reproductivo del pargo lunarejo Lutjanus guttatus, un pez de gran importancia comercial. Los organismos se recolectaron mensualmente desde febrero de 1993 a diciembre de 1994. ...La proporción de sexos poblacional fue de 1M:0.96H y no se encontró una diferencia significativa (P£0,05) de la proporción esperada de 1:1. Las gónadas se analizaron histológicamente y se describieron las fases de desarrollo gonadal. L. guttatus presenta un desarrollo asincrónico de las gónadas y es un desovador parcial. La actividad reproductiva estuvo presente todo el año aunque con dos períodos reproductivos principales (marzo-abril y agosto-noviembre) representados por altos porcentajes de gónadas categorizadas como maduras y en desove. Estos períodos coinciden con valores elevados del índice gonadosomático (IGS) y valores bajos del índice hepatosomático (IH). El factor de condición (FC) presentó una tendencia similar a la del IGS con los máximos valores durante la época de reproducción y disminuyendo hacia las épocas de reposo. Se considera que el IGS representa adecuadamente la actividad reproductiva y que puede haber una relación inversa entre la actividad reproductiva y el IH.
Se presenta el registro de ampliación de ámbito geográfico de cuatro especies de peces marinos del Pacífico oriental tropical mexicano: Anisotremus interruptus; Gymnura crebripunctata; Narcine ...entemedor y Sphoeroides lispus.
PDF
