Morfología de la membrana coriónica de los huevos de Octopus bimaculoides y Octopus hubbsorum (Cephalopoda: Octopodidae)

Recently spawned eggs of Octopus bimaculoides and O. hubbsorum are ovo-cylindrical in shape and have an average of 10.1±1.4 and 2.1±0.1 mm in length, respectively. The egg envelope consists of two main parts: the chorionic membrane (Chorion) and the chorionic peduncle. The chorion of O. bimaculoides eggs shows a single layer of 8 µm in thickness, with pores smaller than 1 µm in diameter, and the internal architecture of the chorion connects to the chorionic peduncle. The chorion of O. hubbsorum eggs has a thickness of 4 µm without pores, and the internal architecture of the chorion does not interconnect with the chorionic peduncle. The chorionic peduncle of O. hubbsorum eggs shows an annular width of 300 µm in the junction with the main body of the chorion. O. hubbsorum eggs have a micropyle shaped as a deep circular cavity, 15 µm in diameter in the center of the pole of the chorion. The micro-structure morphology of O. bimaculoides and O. hubbsorum eggs shows a differentiation between the chorion membranes, which is described in this study for the first time.Los huevos recién desovados de Octopus bimaculoides y de O. hubbsorum son de forma ovocilíndrica, miden 10.1±1.4 y 2.1±0.1 mm de longitud, respectivamente. La envoltura del huevo consta de dos partes principales: la membrana coriónica (corion) y el pedúnculo coriónico. El corion del huevo de O. bimaculoides presenta una sola capa, de un grosor de 8 µm, con poros menores a 1 µm de diámetro y una arquitectura interna en conexión con el pedúnculo coriónico. El corion del huevo de O. hubbsorum tiene un grosor de 4 µm, sin poros y una arquitectura interna sin interconexión con el pedúnculo coriónico. El pedúnculo coriónico del huevo de O. hubbsorum presenta un ensanchamiento anular a 300 µm de la unión con el cuerpo principal del corion. El huevo de O. hubbsorum tiene un micrópilo en forma de cavidad circular profunda de 15 µm de diámetro, en el centro del polo mayor del corion. En este estudio se describe por primera vez que la microestructura morfológica del corion es distinta en los huevos de O. bimaculoides y O. hubbsorum

Descripción de la primera zoea del cangrejo araña Stenorhynchus debilis (Decapoda: Brachyura: Majoidea)

Background: The study of the morphological changes in embryonic development up to the stages of zoea and megalopa, is essential for the culture of crustacean and to distinguish one species from another in the classification of the decapods. Goals: Identify the morphological characteristics of the first zoea of Stenorhynchus debilis (Smith, 1871), to differentiate from the first zoeas of species of the same genus. Methods: S. debilis ovigerous females were collected and kept in captivity. From spawned eggs the stage of embryonic development was identified and the morphology of the first zoea was studied, using a bright field microscope equipped with a digital camera and Image Pro® software. Results: The orange eggs are 380-450 µm of diameter. The embryonic identified stages were: multiple divisions, blastula, gastrula and pre-zoea. The following morphological characteristics of the first zoea were identified: the straight spine 10% larger than the length of the carapace; a triangular spine in the frontal region of the carapace, a pair of chromatophores in the vicinity of each somite and fur branches of the telson with large and curved terminal spines. Conclusions: These morphological characteristics of the first zoea of S. debilis make it possible differentiate from the first zoeas of the same genus, such as S. seticornis and S. lanceolatus.Antecedentes: El estudio de los cambios morfológicos del desarrollo embrionario hasta los estadios de zoeas y megalopa es fundamental para el cultivo de crustáceos y para diferenciar una especie de otra en la clasificación de los decápodos. Objetivos: Identificar las características morfológicas de la primera zoea de Stenorhynchus debilis (Smith, 1871), para diferenciarla de las primeras zoeas de las especies del mismo género. Métodos: Se recolectaron hembras ovígeras de S. debilis y se mantuvieron en cautiverio. De los huevos desovados se identificarón estadios del desarrollo embrionario y se estudió la morfología de la primera zoea con un microscopio compuesto de campo claro, provisto de una cámara digital y el software Image Pro®. Resultados: Los huevos tienen un diámetro de 380-450 µm, son color naranja. Los estadios embrionarios identificados fueron: divisiones múltiples, blástula, gástrula y el de pre-zoea. En las primeras zoeas recién eclosionadas se identificaron las siguientes características morfológicas: la espina dorsal recta es 10% más grande que la longitud del caparazón; una espina triangular en la región frontal del caparazón, un par de cromatóforos en las inmediaciones de cada somita y ramas furcales del telson con espinas terminales grandes y curvadas. Conclusiones: Estas características morfológicas de la primera zoea de S. debilis permiten diferenciarla de las primeras zoeas del mismo género como son S. seticornis y S. lanceolatus

Embryonic development, hatching time and newborn juveniles of Octopus tehuelchus under two culture temperatures

The development of cephalopods early life stages is strongly influenced by environmental variables, especially temperature. Octopus tehuelchus (d'Orbigny, 1834) is an Atlantic Patagonian fishery resource currently being studied as a new species for cultivation; however it is not known how temperature modulates its early life stages. In this work, egg masses were artificially incubated at 13 and 16 °C under controlled aquarium conditions. In each thermal treatment, the stages of embryonic development, embryo morphometry and survival throughout embryogenesis, as well as embryogenesis duration were recorded. After hatching, the morphological description of the juveniles was achieved and survival time in starvation was calculated for both temperatures. At 16 °C the mean embryonic duration was 85 days shorter than at 13 °C. For both thermal treatments, the highest mortalities occurred up to the beginning of organogenesis, and no significant differences in hatching success were observed. The temperature also showed the potential to increase or decrease the juvenile performance at the early post hatching period. This resulted in a significant reduction in size and weight of new born juveniles at 13 °C but also in an average increment of 7 days in their survival in starvation when compared to octopus reared at 16 °C. The chromatophore pattern was similar for both thermal treatments and was characteristic of juveniles of this species. The observed differences seem to show adaptive mechanisms that optimize embryos and juveniles viability under the different environmental temperatures that can be found in the northern Atlantic Patagonian coast. From a practical point of view, our findings are important to define the biological parameters and associated procedures for the cultivation of the early life stages of O. tehuelchus.Fil: Braga, Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Van Der Molen, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; ArgentinaFil: Pontones, Julian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Ortiz, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentin

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Estudios sobre el cultivo de larvas y juveniles de almeja catarina Argopecten ventricosus (=circularis) (Sowerby II, 1842) en el laboratorio.

Impreso y PD

Larval and early juvenile development of Tegula eiseni (Jordan, 1936) (Gastropoda: Trochidae)

Larval and early juvenile development was studied in Tegula eiseni (Jordan, 1936) for 63 days under laboratory conditions at temperatures of 20 ± 2°C in order to have a photographic sequence of the stages that help identify wild early juvenile specimens. Larvae were obtained by induced spawning. Postlarvae and juveniles were fed Nannochloropsis oculata and Phaeodactylum tricornutum. Elapsed time from fertilization to veliger was 2 days. All larvae settled by day 4. Development of the teleoconch began on day 12. Juveniles (570 ± 60 μm long) had a teleoconch with 11 longitudinal ribs on day 51. On days 58 through 63, the umbilicus and shell spiral provided juveniles with adult-like morphological characteristics (610 ± 60 μm long). We conclude that the identification of early juveniles of this and other associated gastropods coming from wild populations should be performed by selecting those specimens that show a teleoconch in advanced stages to assure a correct identification

Larval and early juvenile development of Tegula eiseni (Jordan, 1936) (Gastropoda: Trochidae)

Larval and early juvenile development was studied in Tegula eiseni (Jordan, 1936) for 63 days under laboratory conditions at temperatures of 20 ± 2°C in order to have a photographic sequence of the stages that help identify wild early juvenile specimens. Larvae were obtained by induced spawning. Postlarvae and juveniles were fed Nannochloropsis oculata and Phaeodactylum tricornutum. Elapsed time from fertilization to veliger was 2 days. All larvae settled by day 4. Development of the teleoconch began on day 12. Juveniles (570 ± 60 μm long) had a teleoconch with 11 longitudinal ribs on day 51. On days 58 through 63, the umbilicus and shell spiral provided juveniles with adult-like morphological characteristics (610 ± 60 μm long). We conclude that the identification of early juveniles of this and other associated gastropods coming from wild populations should be performed by selecting those specimens that show a teleoconch in advanced stages to assure a correct identification

Cultivo de larvas y juveniles de almeja voladora Euvola vogdesi (Pteroida: Pectinidae)

El trabajo describe por primera vez el desarrollo larvario hasta juvenil de Euvola vogdesi y las experiencias en el cultivo larvario de esta especie. Los reproductores en acondicionamiento gonádico alcanzaron la madurez total a los 42 ± 5 días. La inducción al desove se realizó con los métodos de shock térmico (18-20°C/20 min) e inyección intragonadal de serotonina (0,3 mL a 0,25 mM). En experimentos del efecto de las temperaturas 20, 23 y 25°C en el crecimiento larvario, se obtuvo a 25°C el mayor crecimiento. A esta temperatura, los cultivos larvarios con cambios en la densidad y dieta entre 1992 y 2001 mostraron diferencias significativas en el crecimiento, logrando disminuir el tiempo de cultivo larvario de 25 días a 11 días. En la etapa de pre-engorda, los juveniles de 3,5-4,0 mm de longitud de concha, tuvieron una supervivencia de 3-5%, a los 55 ± 5 días. Los juveniles de 6-7 mm de longitud presentaron las valvas características de los adultos, después de 25-30 días