Mauricio Palacios

UVB effects on early developmental stages of commercially important macroalgae in southern Chile

High levels of ultraviolet-B radiation (UVB) could represent a danger to seaweeds by affecting their physiological processes and development. The aim of this work was to study the effects of UVB radiation on early developmental stages of commercially and ecologically important marine algal species in southern Chile, considering spores survival and embryos growth. Spores of Mazzaella laminarioides, Gigartina skottsbergii, Sarcothalia crispata and embryos of G. skottsbergii and Macrocystis pyrifera were submitted to treatments of a) photosynthetically active radiation (PAR: Control), b) PAR+UVA (PA) and c) PAR+UVA+UVB (PAB). UV radiation did not affect spore survival of M. laminarioides S. crispata and G. skottsbergii (P = 0.55, P = 0.6 & P = 0.25 respectively), but did provoke differences in the growth rate of G. skottsbergii embryos (P = 0.00). Differences in survival and growth of M. pyrifera embryos were also observed (P = 0.001 & P = 0.007, respectively). Differences in growth of M. pyrifera embryos were observed only in the first five days, whereas changes in survival persisted until the end of the experiment. Additionally, UVB provoked morphological alteration in M. pyrifera embryos, as evidenced by progressive curling. These results suggest that the initial stages of the subtidal algae species G. skottsbergii and M. pyrifera cultivated in laboratory conditions were sensitive to UVA and UVB radiation, and their recruitment and development could be affected as well in natural conditions found in southern South America, where the ozone layer has thinned more than in other parts of the planet.

Effects of UVB Radiation on the Initial Stages of Growth of Gigartina Skottsbergii, Sarcothalia Crispata and Mazzaella Laminarioides (Gigartinales, Rhodophyta)

The effects of UVB radiation on the growth of macroalgal thalli were evaluated using tetrasporophytic fronds of the Rhodophytes Gigartina skottsbergii, Sarcothalia crispata and Mazzaella laminarioides. The tetrasporophytic fronds were collected from nature and the tetrasporophyte sporelings grown in a temperature regulated chamber at 8 ± 2 ∘C with a 12L:12D (Light: Dark) photoperiod, Photosynthetically Active Radiation (PAR) of 55 μmol photons m−2 s−1 and seawater enriched with 20 mL L−1 of Provasoli medium. We exposed the thalli of these macroalgae to PAR (55 μmol photons m−2 s−1) and three treatments using a combination of PAR with three different levels of UVB radiation (0.10, 0.15 and 0.23 W m−2 for G. skottsbergii and S. crispata and 0.02, 0.05 and 0.10 W m−2 for M. laminarioides) during a period of 71 days. Growth of thalli was quantified by measuring their length using digitized photographs of samples.Important differences were detected in the growth of individuals cultured under the effects of UVB radiation, when compared to the control (i.e. plants exposed to PAR only). In the case of G. skottsbergii and S. crispata higher levels of UVB radiation resulted in slower growth of thalli. In nearly all measurements for the first two species, UVB radiation levels of 0.1 W m−2 induced differences in thallus growth, while for M. laminarioides levels of UVB radiation of 0.1 W m−2 were effective only after a prolonged period of exposure.Differential effects of UVB radiation on G. skottsbergii, S. crispata and M. laminarioides could interfere with the natural populations of these economically important macroalgal species in southern Chile, where they occur under the annual influence of the Antarctic Ozone Hole and the general thinning of the ozone layer.

Pseudione tuberculata Richardson, 1904 (Isopoda: Bopyridae): a parasite of juveniles of the king crab Lithodes santolla (Molina, 1782) (Anomura: Lithodidae) in the Magellan Strait, Chile

El isopodo parasito Pseudione tuberculata Richardson, 1904 infesta la cavidad branquial de especies de la familia Lithodidae en el extremo sur de Sudamerica. Ha sido descrito previamente como parasito de Neolithodes en el Archipielago de los Chonos, Chile, y en Paralomis granulosa (Jacquinot, 1847) y Lithodes santolla (Molina, 1782) en aguas someras del canal Beagle, Argentina. Es la primera vez que el parasito es documentado en Chile en el estrecho de Magallanes, ubicado alrededor de 640 km al norte del canal Beagle, parasitando juveniles de L. santolla (23,0 a 51,6 mm LC en hembras y entre 24,0 a 48,7 mm en machos). La frecuencia del parasito en centollas fue de 27,97% en hembras y 21,43% en machos. La frecuencia de infestacion fue mayor a la descrita en otros crustaceos chilenos parasitados por Pseudione. Cada centolla portaba una pareja de P. tuberculata dentro de la cavidad branquial en el lado izquierdo del caparazon. Las altas tasas de parasitismo de P. tuberculata en centollas juveniles en el area podria ocurrir en aguas someras habitadas por Macrocystis pyrifera debido a su efecto en las condiciones hidrodinamicas locales, la reduccion del flujo y la amortiguacion del oleaje, proporcionando habitats para diversos organismos marinos. Se concluye que P. tuberculata como parasito de L. santolla, en el estrecho de Magallanes, responde de manera similar al compararse con los valores de infestacion de estudios previos desarrollados en el canal Beagle, Argentina, en donde ha sido reportada infestando P. granulosa y L. santolla.

Morphological and growth alterations on early development stages of Iridaea cordata (Rhodophyta) under different intensities of UVB radiation

This study describes the effects of different intensities of UVB radiation on growth and morphology of early development stages of Iridaea cordata in germlin...

Presencia de Cistenides Elhersi Hessle, 1917 (Polychaeta Perctinariidae) en aguas someras magallánicas habitadas por praderas de Ruppia Filifolia: Evidencia de Euribatia, Eurihalididad y Euritermia?

A objeto de analizar los impactos potenciales que podrian tener los gradientes de salinidad, asi como los distintos regimenes termicos sobre la distribucion batimetrica de la fauna bentonica estuarina en la zona austral de Chile, se desarrollo una revision bibliografica sobre los hallazgos del poliqueto Cistenides elhersi recolectados en diferentes cruceros Cimar Fiordo. Se consideraron las caracteristicas oceanograficas de las estaciones con profundidades mayores a 50 m, y se adicionaron datos nuevos obtenidos en un sector de baja salinidad (25 psu) y somero del Seno Skyring (52°33’16” S, 71°51’34” W; 0,3 a 2 m profundidad), Region de Magallanes, donde predomina una pradera del pasto acuatico Ruppia filifolia. Los datos analizados en forma conjunta permiten proponer que C. elhersi muestra eurihalinidad, euritermia y euribatia. Se proporcionan antecedentes complementarios sobre la abundancia del poliqueto, tamano y ubicacion dentro de la matriz del pasto. Se destaca la necesidad de desarrollar nuevos estudios para identificar otro tipo servicios ecologicos prestados por esta pradera de R. filifolia.