ABSTRACT
The first zoeal-stage larva of a possibly new species of mud shrimp Naushonia (Decapoda: Gebiidea: Laomediidae) was described from plankton samples taken off the Fernando de Noronha Archipelago, being the first occurrence at the oceanic islands of the Equatorial Atlantic. Five zoea I larvae were obtained and dissected for observation of mouthparts. This zoea I of Naushonia sp. is well distinguished from the first larvae of N. portoricensis (Rathbun 1901) from the Caribbean and N. cangronoides (Kingsley 1897) from the Northwest Atlantic in terms of development and setation of appendages, and possibly belongs to a new, undescribed species. The present study widens the knowledge on tropical oceanic decapod larvae and provides detailed drawings and new photographic illustrations with extended depth of field of these organisms.
Subject(s)
Decapoda , Animals , Caribbean Region , Islands , Larva , Oceans and SeasABSTRACT
Se analizó la composición y abundancia del zooplancton de la laguna El Morro en la isla de Margarita, Venezuela, durante el periodo de surgencia (marzo-mayo 2011) y de relajación (junio-agosto 2011). Las muestras fueron recolectadas en 6 estaciones de las diferentes zonas de la laguna. Se realizaron calados con una red de plancton de 333 µm durante 10 minutos. Se midió in situ la temperatura, salinidad y oxígeno disuelto, además de nutrientes. Se registraron valores medios de temperatura de 29.7 ºC, salinidad de 36 ups, oxígeno disuelto de 5.9 mg.L-1. La concentración de nutrientes fue baja (medias de 0.12; 0.04; 0.03 mg.L-1 para nitrato, nitrito y fosfato, respectivamente). Se detectaron diferencias significativas temporales con mayores registros en la temporada de relajación, mientras que espacialmente no mostró diferencias, a pesar que en las estaciones internas (Est. 4,5,6) se obtuvo mayor abundancia. Se identificaron quince grupos zooplanctónicos, determinándose nueve especies del grupo Copepoda, dos de Cladocera, una de Decapoda, Tunicada y Rotifera y diferentes formas larvarias de distintos taxa. Las larvas de crustáceos presentaron la abundancia media y relativa más alta (47738 ind.m-3 y 46.83%, respectivamente), seguido del copépodo Oithona nana (31740 ind.m-3 y 25.94%, respectivamente) y Paracalanus quasimodo (12958 ind.m-3 y 8.47%, respectivamente). Esta laguna involucra la estacionalidad surgencia-relajación como un efecto importante en la distribución y abundancia del zooplancton.
The composition and abundance of the zooplankton of El Morro lagoon on the island of Margarita, Venezuela, during the upwelling period (March-May 2011) and relaxation (June-August 2011) were analyzed. Samples were collected at 6 stations in different areas of the lagoon. Sampling was performed with a 333 μm plankton net for 10 minutes. Water Temperature, salinity and dissolved oxygen were measured in situ, in addition to nutrients. Average water temperature values of 29.7 °C, a salinity of 36 ups, and dissolved oxygen of 5.9 mg.L-1 were found. The concentration of nutrients was low (averages of 0.12, 0.04, 0.03 mg.L-1 for nitrate, nitrite and phosphate, respectively). Significant seasonal differences were detected with greater records in the relaxation season, whereas spatially did not show differences, although in the internal stations a greater abundance was recorded. Fifteen zooplankton groups were identified, identifying nine species of Copepoda, two of Cladocera, one of Decapoda, Tunicada and Rotifera and different larval forms of different taxa. Crustacean larvae showed the highest average and relative abundance (47738 ind.m-3 y 46.83%, respectively), followed by copepod O. nana (31740 ind.m-3 and 25.94%, respectively) and P. quasimodo (12958 ind.m-3 and 8.47%, respectively). This lagoon involves the emergence-relaxation seasonality as an important effect on the distribution and abundance of zooplankton.
ABSTRACT
The pesticides used by the salmon industry to treat sea lice, are applied in situ via a bath solution and are subsequently discharged into the surrounding medium. The effects of cypermethrin, deltamethrin, azamethiphos and hydrogen peroxide were assessed on the performance of Metacarcinus edwardsii larvae, an important crab for Chilean fishery. All larvae were dead or dying after 30 min of exposure to cypermethrin and after 40 min to deltamethrin at concentrations 100 and 20 times lower (0.15 and 0.1 µg L-1, respectively) than the concentrations and exposure times recommended by the manufacturers (CRM) to treat sea lice. Azamethiphos affected all larvae at a concentration 10 times lower than CRM. Hydrogen peroxide had the lowest detrimental effects, but at the CRM, 100% of the larvae were affected. Sub-lethal effects, i.e prolonged developmental time, were observed at concentrations lower than CRM. Repeated exposure to azamethiphos (0.0625-0.5 µg L-1) and hydrogen peroxide (188-1500 mg L-1) had effects on survival. In conclusion, the pesticides used against parasitic copepod tested here, negatively affect non-target crustacean larvae. Due to the product's characteristics, the lethal effects of the pyrethroids probably are restricted to the time and area of application, while the action of azamethiphos may extend to a wider area. Current data are insufficient to accurately dimension the effects of these compounds in the field. More research is required to evaluate the consequences of prolonged developmental times and/or reduction in appendage mobility, so as the effects of these compounds on the pelagic and benthic communities.