Larval dispersal of Brachyura in the largest estuarine / marine system in the world

For the first time, this study monitored six sites in a wide transect with approximately 240 km radius on the Amazon Continental Shelf (ACS) every three months. The objective was to analyze the larval composition of Brachyura, its abundance in shallow/subsurface and oblique hauls, the extent of larval dispersion related to the estuary/plume, and to predict the probability of occurrence and abundance for the temperature, salinity, and chlorophyll- a profiles of the water column. A total of 17,759 identified larvae are distributed in 8 families and 25 taxa. The water salinity was the best predictor of larval distribution. The statistical models used indicated that Panopeidae and Portunidae larvae are more frequent and more likely to occur in shallow water layers, while Calappidae occur in deeper layers, and Grapsidae, Ocypodidae, Sesarmidae, Pinnotheridae and Leucosiidae occur similarly in both strata. The larval dispersion extent varies among families and throughout the year while the groups are distributed in different salinities along the platform. The probability of occurrence of Portunidae is higher in ocean water (> = 33.5); Grapsidae, Panopeidae, and Pinnotheridae is higher in intermediate and ocean salinity waters (25.5 to 33.5); Ocypodidae, Sesarmidae and Calappidae is higher in estuarine and intermediate salinity waters (5 to 25.5), whereas Leucosiidae, euryhaline, occur in all salinities (5 to 33.5). Furthermore, the Amazon River seasonal flow and plume movement throughout the year not only regulate the larval distribution and dispersion of estuarine species but are fundamental for the ACS species, providing the necessary nutrient input for larval development in the region plankton.

REPRODUCTIVE ASPECTS OF THE PRAWN Macrobrachium amazonicum IN A CONTINENTAL POPULATION LIVING DOWNSTREAM OF A HYDROELECTRIC DAM

The migratory behavior of females of the freshwater prawn Macrobrachium amazonicum (Heller, 1862) can indicate a strategy that optimizes the population establishment. With this idea in mind, we evaluated the reproductive biology of M. amazonicum, hypothesizing that females were evenly distributed downstream of Hydroelectric Dam. Specimens were collected monthly for one year, from six sites of Rio Grande river. The specimens were sexed and measured (carapace length; CL). A total of 14,697 adults were captured, 2,864 males (AM), 11,082 non-breeding females (AF) and 751 breeding females (BF). The smallest BF had 3.8 mm CL. The distribution of demographic groups was assessed by a Principal Component Analysis (PCA), which explained 95.16% of the distribution over the collection sites. Breeding females were more abundant in the sites closest to the dam. This result can be explained by rainfall, which varied significantly throughout the year. As the breeding females migrated upstream toward the dam and were more abundant there, our hypothesis of homogeneous distribution was rejected. This behavior probably optimizes larval dispersion. The reproduction was continuous with peaks in the period preceding the maximum rainfall.

Reproductive biology of the swimming crab Achelous spinimanus (Decapoda, Portunoidea): a potential fishing resource

ABSTRACT This study describes the reproductive and recruitment patterns of the swimming crab Achelous spinimanus (Latreille, 1819) in the Ubatuba region of the northern coast of São Paulo, Brazil. Crabs were captured monthly from January 1998 to December 1999 in 18 sites located in three bays (Ubatumirim, Ubatuba, and Mar Virado), using a commercial fishing boat. In each sampling area, bottom temperature, salinity, and organic matter content were recorded. A total of 1,911 individuals were captured: 350 adult males, 475 non-ovigerous adult females, 584 adult ovigerous females, and 502 immature individuals. Reproductive females were more abundant in deeper areas; this migration might be a strategy to improve larval dispersion and survival. Ovigerous females were found year-round, indicating a continuous reproduction, and their abundance was positively correlated with temperature. During the 2-year survey, crabs with all gonadal development stages were found. We can infer that this region provides suitable resources for the development of A. spinimanus.

DIFERENCIACIÓN MORFOLÓGICA DE LAS ESPECIES DE PIANGUA ANADARA TUBERCULOSA Y ANADARA SIMILIS (ARCIDAE) EN DIFERENTES BOSQUES DE MANGLAR A LO LARGO DE LA COSTA PACÍFICA COLOMBIANA MEDIANTE MORFOMETRÍA GEOMÉTRICA

The morphological characterization of two piangua species Anadara tuberculosa (Sowerby) and Anadara similis (Adams) was performed using geometric morphometric. Shells of both species were collected in nine different areas of the Colombian Pacific coast during 2009 as part of a project on the natural populations of piangua. The left valve of the shell was used to draw seven landmarks and evaluate the geometric configuration of the shell. Pianguas were grouped based on the mangrove cover of the localities where they were collected. Intra-specific comparison showed that areas where the organisms were collected do not affect valve configuration. Contrarily, centroide size showed significant variation in organism collected in different zones. Differences due to size are not sufficient to determine the existence of different populations, mainly because these differences may happen due to differences in fishery patterns increasing the ratio of smaller sizes. Pacific Ocean current might favor the genetic flux of organisms of both species, limiting the possibility of evolution of independent populations. It is important to complement this study with other investigations in genetics and larval dispersion in order to corroborate our findings.

Putative long distance gene flow and evidence of secondary outbreaks of the Crown-of-Thorns Starfish in the Pacific Ocean

Population outbreaks of the corallivorous crown-of-thorns starfish (COTS), Acanthaster ‘planci’ L., are considered among the most important biological disturbances of tropical coral reefs. A local COTS outbreak, a “primary outbreak”, can lead to so-called “secondary outbreaks” in adjacent coral reefs due to increased larval release and subsequent dispersion. Previous analyses have shown that in the Pacific Ocean, this dispersion may be geographically restricted to certain regions. Guam, an island in the western Pacific region, suffered from several COTS outbreaks in the last 50 years, and in this study we test whether Guam is genetically connected with surrounding regions as a consequence of secondary outbreaks. We used microsatellites to measure gene flow and genetic structure among 14 localities in the Pacific Ocean. Our results show substantial genetic structure between geographical regions. There was, however, a lack of significant genetic differentiation between localities separated by large geographic distances (e.g., Guam, Kingman Reef and Johnston Atoll) – a finding consistent with the existence of contemporary long distance larval dispersion and the gradual erasing of ancestral signatures of divergence. Long distance larval dispersion suggests that secondary outbreaks occur across regions in the Pacific, and have occurred in the recent outbreaks in Guam. However, significant genetic differences among outbreak localities around the island of Guam were also detected, revealing the signature of both primary and secondary outbreaks. Our findings highlight the importance of addressing likely triggers of both primary and secondary outbreaks in conservation efforts and programs that strive to control the growth and spread of A. ‘planci’ in the Pacific Ocean.