Production of Excirolana armata (Dana, 1853) (Isopoda, Cirolanidae) on an exposed sandy beach in southeastern Brazil

Abstract

The somatic and gonad productions of the cirolanid isopod Excirolana armata were analyzed by taking monthly samples from December 2003 to November 2005 on Una beach, São Paulo state (24°S), southeastern Brazil. Sampling was performed along three fixed transects established from the base of the foredunes to the waterline. Weight-specific growth rate was used to estimate the E. armata somatic production for 2004 and 2005, separately. The gonad production was estimated based on the monthly reproductive potential (mean number of eggs/ embryos per female 9 monthly abundance of ovigerous females with near-release broods) for 2004. The annual somatic production of E. armata population varied from 15.57 to 17.25 g AFDW m -1 year -1 and the somatic production/biomass ratio (P s /B) from 3.55 to 3.14 year ) contributed about 15 and 6% to the total production (P s ? P g ) of females and the population, respectively. The proportion of gonad to somatic production of females (P g /P s ) increased with individual size (ca 90% in the 7.5 mm size class), and the annual weight-specific gonad production (P g /B ratio) was estimated to 0.24 year -1 . The high P s /B ratios estimated for E. armata derive from the fast growth of individuals and show the importance of this population to the energy flow on Una beach ecosystem. However, the low percentage of juveniles verified in this population and in other studies of populations of the genus Excirolana is discussed as an important source of underestimation of P s /B ratio.

Variability of macrofauna distribution along a dissipative log-spiral sandy beach in Rio de Janeiro, Southeastern Brazil

“…The more exposed area of the beach arc was dominated by the cirolanid, E. armata, which were virtually absent from the first transects. E. armata acts as a scavenger/predator and, at the macroscale, is highly substratum-specific to fine sands of beaches from dissipative to intermediate morphodynamic states (Defeo et al 2001, Lozoya et al 2010, Petracco et al 2010. When only a single beach arc is investigated, the sand particle size emerges as the most immediate environment of the macrofauna (Defeo and McLachlan 2005).…”

Age and growth in three populations of Dosinia exoleta (Bivalvia: Veneridae) from the Portuguese coast

“…With increasing latitude, it has been observed an increasing trend in reproductive effort, egg and larval size, whereas an opposite trend has been shown for age at first maturity, fecundity, reproductive output, growth rate and mortality (e.g. Clarke 1987;Contreras and Jaramillo 2003;Thatje et al 2004;Ward and Hirst 2007;Petracco et al 2010).…”

Population structure, growth and production of Thoracophelia furcifera (Polychaeta: Opheliidae) on a sandy beach in Southern Brazil

“…The mean population density in this study was 3 to 2,000 times greater than on other beaches from southern Brazil to Uruguay (Table 1). A similar pattern of fluctuation in density and biomass was found in other T. furcifera populations, such as the population of Atami Beach (Souza and Borzone 2007), and also in populations of other intertidal polychaetes, such as Scolelepis squamata (Müller, 1806) and Laeonereis culveri (Webster, 1879) (Souza and Borzone 2000;Martín and Batista 2006), as well as in populations of crustaceans such as Emerita brasiliensis (Schmitt, 1935), Excirolana brasiliensis (Dana, 1853), E. armata (Dana, 1853) and Pseudorchestoidea brasiliensis (Dana, 1853) (Defeo et al 1997;Cardoso et al 2003;Veloso et al 2003b;Petracco et al 2010) and bivalves Donax hanleyanus (Philippi, 1842) and Mesodesma mactroides (Deshayes, 1854) (Defeo and Alava 1995;Brazeiro and Defeo 1999). This common feature of beach macrofaunal populations may be associated with biological factors such as recruitment (Veloso and Cardoso 1999), high mortality and migration (McLachlan and Brown 2006) as well as with physical factors such as slope , salinity, temperature (Leber, 1982) and beach morphodynamics (McLachlan and Brown 2006).…”