Growth dynamics in a natural population ofCorbicula fluminea(Bivalvia Sphaeriacea) at Punta Atalaya, Rio de La Plata, Argentina

Abstract

Annual growth of Corbicula fluminea has been estimated by following the shift in size-frequency peaks based upon shell lengths. Normal curves were fitted to mean shell length for each generation, or age group. The study was based upon monthly and bimonthly samples taken from an natural population at Punta Atalaya, Rio de La Plata, Argentina, colonized in September 1982. The age-length relationship was determined using the Von Bertalanffy's equation.The growth of C. fluminea slows markedly during the fall-winter period, April to August. Theoretical growth curves were calculated for spring-summer and fall-winter seasons; the equations corresponding to each seasonal growth rate are respectively: L t = 31.6 (l-e -0268.t ) and L t = 21.0 (l-e -0.0727.t )Growth rate diminishes with increasing shell-length and age. Water temperature seems to be a determining factor for the occurrence of differential seasonal growth rates. Reproduction in C. fluminea occurs once a year at Punta Atalaya, and settlement of juveniles takes place in September.The estimated life span has been calculated to be 36 months.

Growth dynamics in a natural population ofBiomphalaria straminea(Dunker, 1848) from Bella Unión, Artigas, Uruguay

“…In order to obtain an estimate of parameters K and L oo from successive measurements of shell diameter for each generation group, the methodology proposed by Léveque (1973) and applied by Ituarte ( 1985) to data coming from natural populations, was followed. Derivating two sides of the Von Bertalanffy's equation (1) When those monthly increases in shell diameter (L 2 -L!/month) are plotted against the mean shell diameter between two measurements (Fig.…”

Dispersal ofCorbicula fluminea: factors influencing the invasive clam's drifting behavior

“…Young adults with shell length between 11.5 and 17.5 mm tended to be the most abundant size class, dominating the population size structure. The fraction of juveniles (shell length up to 10 mm; Ituarte 1985;Cataldo and Boltovskoy 1998;Mouthon 2001a) in the population was always low compared with that of the adults. Juvenile fraction noticeably increased over June 2012, decreasing in the beginning of the following month.…”

“…Clams were collected by using a shovel to drag sediment into a bag with 1 mm mesh size, used to roughly sieve the sample. Clams with shell length in the range 9-14 mm, corresponding to mature animals that were already proven to be able to produce a mucilaginous drogue line (Prezant and Chalermwat, 1984;Ituarte, 1985), were then selected. Quantitative sampling was used to address the seasonal variation of the clams' body condition and obtain cohort frequencies (see below for details).…”

Stable carbon isotopes in the shell of Corbicula fluminea (Müller 1774): Implications for understanding environmental changes in drainage basins

“…The average length of the clams collected was 20 mm long. Their annual growth rate is around 10 mm/a [37,38], with an average of 0.8 mm/month. Even if the growth rate in December was lower than the annual average [36,39], the slow growth would be offset by fast growth in October-November, when the water temperature is between 22-28°C, as estimated by air temperatures.…”