Differential growth of the barnacle Notobalanus flosculus (Archaeobalanidae) onto artificial and live substrates in the Beagle Channel, Argentina

Abstract

In the Beagle Channel, southern South America (ca. 55°S 67°W), about 20% of false king crabs (Paralomis granulosa) >80 mm carapace length are fouled with the barnacle Notobalanus flosculus. To evaluate differences in growth rates of barnacles attached to artificial and live substrates, clay tiles were anchored as collectors to the bottom at two different sites in the Beagle Channel in September 1996: in Ushuaia harbour (low currents and high levels of suspended matter) and around the Bridges Islands (strong currents and low level of suspended matter). Another set of collectors was deployed at the same sites in October 1998 to collect barnacles for histological studies. Tiles were removed from each place, approximately, on a monthly basis. Carapaces of P. granulosa with the epizoic N. flosculus were sampled between November 1996 and 1997, and between March 1998 and September 1999, to study sexual maturation of barnacles. Growth of barnacles was compared between the collectors and P. granulosa carapaces following a qualitative approach. A sexual maturity scale was defined, based on the stage of development of the female reproductive apparatus of N. flosculus. Growth rate of barnacles was highest in the harbour, intermediate on P. granulosa, and lowest around the Bridges Islands. Presence of oocytes was registered only in epizoic barnacles, suggesting that at least a proportion of these individuals is able to spawn on the carapaces. The potential advantages of settling on a living substrate, namely increased availability of food particles and decreased predation risks are discussed.

Effects of enhanced temperature and ultraviolet B radiation on a natural plankton community of the Beagle Channel (southern Argentina): a mesocosm study

“…Therefore, UVBR irradiance used in the present study is comparable to that of the studies by Longhi et al (2006) and Roy et al (2006) and differences in UVBR cannot explain why there was no overall effect of UVBR on the planktonic community. Beagle Channel waters are characterized by a seasonal turbidity pattern, with clear waters in winter and more turbidity during summer (Venerus et al 2005). Given the season of our experiment (summer), some UVBR could have been absorbed by the particles and the dissolved materials in the water column.…”