PERFORMANCE OF SOMATIC EMBRYOGENESIS DEVELOPMENT UNDER DIFFERENT 2,4-D AND COCONUT WATER CONCENTRATION IN SUGARCANE VAR. BULULAWANG

Mass propagation technology through somatic embryogenesis has become an alternative for producing sugarcane seedlings rapidly.Application of proper plant growth regulator and concentration contribute to support somatic embryogenesis development. This study applied the combination of liquid and solid culture during proliferation stage to promote cell dispersion of embryogenic callus, rapid embryo somatic production, and improve regeneration potency of somatic embryo. Application of 2,4-D and coconut water during proliferation may expected as proper combination for accelerating somatic embryo development and regeneration.Development of somatic embryogenesis in sugarcane var. Bululawang during proliferation were described in this study. Embryogenic callusfrom induction media were transferred to proliferation media containing MS Basal + vitamin supplemented with sucrose different level of 2,4-D (1 mgl-1, 2 mgl-1, 3 mgl-1, 4 mgl-1 ) and coconut water (0% and 5%).Result showed that low concentration of 2,4-D induced optimum somatic embryogenesis development in proliferation and regeneration. Concentration of single 2,4-D 1 mgl-1 without coconut water induced rapid development of scutelar and coleoptilarduring proliferation and resulted in better shoot regeneration. In other way, 4 mgl-1 of 2,4-D concentration affected to inhibit scutelar and coloeptilar formed as the result of failure callus differentiation.

Impact of biofilm resuspension on mesozooplankton in a shallow coastal ecosystem characterized by a bare intertidal mudflat

A prey–predator experimental setup was conducted in a shallow coastal ecosystem characterized by a bare intertidal mudflat to test if benthic biofilm resuspension causing microalgae inputs and carbon export toward nanoflagellates would favour the highest planktonic trophic level (i.e. mesozooplankton) when nutrient concentrations are high in the water column. Mesozooplankton predation and somatic production were studied by comparing the evolution of the prey assemblage (diversity and abundances) in the presence and absence of these predators during 24 h experiments. The results were then statistically analysed according to the cross-calculation method. Biofilm resuspension caused (i) a direct input of benthic microorganisms that had changed prey structure in term of diversity and/or size and (ii) a differential growth ability between prey taxa. Both reasons implied a bottom-up control on both micro- and mesozooplankton. The carbon export toward heterotrophic nanoflagellates favoured pelagic ciliate growth while mesozooplankton benefited from largest diatoms with high growth rates, both benthic and R-strategist pelagic species. Even if these microbial and herbivorous pathways are controlled by benthic inputs, they seemed to be totally disconnected since ciliates represented only a small part of mesozooplankton diet. The sensitivity of mesozooplankton production appeared species-dependent with the most tolerant taxa dominating the zooplankton assemblages. This suggests a role of the intensities and the frequencies of biofilm resuspension on the spatio-temporal structuring of mesozooplankton in macrotidal coastal ecosystems.

Environmental stress and parasitism as drivers of population dynamics of Mesodesma donacium at its northern biogeographic range

Riascos, J. M., Heilmayer, O., Oliva, M. E., and Laudien, J. 2011. Environmental stress and parasitism as drivers of population dynamics of Mesodesma donacium at its northern biogeographic range. – ICES Journal of Marine Science, 68: 823–833. Mesodesma donacium is a commercially important bivalve in Chile and Peru. During strong El Niño events, populations at the northern end of its geographic distribution are wiped out, so to understand its threshold responses to biotic and abiotic factors, the population dynamics of one of the northernmost population remnants was analysed between 2005 and 2007. Strong interannual differences were found in abundance, body mass, growth rate, somatic production, and the prevalence of the parasite Polydora bioccipitalis. A Spearman rank correlation analysis showed that changes in beach slope, seemingly linked to repeated storm surges, negatively affected the clam's abundance and seemingly also affected growth, mortality, body mass somatic production, and parasite prevalence. Infestation by P. bioccipitalis was restricted to adult clams. Juvenile clams suffered high mortality because they inhabit the intertidal zone, where wave action is strong. Larger clams also showed high mortality, which seemed best explained by a synergistic effect of parasite load and environmental stress. This parasite-climate-driven mortality of larger clams had a strong impact on somatic production and implied a dramatic loss of fecundity (82%), which may significantly affect the ability of the species to recover its former abundance and distribution.

Population dynamics of Sterechinus antarcticus (Echinodermata: Echinoidea) on the Weddell Sea shelf and slope, Antarctica

Sterechinus antarcticus inhabits the shelf and the slope of the Weddell Sea and is the predominant echinoid between 450 and 1200 m. Growth lines visible in the half pyramids of the Aristotle's lantern were interpreted as annual growth marks. A Von Bertalanffy growth function was fitted to age-diameter data of 217 specimens (D∞ = 82.4 mm, K = 0.017 y−1, t0 = 1.633 y). Based on 92 trawl samples, a representative size-frequency distriution of S. antarcticus was established. From the growth curve, the size-frequency sample and diameter - weight regressions, mortality and somatic productivity of S. antarcticus were calculated by a size-converted catch curve and the weight specific growth rate method. Gonadal productivity was estimated by an average value for reproductive output of cold water echinoderms. Mortality rate Z as'well as somatic P/B ratio amounted to 0.07 y−1. Annual somatic production was estimated as 0.3 mg m−2y−1, and annual gonadal production as 0.25 mg m−2 y−1 between 100 and 1200 m (0.6 and 0.5 mg m−2 y−1 between 450 and 1200 m).

Croissance et production du bivalve Mesodesma arctatum (Conrad) sur la côte nord du golfe du Saint-Laurent

Samples of Mesodesma arctatum (Pelecypoda) were collected during the summer of 1983 in the subtidal zone of the Saint-Jean River delta, on the north shore of the Gulf of St. Lawrence. Age was estimated by counting successive growth lines. Maximum longevity was estimated to be about 24 years. The von Bertalanffy growth equation was Lt = 48.1 (1−e−0,23(t−0,53)) mm. The instantaneous mortality rate was 0.26, estimated from a log regression of abundance versus age. The theoretical evolution of a single cohort was calculated; according to the model, biomass, expressed in dry weight, reached its maximum at 6 years and the ratio of somatic production to biomass was estimated to be 0.27. The age at first reproduction is between 3 and 4 years. The reproductive period seems to be during July. The reproductive effort was calculated from the weight difference between the reproductive and postreproductive periods and was determined to be 47% of the total production of the cohort.

The Energy Requirements of Trout and Perch Populations in Loch Leven, Kinross

SynopsisThe minimum energy requirements of trout and perch populations in Loch Leven, Kinross, were calculated for the year 1970–71. Use was made of laboratory data relating to oxygen consumption and ammonium nitrogen (NH3–N) output. Estimates of the specific dynamic action (SDA) of food material were made at 5°, 10° and 15°C and used to predict periods of growth. It was found that optimum growth would take place at 10°C, as opposed to 15°C, and that negative somatic production in the overwintering trout population was due to the energy content of the food intake being less than the minimum energy requirements of metabolism.