Growth kinetics of the omnivorous oligotrich ciliate Strombidium sp

Abstract

The marine ciliate Strombidium sp. can bc raised through multiple generations on a monoxenic diet of the bacterium Vibrio natriegens, but Strombidium specific growth rates and yields are 3-4 times higher when a heterotrophic microllagellate is included as prey. In contrast to earlier studies we found that Strombidium grew inefficiently when feeding as a bacterivore, with gross growth efficiencies (K,) of 1 l-20% (determined on a nitrogen-, carbon-, and protein-specific basis). On the same bacterial diet K, of the scuticociliate Uronema sp. was 49-70%. Bacterivorous Uronema attained a 9-fold higher specific growth rate and 30-fold higher cell yield than Strombidium. Thus, the species composition of a ciliate assemblage can markedly influence the fate of microbial loop production.Cell volume of live Strombidium sp. varied > 3-fold during a growth cycle. Cell organic composition also varied: the C: N (mass) ratio decreased from 7.7 in stationary phase cells to 4.5 in exponentially growing cells, reflecting the ingestion of N-rich prey. In addition to these natural variations in cell volume, preservatives can shrink cells to half of their live volume, resulting in spurious values of ciliate growth efficiency if computed on a volume-specific basis.

Experimental and modeling evidence of appendicularian‐ciliate interactions

“…Our estimation of m max is within the higher range of growth rates observed and corresponds to those estimated for several Strombidium species (1.28-2.71; Rivier et al 1985;Fenchel and Jonsson 1988;Ohman and Snyder 1991). Similarly, the range of L can be compared with estimates of ciliate respiration.…”

Effect of acid Lugol solution as preservative on two representative chitineous and gelatinous zooplankton groups

“…In their experiments with ciliates, the initial swelling phase was not observed for neutral Lugol solution. After the immediate shrinkage and maximum body size reduction 24-36 h after treatment, no further reduction in size seems to occur within the next 1 to 3 months (Ohman andSnyder 1991, Montagnes et al 1994, this study).…”

“…When applying an empirical length to carbon regression for larvaceans (Jaspers et al 2009), carbon biomass is underestimated by 46% when shrinkage effects due to Lugol solution are ignored. We therefore suggest that shrinkage should be carefully addressed and different rates in body size reduction be applied as suggested in the common methodology for ciliates (Putt and Stoecker 1989, Ohman and Snyder 1991, Jerome et al 1993, Stoecker et al 1994) and flagellates (Borsheim and Bratbak 1987, Choi and Stoecker 1989, Menden-Deuer et al 2001.…”

“…In general, formalin is reported to show lower cell shrinkage effects than Lugol on protozooplankton (Choi and Stoecker 1989, Ohman and Snyder 1991, Stoecker et al 1994, Karayanni et al 2004, whereas no differences were found for larvacean trunk lengths fixed and preserved with 5% neutralized formaldehyde and acidified Lugol solution (Nakamura et al 1997). The effect of formaldehyde has been examined for larvaceans and crustaceans, with no reported shrinkage effect for the latter (Black andDodson 2003, Põllupüü 2007).…”

“…Most integrated marine plankton community studies with parallel investigation of microbial and mesozooplankton components have been fixed and preserved with Lugol solution and formaldehyde, respectively. These chemicals influence osmotic balance and lead to a change in cell volumes (Ohman and Snyder 1991). Length to dry weight/carbon conversions are often based on live animals (Berggreen et al 1988), and sizes of preserved samples then need to be recalibrated to account for size changes due to fixation.…”