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Arnhem, Netherlands

Janse M.,Burgers Zoo | Schrama J.W.,Wageningen University
Journal of the Marine Biological Association of the United Kingdom | Year: 2010

At Burgers' Ocean 7 male and 3 female blue spotted stingrays, Dasyatis kuhlii were born over a period of 4.5 years. This paper describes the experiences of the captive breeding results of this species. The first two young died within 2 days of birth. One of them had an internal yolk sac, which may feed the young in the first few days. The other eight animals started to feed after 4 to 9 days on a variety of food types. Birth size of the young increased with increasing age of the parents. Mating occurred directly after parturition, so no seasonality could be defined. Gestation length ranged between 138 and 169 days, with a mean of 144.9±9.0 days (N=11). Litter size was one, possibly caused by only one active ovarium. Sexual maturity of the two parent animals is approximately 3.5years. The average feeding rations for the adults ranged between 10.1% BW week1 (131 kcal kg BW1 week1) and 11.3%BWweek1 (172kcalkgBW1week1), with a feeding frequency of 4 times per week. The relationship between body weight (BW) and wingspan (WS) is given as BW=3.6105* WS2.940 (R2=0.9645; N=45). Copyright © Marine Biological Association of the United Kingdom 2009.

Batenburg S.J.,University Utrecht | Reichart G.-J.,University Utrecht | Reichart G.-J.,Alfred Wegener Institute for Polar and Marine Research | Jilbert T.,University Utrecht | And 3 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

High resolution stable isotope and trace elemental ratios of a recent Tridacna squamosa from Vietnam and a Middle to Late Miocene (10-13Ma) Tridacna gigas from Indonesia are presented. The seasonal pattern of modern sea surface temperature (SST) variability offshore Vietnam is faithfully recorded in the δ18O of the T. squamosa shell carbonate, confirming the potential of Tridacna shells as sub-annual resolution climate archives. Cultivation of the T. squamosa specimen in controlled conditions after recovery from the natural environment facilitated a quantitative calibration of the δ18O signal to ambient water temperatures. An age model for the Miocene T. gigas shell from Indonesia was therefore constructed on the basis of its δ18O profile, assuming a single-peak annual SST cycle. The magnitude of these oscillations was 5-7°C. Mg/Ca and the growth-banding pattern in the Miocene T. gigas correlates well with shell δ18O during the later part of the organism's lifespan. Ba/Ca is negatively correlated to Mg/Ca, with a lag of several months, suggesting a different phasing of the annual primary productivity cycle from that of SST. Furthermore, δ18O and Mg/Ca show prominent deviations to warmer conditions with a periodicity of ~3years. These shifts demonstrate the existence of substantial interannual sea surface temperature variability in the Miocene, a period with elevated global temperatures compared to the present day. © 2011 Elsevier B.V.

Ernst S.,University Utrecht | Janse M.,Burgers Zoo | Renema W.,National Natural History Museum Naturalis | Kouwenhoven T.,University Utrecht | And 3 more authors.
Journal of Foraminiferal Research | Year: 2011

Live (rose Bengal-stained) benthic foraminifera were studied from one of the largest coral reef aquaria in the w orld (Burgers' Ocean, Arnhem, the Netherlands). Benthic foraminifera were unintentionally transported to the aquarium with live rock (i.e., natural reef substratum) from Java and Bali (Indonesia) during initial setup in 2000. After eight years and stabilization of the water chemistry, the foraminifera were found to have successfully colonized this artificial environment. Fifty benthic foraminiferal taxa (>125 pm) were identified in samples from the various subenvironments within the aquarium. The ecological conditions in the aquarium appeared to be optimal for both symbiont-bearing foraminifera and hermatypic corals. Among the four symbiontic foraminiferal species identified, Heterostegina depressa was the most abundant and it was dominant in all samples. Overall, foraminiferal densities in the aquarium were relatively high compared to those in the natural environment emulated. Although foraminifera are not generally recognized as inhabitants of saltwater aquaria, they can play an important ecological role in this type of closed environment.

Schutter M.,Wageningen University | Van Der Ven R.M.,Wageningen University | Janse M.,Burgers Zoo | Verreth J.A.J.,Wageningen University | And 2 more authors.
Journal of the Marine Biological Association of the United Kingdom | Year: 2012

Light is one of the most important abiotic factors influencing the (skeletal) growth of scleractinian corals. Light stimulates coral growth by the process of light-enhanced calcification, which is mediated by zooxanthellar photosynthesis. However, the quantity of light that is available for daily coral growth is not only determined by light intensity (i.e. irradiance), but also by photoperiod (i.e. the light duration time). Understanding and optimizing conditions for coral growth is essential for sustainable coral aquaculture. Therefore, in this study, the question was explored whether more light (i.e. more photons), presented either as irradiance or as light duration, would result in more growth. A series of nine genetically identical coral colonies of Galaxea fascicularis L. were cultured for a period of 18 weeks at different light duration times (8 hours 150 μE m-2 s-1:16 hours dark, 12 hours 150 μE m-2 s-1:12 hours dark, 16 hours 150 μE m-2 s-1:8 hours dark, 24 hours 150 μE m -2 s-1:0 hours dark) and different irradiance levels (8 hours 150 μE m-2 s-1:16 hours dark, 8 hours 225 μE m-2 s-1:16 hours dark and 8 hours 300 μE m-2 s-1:16 hours dark). Growth was determined every two weeks by measuring buoyant weight. Temperature, salinity and feeding levels were kept constant during the experiment. To detect possible acclimation of the corals to an increased light duration, rates of net photosynthesis and dark respiration were measured, hereby comparing coral colonies grown under an 8:16 hours light (150 μE m-2 s-1):dark cycle with corals grown under a 16:8 hours light (150 μE m-2 s-1):dark cycle. No increase in growth was detected with either increasing photoperiod or irradiance. Continuous lighting (24 hours 150 μE m-2 s -1:0 hours dark) resulted in immediate bleaching and the corals died after 14 weeks. Hourly photosynthetic rates were significantly reduced in the 16 hour light treatment compared to the 8 hour light treatment. As a result, daily net photosynthetic rates were not significantly different, which may explain the observed specific growth rates. Acclimation to photoperiod duration appeared neither to be mediated by changes in chlorophyll-a concentration nor zooxanthellae density. Based on the results of this study, we can conclude that the enhancing effect of light on coral growth is not only a matter of photons. Obviously, the availability of light was not limiting growth in these experiments and was probably in excess (i.e. stressful amounts). Other factors are discussed that play a role in determining growth rates and might explain our results. Copyright © Marine Biological Association of the United Kingdom 2011.

Osinga R.,Wageningen University | Van Delft S.,Wageningen University | Lewaru M.W.,Wageningen University | Lewaru M.W.,Padjadjaran University | And 2 more authors.
Journal of the Marine Biological Association of the United Kingdom | Year: 2012

In order to determine optimal feeding regimes for captive corals, prey capture by the scleractinian coral Galaxea fascicularis was determined by measuring clearance of prey items from the surrounding water. Colonies of G. fascicularis (sized between 200 and 400 polyps) were incubated in 1300 ml incubation chambers. Nauplii of the brine shrimp Artemia sp. were used as the prey item. A series of incubation experiments was conducted to determine the maximal capture per feeding event and per day. To determine maximal capture per feeding event, total uptake of nauplii after one hour was determined for different prey item availabilities ranging from 50 to 4000 nauplii per polyp. To determine maximal capture per day, the corals were subjected to four repetitive feeding events at three different prey item densities (50, 100 and 150 nauplii per polyp). Alongside these quantitative experiments, it was tested to what extent the feeding response of corals is triggered by chemical cues. One hour after food addition, extract of Artemia nauplii was added to the incubation chambers to test its effect on subsequent prey capture rates. In all experiments, prey capture was expressed as the number of nauplii consumed per coral polyp. Total capture of Artemia nauplii by G. fascicularis after a single feeding event increased linearly up till a prey item availability of 2000 nauplii per polyp. Maximal capture per feeding event was estimated at 1200 nauplii per polyp, which is higher than rates reported in previous studies. It became apparent that at high densities of Artemia nauplii, the clearance rate method does not discriminate between active capture and passive sedimentation. Repetitive feeding with 50 nauplii per polyp resulted in a constant total prey capture per feeding event. At a supply of 100 nauplii per polyp, total capture decreased after the first feeding event, and remained constant during the subsequent feeding events at a level comparable to the lower food availability. However, at a supply of 150 nauplii per polyp, total capture per event was higher throughout the entire four-hour incubation period, which obfuscates an accurate estimation of the maximal daily food uptake. In all incubations, a decrease in capture efficiency was observed within the course of the feeding event. In all repetitive feeding experiments, capture efficiency increased immediately upon addition of a new batch of food. This increase in efficiency was not caused by a priming effect of extract of Artemia. The inconsistencies in the data show that estimates of prey capture based on clearance rates should be interpreted with caution, because this method does not take into account potential dynamics of prey capture and release. Copyright © Marine Biological Association of the United Kingdom 2011.

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