Waldeckia Obesa Research Articles

The excretion of nitrogen and phosphorus and changes in nitrogen content in the Antarctic amphipod Waldeckia obesa and isopod Glyptonotus antarcticus during long-term starvation

Seasonal food availability for benthic feeders in Antarctica can influence the level of excreted metabolites, which may then be a source of N and P for autotrophs. In this study, we examined the effects of starvation of Waldeckia obesa and Glyptonotus antarcticus on the excretion of both N and P, and the chemical composition of their bodies. N-NH4 + dominated in the pool of excreted nitrogen (93% and 77% of inorganic nitrogen, and 76% and 67% of total nitrogen, for W. obesa and G. antarcticus, respectively). Reactive phosphorus dominated in the pool of excreted phosphorus (72% and 65% of total phosphorus for G. antarcticus and W. obesa, respectively). The excretion of N-NH4 + (in µmol N h−1 100 g−1) dropped from 3,687 (W. obesa) and 1,336 (G. antarcticus) in the first day to about 0.6 after 10 days of starvation (for both species). Phosphorus excretion was generally lower than that of nitrogen (on average 0.046 and 0.017 µmol P h−1 100 g−1 for G. antarcticus and W. obesa, respectively), but no clear trend appeared with N as a result of starvation. The greatest decrease in nitrogen and protein content in W. obesa was recorded on the 3rd day of starvation (nitrogen: from 1.30% to 0.93%; protein: 8.15% to 5.80%) and in G. antarcticus on the 5th day of starvation (nitrogen: from 2.22% to 1.43%; protein: from 13.86% to 8.94%). Conclusions: (i) nitrogen and phosphorus compounds released by crustaceans may be a supplementary source of biogenic salts for autotrophs, (ii) nitrates constituting approx. 20% nitrogen may be used by phytoplankton in the period of new production, (iii) starvation reduces the excretion of N and P and the content of nitrogen and protein in crustaceans.

Starvation and chemoreception in antarctic benthic invertebrates

Sensitivity (chemoreception) to different amino acids was studied in six invertebrate species: Serolis polita, Glyptonotus antarcticus, Abyssochromene plebs, Waldeckia obesa, Odontaster validus, and Sterechinus neumayeri. The sensitivity was estimated by the changes in basic metabolism (respiration rate). Starvation increased the sensitivity in all the species. The metabolism rates increased in the presence of L-glutamic acid in G. antarcticus, A. plebs, O. validus, and S. neumayeri. The serine and arginine amino acids had a significant impact on the metabolism of the necrophagous species S. polita and W. obesa. The chemical information may be mediated by means of L-glutamic acid via glutamate receptors, which can be blocked by kynurenic acid, as occurs in the experiments with G. antarcticus and A. plebs.

Significance and Interspecific Variability of Accumulated Trace Metal Concentrations in Antarctic Benthic Crustaceans

AbstractTrace metals (Cd, Cu, Pb and Zn) were analysed in crustaceans collected on Polarstern cruises ANT XVI/2 (1999) and ANT XXI/2 (2003/04, BENDEX) to the Weddell Sea. Our study provides further evidence for the frequently reported “Cd anomaly” in polar crustaceans, with data ranging from 1.2 (Ceratoserolis trilobitoides) to 6.2 mg Cd kg–1 DW (Notocrangon antarcticus) in 1999 and from 1.2 (Waldeckia obesa) to 20.3 mg Cd kg–1 (Tryphosella murrayi) in 2003. Pb concentrations well below 1 mg kg–1 in most of the samples analysed might serve as a regional or even global background value for comparison in biomonitoring studies. Increasing Cu concentrations from eggs of decapods (e.g., 5 vs. 51 mg kg–1 in N. antarcticus) or juveniles in the brood pouch of an amphipod species to adult females indicate that the enzymatic requirements and haemocyanin component demand for Cu in early life‐history stages is probably not met without a distinct bioaccumulation of this essential element after hatching. Most interestingly, Cd also increases (<0.1 vs. 6.2 mg kg–1 in N. antarcticus). This could be the consequence of efficient uptake mechanisms for Cu that cannot discriminate between this element and Cd. Cu and Zn concentrations in decapods of this study are largely within the range reported worldwide (40–90 mg Cu kg–1 and 40–80 mg Zn kg–1), indicating that these elements are regulated. The enormous heterogeneity of Cd and Zn in many amphipod species investigated (e.g., from 0.6 in Gnathiphimedia mandibularis to 34.4 mg Cd kg–1 in Orchomenopsis acanthura and from 41 in Eusirus antarcticus to 1244 mg Zn kg–1 in Iphimediella bransfieldi) supports the hypothesis of the “Cd anomaly” and suggests that there is probably no consistent metabolic demand for the essential element Zn in this taxonomic group. The heterogeneity of Cu in amphipods is less pronounced. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fish blood as a chemical signal for Antarctic marine invertebrates

Chemical cues released from dead or injured organisms constitute important signals informing nearby animals about a feeding possibility. The ability to detect the signal, evaluate its meaning and locate its source can help organisms to exploit food resources efficiently, which is especially important to animals living in environments with limited food supply. Experiments were carried out to study the behavioral responses of several Antarctic benthic invertebrates to fish (Notothenia corriceps) blood. Necrophagous species such as sea stars Odontaster validus and Lysasterias sp., amphipod Waldeckia obesa and nemertean Parborlasia corrugatus responded to fish blood with changes in their behavior. The behavior common to all these species was locomotion directed towards the stimulus source. Behavioral components consistent with food consumption were observed in O. validus and P. corrugatus. The reaction of herbivorous limpets Nacella concinna to fish blood depended on the animal size. Large (>10 mm) limpets showed no behavioral response, whereas small ones (<10 mm) reacted to the stimulus by moving a short distance away. These results indicate that blood released from the tissues of injured or dead animals may be an important chemical signal for organisms belonging to different taxa.

The Influence of Starvation and Amino Acids on Metabolism of the Antarctic Amphipod Waldeckia Obesa

The average oxygen consumption of well-fed Waldeckia obesa individuals, whose average wet weight equals |$318.3\;{\rm{mg}}$| is, |$74.7\;{\rm{\mu L}}\;{{\rm{O}}_2}\;{{\rm{ind}}^{ - 1}}\;{{\rm{h}}^{ - 1}}$| at the temperature |$0^\circ {\rm{C}}$|⁠. On average, 10-day-long starvation reduces the metabolism level by |$36\% $|⁠, and 30-day-long starvation by |$66\% $|⁠, compared to well-fed individuals. Investigations concerned the influence of 12 amino acids at the |$10\;{\rm{mM}}$| concentration on W. obesa respiration. Amongst animals starved for 10 days, the addition of amino acids does not lead to statistically significant changes in metabolism rates, while amongst animals starved for 30 days, arginine leads to an |$241\% $| increase in metabolism rates. Glutamic acid constitutes about |$10\% $| of all amino acids in the body of W. obesa and more than |$15\% $| in the Nototenia neglecta fish, which is a food resource for this crustacean.

Combined lipid, fatty acid and digestive tract content analyses: a penetrating approach to estimate feeding modes of Antarctic amphipods

Antarctic amphipods from the Weddell Sea and Bransfield Strait were collected to investigate the impact of various species and feeding types on lipid and fatty acid compositions. In combination with digestive tract content analyses, such information can help clarify the type of feeding mode of the various amphipod species. Micro- and macropredatory amphipod species had only small amounts of triacylglycerols as storage lipids, whereas the deposit-feeder Epimeria georgiana was rich in triacylglycerols (55% of total lipids). The fatty acids 22:6(n-3), 20:5(n-3), 18:1(n-9) and 16:0 were major lipid components of most species. Ampelisca richardsoni, a suspension feeder, had a high amount of 18:4(n-3), a major component of cryptophytes and/or haptophytes, connected with feeding on sedimenting phytoplanktonic material and with a strong bentho-pelagic coupling. In Oradarea edentata, fragments of brown algae were found almost exclusively. The major fatty acid of the macroalgae, 20:4(n-6), replaced the 22:6(n-3) in the phospholipids and triacylglycerols of the amphipod. The sponge eater, Echiniphimedia hodgsoni, was rich in 16:1(n-7) and 18:1(n-7), suggesting that the unidentifiable organic matter was of diatom origin. Eusirus perdentatus, a typical predator, had high proportions of saturated and monounsaturated fatty acids, showing no specialisation in lipid and fatty acid composition. The fatty acid composition of Epimeria georgiana was similar to that of Eusirus perdentatus. However, high levels of triacylglycerols in Epimeria georgiana reflect periodical food plenty and starvation, due to its dependence on dead items. The fatty acid composition of the necrophage Waldeckia obesa was clearly different because of the predominance of 18:1(n-9) (>40% of total fatty acids). This dominance is probably the result of feeding on highly degraded carrion-derived organic matter, which is the major food of W. obesa.

Occurrence of the autofluorescent pigment, lipofuscin, in polar crustaceans and its potential as an age marker

In crustaceans, the lack of reliable methods often prevents the determination of individual age. The quantification of the autofluorescent age pigment, lipofuscin, has revealed promising results in boreal and tropical species. We studied the presence of morphological lipofuscin and its possible application as an age marker in five Arctic and five Antarctic species, comprising decapods, amphipods and a euphausiid. Lipofuscin granules were located in the brain, using confocal fluorescence microscopy, and quantified from digital images. The pigment was found in 94 of 100 individuals and in all 10 species, and granules occurred in easily detectable amounts in 5 species. Two scavenging amphipod species, the Antarctic Waldeckia obesa and the Arctic Eurythenes gryllus, revealed the most conspicuous and numerous granules. There was a broad, though weak, correlation of lipofuscin concentration with individual body size within a species, but not with absolute body size of one species compared to another. In larvae of the decapod Chorismus antarcticus, lipofuscin accumulation was quantified over the 1st 4 months after larval release. Morphological lipofuscin is a potential index of age in those investigated species with a sufficient accumulation rate of the pigment.

The autofluorescent age pigment lipofuscin: key to age, growth and productivity of the Antarctic amphipod Waldeckia obesa (Chevreux, 1905).

Peracarid crustaceans are among the most important taxa in terms of biodiversity and carbon-flow within the Weddell Sea benthos; however, very few data on their age, growth and productivity are available. This study uses the pigment lipofuscin as an age marker in the scavenging amphipod Waldeckia obesa (Chevreux, 1905) from the eastern Weddell Sea. Resin brain sections of 159 trap-caught specimens (1.2 to 7.7 mm coxal plate length L(cox) equal to 5 to 31 mm total length) were recorded digitally by confocal microscopy, and images were analysed. A modal progression analysis of the lipofuscin concentration-frequency distribution revealed five regularly spaced modes presumed to reflect consecutive annual age classes. Single females outside the range of mode V occurred, indicating maximum age of up to 8 years in females. No regular modes were obvious from the comparable length-frequency distribution of 386 individuals. Average yearly pigment accumulation was linear, and accumulation rates did not differ between sexes. The estimates of the growth parameters L(infinity) and k of the von Bertalanffy growth function were 7.47 mm L(cox) and 0.50 per year in females, respectively, and 6.92 mm L(cox) and 0.60 per year in males, respectively. Mortality, estimated from catch curves, amounted to 0.27 per year in females and 0.43 per year in males. P/B ratio, calculated from the mass specific growth rate method, was 0.38 per year for the pooled population (0.25 per year in females, 0.31 per year in males, 2.26 per year in juveniles). The results are discussed with regard to advantages and drawbacks of the methodology, and are compared with results from warmer water habitats.

Necrophagous lysianassoid Amphipoda in the diet of Antarctic tern at King George Island, Antarctica

Amphipod crustaceans constituted 30% of the food biomass from the stomachs of Antarctic tern (Sterna vittata) captured at King George Island in three consecutive seasons. Five species of lysianassoid amphipods occurred in the material: Abyssorchomene plebs, Cheirimedon femoratus, Hippomedon kergueleni, Waldeckia obesa and Orchomenella rotundifrons. All these amphipods are known as necrophages inhabiting the upper and middle sublittoral of western Antarctic. They are commonly caught in masses in baited traps, but never occur in the littoral zone or in tidal pools. It is suggested that the source of the amphipod diet of S. vittata are seal or penguin carcasses and dead fish brought by waves to the tidal zone, serving as a bait for necrophagous amphipod crustaceans when submerged in water before stranding on the beach.

Estudo do metabolismo de rotina e excreção de amônia do antípoda antártico Waldeclàa obesa em duas temperaturas distintas

Realizaram-se estimativas, a 0ºC e a 3ºC, do consumo médio e específico de oxigênio e da excreção média e específica de amónia de anfípodas antárticos da espécie Waldeckia obesa, coletados na Baía do Almirantado, Ilha Rei George, Antártica. Os experimentos foram realizados na Estação Antártica Brasileira "Comandante Ferraz" e no Laboratório de Ecologia Polar do Instituto Oceanográfico da Universidade de São Paulo. Foram empregados animais entre 120 mg a 620 mg e entre 40 mg e 690 mg de peso úmido, nos experimentos a 0ºC e a 3ºC, respectivamente. Dentro dessas faixas de peso, o consumo médio de oxigênio, a 0ºC, variou de 2,22µl/h a 10,81µl/h e o específico de 0,011µl/mg/h a 0,018µl/mg/h. A 3ºC, o consumo médio de oxigênio variou de 1,83µl/h a 14,19µl/h e o específico de 0,033µl/mg/h a 0,022µl/mg/h. O Q10, calculado a partir das médias das classes, foi de 6,95. Por sua vez, a excreção média de amónia, a 0ºC, variou de 13,84 ng.at/h a 55,34 ng.at/h e a específica entre 0,090 ng.at/mg/h a 0,042 ng.at/mg/h. A 3ºC, a excreção média de amónia variou de 5,11 ng.at/h a 38,33 ng.at/h e a específica de 0,088 ng.at/mg/h a 0,059 ng.at/mg/h. A relação 0:N indica que uma mistura de proteínas e lipídios é utilizada como substrato para o catabolismo. A 3ºC, entretanto, há uma tendência a aumentar a contribuição dos lipídios nesse substrato. O consumo de oxigênio de Waldeckia obesa é bastante baixo estando de acordo com os valores encontrados, a 0ºC, por outros autores. Esses dados, juntamente com resultados recentes encontrados na literatura, indicam a fragilidade da hipótese de "adaptação metabólica ao frio", que supõe terem os animais marinhos ectotérmicos antárticos taxas metabólicas elevadas, como resposta adaptativa às baixas temperaturas. Os dados de consumo de oxigênio e excreção de amónia fornecem material básico para extrapolação a parâmetros populacionais, fornecendo subsídios para a avaliação do papel ecológico desses animais no ecossistema em que vivem.

Effects of feeding and starvation on the metabolic rate of the necrophagous Antarctic amphipod Waldeckia obesa (Chevreux, 1905)

The marked seasonality of high latitude marine ecosystems means that the relationship between nutrition and metabolism is of particular interest, for many polar organisms must survive long periods without food. One hundred individuals of the scavenging lysianassoid amphipod Waldeckia obesa (Chevreux, 1905) were collected from Antarctica and then maintained in cold-water aquaria at the British Antarctic Survey in Cambridge. One group were fed and then starved for 64 days, during which time oxygen consumption fell to 60% of the initial value, and ammonia excretion to 20%. The initial decrease in metabolism occurred in about 5 days, after which time ammonia excretion remained roughly constant whereas oxygen consumption (and hence O:N atomic ratio) oscillated. O:N ratio and proximate composition estimated stoichiometrically from elemental composition both indicated the use of protein and lipid as metabolic substrates during starvation. Fed amphipods exhibited a classic post-prandial increase in metabolism (specific dynamic action, SDA): oxygen consumption and ammonia excretion increased rapidly to a level between 4 and 7.5 times the prefeeding levels, respectively. These are the largest increases of metabolic rate with feeding so far reported for a marine invertebrate and the overall SDA response lasted 8–10 days. O:N ratios indicated that metabolism 2–4 days after feeding was dominated by protein metabolism.

Chromosomes of the Antarctic amphipod Waldeckia obesa Chevreux

Mitotic and meiotic chromosomes of the Antarctic lysianassoid amphipod Waldeckia obesa are described. The modal chromosome number is n = 25 and 2n = 50. The potential applications of cytogenetical studies in this group are discussed.

Respiration of Orchomene plebs (Hurley, 1965) and Waldeckia obesa (Chevreux, 1905) from Admiralty Bay (South Shetlands Islands, Antarctic)

Respiration of Orchomene plebs (Hurley, 1965) and Waldeckia obesa (Chevreux, 1905) from Admiralty Bay (South Shetlands Islands, Antarctic)