WR Chemosynthetic (12)

Question 1

LECTURE 13 - CHEMOSYNTHETIC SPECIALISTS

Study 1: Yeti crab and how it utilises its episymbionts at methane seep

the study

Answer 1

• Study 1: Yeti crab and how it utilises its episymbionts at methane seep
• Dancing for Food in the Deep Sea: Bacterial Farming by a New Species of Yeti Crab – (Thurber et al., 2011)
• · How this new species farms its epibiotic bacteria in a unique form of symbiosis.
• · Specimens collected from depths of 1000–1040 m from Costa Rica – Preserved in ethanol
• · Looked at isotopic and Fatty acid biomarkers to determine the food source of Kiwa puravida

Question 2

Study 1: Yeti crab and how it utilises its episymbionts at methane seep

the results

Answer 2

Results:

· Individuals were commonly observed slowly waving their chelipeds back and forth in these areas of active methane seepage

· Isotopic and Fatty acid (FA) biomarker approaches provided evidence to indicate that K. puravida used its epibiotic bacteria as a main food source

· Chelipeds have setae which house the episymbionts – Bacteria harvesting – chemosynthetic bacteria which generate organic carbon

· highly-modified setae (hairs) on its 3rd maxilliped (a mouth appendage) which it uses to harvest these bacteria

· Hypothesised that it waves its arm in reducing fluid to increase the productivity of its epibionts by removing boundary layers which may otherwise limit carbon fixation

Question 3

Study 1: Yeti crab and how it utilises its episymbionts at methane seep

Answer 3

Critical analysis:

· Good – because Compared the isotopic analysis and the FA biomarkers to that of phytoplankton origin to prove the difference in food source origin

Question 4

Study 2: Sulphide uptake adaption

The study

Answer 4

Study 2: Sulphide uptake adaption

• Habitat, growth and physiological ecology of a basaltic community of Ridgeia piscesae from the Juan de Fuca Ridge – Urcuyo et al., 2003
• Study looking into the physiological ecology of a vestimentiferan tube worm, Ridgeia piscesae, from the Juan de Fuca Ridge, NE pacific
• Unlike in Riftia pachpatila, Ridgeia piscesae are located in reduced vent flows with low ambient sulphide conc. – SO how do they obtain sulphide for endosymbionts?
• In-situ temperature and chemical surveys were combined with long-term temperature monitoring, to understand the physiology and ecology of the tube worms
• Used paired temperature and sulphide values, to determine a relationship between environmental temperature and sulphide concentration for this particular tubeworm aggregation

Question 5

Study 2: Sulphide uptake adaption

The Results

Answer 5

Results:

· Plume-level temperature records indicate that most of the time individuals in this aggregation were exposed to extremely low levels of vent fluid, and therefore sulphide (<0.1 μM)

· Only Posterior ends of R. piscesae exposed to significant sulphide levels (approx. 100 μM range)

· Potential for absorption of sulphide through Posterior end (rootballs), with portions of the tubes within the “rootball” freely permeable to sulphide – enabling survival of host and endosymbionts

Question 6

Study 2: Sulphide uptake adaption

Habitat, growth and physiological ecology of a basaltic community of Ridgeia piscesae from the Juan de Fuca Ridge – Urcuyo et al., 2003

Critical analysis

Answer 6

Critical analysis:

· Only one aggregation of Ridgeia piscesae was used during this study – may not be able to generalise the adapations and sulphide uptake at other vents containing the same species

Question 7

Study 3: Amino acid transport and storage of sulphur to prevent toxicity

The study

Answer 7

Possible Roles of Sulfur-Containing Amino Acids in a Chemoautotrophic Bacterium-Mollusc Symbiosis – Joyner et al., 2003

· Tested the hypothesis that taurine and thiotaurine levels in intact gills of Solemya velum increase upon exposure to sulphide, which would occur if these amino acids are involved in sulphur storage or cycling.

· Tested symbiotic clam from sulphide habitat, and used non-symbiotic clams that are sulphide tolerance

· Used Solemya velum (Symbiotic species) and estuarine mussel, Eukensia demissa and the protobranch bivalve, Yoldia limatula (Non-symbiotic, but sulphide tolerant species)

Question 8

Study 3: Amino acid transport and storage of sulphur to prevent toxicity

The results

Answer 8

Results:

· Taurine and thiotaurine levels in Solemya velum gills increase after sulphide exposure

· Two amino acids may function as nontoxic sulphide storage compounds

o magnitude of changes in taurine and thiotaurine pools observed after sulphide exposure in the present study is sufficient for these amino acids to be physiologically significant sulphide storage compounds

· Storage using amino acids may allow S. velum to maintain low levels of intracellular sulphide

· Maintenance of free amino acid pools depended upon the presence of functioning symbionts, sulphide consumption, and host ammonia assimilation

o Inhibition of host ammonia assimilation and symbiont and host protein synthesis blocked sulphide-stimulated taurine synthesis

o Only inhibition of symbiont metabolism decreased the sulphide-stimulated thiotaurine synthesis

· Free amino acid pool did not increase in non-symbiotic sulphide tolerant clams – showing that sulphur-containing amino acids function in sulphide detoxification in symbiotic invertebrates

Question 9

Critical analysis

Answer 9

Critical analysis:

· Good – Because the temperature of the laboratory experiment matched that of the ambient temperature at which they were found

· Bad – Used ‘instant ocean’ to create salinity, therefore the seawater won’t represent that of the natural seawater as many micronutrients missing – to combat this they added ammonia which is involved in the sulphide detoxification