Download - Previously unsuspected dietary habits of Rimicaris hybisae

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Page 1: Previously unsuspected dietary habits of Rimicaris hybisae

Emma Versteegh (382D), Cindy Van Dover (Duke Marine Lab), Max Coleman (382D)

National Aeronautics and Space Administration

Questions •  What causes the wide range of δ13C values?

•  Are δ13C values related to dense and sparse assemblages? •  Do dense and sparse have different diets?

•  Do dense and sparse differ in δ15N and δ34S values? •  How do δ15N and δ34S relate to diet?

Hypothesis: Dense and sparse Rimicaris differ in diet: varying δ13C values show real differences in food sources between individuals.

Results

Gut contents dense: bacteria Sparse: crustacea (5 out of 13)

bacteria and crustacea (3 out of 13) bacteria only (5 out of 13)

Sparse and dense R. hybisae have different δ13C, δ15N & δ34S values •  Sparse / crustacea-eating: -  Lower δ13C values (-2.38 ‰) -  Elevated δ15N values (+0.34 ‰) -  Lower δ34S values (-2.22 ‰)

•  Carnivorous Lebbeus virentova δ13C and δ15N overlap with R. hybisae, differ from sparse in δ34S only

•  R. hybisae exoskeleton same δ15N and δ34S as guts, but different δ13C Tail δ13C and δ34S reflect gut content, no enrichment

•  Tail δ15N enriched by +3.4 ‰ vs. gut •  Bacteria in gut: higher tail δ13C and δ34S •  Crustacea in gut: lower tail δ34S

Conclusions •  Dense and sparse R. hybisae use different food sources •  Dense R. hybisae eat / absorb episymbiotic bacteria only •  Sparse shrimp eat bacteria, crustacea, and possibly gastropods •  They might have different episymbiotic bacterial communities •  Diet switch possibly related to molting cycle

Implications Contributes to understanding energy fluxes and elemental cycling for life at deep-sea hydrothermal vents. Ultimately helps solar system exploration mission planners determine how best to seek, identify, and characterize life that may (have) exist(ed) on Europa or other planetary bodies with sub-surface oceans.

® Rimicaris hybisae tail (sparse)¯ R. hybisae tail (dense)� Lebbeus virentova wholep R. hybisae gut (crustacea)p R. hybisae gut (bacteria & crustacea)r R. hybisae gut (bacteria)£ R. hybisae gill covers (dense)

® R. hybisae (crustacea)® R. hybisae (bacteria & crustacea)¯ R. hybisae (bacteria)

Introduction Biological research at the world’s deepest hydrothermal vent fields:

Earth analogs for environments on Europa Objectives: 1.  Quantification of the efficiency of uptake of hydrothermal vent energy into

biomass 2.  Understanding of the C cycle at hydrothermal vent environments Supported by NASA ASTEP (Astrobiology Science and Technology for Exploring Planets)

Life in the dark Photosynthesis: 6 CO2 + 12 H2O + sunlight → C6H12O6 + 6 H2O + 6 O2 Chemosynthesis: 6 CO2 + 6 H2O + 3 H2S → C6H12O6 + 3 H2SO4

→ Would work on Europa too Quantify biomass expected? → look on Earth How much new biomass/time? → food web Hydrothermal vent fields at Mid-Cayman Rise (MCR) •  The world’s deepest, Piccard vent field, 4960 m, 398 °C •  Von Damm vent field, 2309 m, off-axis, diffuse venting, 226 °C

Rimicaris hybisae - Dense and sparse Abundant at both known MCR vent fields Dense aggregations on active chimneys, or sparse peripherally High degree of spatial variability in population structure Feeds on chemosynthetic bacteria that are episymbiotic (gill cover, mouth parts)

Von Damm food web

Stable isotopes Stable isotopes of carbon, nitrogen and sulfur (δ13C, δ15N, δ34S values) can be used to disentangle food webs. You are what you eat: +1 (δ13C ‰ vs. VPDB) +3 (δ15N ‰ vs. AIR) +? (δ34S ‰ vs. VCDT) Large variations in R. hybisae tissue δ13C values have been unexplained. Are δ13C values not a good food web tracer in hydrothermal vent ecosystems?

National Aeronautics and Space Administration

Jet Propulsion Laboratory California Institute of Technology

Pasadena, California www.nasa.gov

Copyright 2014. All rights reserved.

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