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Metabolic interactions between algal symbionts and invertebrate hosts
Author(s) -
YELLOWLEES DAVID,
REES T. ALWYN V.,
LEGGAT WILLIAM
Publication year - 2008
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2008.01802.x
Subject(s) - algae , biology , autotroph , symbiosis , photosynthesis , ecology , nutrient , invertebrate , host (biology) , carbon fixation , botany , genetics , bacteria
Some invertebrates have enlisted autotrophic unicellular algae to provide a competitive metabolic advantage in nutritionally demanding habitats. These symbioses exist primarily but not exclusively in shallow tropical oceanic waters where clear water and low nutrient levels provide maximal advantage to the association. Mostly, the endosymbiotic algae are localized in host cells surrounded by a host‐derived membrane (symbiosome). This anatomy has required adaptation of the host biochemistry to allow transport of the normally excreted inorganic nutrients (CO 2 , NH 3 and PO 4 3− ) to the alga. In return, the symbiont supplies photosynthetic products to the host to meet its energy demands. Most attention has focused on the metabolism of CO 2 and nitrogen sources. Carbon‐concentrating mechanisms are a feature of all algae, but the products exported to the host following photosynthetic CO 2 fixation vary. Identification of the stimulus for release of algal photosynthate in hospite remains elusive. Nitrogen assimilation within the symbiosis is an essential element in the host's control over the alga. Recent studies have concentrated on cnidarians because of the impact of global climate change resulting in coral bleaching. The loss of the algal symbiont and its metabolic contribution to the host has the potential to result in the transition from a coral‐dominated to an algal‐dominated ecosystem.