Mixing it up: Multiple symbiont acquisition strategies as an adaptive mechanism in the coral Stylophora pistillata

In obligate symbioses, the host's survival relies on the successful acquisition and maintenance of symbionts, which can be transferred from parent to offspring via direct inheritance (vertical transmission) or acquired anew each generation from the environment (horizontal transmission). Vertical transmission ensures progeny acquire their obligate symbionts, but progeny encountering an environment that differs from that of their parent may be disadvantaged by hosting a suboptimal symbiont. Conversely, horizontal symbiont acquisition provides hosts the benefit of acquiring symbionts well suited to the prevailing environment, but progeny may fail to acquire their obligate symbionts. Here I show that the coral <italic>Stylophora pistillata</italic> may garner the benefits of both transmission modes by releasing progeny with maternally derived symbionts that are also capable of subsequent horizontal symbiont acquisition. The algal symbionts (<italic>Symbiodinium</italic>) present in <italic>S. pistillata</italic> adults, juveniles, and larvae (planulae) were identified using denaturing-gradient gel electrophoresis (DGGE) and real-time PCR. DGGE confirmed previous reports that in the Gulf of Eilat, Red Sea, shallow water (2-6m) <italic>S. pistillata</italic> adult coral colonies host clade A <italic>Symbiodinium</italic>, while deep-water (24-26m) colonies host clade C. Real-time PCR uncovered previously undetected <italic>Symbiodinium</italic> present at low-levels in some deep, but no shallow water adult colonies. Planulae only inherited the dominant symbiont clade from their maternal colony. While most shallow water juveniles hosted only clade A <italic>Symbiodinium</italic>, deep-water juveniles either hosted clade C, clade A, or a mixture of both clades. As all planulae analyzed hosted only one symbiont clade, while some juvenile colonies hosted either multiple symbionts, or symbionts not characteristic of the depth in which they occurred, these data support environmental <italic>Symbiodinium</italic> acquisition, in addition to vertical symbiont inheritance, in the coral <italic>S. pistillata</italic>. Reciprocal depth transplant experiments of juvenile <italic>S. pistillata</italic> colonies were executed to monitor potential changes in the <italic>Symbiodinium</italic>. Hosting physiologically distinct <italic>Symbiodinium</italic> may allow coral host survival under varied environmental conditions. Therefore, horizontal symbiont acquisition may enable coral species with vertical transmission to acquire advantageous symbionts. In turn, this may provide genetic variation in the symbiosis on which natural selection can act, providing a mechanism for coral adaption to global climate change.

Name thesis:degree_name

M.S. in Biological Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biology

Year dc:date.available

2012

Author dc:creator

• Byler, Kristen A.

Contributors dc:contributor

• Tamar L. Goulet
• Brice P. Noonan
• Jason Hoeksema

• horizontal transmission
• Symbiodinium
• juvenile
• obligate mutualism
• Red Sea
• vertical transmission
• Biology

Repository record dc:identifier

https://egrove.olemiss.edu/etd/1268

OAI identifier oai:identifier

oai:egrove.olemiss.edu:etd-2267