Immunity through early development of coral larvae

Area of Science:

• Marine Biology
• Immunology
• Coral Reef Ecology

Background:

• Coral larvae dispersal and recruitment are crucial for reef survival.
• The presence and function of immune defenses in coral larvae remain largely unknown.
• Understanding larval immunity is vital for coral resilience in changing oceans.

Purpose of the Study:

• To investigate the presence and variation of immune responses in Acropora tenuis larvae.
• To examine the roles of melanin-synthesis pathways and fluorescent proteins during larval development.
• To determine if coral larvae possess innate immune defenses against pathogens.

Main Methods:

• Quantified enzymes indicative of tyrosinase and laccase-type melanin-synthesis.
• Measured concentrations of three coral fluorescent proteins across six developmental stages.
• Assessed changes in these parameters following exposure to crustose coralline algae (CCA) and Symbiodinium.

Main Results:

• Both melanin-synthesis pathways and fluorescent proteins were present throughout larval development.
• Laccase-type activity and red fluorescence increased after exposure to CCA (settlement cue).
• Tyrosinase-type activity and cyan fluorescence increased post-settlement, suggesting a cytotoxic defense role.

Conclusions:

• This study provides the first evidence of immune responses in coral larvae.
• Melanin-synthesis pathways appear to have distinct roles, with tyrosinase-type activity linked to defense.
• Coral larvae exhibit potential for resisting infection from their earliest life stages.