The distribution and function of sea urchin histamine receptor 1 in larval Strongylocentrotus purpuratus

In marine invertebrate complex life histories, planktonic larvae metamorphose into benthic juveniles that then develop into sexually mature adults. Hormonal or neurotransmitter-based signalling systems have evolved to regulate complex life histories and ensure settlement on the benthos and metamorphosis into juveniles occur after sufficient growth (i.e. metamorphic competence), in appropriate habitats. Modulators of metamorphic competence keep larvae prepared to settle and metamorphose until reception of a specific settlement cue. Histamine modulates metamorphic competence in Strongylocentrotus purpuratus; however, this signalling system is not fully understood. I determined the distribution and function of sea urchin histamine receptor 1 (suH1R) throughout S. purpuratus larval development. suH1R is found in the mouth and arm tips of larvae, and expression increases exponentially through development. Knockdown of suH1R leads to cell death in the arms. I suggest that suH1R inhibits apoptosis and/or maintains cell viability throughout larval development and may maintain metamorphic competence in S. purpuratus.