Responses of the pea crab Pinnotheres taichungae to the life history patterns of its primary bivalve host Laternula marilina

Abstract

At the Kaomei tidal flat in Taiwan, the population dynamics and growth of the bivalve Laternula marilina (Reeve, 1860) and responses of the symbiont pea crab Pinnotheres taichungae Sakai, 2000 to the life history patterns of its primary host were studied. The population cycle of the bivalve appears to be initiated by larval settlement occurring as early as late March culminated by die off at the beginning of December of the same year. The maximum host life span is estimated at nine months. Pea crabs, regardless of size, preferred utilizing bivalves with a shell length exceeding 28 mm. This suggests they only spend about three months as a commensal with the primary host because the latter may take five months from the time of settlement to grow to an average size of 32 mm. In response to the brief presence of large primary hosts, the pea crab may: (1) synchronize megalopal recruitment shortly prior to the presence of large primary hosts; (2) evolve a dual infestation mode, invading the bivalve during both invasive and hard stages; and (3) have a fast growth rate while commensal with the primary host.

Keywords:

• Life History Patterns
• The Crab-bivalve Symbiotic Relationship
• Pinnotheres Taichungae
• Laternula Marilina