Research Technical Report

Development, Temperature Tolerance, And Settlement Preference Of Embryos And Larvae Of The Articulate Brachiopod Laques californianus

Pennington, J.T., M.N. Tamburri, and J.P. Barry (June 1999)

Abstract No. 245-256, Biol. Bull. 196, June 1999.

ABSTRACT:

Populations of the articulate brachiopod Laques californianus occur in dense single-species aggregations near the continental shelf/slope break (100-200 m) in Monterey Bay, California. The development of embryos and larvae of L. californianus has been examined by scanning electron microscopy. Fertilizable eggs are 130-140 µm in diameter, and sperm are unmodified. Cleavage is holoblastic and radial. At 10 degrees C an up-swimming blastula develops by 72h, and gastrulation occurs within 24-38 h. A trilobed articulate brachiopod larva with attachment disk is attained in 7 days. Competent larvae swim downwards.

Effects of temperature on larval survival and development rate have also been examined. Larvae die within 1 day at 25 degrees C. At 20 degrees C, development appears normal but results in spontaneous abnormal settlement of larvae 5-6 days old. At 15 degrees , 10 degrees, and 5 degrees C, most larvae achieve competence in 5, 7, and 9 days, respectively. Many larvae survive for 71 days at 10 degrees; and 15 degrees C.

Paterns of larval settlement vary among substrates, but larvae show strong preference for shells of living conspecific adults. Settlement and metamorphosis can occur within 24 h upon exposure of larvae to substrate.