Abstract
At 27·0–28·0°, the lapilli of Hoplosternum littorale developed rapidly in the embryo between 35 and 21 h before hatching. At hatching, lapilli averaged 78 μ;m on their longest axis and 69 μ;m on their shortest axis, and had up to three faint narrow microstructures. Primordia were fused and the large core was surrounded by a conspicuous discontinuous zone, formed at hatching, and visible in both sagittal and transverse preparations. The deposition rate of microincrements, counted in transverse thin sections of lapilli, was daily at least for the first 50 days and the innermost microincrements were deposited from hatching on. The growth rates of H. littorale differed significantly between two different rice field habitats in Suriname.