Larval Development of Limnoperna fortunei

Abstract

Mature sperm cells of Limnoperna fortunei measure about 4 µm, and ova are typically spherical, 80–100 µm in diameter. Forty minutes after spawning, the first polar lobe appears, and the first division occurs 14 min later. Slightly over an hour after spawning, the second polar lobe appears and the second division yields a 4-cell stage. The third division occurs 90 min after spawning, and the fourth 115 min after spawning. Approximately 3.5 h after spawning (at 26 °C) the morula stage is reached. Six hours after spawning, the first trochophores appear (95–110 µm in length) at 28 °C. Subsequently, the prodissoconch I starts developing, initially as small rosette-shaped structures on the dorsal side of the trochophore. Straight-hinged veligers (115–160 µm) start appearing 24 h after spawning. These larvae start feeding externally and secrete the prodissoconch II. Umboned veligers (156–220 µm) are reached 287 (at 28 °C), 165 (25 °C) and 118 (20 °C) h after spawning. From there on, the larva reabsorbs its velum and develops a muscular, adhesive foot, yielding a plantigrade larva (250–405 µm), which shortly thereafter settles and attaches to the substrate. Development times are therefore strongly influenced by water temperature.