Biology and reproductive processes of the larger foraminiferan Cycloclypeus carpenteri (Protozoa, Nummulitidae)

Abstract

Summary Gamonts and agamonts of the extant nummulitid Cycloclypeus carpenteri were collected from a depth between 45 and 61 m, near Okinawa (Ryukyu Islands, Japan) and maintained in the laboratory in Kiel (Germany) until they reproduced. All of them grew in the laboratory, including damaged specimens, which regenerated more or less regular tests. Like other nummulitids, they formed sheaths for attachment, complete in young and incomplete in adult specimens. Eighteen agamonts formed gamonts in the laboratory, the first reproducing after 5.5 months and the last after 9.2 months of maintenance. The process of multiple fission can be divided into 5 well defined periods. During the formation of the two-chambered embryonic apparatuses, the symbiotic diatoms are apportioned to the daughter cells by a highly organized process that is identical in all nummulitids. The number of gamonts provided by 3 agamonts was 1740, 1910 and 2540. The mean prolocular size in the two-chamber stage of the gamonts was 263 pm (minimum 200 µm, maximum 327 µm). The mean size of 5 gamonts from the natural habitat was 8.1 mm on the day of reproduction. The mean size of 39 gamonts from laboratory culture was 8.6 mm. Gamete formation began at an age of about 11 months and ended at an age of about 13 months. Gamonts released their 2.5-3.0 Nm biflagellated gametes over 0.7 to 15 hours mainly during the light period.