An improved cultivation device for appendicularians with notes on the biology ofFritillariasp. collected in Sagami Bay, Japan

Abstract

AbstractTo cultivate zooplankton species with highly fragile mucoid structures, a new type of cultivation device was developed, which uses a novel method to gently circulate the water in the culture vessel. Using this device, a species of the fritillarid appendicularia (Fritillariasp.) collected in Sagami Bay was successfully cultivated. This form resemblesFritillaria haplostomaorFritillaria formica tuberculata, but some taxonomical characteristics differed from those of the latter forms. A novel device comprising a polycarbonate bucket with a motor-driven rotating cylinder inserted into the water in the bucket was developed and maintainedFritillariasp. over ten filial generations in the laboratory. The animals reached trunk lengths of 1026 ± 85μm (mean ± SD) four days after fertilization at 23°C. The instantaneous growth rates were calculated as 1.11–1.72 at 20–26°C, representing a 3.0–5.6-fold daily increase in body weight. The house constructed by this species is extraordinarily fragile, typically has a barrel-like or cylindrical shape, and accommodates its entire body and food-concentrating filter. At 23°C, the species produced houses at a rate of 28 ± 2.8 houses d−1. The new device is useful for the continuous cultivation of the fragile form of fritillarid appendicularia, and even for various other zooplankton. It also shows thatFritillariasp. could be a significant secondary producer and transporter of organic matter in marine ecosystems due to its high growth and house production rates.