Feeding rates of planktonic copepods from inshore waters, near Townsville, north Queensland

Laboratory experiments were carried out to investigate the feeding rates of 5 species of tropical planktonic copepods. Calanopia elliptica, Eucalanus subcrassus, Paracalanus aculeatus, Tortanus gracilis and Temora turbinata were selected from plankton samples collected from inshore waters near Townsville, from May to October, 1976. Seawater was also collected from the sampling sites and filtered for use in experiments.Prior to commencement of experiments, subsamples of copepods were taken for dry body weight measurements. Experiments commenced 3-4 hours after collection. Individual Eucalanus, Tortanus or Calanopia were placed in 50 or 75 ml beakers of filtered seawater and 20 to 50 Artemia nauplii were added. Beakers were placed in a glass incubator so that the copepods were subjected to natural light cycles. Temperatures were maintained close to that of the water where the copepods were collected (22-25°C). To examine differences in feeding rates between day and night, each copepod was removed and placed in a new beaker, under the same conditions, twice a day (0800 and 1700hr) until the copepod died. Artemia nauplii remaining in the beaker after removal of the copepod were counted and the feeding rate calculated. The effect of container volume on feeding rates was also tested by placing single females of Eucalanus subcrassus or Tortanus gracilis in containers of different volumes (50, 200, 1000 ml).Experiments with Temora turbinata and Paracalanus aculeotus were carried out in 24.5 ml vials instead of beakers and each copepod was removed and placed in a new vial once per day. The concentration of the phytoplankton food cells introduced to each copepod was between 1-3 x 10^6 µm³/ml. Incubations were carried out in the dark to prevent cell sedimentation and addition growth of food cells. The concentration of cells prior to and after incubations were determined in terms of total cell volume with a Coulter Counter TAII.The experimental results were used to calculate daily ration for each copepod species, expressed as a percentage of body weight. This research was initiated to 1. measure feeding rates of copepods from tropical waters2. enable comparisons with published feeding rates of copepods from temperate and boreal seas. Food species:Eucalanus, Tortanus and Calanopa: newly hatched Artemia naupliiTemora: Dunaliella salina Paracalanus: Skeletonema costatum

本研究通过室内受控实验，探究5种热带浮游桡足类的摄食速率。实验所用桡足类分别为椭圆卡兰水蚤（Calanopia elliptica）、厚真哲水蚤（Eucalanus subcrassus）、刺拟哲水蚤（Paracalanus aculeatus）、纤细角毛哲水蚤（Tortanus gracilis）与旋回哲水蚤（Temora turbinata），均采集自1976年5月至10月汤斯维尔附近近岸海域的浮游生物样本。
实验所需海水同样采集自采样海域，经过滤处理后用于实验。
正式实验启动前，先采集桡足类子样本用于体干重测定；所有实验均在样本采集后3~4小时内启动。
将单只厚真哲水蚤、纤细角毛哲水蚤或椭圆卡兰水蚤置于盛有过滤海水的50 mL或75 mL烧杯中，加入20~50只卤虫无节幼体（Artemia nauplii）作为食物。将烧杯放置于玻璃培养箱内，使桡足类处于自然光照周期下，实验温度维持在桡足类原栖息海域水温附近（22~25℃）。
为探究昼夜摄食速率差异，每日分两次（08:00与17:00）将单只桡足类转移至相同条件的新烧杯中，直至该个体死亡。移除桡足类后，计数烧杯内剩余的卤虫无节幼体数量，以此计算摄食速率。
本实验还设置了容器体积梯度实验，以探究容器体积对摄食速率的影响：将单只厚真哲水蚤雌性个体置于体积分别为50 mL、200 mL、1000 mL的容器中，其余实验条件保持一致。
针对旋回哲水蚤与刺拟哲水蚤（原文误写为Paracalanus aculeotus）的实验则采用24.5 mL小瓶而非烧杯开展，每日将单只桡足类转移至新小瓶一次。向每只实验个体投喂的浮游植物食物细胞浓度为1~3×10^6 μm³/mL。
实验培养过程全程避光，以避免食物细胞沉降及额外增殖。利用库尔特计数器TAII（Coulter Counter TAII）测定培养前后的细胞总容积，以此表征食物细胞浓度。
基于实验结果，可计算各桡足类物种的日摄食量，以体干重百分比的形式表征。本研究的核心目标包括：1. 测定热带海域桡足类的摄食速率；2. 对比已发表的温带与寒带海域桡足类摄食速率数据。
实验所用食物种类如下：
厚真哲水蚤、纤细角毛哲水蚤与椭圆卡兰水蚤：初孵卤虫无节幼体；
旋回哲水蚤：盐生杜氏藻（Dunaliella salina）；
刺拟哲水蚤：中肋骨条藻（Skeletonema costatum）。