Effect of food and light on behavioral patterns of coastal and estuarine copepods

• Main Authors: Cheng-Han Wu, 吳政翰
• Other Authors: Hwang, Jiang-Shiou
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/35650208750862171652

博士 === 國立臺灣海洋大學 === 海洋生物研究所 === 98 === In the present doctoral dissertation is thesis, I have studied copepod behavior using three different approaches (i) effects of food and light on the swimming behavior of nauplii of the cyclopoid Apocyclops royi and the calanoid Pseudodiaptomus annandalei (ii) behavioral interactions between the potentially predatory calanoid Temora turbinata and its prey ciliated protists (Strombidium sp. and an undetermined species of spinning ciliate) (iii) swimming behavior of copepods taking three dimensional approach . (i) In order to understand the effects of food and light on the swimming behavior of copepod nauplii two species Apocyclops royi and Pseudodiaptomus annandalei common representative of cyclopoid and calanoid respectively were chosen for the study. Important behavioral parameter such as swimming patterns, swimming speed, and swimming trajectories were investigated videographically. The nauplii of the two copepod species exhibited distinct differences in their swimming speed, and trajectories. In presence of the most commonly used diet the dinoflagellate Isochrysis galbana (Isochrysidales, Haptophyta) the nauplii of A. royi showed fast and periodically jerky swimming behavior in circular path in contrast the calanoid P. annandalei nauplii never exhibited such behavior neither with algae nor without. The differential swimming patterns in nauplii of the two copepod species are suggestive of different foraging strategies of the two copepod species in detecting and capturing food. (ii) The behavioral interactions between the potentially predatory Temora turbinata (Copepoda: Calanoida) and two prey species (differing in swimming pattern) belonging to ciliated protists Strombidium sp. and an undetermined species of spinning ciliate were video-documented and analyzed. Videotaped copepod-ciliate encounters were image-analyzed to calculate ciliate swimming trajectories, T. turbinata attack kinematics and reaction distances of the ciliate preys to the predatory copepod. The swimming speed of either of the ciliate in the presence of copepod was lower than that in control. The two ciliate species differed widely in their reaction distances to the predator. The unidentified spinning ciliate was able to sense its copepod predator from a longer distance and escaped from the feeding current with a faster response than Strombidium sp. Our observations suggest that spinning and other evasive behaviors such as jumping are evolutionary adaptive as predator deterrent strategies of ciliates. The copepods were able to differentiate between living organisms versus inert particle of similar size as it used to eject non-ingestible particles. My results suggest that incorporating species-specific prey-predator interactions elicited from behavioral studies will improve future food web models. (iii)Prior to my study all behavioral observations in Taiwan are confined to the 2-dimensional video-based observations only. Keeping in view the experimental artifacts and limitations of 2-dimensional observations in interaction studies I used 3-dimensional approach to observe the swimming behavior of copepods. The 3-dimensional video-based observations observation provides accurate information of interactions and minimizes the errors. I designed 3-dimensional experiments, in order to eliminate limitations of 2-dimensional experiments. Behavior patterns of male and female adult copepods Acartia southwelli and Apocyclops royi were compared under light and dark. In case of a calanoid Acartia southwelli the average swimming speed (2.73 mm/s) of female copepod was greater than that of male (1.98 mm/s). Furthermore either in male or in female of A. southwelli the average swimming speed was higher in dark (infrared) environment than that in the bright light condition. In contrast, in case of either male or female cyclopoid Apocyclops royi the average swimming speed was faster under bright light condition than that under dim light environment. Furthermore, the average swimming speed of the ovigerous female of A. royi (5.59 mm / s) was greater than that of conspecific male (average swimming speed: 4.59 mm / s), in both bright and dim light environment. Finally considering the two species of copepods representing the two planktonic copepod orders Cyclopoida and Calanoida the average swimming speed of the cyclopoid A. royi (5.1 mm/s) was higher than that of the calanoid Acartia southwelli (2.4 mm/s). The use of multi-scale NGDR analysis which divides the 3-dimensional trajectory into three different planes of the 2-dimensional trajectory (XZ, YZ and XY, Z for the vertical axis) elicited finer details of the trajectory. Under bright environment condition the activities of copepods were affected by the gravity as the trajectory of XY plane showed more twists and turns than XZ and YZ plane. However, in dim light environment, NGDR trajectory analysis did not reveal any difference in the three planes, indicating that the gravity effect on the swimming trajectories was not significant in dim light environments. Convincingly the illumination conditions affect our NGDR analysis results.