Individuals were collected from their natural habitats and transported to the laboratory, where they were immediately transferred to aerated holding aquaria containing water from Stonemeal Creek. There were three holding tanks for each species, with individuals divided into size classes using the same criteria as were used in the field surveys. Fifty per cent water changes were made on a daily basis. Tanks were covered to limit evaporation and the escape of animals. All individuals were acclimated to laboratory conditions for at least 24 h before the tests were
conducted. At the end of experimentation all animals were returned to the site from which they were collected. Choice experiments were carried out in a plastic tank(45 31 cm and 28 cm high) with 10-cm water depth.
The tank had opaque sides to minimize visual distractions
and was divided into three sections, each end separated
from the central section by a sheet of clear acetate. Water
circulation was possible via small holes in the acetate,
allowing chemical and visual stimulation of the target individual
(although the diffusion rate between compartments
was not quantified). ‘End-zones’ were marked out
within the central compartment, which, at 7.5 cm in
width, ensured that even the largest individuals would
be wholly within the zone if they were adjacent to the
acetate ‘window’ (see Fig. 1).
The stimulus animals, located behind the windows,
were allowed to acclimatize for 5 min before introduction
of the test individual. The test individual was allowed to
acclimate for 5 min in an acetate cylinder (8.5 cm in diameter),
located in the centre of the ‘neutral zone’. The cylinder
was subsequently removed, and the test individual’s
preference was scored by recording the amount of time
Individuals were collected from their natural habitats and transported to the laboratory, where they were immediately transferred to aerated holding aquaria containing water from Stonemeal Creek. There were three holding tanks for each species, with individuals divided into size classes using the same criteria as were used in the field surveys. Fifty per cent water changes were made on a daily basis. Tanks were covered to limit evaporation and the escape of animals. All individuals were acclimated to laboratory conditions for at least 24 h before the tests wereconducted. At the end of experimentation all animals were returned to the site from which they were collected. Choice experiments were carried out in a plastic tank(45 31 cm and 28 cm high) with 10-cm water depth.The tank had opaque sides to minimize visual distractionsand was divided into three sections, each end separatedfrom the central section by a sheet of clear acetate. Watercirculation was possible via small holes in the acetate,allowing chemical and visual stimulation of the target individual(although the diffusion rate between compartmentswas not quantified). ‘End-zones’ were marked outwithin the central compartment, which, at 7.5 cm inwidth, ensured that even the largest individuals wouldbe wholly within the zone if they were adjacent to theacetate ‘window’ (see Fig. 1).The stimulus animals, located behind the windows,ได้รับอนุญาตให้ acclimatize ใน 5 นาทีก่อนที่จะแนะนำของการทดสอบแต่ละรายการ ทดสอบแต่ละได้รับอนุญาตให้acclimate สำหรับ 5 นาทีในถังเป็น acetate (8.5 ซม.เส้นผ่านศูนย์กลาง),ตั้งอยู่ในศูนย์กลางของ 'โซนกลาง' ถังมาลบออก และของแต่ละการทดสอบตั้งค่าเป็นคะแนน โดยบันทึกเวลา
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