Development of sensory organs and changes of behaviour in early larvae of mouse grouper, Cromileptes altivelis.

Audrey Daning Tuzan, (2007) Development of sensory organs and changes of behaviour in early larvae of mouse grouper, Cromileptes altivelis. Masters thesis, Universiti Malaysia Sabah.

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Abstract

This study was conducted to clarify the development of the sensory organs with larval growth In mouse grouper Cromileptes attivelis for the purpose of understanding larval behaviour and improving larval rearing methods. Larvae of the mouse grouper were reared from hatching to 20 days old, sampled every day, and observed under. light microscope and scanning electron microscope for morphological development of the sensory organs. Eggs were collected from the hatchery of Borneo Marine Research Institute. larvae were fed with rotifers, Artemia nauplii, copepods and artlfidal powder feed. The newly hatched larvae were 1.87±0.20 mm (mean ±S.D) In total length (TL) and floated motionless In the water column. A pair of free neuromasts (15-17µm diameter and 35-40 sensory cells) was observed behind the eyes in newly hatched larvae. The inner ears of the newly hatched larvae were only oval-shaped vesicle. One-day-old larvae (TL.2.47±0.47 mm) still showed suspended posture, and were repeatedly moving up and down in the water column. The eyes of one-day-old larvae had a lens and several layered retina, and olfactory pits were opened with epithelium cilia. Two-day-old larvae (TL. 2.60±0.39 mm) swam with a horizontal posture, the eyes were slightly pigmented, the mouth was opened, and lower jaw movements were observed. Three-day-old larvae (TL2.64±0.35 mm) had well pigmented eyes when they commenced ingesting rotifer Branchionus sp. Six pairs of free neuromasts were found on the head and 4 pairs on the unilateral side of the trunk of 3-day-old larvae. Free neuromasts were distributed around the eyes on the head, and the middle of the trunk. On the head the free neuromasts were oriented on lines tangential to concentric circles around the eye; hence the free neuromasts on the head could detect the stimuli from various angles. It was considered that free neuromasts of mouse grouper play an important role In avoiding predators especially until the eyes begin to function. The apical surface of free neuromasts changed In outline from a circular shape to a lozenge shape, suggesting that the shape of the cupula changes from a stick-like shape to a vane-like shape. larvae of 5 days old start to show positive phototaxis. At 20 days old, taste buds were observed on the epithelium of the gills. The development of the sensory organs Is accompanied by behavioural changes that have Important Implications for larval ecology at sea and mouse grouper larva rearing.

Item Type:Thesis (Masters)
Uncontrolled Keywords:Mouse Grouper, larval rearing, sensory organs, egg collection, behaviour
Subjects:S Agriculture > SH Aquaculture. Fisheries. Angling
Divisions:SCHOOL > Borneo Marine Research Institute
ID Code:9519
Deposited By:IR Admin
Deposited On:11 Dec 2014 14:29
Last Modified:11 Dec 2014 14:29

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