Document Details
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Document Type |
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Thesis |
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Document Title |
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RESPONSE OF MARINE INVERTEBRATE LARVAE TO MULTIPLE SETTLEMENT CUES AND ENVIRONMENTAL STRESSORS إستجابة يرقات اللفقاريات البحرية لمنبهات اللتصاق بالقاع المتعددة والضغوط البيئية |
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Subject |
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Faculty of Marine Sciences |
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Document Language |
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Arabic |
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Abstract |
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Marine invertebrate larval settlement and metamorphosis plays a crucial role in the determination of marine benthic population. This study describes the response of marine invertebrate larvae to multiple settlement cues and environmental stressors. Surface physical properties, substrate colour, hydrodynamics, biochemical cues, light, orientation and temporal scales play an important role in invertebrate larval recruitment on artificial substrates. Two different experiments were conducted in the central Red sea to test the hypothesis of this study. In the first experiment, four different hard substrates like ceramic tiles, concrete, stainless steel and acrylic panels were deployed in horizontal and vertical orientations during four seasons. Barnacles, polychaetes, bivalves, bryozoans and gastropods were the common invertebrate organisms recruited on the tested artificial substrates. Results indicate that the invertebrate recruitment on artificial substrates is regulated by a combination of factors which include substrate type, orientation and submersion season. In the second experiment, the interaction between the substrate colour and light were studied. Here, acrylic panels prepared from four different colours such as red, green, blue, yellow and another colourless (total five treatments) were submerged under shade and exposed to light in the Sea. The maximum number of invertebrates was recruited on the dark colour panels (blue and red) exposed to shade. Extracellular polymeric substances of three marine biofilm forming bacteria (Pseudoalteromonas shioyasakiensis, Vibrio harveyi and Planomicrobium sp.) isolated from the natural biofilm developed in the net cage submerged in the central Red Sea were tested for settlement activity. These exopolymers induced the settlement of cypris larvae of barnacle Amphibalanus amphitrite. The chemical characterization of extracellular polymeric substances revealed the presence of polysaccharides and protein contents. The environmental stressors like temperature (25, 28, 30 and 32oC), salinity (36, 39 and 42 psu) and heavy metals (Cadmium, mercury and lead) were synergistically tested against the nauplii and cyprids of A. amphitrite. The results showed that different temperature treatments have some effects on the larval survival when exposed to various concentrations of cadmium and lead, whereas for mercury treatments, the concentration of the metal has a significant effect on larval survival. In addition, the temperature has a significant effect on cyprid settlement inhibition on substrates.
In general, results showed that the preference of artificial substrates for recruitment depends on the benthic invertebrate organisms. In addition, the light plays a crucial role in the settlement of marine invertebrate organisms. The extracellular polymers extracted from marine biofilm bacteria also induced the barnacle larval settlement. The effect of environmental stressors (temperature, salinity and heavy metals) on A. amphitrite larvae are also notable. Furthermore, the inclusion of robust techniques like gene expression studies on invertebrate organisms can reveal their genomic response to settlement cues and environmental stressors. |
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Supervisor |
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Dr. Satheesh Sathianeson |
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Thesis Type |
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Doctorate Thesis |
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Publishing Year |
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1441 AH
2019 AD |
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Added Date |
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Sunday, September 29, 2019 |
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Researchers
| أبوبكر صديق ابوالقاس | Abul Kasim, Aboobucker Siddik | Researcher | Doctorate | |
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