Nereis succinea Essay Example | Topics and Well Written Essays - 11000 words

Nereis succinea - Essay Example Even as the decrease in feeding may indicate a decrease in olfactory sensing, greater levels of activity may refer to compensation through visual detection, i.e. a certain amount of time would have to be devoted in finding food. It is crucial to evaluate both parties in the interactions of predator and prey especially as both parties would likely be affected differently, eventually implying changes in the life of each party. Nereis succinea reproduction: (la) The mass spawning for the N. succinea is mostly seen from June to September at night during a new or full moon with temperatures higher than 16oC. This must however be influenced by the location population (Ram et al., 1999). The females give off the cysteine-glutathione disulphide (CSSG) when they swim. Such pheromone, first discovered by Zeeck et al. in 1998, seems to attract mates at depressed concentrations. The swimming of the male spawns becomes elevated (Ram et al., 2008) leading to a rise in the possibility of being face d with a sexually ready female (Fei et al., 2008). As these spawns meet, both males and females swim around each other in tight circles gradually becoming smaller in size. Males unleash some sperm along with the egg release pheromone (ERP) (Zeeck et al. 1996, 1998). Such ERP is made up mostly of inosine with glutamic acid and glutamine; it leads to the females releasing both eggs as well as significant amounts of sperm release pheromone (SRP), CSSG, at elevated levels (Hardege et al., 2004). Consequently, the males then unleash significant amounts of sperm, thereby leading to the fertilization of the female egg. Chemical nature of nereidid sex pheromones (la) Nereis succinea 1. Cysteine-glutathione disulphide (CSSG) Cysteine-glutathione disulphide (‘nereithione’) (CSSG) (Figure 10) is released by the female N. succinea while swimming; it is also considered a tetra- peptide pheromone. At low levels of concentration (10-9 M), CSSG causes the males to increase the pace and speed of their swimming; allowing the faster access to the slow-paced females. At elevated levels, (in excess of 10-6 M) CSSG causes the release of gametes by the male spawns (Ram et al., 1999). Glutathione (GSH) found in the body fluids and cysteine (amino acid) is utilized to provide synthesis for CSSG as needed. This production happens only during the heteronereid level of the life cycle (Hardege et al., 2004). Figure 10. Structure of the sex pheromone in N. succinea, CSSG (Source: Guidechem). Spawning hormones and pheromonal communication are responsible for the transduction of this information (Bentley and Pacey, 1992) eventually leading to the mass spawning phenomenon often seen for the nereidid species. 1. Males usually cover large distances as they swim over water surfaces seeking the slow swimming females. At some point, females may shift their swimming patterns, often swimming in circles for a few seconds. At which point, they may give off the sex pheromone 5-methyl-3-hep tanone and start to swim in tighter circles (Zeeck et al., 1988). 2. Ripe males detecting swimming females may notice the pheromone in the water and change the quality of their swimming. They then return to the source of the ‘smell’ of the female while also giving off some coelomic fluid, which is otherwise referred to as a ‘sperm cloud’ (Hardege, 1999). Such sperm cloud includes the egg release pheromone (ERP), L – Ovothiol A (Rohl et al., 1999) (Figure 6). 3. The ERP then prompts the female to swim