Houghton, J.D.R. Doyle, T.K. Davenport. J. Lilley, M.K.S. Wilson, R.P. Hays, G.C. 2007. Stranding events provide indirect insights into the seasonality and persistence of jellyfish medusae (Cnidaria: Scyphozoa). Hydrobiologia 589:1-13.
-What is the seasonality and reproductive strategy of jellyfish? If the bell diameter or net weight of stranded medusae was increased over time is this a single reproductive group or does this suggest the release of ephyrae over many months? Also are the jellyfish over wintered as pelagic medusa as previously reported?
-3 different species were recorded (C. capillata, C. hysoscella, R. octopus) at 5 sites over a 3 year period. Bell diameter was measured at a random sample of the first 50 jellyfish encountered from the last incoming tide. Using equations the wet weight was derived for each measurement.
- The broad range of size and weight found over all sites suggests that the release of ephyrae may be lengthened and individuals of all sizes are in the water coulomb during summer months. Evidence also showed that there is over wintering involved in rhizostome jellyfish that gives these species an advantage to the early year prey.
Monday, October 15, 2007
Journal Articles of Relevance
Piriano, S. DeVito, D. Schmich, J. Bouillon, J. Boero, F. 2004. Reverse development in Cnidaria. NRC Research: Canadian Journal of Zoology. 82:1748-1754.
-The authors wanted to study the reverse development or ontogeny of Cnidarians and how these animals can reactivate earlier stages of development leading to rejuvenation and how these studies relate to ecology and unfavorable conditions.
- The simple life cycle of the Cnidarians has many known conversions leading to form resting states by shrinking and decrease in metabolic processes when the going gets tough. This can also be known as renovation. Also there are certain species that can regenerate damaged or lost organs and tissues and new polyps formed from individual ones.
- While this paper had no real methods or results the author collected data from previous research that related to the development of an older stage to a previous stage of development in many species of Cnidarians.
- The authors found, through research that the medusa stages have the ability to bud and produce polyp stages in some species and polyps can regenerate into planula larvae in others. These cases are due to many unfavorable factors such as current, starvation, mechanical stress, and temperature and salinity changes.
-The authors wanted to study the reverse development or ontogeny of Cnidarians and how these animals can reactivate earlier stages of development leading to rejuvenation and how these studies relate to ecology and unfavorable conditions.
- The simple life cycle of the Cnidarians has many known conversions leading to form resting states by shrinking and decrease in metabolic processes when the going gets tough. This can also be known as renovation. Also there are certain species that can regenerate damaged or lost organs and tissues and new polyps formed from individual ones.
- While this paper had no real methods or results the author collected data from previous research that related to the development of an older stage to a previous stage of development in many species of Cnidarians.
- The authors found, through research that the medusa stages have the ability to bud and produce polyp stages in some species and polyps can regenerate into planula larvae in others. These cases are due to many unfavorable factors such as current, starvation, mechanical stress, and temperature and salinity changes.
Sunday, October 14, 2007
Journal Articles of Relevance
Bassim, K.M. Sammarco, P.W. Snell, T.L. 2002. Effects of temperature on success of (self and non-self) fertilization and embryogenesis is Diploria strigosa (Cnidaria, Scleractinia). Marine Biology 140:479-488.
-The authors of this study wanted to find out the effects that elevated sea water temperature has on both sexual and asexual fertilization and embryogenesis of scleractinian corals. They wanted to know what level of development the higher temperatures effected and how this in part determined their success over generations.
-Earlier research suggested that optimum temperatures for coral development range from 25 to 29 degrees Celsius. Most tropical corals live at the upper level of this. There have been increasing temperatures of coral waters and the bleaching of many reefs due to high temperatures over a long period of time. This puts stress on the zooxanthellae and their coral hosts. But the information on the effect on the particular stage of development has not been significantly researched.
-The procedure used collections of egg and sperm bundles from different colonies during the spawning season. These colonies were randomly placed in 3 different water baths of 30, 31, and 32 degrees Celsius for self fertilization and another 3 baths for cross fertilization and the 6 baths were replicated again. Levels of development were monitored and examined. The results found that there was no significant difference in fertilization success across the samples but embryonic development in the 31 and 32 degree baths showed significant differences on the fourth and higher cleavage stages.
-temperature does have an impact on the development of coral in the higher cleavage stages of embryogenesis. This surprisingly has no effect of the fertilization process. As the time increased at the higher water temperature there was a significant increase in the time of development to the next embryonic stage even at just a temperature change of 1 degree Celsius. With a decrease in the production of healthy larvae we may witness a decrease in the success and abundance of corals in the future.
-The authors of this study wanted to find out the effects that elevated sea water temperature has on both sexual and asexual fertilization and embryogenesis of scleractinian corals. They wanted to know what level of development the higher temperatures effected and how this in part determined their success over generations.
-Earlier research suggested that optimum temperatures for coral development range from 25 to 29 degrees Celsius. Most tropical corals live at the upper level of this. There have been increasing temperatures of coral waters and the bleaching of many reefs due to high temperatures over a long period of time. This puts stress on the zooxanthellae and their coral hosts. But the information on the effect on the particular stage of development has not been significantly researched.
-The procedure used collections of egg and sperm bundles from different colonies during the spawning season. These colonies were randomly placed in 3 different water baths of 30, 31, and 32 degrees Celsius for self fertilization and another 3 baths for cross fertilization and the 6 baths were replicated again. Levels of development were monitored and examined. The results found that there was no significant difference in fertilization success across the samples but embryonic development in the 31 and 32 degree baths showed significant differences on the fourth and higher cleavage stages.
-temperature does have an impact on the development of coral in the higher cleavage stages of embryogenesis. This surprisingly has no effect of the fertilization process. As the time increased at the higher water temperature there was a significant increase in the time of development to the next embryonic stage even at just a temperature change of 1 degree Celsius. With a decrease in the production of healthy larvae we may witness a decrease in the success and abundance of corals in the future.
Phylogeny
•First documented fossil found in South Australia and dates back 600 million years ago. (dated from Precambrian).
•Evolutionary relationships are subject to lots of debate.
•Reasoning suggests that the polyp stage was evolved second, and loss of the original body form, the medusa, places Anthozoa as the most derived taxon.
•Allied with ctenophores? one body opening....but lack cnidae
life cycle
Characteristics
- A diploblastic metazoan. Has an endoderm and ectoderm that is seperated by acellular mesoglea or cellular mesenchyme that is ectoderm in origin.
- Has radial symmetry with a oral-aborl body axis.
- Has stinging or adhesive "cnidae" that are produced by cnidocytes. They are normally called nematocysts, spirocysts, and ptychocysts.
- Musculature is made of myoepitheilial cells that are ecto/endoderm of origin.
- Has an alternation in reproduction: Asexual polypoid and sexual medusoid generations. (varries with species)
- Has only one gastrovascular body cavity called the coeleteron that is entodermally derived.
- Single opening that is both the mouth and anus.
- No head or central nervous system but has nerve nets that are large, naked nonpolar neurons.
- Planula larvae that are ciliated and motile.
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