Reproductive Biology

 

Porifera are innumerable in reference to population and biodiversity, but how do they keep their numbers and populations on a consistent growth pattern? Like humans, sponges need to propogate themselves. However, poriferan methods of reproduction are quite different. As discussed previously, porifera reproduce in a few general ways:

 

Asexual methods of reproduction

1) Budding and Gemules- A mini-sponge branch forms on the exterior of the sponge. After a period of time, currents may cause this to break off from the rest of the sponge.

 

2) If a conglomeration of sponge cells is extracted from the main body of the sponge, it will develop into another porifera.

 

 

 

Sexual methods of reproduction

 

1) Basically, most sponges are hermoprhoditic (being of both genders or able to change between these genders). Eggs and sperm are released, and these cells are cross fertilized. Whence, they float to some uninhabited section of the ocean floor and initiate their life as a sponge. This is actually synchronized between species.

 

Two important terms to remember are viviparous and oviparous. Viviparous sponges incubate the eggs within their branches before releasal. Oviparous simply release the sponges.

 

Dr. Jane Fromont of Australia has worked extensively to use reproductive biology to compare and contrast different species. Use of reproductive biology can help scientists to better define taxonomic trees. We thank Doctor Fromont for her continuous contributions to our page. We wish her the best of luck with future research.

 

When the idea of using reproductive biology to differentiate between sponge classifications was created, it helped to clarify a lot of confusion. Theoretical observations developed into more concrete facts. In the demosponge class, two new subclasses were developed. Tetractinomorpha was composed of oviparous porifera, and Ceractinomorpha, the other subclass, contained oviparous sponges. However, there are a couple exceptions that still need to be disputed, discussed, et cetera. Fortunately, such disputes are only inspiring new work, such as the studies of Dr. Fromont.

 

In previous years, Dr. Fromont has worked extensively and thoroughly with the porifera species of the orders of Haplosclerida and Petrosida. Prior to this the Petrosida were actually a family of the Haplosclerida. However, as research techniques were updated, so was the taxonomic tree. These orders are both assigned to the Ceractinomorpha, which would imply that the species within the orders were all oviparous. But there are always exceptions to the rule.

 

While species within the Petrosida are oviparous, Haplosclerida sponges are viviparous. This theory substantiated the differentiation between the two orders, despite their other apparent similarities. For now, the exception was overlooked until further research could isolate the order of Haplosclerida from the Ceractinomorpha.

 

Dr. Jane Fromont researched, in 1994 and other years, the orders of the Haplosclerida and the Petrosida, taking into special account their genetic and reproductive biology. Her results have been featured in several publications. She also published her findings as a part of the proceedings of the Fourth International Porifera Congress.

 

In the studies conducted by Dr. Fromont, specific emphasis was placed upon the tropical species of the Great Barrier Reef. The following observations were made on the order of Haplosclerida:

 

• All three species having been examined were viviparous
• Male sperm were distributed evenly throughout each species.
• Only two of the species utilized female gamete chambers. The other species simply lined up the cells on branches.
• The species with female gamete chambers did not have a life expectancy more than a few years.

Observations on the reproductive biology of the Petrosida included:

 

• All the three species were oviparous.
• There was even distribution of male and females.
• Some species lived longer than others.

And the quest for clarification within sponge taxonomy will continue forever. Maybe one of our readers could help in solving age-old mysteries!