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Homework Assignment I – Sponges and Jellies - Answers 1. What body type (asconoid, syconoid or leuconoid) does Spongilla have? What are the advantages of this body type? Spongilla has a leuconoid body type, which has the highest amount of internal folding, creating flagellated chambers. The body type has the overall largest internal surface area and is competent to carry out the most filtration. 2. Why are there spicules surrounding the gemmules of sponges? Be inclusive with the justification of this answer. Gemmules are overwintering bodies of fresh and shallow water sponges. As such, they contain undifferentiated archaeocytes that, once the overwintering bodies burst open will give rise to new sponges. Since overwintering bodies are formed prior to the cold times of the year, the spicules are a means of protecting the internal archaeocytes from exposure to the elements. The mineralized nature of the spicules also makes it difficult for predators to open the overwintering bodies and consume the archaeocytes. In addition, the mineralized nature of the protective spicules prevents any bacterial infection of the archaeocytes. 3. Why does Cassiopeia swim upside down? Bes specific and provide all information necessary to discuss this phenomenon. Remember: Most jellyfish do not have a constant upside down swimming motion. The upside down or mangrove jellyfish Cassiopeia contains zooxanthellae in the oral arms. Zooxanthellae (dinoflagellates) are photosynthetic organisms that require light in order to be able to produce oxygen and simple sugars. Since Cassiopeia in part relies on nutrition and oxygenation through the zooxanthellae they expose their oral arms to light by swimming with the arms pointing towards the light so that the zooxanthellae have maximum exposure to light. 4. What is the lifecycle for members of the Octocorallia (Phylum Anthozoa) (draw, label and describe in a few words) (2 pts) Anthozoans lack a medusa stage entirle, therefor a polyp is either male or female. During reproductive times the polyps will release their respective gametes (eggs or sperm). Fertilization is external and the resulting larval stage is the planula. The mobile planula will eventually settle and grow into an adult polyp that has eightfold symmetry. 5. Pleurobranchia display tentacles as part of their morphology. What is the function of these tentacles? The tentacles of Pleurobranchia are used to capture prey and stuff it into the mouth for digestion. These tentacles are not generally means of locomotion, which is accomplished by the ctene rows and their synchronized ciliary beats. 6. What are the morphological and developmental differences of members of the orders Cydippida, Lobata and Beroida? Morphological differences: Cydippida = oval to cylindrical with distinct tentacles used in capturing prey, Lobata = large lobes growing out at or near the oral end, Beroida = oval to cylindrical but lacking both tentacles and lobes to aid in feeding, instead beroid ctenophores open up their mouth giving the organism a sac-like appearance in order to engulf their prey. Developmental differences: Cydippida and Beroida do not show the presence of true cydippid larvae and are therefore considered to be more primitive, Lobata display a typical cydippid larva. 1