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More Mysteries to Unravel
Ames’ findings, which were published in the journal Marine Biology in March 2005, clearly documented the steps of Copula sivickisi’s mating dance (originally described as Carybdea sivickisi), but the mysteries associated with these tiny creatures are far from solved.
One unanswered question is how males recognize sexually mature females as potential mates. Scientists identify them by dark orange markings, known as velar spots, which appear around the margin of their bells when they are old enough to mate (Fig 9), but can the male Copula sivickisi see these spots? Box jellies have remarkably complex eyes (Fig 10a,b), which researchers believe are capable of sensing light and forming an image of their surroundings. But it’s not clear exactly how well they see or whether they are capable of perceiving fine detail, such as velar spots on a mate.
Ames observed that males did not court females who lacked velar spots, but she can’t say for sure whether they were responding to visual signals, chemical cues the researchers were unaware of, or something else entirely.
Ames hopes that there will be more research to investigate this question and others, such as why do the males have red sperm? Why do females accept multiple spermatophores from several males when one is likely sufficient to fertilize her eggs? Why do females sometimes continue to ingest spermatophores after releasing their embryo strands? And how can we better rear these creatures and their young, which are called polyps (Fig 11a-d) in the lab so we can observe their entire life cycle up close?
At present, Copula sivickisi has been reported from a range of tropical, subtropical, and mild temperate localities in the Pacific, with one exception in the Indian Ocean. You can check out the distribution map (Fig 12) to see if you may have encountered these intriguing little jellyfish while snorkel or night-diving in the ocean somewhere.
Interview with Cheryl (Lewis) Ames, Research Associate at the Smithsonian National Museum of Natural History. July 27th, 2007.
Lewis, C., Kubota, S., Migotto, A. E., & Collins, A. G. (2008). Sexually dimorphic Cubomedusa Carybdea sivickisi (Cnidaria: Cubozoa) in Seto, Wakayama, Japan. Publications of the Seto Marine Biological Laboratory, 40 (5/6), 1-8.
Lewis, C. & Long, T. A. F. (2005). Courtship and reproduction in Carybdea sivickisi (Cnidaria: Cubozoa). Marine Biology, 147, 477-483.
Nilsson, D. E., Gislén, L., Coates, M. M., Skogh, C., & Garm, A. (2005) Advanced optics in a jellyfish eye. Nature, 435, 201-205.
Web and multimedia support courtesy: Dana Dolan.
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