Sea Wasp, Carybdea alata

Sea Wasp (Carybdea alata)

Nicole Baker
and
James B. Wood (Ed)

Taxonomy Habitat Ecology Recent Research Commercial Importance Bermuda Laws Personal Interest References Links

Taxonomy

Phylum: Cnidaria
  Class: Cubozoa
    Order: Cubomedusae
      Family: Carybdeidae

Abstract

Until 1971, Cubozoa had been grouped with the Scyphozoa (Arneson and Cutress 1976). Observations and further investigation of specific anatomical structures and reproductive methods conclude that they are in fact taxonomically different. C. alata and Scyphozoa find their main difference in reproduction and their life cycle. Most cnidarians have a planulae larvae stage, whereas cubozoans specifically have a pear shaped larvae with light spots and cilia. Each polyp metamorphoses into one meduase in the cubozoans as opposed to the strobilation of scyphozoans. Other aspects of the life histories are fairly similar. C. alata live primarily in areas of low tide out to the continental shelf (Hartwick 1991). In Bermuda specifically, only the medusae are found, and only in offshore waters (Sterrer 1986). C. alata feeds using the nematocysts found on their tentacles, hanging over the bottom preying on mysids and fish hatchlings (Martin 2004). The nematocysts are also used as the primary method of defense against predators. The toxic stings of the C. alata can be fatal to humans, and research is focused on isolating the best method to treat the stings (Nomura et al. 2002).

Habitat

Carybdea alata is distributed throughout the saltwater tropics in relatively shallow areas from the low tide line to the continental shelf, though they can withstand salinities down to 13 psu (Hartwick 1991). They are most abundant in the benthic community, average depth of 4 metres, during the day and at night rise to the surface for feeding (Arneson and Cutress 1976). They usually occur in densities of 1-2 per 9 square metres, but have been observed in 30-50 per square metre near Santa Barbara CA (Martin 2004). Specifically in Bermuda the medusae are occasionally found in offshore waters, but the polyps have not been observed (Sterrer 1986).

Ecology

Anatomy
Cubozoa have a square shaped bell (Waggoner 1995) with tentacles in multiples of four (Pechnick 2005), up to a maximum of 24. C. alata specifically has 4 (Arneson and Cutress 1976). Pads of tissue, called pedalia, are connected to the corners of each bell, and the number of tentacles extending from each pad is how the two main groups of Cubozoa, Chirodropidae and Carybdeidae, are distinguished. The Chirodropidae have one tentacle per pedalium while the Carybdeidae have multiple tentacles, as in the case of C. alata (Waggoner 1995).

Inside the bell is a sensory structure called a rhopalia, attached to the bell by a muscular stalk which can rotate 180 degrees. The rhopalia contains complex eyes, which are sensitive to light (Waggoner 1995). These complex eyes have evolved from eye cups as a result of an increase in detectable spatial information. Each of the eight eyes has a cornea, lens, and retina of ciliated photoreceptor cells that resemble vertebrate rod cells (Martin 2004). It is not clear how the images produced by the eyes are interpreted, as the Cubozoa have only a nerve net to process information, not a brain (Waggoner 1995). This developed sense of vision is potentially used for feeding, navigation as well as reproduction (Martin 2004). The Cubozoa have been observed to navigate around people and pier pilings in order to protect thmselves (Martin 2004).

Statocysts are present in the rhopalia. The statocysts contain a structure called a statolith that allows the Cubozoa to know their orientation (Waggoner 1995). It works as a pendulum, stimulating one side of the bell when it is in a horizontal position, alerting the cubozoans to their orientation.

Defense
Like other cnidarians, cubozoans use nematocysts for defense. They fire a barb that is normally in a coiled position into the tissue of the prey. Venom is then released inside the tissue (Waggoner 1995). The nematocysts are arranged in a ring formation around each tentacle for maximum surface area contact. There are three hypotheses as to how the nematocysts discharge, the contraction hypothesis, osmotic hypothesis and tension hypothesis (Endean et al. 1991). The contraction hypothesis focuses on the compression of the nematocyst by a net that provides enough pressure to discharge the capsule. The osmotic hypothesis relies on the osmotic inflow to the capsule to cause enough pressure to cause discharge of the capsule. The tension hypothesis works by using stored energy in the coiled nematocysts that has been stored since the formation of the capsules (Endean et al. 1991).

Feeding
During the day, Cubozoa are part of the benthic community and hang their tentacles over the sand where they feed on mysids and fish hatchlings (Martin 2004). Besides plankton and mysids, Cubozoa have also been observed to chase, catch and eat fish as well as feed on polychaetes (seasonal swarms) and crustaceans (Larson 1976).

The capture of prey takes place within the tentacles. The nematocysts discharge and adhere to the prey. The tentacles contract from their normal size of 30cm to a few centimeters and stiffen (Larson 1976). The tentacles then pass the prey to the mouth. Larson (1976) observed this process occuring as a response to amino acid concentrations in the prey. Once the prey enters the swimming bell, the jellyfish's swimming ability is inhibited and the medusae is still. Through a combination of ciliated action and muscular action, a 20mm long prey can be swallowed in less that one minute (Larson 1976).

Reproduction
Cubozoans engage in copulation. The male medusae chases the females, grabs them with its tentacles and then injects spermatophores onto the tentacles of the female (Martin 2004). The female then passes the spermatophore to the manubrium to complete the process of internal fertilization (Lewis and Long 2005). The female gonads, normally transparent, turn to opaque white after fertilization has taken place. Reproduction takes place mostly in late July, early August (Arneson and Cutress 1976) if bell diameter exceeds 5mm. The gestation period lasts about 55h, after which the females releases the string of embryos (Lewis and Long 2005).

The cubozoan larve are slightly different than that of cnidarians (Arneson and Cutress 1976). Cnidarians have a planulae larval stage, while cubozoans have a pear-shaped larvae that contain light sensitive spots and cilia. The cilia provide the larvae with a method of chosing an approriate substrate before they settle approximately 6 days after release. The larvae then develop into a polyp within 8 days after release. Asexual reproduction occurs through budding within 54 days after release. The polyp metamorphosis is not similar to that of scyphozoans, as there is no strobilation. One polyp metamorphoses completely into a medusae. The process takes approximately 90 days but is heavily dependent on the amount of food the polyp receives (Arneson and Cutress 1976).

Recent Research

Because the stings of Carybdea alata are so toxic to humans, research is aimed at determining the most effective treatment for treating the stings. Nomura et al (2002) compared the treatments of hot water versus meat tenderizer or vinegar. Adults who volunteered received a single tentacle sting on their forearm. One forearm was treated with hot water (40-41 C) while the other was treated with either meat tenderizer or vinegar. The results indicated that hot water is more effective at reducing the pain then either meat tenderizer or vinegar.

Commercial Importance

There appears to be no commercial importance of Carybdea alata.

Bermuda Laws

There is no current legislation regarding Carybdea alata.

Personal Interest

When first learning about Cubozoa, I found it fascinating that there were organisms that were so deadly to humans, but so small. So even though I was hoping that there weren’t any in the waters of Bermuda for snorkeling and diving reasons, I was hoping there was so I could do this project on them and learn about what makes them so toxic, as well as other information on this interesting class of jellyfish.

References

Arneson, A. C. and C. E. Cutress. (1976). “Life History of Carybdea alata”. In: Mackie, G. O. Coelenterate ecology and behavior. Plenum, New York. pp 227-236.

Endean, R., J. F. Rifkin, Y. M. Daddow. (1991). “Envenomation by the box jellyfish Chironex fleckeri: how nematocysts discharge. Hydrobologia. 216/217: 641-648.

Hartwick, R. F. (1991). “Distributional ecology and behavior of the early life stages of the box jellyfish Chironex fleckeri”. Hydrobologia. 216/217: 181-188.

Larson, R. J. (1976). “Cubomedusae: Feeding – Functional morphology, behavior and phylogenetic position”. In: Mackie, G. O. Coelenterate ecology and behavior. Plenum, New York. pp 237-245.

Lewis, C. and T. A. F. Long. (2005). “Courtship and reproduction in Carybdea sivickisi (Cnidaria: Cubozoa)”. Marine Biology. 147: 477-483.

Nomura, J. T., R. L. Sato, R. M. Ahern, J. L. Snow, T. T. Kuwaye, L. G. Yamamoto. (2002). “A randomized paired comparison trial of cutaneous treatments for acute jellyfish (Carybdea alata) stings. Am. J. Emerg. Med. 20(7): 624-626.

Martin, V. J. (2004). “Photoreceptors of cubozoan jellyfish”. Hydrobologia. 530/531: 135-144.

Pechenik, J. (2005). Biology of the Invertebrates, Fifth Edition. Boston, McGraw-Hill. pp 105.

Sterrer, W. (1986). ed. Marine Fauna and Flora of Bermuda: A Systematic Guide to the Identification of Marine Organisms. New York, John Wiley and Sons. pp 158.

Waggoner, B. Introduction to Cubozoa: The Box Jellies. 30 August 1995. Online. Internet. University of California at Berkeley. 30 October 2006. http://www.ucmp.berkeley.edu/cnidaria/cubozoa.html.

Links

Carybdea alata Swimming
Sea-Wasp on Wikipedia
Sting Aid
Irukandji Syndrome