Cubomedusae and Scyphomedusae
Methods

It cannot be stressed too strongly that several jellyfish sting humans severely. Special care should be taken to avoid this. Being a serious student does not diminish the danger — rather, the danger increases since it is natural to become blasé. A sting in the eye from a usually harmless species can be extremely serious and might permanently damage human sight. Techniques for avoiding stings are mentioned below, and should be taken very seriously.

Extremely important. With the most venomous species, eyes should be protected by spectacles or goggles. Avoid splashes to the eyes. Do not rub your eyes after handling medusae — even apparently harmless species — since the nematocysts can readily penetrate the soft tissues in and around the eyes. Rubber gloves, long sleeves and leg-covering are necessary with the most dangerous species, as well as socks and closed footwear. A gallon (5 litres) of vinegar should be available for use in emergencies, to kill undischarged nematocysts (but vinegar should not be used with the siphonophore Physalia sp.).

Most of the records of Scyphozoa and Cubozoa from South America are based on single findings of specimens on coastlines or on the sea-surface, rather than on plankton sampling surveys (Vannucci, 1951, 1954, 1957a; Vannucci and Tundisi, 1962; Mianzan, 1986b, 1989; Olagüe et al., 1990). This group is not usually well sampled with the standard available plankton nets. Conventional plankton surveys are inadequate for obtaining these large animals, since current plankton nets (Bongo, Nakthai, Multinet) usually sample small volumes of water (Omori and Hamner, 1982; Larson, 1986; Arai, 1988, 1997). Estimates of scyphozoan and cubozoan abundance and biomass are also biased for the same reasons. The use of midwater nets (IKMT, RMT, METHOT) makes possible the obtaining of acceptable information on the distribution and abundance of species (e.g., Larson, 1986; Pagès et al., 1992), but still with some restrictions for larger species.

As with other zooplankton groups, analyses of scyphozoan and cubozoan vertical distribution patterns are usually made with the aid of vertically stratified midwater plankton tows. However, the nets usually used have no opening-closing mechanism so precise depth data can be missing (Larson, 1986).

SCUBA enables some kinds of observation to be made on these large animals. For mid-water forms, submersibles have been used but medusa encounter is sometimes rare (Larson et al., 1991). As in other jelly groups (see "Ctenophora" in this volume), the finding of new species is still possible.

Fixation and preservation are not a problem for Cubozoa and Scyphozoa. 5% formaldehyde solution is generally suitable for preserving most of the small medusae, but at least 10% solution is initially needed for large specimens owing to the high percentage of water in their mesoglea.

Storage may present a problem. Other small planktonic groups are well represented in museum collections. For Scyphomedusae, typically only small specimens can be found in such institutions. Large species are often neglected for storage due to the difficulties of having the appropriate containers, and additional space to be kept in collections (Mianzan, 1986b).

For transport, specimens should be placed in a strong screw-top plastic jar which is then filled to the top with fluid (usually, formaldehyde solution). A sink is filled with tap water. The filled jar is placed in the sink, and the lid quickly placed on it so that only little dilution occurs and so that no air is included. The jar can then be tipped, shaken, and even dropped, without damage to the specimen inside. If a perfectly shaped specimen is not needed, or if weight is limiting (as for postage), the following can be done. A well-preserved specimen is placed in a self-sealing plastic bag and excess fluid tipped off. Some fluid should remain, since air bubbles under a specimen can hinder later observation. The bag is then lowered into a sink of water slowly, so that the sides of the bag are pressed gently by the water pressure, excluding air and gripping the medusa firmly. When all the air is out, the top of the bag is sealed. The bag can be placed in another, similar bag, to avoid risk of leaks; a label placed outside this second bag, and the whole placed in a third bag, and even a fourth, for near-complete safety from leaks. The whole package can be placed in a plastic kitchen-ware container with lid, and the lid taped. Material should be unpacked immediately after arrival to minimize distortion.