Ten species of sea anemones (Anthozoa: Actiniaria) are documented in the Mexican Caribbean based on observations andcollections in 11 coral reef localities during 2006–2011; three of them are new records for Mexico. These species belongto families Actiniidae, Aiptasiidae, Aliciidae, Boloceroididae, Phymanthidae, and Stichodactylidae. Although these do notrepresent all species reported in the Mexican Caribbean, these are the most abundant and conspicuous. This work represents the first inventory of sea anemones of the Mexican Caribbean.

This paper describes one neurotoxin and three cytolysins isolated from the venom of the Caribbean box jellyfish Carybdea marsupialis. To assess the cytolytic and neurotoxic activity of the nematocyst venom, several bioassays were carried out, and to evaluate the effect of the toxin, the dose causing 50% lethality (LD(50)) was determined in vivo using sea crabs (Ocypode quadrata). The proteins with neurotoxic and cytolytic effects were isolated using low-pressure liquid chromatography. The fraction containing the neurotoxic activity was analyzed by SDS-PAGE and showed a single protein band with an apparent molecular weight of 120 kDa (CmNt). To demonstrate the neurotoxic activity of this protein, a small fraction of the purified protein was injected into a crab, and the typical convulsions, paralysis, and death provoked by neurotoxins were observed. Three fractions containing cytolysins had protein bands in SDS PAGE with apparent molecular weights of 220, 139, and 36 kDa, and their cytolytic activity was confirmed with the haemolysis assay.

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A list of 169 medusae species in 45 families recorded in Mexican waters is presented for the first time. 86 species (50.8%) were found in the Pacific Ocean, 75 species (44.3%) in the Gulf of Mexico, and 88 (52%) in the Mexican Caribbean Sea. Only 17 species (10%) were common to the three regions. The superclass Hydrozoa, the most diverse one, is represented by 151 species (89%), the Scyphozoa by 16 species (9.5%) and the Cubozoa by 3 (1.8%). Among the Hydrozoa, up to 6 new species have been described from Mexican waters. It is expected that the number of species will grow as surveys that include the hydroid stages and their laboratory-released medusae, as well as benthic and deep-living medusofauna are undertaken in both the Atlantic and the Pacific coasts of Mexico.

Aurelia aurita is a scyphozoan, abundant in the Mexican Caribbean during summer. Although usually innocuous, there is evidence of it causing harm to humans. This work investigates the biological activities of crude and fractionated extracts of A. aurita. Live specimens were collected between July and September 1999 from the Mexican Caribbean. The tentacular margin was dissected immediately and frozen at -50ºC. A nematocyst suspension was prepared, discharged, and the supernatants lyophilized. Hemolytic assay was performed with lyophilized crude extract on bovine, sheep, and human red blood cells. Erythrocyte sensitivity to the toxin was ranked in descending order: human, sheep, and bovine. Toxic activity on Artemia nauplii was evaluated using the same crude extract for different exposure periods (3, 5, and 10 hours); only 48 and 72 hour old Artemia nauplii showed 50% mortality. Partial toxin purification was completed by sequential liquid chromatography using three gels (Sephadex G-200, DEAE Sephadex A-50, and Sephadex G-100). Intramuscular neuroactivity was detected in the crab Ocypode quadrata for two partially purified fractions. These fractions were found to have molecular weight components of 66 and 45 kDa, respectively