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.

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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.

Coral bleaching caused by global warming has resulted in massive damage to coral reefs worldwide. Studies addressing the consequences of elevated temperature have focused on organisms of the class Anthozoa, and up to now, there is little information regarding the mechanisms by which reef forming Hydrozoans face thermal stress. In this study, we carried out a comparative analysis of the soluble proteome and the cytolytic activity of unbleached and bleached Millepora complanata (“fire coral”) that inhabited reef colonies exposed to the 2015–2016 El Niño-Southern Oscillation in the Mexican Caribbean. A differential proteomic response involving proteins implicated in key cellular processes, such as glycolysis, DNA repair, stress response, calcium homeostasis, exocytosis, and cytoskeleton organization was found in bleached hydrocorals. Four of the proteins, whose levels increased in bleached specimens, displayed sequence similarity to a phospholipase A2, an astacin-like metalloprotease, and two pore forming toxins. However, a protein, which displayed sequence similarity to a calcium-independent phospholipase A2, showed lower levels in bleached cnidarians. Accordingly, the hemolytic effect of the soluble proteome of bleached hydrocorals was significantly higher, whereas the phospholipase A2 activity was significantly reduced. Our results suggest that bleached M. complanata is capable of increasing its toxins production in order to balance the lack of nutrients supplied by its symbionts.

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

BackgroundScleractinian corals (stony corals) are the most abundant reef-forming cnidarians found in coral reefs throughout the world. Despite their abundance and ecological importance, information about the diversity of their toxins and their biological activities is very scarce. In this study, the chemical composition and the biological activities of the aqueous extracts of Pseudodiploria strigosa, Porites astreoides and Siderastrea siderea, three scleractinian corals from the Mexican Caribbean, have been assessed for the first time.MethodsToxicity of the extracts was assessed in crickets; the presence of cytolysins was detected by the hemolysis assay; the vasoconstrictor activity was determined by the isolated rat aortic ring assay; the nociceptive activity was evaluated by the formalin test. The presence of phospholipases A2 (PLA2), serine proteases, and hyaluronidases was determined by enzymatic methods. Low-molecular-weight fractions were obtained by gel filtration chromatography and ultrafiltration.ResultsExtracts from the three species were toxic to crickets, induced hemolysis in human and rat erythrocytes, produced vasoconstriction on isolated rat aortic rings, and presented phospholipase A2 and serine-protease activity. Despite the fact that these corals are not considered to be harmless to humans, the extracts generated significant nociceptive responses. The matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysis of the low-molecular-weight fractions revealed the presence of peptides within a mass range of 3000 to 6000 Da. These fractions were toxic to crickets and two of them induced a transitory vasoconstrictor effect on isolated rat aortic rings.ConclusionThis study suggests that scleractinian corals produce low-molecular-weight peptides that are lethal to crickets and induce vasoconstriction.

The neurotoxic effects produced by a tentacle venom extract and a fraction were analyzed and correlated by in vivo and in vitro approaches. The tentacle venom extract exhibited a wide range of protein components (from 24 to >225 kDa) and produced tetanic reactions, flaccid paralysis, and death when injected into crabs. Two chromatography fractions also produced uncontrolled appendix movements and leg stretching. Further electrophysiological characterization demonstrated that one of these fractions potently inhibited ACh-elicited currents mediated by both vertebrate fetal and adult muscle nicotinic acetylcholine receptors (nAChR) subtypes. Receptor inhibition was concentration-dependent and completely reversible. The calculated IC50 values were 1.77 μg/μL for fetal and 2.28 μg/μL for adult muscle nAChRs. The bioactive fraction was composed of a major protein component at ~90 kDa and lacked phospholipase A activity. This work represents the first insight into the interaction of jellyfish venom components and muscle nicotinic receptors.

BackgroundMillepora complanata is a plate-like fire coral common throughout the Caribbean. Contact with this species usually provokes burning pain, erythema and urticariform lesions. Our previous study suggested that the aqueous extract of M. complanata contains non-protein hemolysins that are soluble in water and ethanol. In general, the local damage induced by cnidarian venoms has been associated with hemolysins. The characterization of the effects of these components is important for the understanding of the defense mechanisms of fire corals. In addition, this information could lead to better care for victims of envenomation accidents.MethodsAn ethanolic extract from the lyophilized aqueous extract was prepared and its hemolytic activity was compared with the hemolysis induced by the denatured aqueous extract. Based on the finding that ethanol failed to induce nematocyst discharge, ethanolic extracts were prepared from artificially bleached and normal M. complanata fragments and their hemolytic activity was tested in order to obtain information about the source of the heat-stable hemolysins.ResultsRodent erythrocytes were more susceptible to the aqueous extract than chicken and human erythrocytes. Hemolytic activity started at ten minutes of incubation and was relatively stable within the range of 28-50°C. When the aqueous extract was preincubated at temperatures over 60°C, hemolytic activity was significantly reduced. The denatured extract induced a slow hemolytic activity (HU50 = 1,050.00 ± 45.85 μg/mL), detectable four hours after incubation, which was similar to that induced by the ethanolic extract prepared from the aqueous extract (HU50 = 1,167.00 ± 54.95 μg/mL). No significant differences were observed between hemolysis induced by ethanolic extracts from bleached and normal fragments, although both activities were more potent than hemolysis induced by the denatured extract.ConclusionsThe results showed that the aqueous extract of M. complanata possesses one or more powerful heat-labile hemolytic proteins that are slightly more resistant to temperature than jellyfish venoms. This extract also contains slow thermostable hemolysins highly soluble in ethanol that are probably derived from the body tissues of the hydrozoan.