Abstract. Reef-forming cnidarians are essential for maintaining ecological balance. Unfortunately, coral reefs are endangered due to coral bleaching, which interrupts mutualistic symbiosis between Symbiodiniaceae algae and their coral hosts. Bleaching events result in very high coral mortality and the rapid deterioration of reef structures. Studies aimed at explaining the causes, mechanisms, and consequences of coral bleaching have been mainly conducted with anthozoans, while the impacts of thermal stress responsible for coral bleaching have been scarcely studied in hydrozoans, such as Millepora species (phylum Cnidaria, class Hydrozoa), which are the second most important reef-forming cnidarians. In the present study, the effects of thermal stress caused by the 2015-2016 El Niño on symbiont abundance, exoskeleton structure, and the biochemical composition of Millepora alcicornis were analyzed. Unbleached M. alcicornis specimens exhibited a higher abundance of Breviolum and Durisdinium species, which suggests that unbleached hydrocoral colonies might counteract thermal stress by hosting thermotolerant symbionts of the Durisdinium genus. Bleached hydrocorals exhibited lower levels of calcification than unbleached hydrocorals as well as changes in the microstructure of trabeculae and zooid pores. In contrast, thermal stress did not affect total calcium carbonate and carbohydrate content. Bleached tissues showed significantly higher levels of protein and refractory material, whereas their lipid content decreased considerably. The present study provides evidence that bleached M. alcicornis colonies suffered a decline in calcification and changes in the structure of their exoskeletons after being exposed to the 2015-2016 El Niño. The significant decrease in lipid content suggests that M. alcicornis primarily uses energy stores to maintain vital cellular processes at the expense of calcification.

Resumen. Los cnidarios formadores de arrecifes son esenciales en la ecología marina. Desafortunadamente, están amenazados por el fenómeno de blanqueamiento, el cual rompe la simbiosis mutualista entre algas de la familia Symbiodiniaceae y sus hospederos coralinos. El blanqueamiento causa un alto índice de mortalidad de corales y un rápido deterioro de las estructuras arrecifales. Los estudios dirigidos a explicar causas, mecanismos y consecuencias del blanqueamiento se han realizado principalmente con antozoos, mientras que los impactos del blanqueamiento de corales se han estudiado escasamente en especies de Millepora (phylum Cnidaria, clase Hydrozoa), que son los segundos constructores de arrecifes más importantes. En el presente estudio se analizó el efecto del estrés térmico causado por el evento El Niño 2015-2016 sobre la abundancia de simbiontes, la estructura del exoesqueleto y la composición bioquímica de Millepora alcicornis. Los especímenes sin blanquear de M. alcicornis contenían una mayor abundancia de especies de Breviolum y Durisdinium, lo que sugiere que las colonias de hidrocorales sin blanquear podrían estar contrarrestando el estrés térmico al albergar simbiontes termotolerantes del género Durisdinium. Los hidrocorales blanqueados mostraron niveles más bajos de calcificación y cambios en la microestructura de zooides y trabéculas. En contraste, el estrés térmico no modificó el contenido total de carbonato de calcio y carbohidratos en los hidrocorales. Los tejidos blanqueados mostraron niveles significativamente más altos de proteína y material refractario, mientras que su contenido de lípidos disminuyó considerablemente. El presente estudio muestra que las colonias blanqueadas de M. alcicornis sufrieron una disminución en la calcificación y cambios en la estructura de su exoesqueleto después de estar expuestas al estrés térmico provocado por el evento El Niño 2015-2016. La disminución significativa en el contenido de lípidos sugiere que M. alcicornis está utilizando sus reservas de energía principalmente para mantener sus procesos celulares vitales a expensas de la calcificación.

Abstract Background: Heliopsis longipes root is the widely used organ from the plant due to its culinary and medicinal importance. Nevertheless, during its collection the foliage is discarded. Therefore, it is required to perform studies about the phytochemical content with biological activity present in the different plant organs of the foliage, for a better exploitation of the plant. Hypothesis: The concentration of phenolic compounds with antioxidant activity varies according to the type of plant organ and the geographic location of the plant collection. Study species: Heliopsis longipes Site and years of study: The H. longipes plants were collected in three locations (Conca, San Juan Buenaventura and Beltran) from Sierra Gorda of Mexico, between 2017 and 2018. Methods: In this study, they were analyzed the methanolic extracts from H. longipes leaves and flowers, in order to determine the content of the phenolic compounds and scavenging of radicals activity (DPPH• and ABTS•+). Further characterization of the extracts was carried out by chromatography (UPLC). Results: The total content of polyphenols, flavonoids and condensed tannins varied in depending on the type of plant organ and the origin site of H. longipes, being the leaves of Beltran those that represent the best source of phenolic compounds with scavenging activity of the radicals DPPH• and ABTS•+. In the extracts, phenolic acids and flavonoids were identified. Conclusions: The geographical climatic conditions influence the phenolic content and antioxidant activity of the methanolic extracts from leaves and flowers of H. longipes.

Resumen Antecedentes: La raíz de Heliopsis longipes es el órgano de la planta que se usa ampliamente debido a su importancia culinaria y medicinal. Sin embargo, durante su colecta el follaje es desechado. Por lo tanto, se requiere realizar estudios acerca del contenido de fitoquímicos con actividad biológica presentes en los distintos órganos vegetales del follaje, para un mejor aprovechamiento de la planta. Hipótesis: La concentración de compuestos fenólicos con actividad antioxidante varía de acuerdo con el tipo de órgano vegetal y la ubicación geográfica de recolecta de la planta. Especies de estudio: Heliopsis longipes. Sitio y años de estudio: Las plantas de H. longipes se recolectaron en tres localidades (Concá, San Juan Buenaventura y Beltrán) de la Sierra Gorda de México, entre 2017 y 2018. Métodos: En este estudio, se analizaron los extractos metanólicos de hojas y flores de H. longipes para determinar el contenido de compuestos fenólicos y la actividad reductora de radicales (DPPH• y ABTS•+). Adicionalmente, la caracterización de los extractos se realizó mediante cromatografía (UPLC). Resultados: El contenido total de polifenoles, flavonoides y taninos condensados varió en función del tipo de órgano vegetal y sitio de origen de H. longipes, siendo las hojas de Beltrán las que representan la mejor fuente de compuestos fenólicos con actividad reductora de radicales DPPH• y ABTS•+. En los extractos, se identificaron ácidos fenólicos y flavonoides. Conclusiones: Las condiciones geográficas climáticas influyen en el contenido fenólico y actividad antioxidante de los extractos metanólicos de hojas y flores de H. longipes.

Abstract Background: Scleractinian 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. Methods: Toxicity 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. Results: Extracts 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. Conclusion: This study suggests that scleractinian corals produce low-molecular-weight peptides that are lethal to crickets and induce vasoconstriction.

AbstractBackground Millepora alcicornis is a branching hydrocoral common throughout the Caribbean Sea. Like other members of this genus, this species is capable of inducing skin eruptions and blisters with severe pain after contact. In the present study, we investigated the toxicity of theM. alcicornis aqueous extract on several animal models. Considering that some cnidarian hemolysins have been associated to local tissue damage, since they also induce lysis of other cell types, we also made a partial characterization of the hemolytic activity of M. alcicornis aqueous extract. This information is important for understanding the defense mechanisms of the “fire corals”.Methods The effects of pH, temperature, and some divalent cations on the hemolytic activity of the extract were assayed, followed by a zymogram analysis to detect the cytolysins and determine their approximate molecular weight. The toxicity of the aqueous extract was assayed in mice, by intravenous administration, and histopathological changes on several tissues were analyzed by light microscopy. The toxicity of the extract was also tested inArtemia salina nauplii, and the damages caused on the crustaceans were analyzed by transmission and scanning electron microscopy.Results The hemolytic activity of the hydrocoral extract was enhanced in the presence of Ca 2+ (≥2 mM), Mg 2+ (≥6 mM), and Ba2+ (≥0.1 mM); however, it was reduced in the presence of Cu2+(≥0.1 mM), Zn 2+ (≥6 mM), and EDTA (≥0.34 mM). Differences in the pH did not affect the hemolytic activity, but it was temperature-sensitive, since preincubation at ≥ 50 °C sharply reduced hemolysis. The zymogram showed the presence of two types of hemolysins: ~ 28–30 kDa proteins with phospholipase A 2 activity and ~ 200 kDa proteins that do not elicit enzymatic activity. The aqueous extract of this cnidarian was lethal to mice (LD 50 = 17 μg protein/g), and induced kidney, liver, and lung damages. Under denaturing conditions, the aqueous extract completely lost its toxic and hemolytic activities.Conclusions The results showed that the M. alcicornis aqueous extract contains two types of thermolabile hemolysins: proteins of approximately 28–30 kDa with PLA 2 activity, while the others are larger proteins of approximately 200 kDa, which do not possess PLA 2activity. Those thermolabile cytolysins, which are stable to pH changes and whose activity is calcium dependent, are capable of inducing damage in lung, kidney and liver tissues, resulting in a slow death of mice. M. alcicorniscytolysins also provoke tissue dissociation inArtemia salina nauplii that might be attributed to pore forming mechanisms.