Since the mid-1990s, coral diseases have increased in number, species affected, and geographic extent. To date, 18 coral diseases, affecting at least 150 scleractinian, gorgonian, and hydrozoan zooxanthellate species, have been described from the Caribbean and the Indo-Pacific. These diseases are associated with pathogens including bacteria, cyanobacteria, fungi, and protists and with abiotic stressors including elevated seawater temperature, sedimentation, eutrophication, and pollution. Etiologies of only 5 of the 18 coral diseases have been determined through fulfillment of Koch's postulates. Corals and other invertebrates utilize innate immune mechanisms including physiochemical barriers and cellular and humoral defenses against pathogens. Here we review the described coral diseases, known etiologies, and efforts to determine unknown etiologies. We define disease terms, discuss the limitations of Koch's postulates, describe alternative techniques for identifying disease-causing organisms, and review coral immunology.

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Tropical dry forest, such as that found in Mexico, is a biome where very few alimentary resources are available during 6 months of the year. Within some families of Lepidoptera such as Nymphalidae, some species are known to survive the dry season as adults using the few decayed pulp fruits available as a food source. We compared the temporal abundance and sex ratio of two model species, one belonging to the subfamily Charaxinae, found world-wide, and one belonging to the subfamily Biblidinae, endemic to the Americas. We used baited traps to measure feeding frequency of both species to asses monthly temporal resource use curves. The butterfl y frequency of feeding drops dramatically in the dry season for all species-gender, except for females of the Biblidinae species. There are few differences between the sexes in the relative feeding frequency, assimilated to activity pattern, of Charaxinae between the dry and rainy seasons, while the activity pattern of Biblidinae is very different depending on the sex. These results suggest differential consequences on mate choice competition for both species. Females of the Charaxine species showed a use curve nested on the male curve, while for all other pair-wise comparisons between gender-species, the use curves were signifi cantly different. These differences in the temporal foraging pattern could explain at least in part, the coexistence between both sympatric species in the stressful season.Resumé. Activité saisonnière de nourrissage dépendante du sexe chez deux espèces de Nymphalidae (Lepidoptera) de la forêt tropicale sêche Mexicaine. La forêt tropicale sèche, comme celle que l'on trouve au Mexique, est un biome où très peu de ressources alimentaires sont disponibles durant 6 mois de l'année. Au sein d'une famille de lépidoptères ; les Nymphalidae, certaines espèces dépassent la saison sèche comme imagos en utilisant les rares fruits à pulpe disponible comme nourriture. Nous avons comparé les ressources temporelles et l'abondance de deux espèces modèles, une appartenant à la sous-famille des Charaxinae, qui est distribuée dans tous les continents, et une appartenant à la sous-famille des Biblidinae, restreinte à l'Amérique tropicale. Nos résultats montrent qu'il y a peu de différences d'activité de vol entre sexes chez les Charaxinae entre la saison des pluies et la saison sèche alors que des différences importantes s'observent pour les Biblidinae. Ces résultats suggèrent des stratégies différentes de concurrence pour l'accouplement. La coexistence entre les deux espèces pourrait s'expliquer, au moins en partie, par des différences dans la structure temporelle de la recherche de la nourriture.

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