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Gelidiella acerosa is a widely distributed species, with type locality in Yemen, whose morphology has been characterized by decumbent axes from which numerous abundantly branched erect axes emerge, pectinate, alternate or radial. Recent phylogenetic studies have revealed the presence of genetically independent groups throughout its distribution range. However, these groups cannot be described as independent since there are no sequences from the type locality that allow us to establish the genetic group to which the true G. acerosa belongs, generating a complex of cryptic species. In the present study, from COI-5P and rbcL sequence data, we detected six genetically differentiated groups, one of which is represented only by specimens from the Western Atlantic region. Given the allopatric pattern, it is possible to describe the Atlantic group as an independent species of the cryptic complex in the Indo-Pacific. Gelidiella papillosa sp. nov. shares several morphological features with other specimens previously identified as G. acerosa in other countries, like the appearance of the thallus, branching patterns, the presence of multiple superficial hairs on the branches or cell measurements. However, these characters have not been evaluated in detail among the different genetic groups within Gelidiella acerosa, consequently, G. papillosa can be supported only by its genetic independence and allopatric distribution. [ABSTRACT FROM AUTHOR]

Digenea is a widely distributed genus in the Mexican Atlantic, and until a few years ago the only morphospecies D. simplex was recorded. Recent molecular research on this species from a locality in the Mexican Caribbean revealed the new species D. mexicana, whose morphological similarity with specimens from Gulf of Mexico suggests that its distribution range could extend to this area. The aim of this work was to characterize the molecular and morphological characters of Digenea specimens from different sites in the Mexican Atlantic, to confirm this hypothesis and even reveal the presence of new species or records for the country. Our phylogenetic analysis of COI-5P and rbcL markers revealed a new record of D. arenahauriens in Mexico and confirm the presence of D. mexicana in the southern Gulf of Mexico. The species delimitation methods showed potential new species for Australia, Japan, and Brazil. The true D. simplex was not recorded molecularly for Mexico. Morphological comparisons indicated an overlap among most of the species of the genus. Future studies about molecular and morphological characterization of Digenea specimens from around the world could help to clarify the problem of specific delimitation, and even reveal new species for the genus. [ABSTRACT FROM AUTHOR]