The reproductive biology of the massive coral Pavona gigantea has been studied along Mexico’s Pacific coast, but basic aspects such as its relation to local environmental variables and its variation on a mesoscale level have not been addressed. The reproductive cycle of P. gigantea was monitored monthly over a two-year period (2010–2012) at four sites along the coast of Oaxaca (southwestern Mexico). Except for one hermaphroditic colony, P. gigantea was gonochoric and exhibited asynchronous development. The data suggest that, in the study area, the species may reproduce seasonally, with minor interannual differences (May–September 2010, April–August 2011, April–May 2012). There were spatial and temporal variations in the percentage of reproductively active colonies and the presence of mature sex cells. A multiple regression analysis revealed that the percentage of reproductively active colonies was significantly explained (69.6%) by mesoscale variations in environmental variables such as sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient, percentage of lunar illumination, and photoperiod, the latter being the most relevant variable in the model. The data suggest that temporal mesoscale variations can exert a meaningful influence on coral reproduction in the study area.

Porpita porpita is a colonial polymorphic hydrozoan distributed in temperate and tropical zones. This species, like most hydrozoans, possesses a metagenetic life cycle with alternating life forms: medusa stage, polypoid colony, and planula larva. However, a characterization of its early stages of development is still lacking. For this study, an integrative description of the larval stages and the hydroid colony was performed using molecular and histologic tools. The results show that P. porpita develops through three larval stages: preplanula, planula, and premetamorphic planula. The preplanula is distinguished by an absence of polarity, the planula by differentiation of the oral–aboral poles, and the premetamorphic stage by cellular differentiation. Furthermore, two morphologies of young hydroids with different developmental patterns of gonozooids and dactylozooids were observed; notably, it was not possible to observe the gastrozooid in either. Taxonomic identification was confirmed using mitochondrial (COI) and ribosomal (18S and 28S) markers. Our analysis indicates that the COI gene exhibits higher intraspecific variability compared to the 18s and 28s rDNA ribosomal genes. The presented results support the future identification of P. porpita based on morphological characteristics, regardless of the stage of development. Specifically, they shed light on the diversity of mesozooplankton in reef communities.

Introduction: The scleractinian coral life cycle includes planktonic larvae that settle on the benthos, allowing the primary polyp to clone and build a sexually reproducing adult colony. The larval physiology and ecology of Eastern Tropical Pacific scleractinians needs the exploration of basic aspects such as the internal morphology of planulae. Objective: To describe histological and cytological characteristics of Porites panamensis larvae. Methods: During August-July 2019, at Islas Marias Biosphere Reserve, Central Mexican Pacific, we made 14 collections of coral larvae and identified the species with C cytochrome oxidase subunit 1 gene. We used a scanning electron microscope and other techniques. Results: The ectoderm was composed by heterogeneous, mono-ciliated, columnar epithelial cells. Nematocysts were clustered at the oral pole of the ectoderm, and cells were evident in the aboral pole of the ectoderm gland. The endoderm had secretory cells, lipids and symbionts. Conclusions: The abundance of secretory cells and nematocysts in the aboral pole suggests their importance in substrate exploration and larval settlement. Our results support previous descriptions of larval ultrastructure in other coral species.

Introduction: The genus Pocillopora comprises coral species distributed throughout tropical and subtropical regions. In the Central Mexican Pacific region, Pocillopora verrucosa is the main reef-building species. In response to the recent decline in coral coverage, restoration protocols have been implemented over the past decade. However, to date, no genetic diversity records are available as potential markers to evaluate the effect of assisted recruitment on site dynamics in the area. Objective: Determine the genetic diversity of P. verrucosa in an insular (Islas Marietas National Park) and a coastal (Punta de Mita) restoration site within the Central Mexican Pacific. Methods: A 2 cm2 fragment from 15 colonies per site was collected. Mitochondrial markers for the COI and ATP6 genes were amplified. A total of 40 sequences of the COI (n = 19) and ATP6 (n = 21) genes were obtained, and the haplotype and nucleotide diversity were determined. Results: For the COI gene, two haplotypes shared between the sites were identified, with H1 being the most abundant. For the ATP6 gene, one exclusive haplotype was detected in Islas Marietas National Park, and one more abundant haplotype was shared between the two sites. The AMOVA results revealed a homogeneous pattern with Fst values of 0.21603 (p < 0.10655) for COI and Fst = 0.04174 (p < 0.3753) for ATP6. Conclusions: The low genetic diversity suggests that, as previously reported, asexual reproduction has been the predominant mode throughout the site’s history, and that the assisted propagation implemented may promote the maintenance of the individuals that have historically shown resistance to thermal stressors. However, it is essential to explore alternative propagation techniques in future restoration initiatives, as the long-term success of restoration also relies on reducing the vulnerability of these ecosystems to future environmental stressors.

Pelagic nudibranchs exemplify evolutionary convergences towards streamlined, transparent body forms adapted for life in the planktonic environment. Here, we describe a new genera and species, designated as Pleuropyge melaquensis gen. et sp. nov. This species belongs to the family Phylliroidae and is distinguished by key diagnostic characters, including a laterally positioned anus approximately one-third of the body length from the head, the absence of a cephalic disc, and an anterior hepatic caecum that is longer than the intestine. The description of P. melaquensis contributes to the classification of a third genus and a fourth species within the Phylliroidae family. This study offers novel insights into the functional and structural traits that have enabled nudibranchs to transition from benthic to pelagic environments.