José Antonio Cruz-Barraza

Boring sponges, an increasing threat for coral reefs affected by bleaching events

Coral bleaching is a stress response of corals induced by a variety of factors, but these events have become more frequent and intense in response to recent climate-change-related temperature anomalies. We tested the hypothesis that coral reefs affected by bleaching events are currently heavily infested by boring sponges, which are playing a significant role in the destruction of their physical structure. Seventeen reefs that cover the entire distributional range of corals along the Mexican Pacific coast were studied between 2005/2006, and later between 2009/2010. Most of these coral reefs were previously impacted by bleaching events, which resulted in coral mortalities. Sponge abundance and species richness was used as an indicator of bioerosion, and coral cover was used to describe the present condition of coral reefs. Coral reefs are currently highly invaded (46% of the samples examined) by a very high diversity of boring sponges (20 species); being the coral reef framework the substrate most invaded (56%) followed by the rubbles (45%), and the living colonies (36%). The results also indicated that boring sponges are promoting the dislodgment of live colonies and large fragments from the framework. In summary, the eastern coral reefs affected by bleaching phenomena, mainly provoked by El Niño, present a high diversity and abundance of boring sponges, which are weakening the union of the colony with the reef framework and promoting their dislodgment. These phenomena will probably become even more intense and severe, as temperatures are projected to continue to rise under the scenarios for future climate change, which could place many eastern coral reefs beyond their survival threshold.

Integrative Taxonomy and Molecular Phylogeny of Genus Aplysina (Demospongiae: Verongida) from Mexican Pacific

Integrative taxonomy provides a major approximation to species delimitation based on integration of different perspectives (e.g. morphology, biochemistry and DNA sequences). The aim of this study was to assess the relationships and boundaries among Eastern Pacific Aplysina species using morphological, biochemical and molecular data. For this, a collection of sponges of the genus Aplysina from the Mexican Pacific was studied on the basis of their morphological, chemical (chitin composition), and molecular markers (mitochondrial COI and nuclear ribosomal rDNA: ITS1-5.8-ITS2). Three morphological species were identified, two of which are new to science. A. clathrata sp. nov. is a yellow to yellow-reddish or -brownish sponge, characterized by external clathrate-like morphology; A. revillagigedi sp. nov. is a lemon yellow to green, cushion-shaped sometimes lobate sponge, characterized by conspicuous oscules, which are slightly elevated and usually linearly distributed on rims; and A. gerardogreeni a known species distributed along the Mexican Pacific coast. Chitin was identified as the main structural component within skeletons of the three species using FTIR, confirming that it is shared among Verongida sponges. Morphological differences were confirmed by DNA sequences from nuclear ITS1-5.8-ITS2. Mitochondrial COI sequences showed extremely low but diagnostic variability for Aplysina revillagigedi sp. nov., thus our results corroborate that COI has limited power for DNA-barcoding of sponges and should be complemented with other markers (e.g. rDNA). Phylogenetic analyses of Aplysina sequences from the Eastern Pacific and Caribbean, resolved two allopatric and reciprocally monophyletic groups for each region. Eastern Pacific species were grouped in general accordance with the taxonomic hypothesis based on morphological characters. An identification key of Eastern Pacific Aplysina species is presented. Our results constitute one of the first approximations to integrative taxonomy, phylogeny and evolutionary biogeography of Eastern Pacific marine sponges; an approach that will significantly contribute to our better understanding of their diversity and evolutionary history.

Testing the genetic predictions of a biogeographical model in a dominant endemic Eastern Pacific coral (Porites panamensis) using a genetic seascape approach

The coral fauna of the Eastern Tropical Pacific (ETP) is depauperate and peripheral; hence, it has drawn attention to the factors allowing its survival. Here, we use a genetic seascape approach and ecological niche modeling to unravel the environmental factors correlating with the genetic variation of Porites panamensis, a hermatypic coral endemic to the ETP. Specifically, we test if levels of diversity and connectivity are higher among abundant than among depauperate populations, as expected by a geographically relaxed version of the Abundant Center Hypothesis (rel-ACH). Unlike the original ACH, referring to a geographical center of distribution of maximal abundance, the rel-ACH refers only to a center of maximum abundance, irrespective of its geographic position. The patterns of relative abundance of P. panamensis in the Mexican Pacific revealed that northern populations from Baja California represent its center of abundance; and southern depauperate populations along the continental margin are peripheral relative to it. Genetic patterns of diversity and structure of nuclear DNA sequences (ribosomal DNA and a single copy open reading frame) and five alloenzymatic loci partially agreed with rel-ACH predictions. We found higher diversity levels in peninsular populations and significant differentiation between peninsular and continental colonies. In addition, continental populations showed higher levels of differentiation and lower connectivity than peninsular populations in the absence of isolation by distance in each region. Some discrepancies with model expectations may relate to the influence of significant habitat discontinuities in the face of limited dispersal potential. Environmental data analyses and niche modeling allowed us to identify temperature, water clarity, and substrate availability as the main factors correlating with patterns of abundance, genetic diversity, and structure, which may hold the key to the survival of P. panamensis in the face of widespread environmental degradation.

New species of excavating sponges (Porifera: Demospongiae) on coral reefs from the Mexican Pacific Ocean

Three new species of coral reef boring sponges were found in remote coral reefs from Revillagigedo Island, an archipelago that is 386 km from the continent. Cliona medinae sp. nov. is a sponge with orange-yellow papillae characterized by short almost straight spirasters. Cliona tropicalis sp. nov., is a yellow papillate sponge with a spicule complement similar to the species included in the Cliona viridis complex. However, the new species differs from the rest of the species mainly in its external morphology and by differences in the size and shape of spicules. Thoosa purpurea sp. nov. is characterized by its purple colour, and the spicular complement formed by tylostyles, two amphiaster categories, bi- tri- and tetra-radiate oxyasters and smooth or microspined centrotylote oxeas. In addition, Cliothosa tylostrongylata sp. nov. is also described from coral reefs from the southern Mexican Pacific Ocean. This is a light red species, with tylostyles and tylostrongyles as megascleres and ramose and nodulose amphiasters as microscleres. The four species were found exclusively excavating skeletons of live or dead corals of the genus Pocillopora. This study increases the number of boring sponges known from the Mexican Pacific Ocean to 22 species and it is the first study on marine sponge fauna from the Revillagigedo archipelago.

Restriction of sponges to an atoll lagoon as a result of reduced environmental quality

The lagoon at Palmyra Atoll in the central Pacific was subject to major military modifications during WWII and now the dominant fauna on the lagoons hard substrate are sponges, not corals. In this study, we quantified the physical and biological factors explaining the variation in sponge distribution patterns across 11 sites to determine the potential for the sponges in the lagoon at Palmyra to invade the surrounding reef systems. Significant differences in sponge assemblages were found among all but three sites. For all the models we examined the strongest environmental relationships were found for variables related to sedimentation/turbidity and food/habitat availability. Our findings suggest that the sponges in Palmyras lagoon are likely to be restricted to this habitat type where they are associated with conditions resulting from the earlier heavy disturbance and are unlikely to spread to the outer reef environments unless there is a dramatic decline in environmental quality.

Coral boring Aka-species (Porifera: Phloeodictyidae) from Mexico with description of Aka cryptica sp. nov.

This paper focuses on Aka species boring coral of the East Pacific Ocean and the Caribbean Sea (Mexico). The new species Aka cryptica sp. nov. is described from Mexican Pacific coral reefs, which constitutes the first time that a species of the genus Aka is reported from the East Pacific Ocean. The new species lives cryptically boring coral species of the genus Pocillopora . It is characterized by the small size of their papillae (from 1 to 4.5 mm high and from 0.8 to 1.8 mm in diameter), and oxeas (from 67 to 120 μm), and their exposed parts blend in well with background colours which tend to be overlooked during benthic marine surveys. In addition, Aka coralliphaga and Aka brevitubulata from Mexican Caribbean coral reefs are redescribed. The latter species is reported for the first time in Mexico.

Marine Biodiversity of Eastern Tropical Pacific Coral Reefs

The eastern tropical Pacific (ETP) is an isolated oceanic region exposed to extreme oceanographic conditions, including low salinity, low pH, high temperatures during El Nino, and low temperatures during La Nina and seasonal upwelling. The coral reefs in this region have a relatively limited suite of species compared to other coral reef areas of the world, but much like more diverse reefs the species present interact in complex ways. Here we synthezise the knowledge of taxonomic groups of reef organisms from prokaryotes to vertebrates, including algae, sponges, cnidarians, annelids and other worms, molluscs, crustaceans, echinoderms and fishes. We also present summaries on the biodiversity of associated functional groups and habitats, including (a) reef zooplankton and cryptic fauna, and (b) soft benthic environments, rhodolith beds and mesophotic environments. Several factors that structure the biodiversity of ETP coral reefs are explored, including biological, physical and chemical controls. ETP coral reefs are relatively simple systems that can be used as models for studying biodiversity and interactions among species. We conclude this review by highlighting pressing research needs, from very basic inventories to more sophisticated studies of cryptic assemblages, and to investigations on the impacts of natural and anthropogenic effects on ETP coral reef biodiversity.

Integrative taxonomy reveals the first record and a new species for the previously monotypic genus Tethytimea (Tethyida: Tethyidae) in the Gulf of Mexico

The first record of the previous monotypic genus Tethytimea and the description of a new species from cryptic habitats of Gulf of Mexico are presented. Tethytimea carmelita sp. nov., is a red orange cushion shaped sponge (about 5 mm thick) with a tuberculate to granular surface. The spicular complement is formed by tylostyles (200-1120 µm length), smooth spheres (12.5-55 µm in diameter); megasters-spheroxyasters (12.5-90 µm in diameter); and micrasters in two categories: oxy-strongylasters (12.5-27.5 µm in diameter) and spherotylasters (2.5-25 µm in diameter). The new species differs from the only species known T. tylota (Hentschel, 1912) mainly by differences in the size and shape of spicules. T. tylota possesses tylostyles in two size categories; megasters include giant oxyspherasters up 250 µm and micrasters in a single category. Additionally, to the morphological characteristics, we integrated partial sequences of a large sub-unit ribosomal 28S rDNA gene region (D1-D2 domains), in order to establish the molecular taxonomic position of our new species (and genus). Tree topologies (Maximum Likelihood and Bayesian Inference) were congruent in phylogenetic hypothesis, retrieving the Order Tethyida as monophyletic. In this clade, the family Timeidae was separated from the other families Tethyidae + Hemiastrellidae. Inside this latter group and according to the taxonomic hypothesis based on morphology, Tethytimea carmelita sp. nov. was included in Tethyidae clade, together with a sequence of Tethya sp. (AY626300), forming a sister group with representatives of genera Xenospongia and Thectitethya. Our new species constitutes the second valid known species for the genus Tethytimea and the first record of genus for the Atlantic Ocean.

Description and molecular phylogeny of Axinella nayaritensis n. sp. (Porifera: Axinellida) from East Pacific and remarks about the polyphyly of the genus Axinella

Axinella nayaritensis n. sp. is a typical species of the genus Axinella in spiculation (oxeas and styles), skeletal arrangement (axial condensation from which radiate an extra-axial plumoreticulated skeleton), and external form (arborescent). The new species is orange, branching, up to 25 cm in height, and which usually live in soft bottoms. One of the most conspicuous characteristic of the new species is its aquiferous system, which is formed by a system of superficial canals and meandering ridges which run around the entire length of the branches. The species is compared with Axinella polycapella from Gulf of Mexico, which is very close in morphology, and which it shares a high similarity in the 18S ribosomal RNA region. It was also compared with Axinella aruensis, a very different species from a morphological point of view, which is distributed throughout the northern Australia, Indonesia and Papua New Guinea as both species share a high similarity in the COI mitochondrial gene region. The new species was included in the clade named Axinella by Gazave et al. (2010) for 18S and COI, where also are included eight Axinella-species. Species in this clade are typically arborescent with a choanosomal skeleton differentiated between axial and extra-axial regions. Axinella nayaritensis n. sp. constitute the first record of an Axinella for the east Pacific coast.

Molecular and morphological data from Thoosidae in favour of the creation of a new suborder of Tetractinellida

The Thoosidae (Porifera, Demospongiae, Tetractinellida) currently includes the genera Thoosa, Alectona, and Delectona. To this date, molecular data are only available for Alectona. In this study, the phylogenetic affinities of the genera Thoosa and Alectona have been investigated with the species T. mismalolli, T. calpulli, and T. purpurea from the Mexican Pacific using morphology and three molecular loci: the mitochondrial cytochrome oxidase subunit 1 (CO1 mtDNA), 28S rRNA (fragment D2), and 18S rRNA. Morphology and embryology showed that these genera are quite different from the rest of the tetractinellids because larvae of Alectona and Thoosa have unique features in sponges, such as the presence of monaxonic discs in Thoosa and tetraxonic discs in Alectona which disappear in the adult stages. A phylogenetic analysis using selected species from the order Tetractinellida revealed that Thoosa groups with Alectona thus confirming morphological studies. The peculiarities in spiculation and embryology of the Thoosa and Alectona larvae, which are markedly different from species belonging to the suborders Astrophorina and Spirophorina and their distant phylogenetic position (based on three molecular loci), suggest that Thoosidae could be placed in the new suborder Thoosina.