Diving into the unknown: fourteen new species of haplosclerid sponges (Demospongiae: Haplosclerida) revealed along the Peruvian coast (Southeastern Pacific)

The Peruvian coast is certainly one of the poorest studied areas in the world for marine sponges biodiversity, with only 20 species registered so far from over 2,400 km coastline. In spite of its great species richness worldwide, there is not a single record of Haplosclerida in Peru. Accordingly, in this study we aimed to describe the species belonging to this order present in the relatively recent collections undertaken along the Peruvian coast by two of us (PhW, EH). Here, we describe fourteen new species, provisionally endemic to the Peruvian coast. This finding represents a major addition to the knowledge of the biodiversity of sponges along the Peruvian coast, increasing the list of species known to occur in this area by about 68%. This is also the largest single proposal of new Haplosclerida in over 37 years of sponge taxonomy worldwide. Niphates is for the first time recorded in the Southeastern Pacific, and an identification key to the Haplosclerida from the Peruvian coast is provided. Regarding the distribution of the described species, most of them—except for Chalinula chelysa sp. nov.—have a narrow geographic range, which might indicate their rarity or that the haplosclerid fauna in Peru is still poorly known.

Distribution and abundance of planktonic mollusks along a longitudinal gradient in the Southeastern Pacific off Chile

The objectives of this research were to estimate the abundance of the main groups of planktonic mollusks (meroplanktonic larvae, holoplanktonic gastropods and cephalopod paralarvae), and relate these groups to the physical-chemical water properties along a longitudinal gradient between Caldera, on the coast of mainland Chile, and the Easter Island ecoregion (Rapa Nui Island and Salas y Gómez Island), in the Southeast Pacific Ocean. Plankton samples were collected over the course of the CIMAR 21-Islas Cruise, from October to November 2015, at 33 oceanographic stations via vertical hauls of a WP2 net (180-µm mesh size) from a maximum depth of 300 m to the sea surface. Mollusks were sorted, counted and initially assigned to Class rank, later being identified to lower taxonomic ranks. Planktonic mollusks were obtained at all stations, and were composed of 92.7% of Gastropoda and 7.3% of Bivalvia. The total abundance of mollusks varied between 55 and 4,922 individuals 100 m-3.Euthecosomate gastropods exhibited the highest occurrence within the oceanic area. Meanwhile, no paralarvae were captured. Differences in the composition of planktonic mollusks between the continental and oceanic zones were evident. Bivalve larvae increased their abundance in warmer, salty and vertically mixed waters. These results are the first record of meroplanktonic mollusks in waters near the Chilean oceanic islands, and suggest that planktonic mollusks display spatial variation at the scale of the South Pacific Basin, which could be related to the hydrographic conditions and the water column structure.

Phylogeny, Connectivity and Dispersal Patterns of the Giant Kelp Macrocystis (Phaeophyceae)

<p>Macrocystis represents the most widely distributed kelp genus, providing structure and energy for one of the most productive ecosystems on earth. Despite its ecological and economical importance, many aspects of its taxonomy, distribution and dispersal still remain unknown. Using different molecular markers I studied the taxonomy, phylogeography and dispersal patterns of Macrocystis. The analysis involves samples from different populations throughout the world. Using the DNA barcoding method I, confirmed previous suggestions that the genus must be considered as monospecific, M. pyrifera being the only species. The effects of historical and contemporary events on the haplotype distribution were determined by analyzing samples from the southeastern Pacific (SEP) using the atp8-S mitochondrial marker. The last glacial maximum as well as oceanographic anomalies (El Niño phenomena) may be important factors driving the genetic pattern along the SEP. The genetic structure in southern Chile was also analyzed in more detail, especially in the Chilean Fjords. Samples from attached and floating kelp individuals revealed that dispersal via kelp rafts is possible. Finally, a global analysis using COI sequences showed shared haplotypes along vast distances in the Northern and Southern hemispheres, recent dispersal and high gene flow can explain such genetic homogeneity. Additionally, microsatellite analysis confirmed that gene flow along the Southern Ocean is occurring over ecological time scales, where rafting of detached reproductive kelps seems to be facilitated by the Antarctic Circumpolar Current connecting populations in the Southern Hemisphere. This study has provided valuable genetic evidence to understand factors shaping the genetic structure of this important ecologically and economically species. It also contributes important knowledge for conservation and management strategies, especially in places where M. pyrifera has been harvested. In summary, the results of this study confirm previous suggestions of high gene flow among M. pyrifera populations at different scales. It also provides evidence suggesting that kelp rafts act as an important dispersal mechanism in this species, thus giving important information to understand the factors shaping the evolution of the largest seaweed on earth.</p>

Phylogeny, Connectivity and Dispersal Patterns of the Giant Kelp Macrocystis (Phaeophyceae)

<p>Macrocystis represents the most widely distributed kelp genus, providing structure and energy for one of the most productive ecosystems on earth. Despite its ecological and economical importance, many aspects of its taxonomy, distribution and dispersal still remain unknown. Using different molecular markers I studied the taxonomy, phylogeography and dispersal patterns of Macrocystis. The analysis involves samples from different populations throughout the world. Using the DNA barcoding method I, confirmed previous suggestions that the genus must be considered as monospecific, M. pyrifera being the only species. The effects of historical and contemporary events on the haplotype distribution were determined by analyzing samples from the southeastern Pacific (SEP) using the atp8-S mitochondrial marker. The last glacial maximum as well as oceanographic anomalies (El Niño phenomena) may be important factors driving the genetic pattern along the SEP. The genetic structure in southern Chile was also analyzed in more detail, especially in the Chilean Fjords. Samples from attached and floating kelp individuals revealed that dispersal via kelp rafts is possible. Finally, a global analysis using COI sequences showed shared haplotypes along vast distances in the Northern and Southern hemispheres, recent dispersal and high gene flow can explain such genetic homogeneity. Additionally, microsatellite analysis confirmed that gene flow along the Southern Ocean is occurring over ecological time scales, where rafting of detached reproductive kelps seems to be facilitated by the Antarctic Circumpolar Current connecting populations in the Southern Hemisphere. This study has provided valuable genetic evidence to understand factors shaping the genetic structure of this important ecologically and economically species. It also contributes important knowledge for conservation and management strategies, especially in places where M. pyrifera has been harvested. In summary, the results of this study confirm previous suggestions of high gene flow among M. pyrifera populations at different scales. It also provides evidence suggesting that kelp rafts act as an important dispersal mechanism in this species, thus giving important information to understand the factors shaping the evolution of the largest seaweed on earth.</p>

A Regime Shift in the Interhemispheric Teleconnection between the Yellow and East China Seas and The Southeastern Tropical Pacific in The Southern Hemisphere during The Boreal Summer

Through statistical estimations on reconstructed datasets for the period 1982−2020 after removing a long-term trend, we observed that there was a drastic regime shift in the early summer’s connection between the YECS and the tropical Pacific in the early 2000s. The summer YECS SSTs had seemed to be modulated by local oceanic and atmospheric processes along with their marginal coupling to the tropical Pacific during the pre-2003 period before the regime shift. In contrast, an interhemispheric YECS−tropical southeastern Pacific (SEP) coupling appeared after the regime shift. This teleconnection was at least partially attributed to a reduced El Niño signature in the tropical Pacific, which favors the emergence of the South Pacific meridional mode (SPMM) independently from ENSO signals. Precipitation anomalies in the western tropical Pacific act as an atmospheric bridge to mediate the air-sea interacted variability associated with the SPMM into the North Pacific. The susceptibility of the YECS to atmospheric forcing may highlight the role of SST over the YECS as a potential indicator of basin-scale climate changes.

First report of an egg-predator nemertean worm in crabs from the south-eastern Pacific coast: Carcinonemertes camanchaco sp. nov

Nemertean worms belonging to the genus Carcinonemertes have been tied to the collapse of crab fisheries in the northeastern Pacific Ocean. A new species is described from egg masses of two commercial crabs, Cancer porteri and Romaleon setosum, inhabiting the central-north Chilean coast. This is the first species of Carcinonemertes described from the southeastern Pacific Ocean. Total body length of Carcinonemertes camanchaco sp. nov. ranged from 2.38 to 4.93 and from 4.29 to 8.92 mm, in males and females, respectively. Among others, traits that distinguish this new species from other previously described congeneric species include: presence of two gonad rows on each side of the intestine, a simple (not decorated) mucus sheath, and a relatively wide stylet basis. Maximum likelihood and Bayesian inference phylogenetic analyses distinguished this new species from all other species of Carcinonemertes with available cox1 sequences in GenBank. Prevalence and mean (± SD) intensity of C. camanchaco sp. nov. was 24% and 2.6 (± 2.07) worms per egg mass in C. porteri and 38.1% and 3.8 (± 2.4) worms per egg mass in R. setosum. The formal description of this new species represents the first step towards the understanding of this worm's impact on the health of crab fisheries in the southeastern Pacific Ocean.

Evolutionary drivers of the hump-shaped latitudinal gradient of benthic polychaete species richness along the Southeastern Pacific coast

Latitudinal diversity gradients (LDG) and their explanatory factors are among the most challenging topics in macroecology and biogeography. Despite of its apparent generality, a growing body of evidence shows that ‘anomalous’ LDG (i.e., inverse or hump-shaped trends) are common among marine organisms along the Southeastern Pacific (SEP) coast. Here, we evaluate the shape of the LDG of marine benthic polychaetes and its underlying causes using a dataset of 643 species inhabiting the continental shelf (<200 m depth), using latitudinal bands with a spatial resolution of 0.5°, along the SEP (3–56° S). The explanatory value of six oceanographic (Sea Surface Temperature (SST), SST range, salinity, salinity range, primary productivity and shelf area), and one macroecological proxy (median latitudinal range of species) were assessed using a random forest model. The taxonomic structure was used to estimate the degree of niche conservatism of predictor variables and to estimate latitudinal trends in phylogenetic diversity, based on three indices (phylogenetic richness (PDSES), mean pairwise distance (MPDSES), and variation of pairwise distances (VPD)). The LDG exhibits a hump-shaped trend, with a maximum peak of species richness at ca. 42° S, declining towards northern and southern areas of SEP. The latitudinal pattern was also evident in local samples controlled by sampling effort. The random forest model had a high accuracy (pseudo-r2 = 0.95) and showed that the LDG could be explained by four variables (median latitudinal range, SST, salinity, and SST range), yet the functional relationship between species richness and these predictors was variable. A significant degree of phylogenetic conservatism was detected for the median latitudinal range and SST. PDSES increased toward the southern region, whereas VPD showed the opposite trend, both statistically significant. MPDSES has the same trend as PDSES, but it is not significant. Our results reinforce the idea that the south Chile fjord area, particularly the Chiloé region, was likely the evolutionary source of new species of marine polychaetes along SEP, creating a hotspot of diversity. Therefore, in the same way as the canonical LDG shows a decline in diversity while moving away from the tropics; on this case the decline occurs while moving away from Chiloé Island. These results, coupled with a strong phylogenetic signal of the main predictor variables suggest that processes operating mainly at evolutionary timescales govern the LDG.