Now you see me: "first" records of the greater amberjack Seriola dumerili at Rapa Nui range extension or increased scientific effort?

We report new records of the fisheries-harvested subtropical greater amberjack Seriola dumerili for the south-east Pacific Ocean. Despite local fishers' asserting that three Seriola morphotypes exist in the region, only one species (the yellowtail amberjack Seriola lalandi) was previously scientifically recorded for Rapa Nui (also known as Easter Island). Whilst we present the first "scientific record", S. dumerili, traditional ecological knowledge suggests that this is likely a pre-existing (albeit transient) species of the Rapa Nui ecoregion. Establishing the existing/historic distributional limits of commercially and ecologically valuable species is key for observing climate-driven distribution shifts, and the inclusion of traditional ecological knowledge is particularly important in areas with relatively lower scientific effort.

Complete mitochondrial genomes of two species of Stichopathes Brook, 1889 (Hexacorallia: Antipatharia: Antipathidae) from Rapa Nui (Easter Island)

We report the complete mitochondrial genomes of two antipatharian species, Stichopathes sp. SCBUCN-8849 and Stichopathes sp. SCBUCN-8850, collected between 120 and 180 m depth off Rapa Nui (∼ -27.1°, -109.4°). The size of the two mitogenomes are 20,389 bp (29.0% A, 15.2% C, 19.9% G, and 35.9% T) and 20,463 bp (29.0% A, 15.3% C, 19.9% G, and 35.8% T), respectively. Both mitogenomes have the classic Hexacorallia gene content of 13 protein-coding, two rRNA, and two tRNA genes plus a COX1 intron with embedded HEG as found in the Antipathidae and other antipatharian families.

Deep-sea biodiversity at the extremes of the Salas y Gómez and Nazca ridges with implications for conservation

The Salas y Gómez and Nazca ridges are underwater mountain chains that stretch across 2,900 km in the southeastern Pacific and are recognized for their high biodiversity value and unique ecological characteristics. Explorations of deep-water ecosystems have been limited in this region, and elsewhere globally. To characterize community composition of mesophotic and deep-sea demersal fauna at seamounts in the region, we conducted expeditions to Rapa Nui (RN) and Salas y Gómez (SyG) islands in 2011 and Desventuradas Islands in 2013. Remote autonomous baited-cameras were used to conduct stationary video surveys between 150-1,850 m at RN/SyG (N = 20) and 75-2,363 m at Desventuradas (N = 27). Individual organisms were identified to the lowest possible taxonomic level and relative abundance was quantified with the maximum number of individuals per frame. Deployments were attributed with associated environmental variables (temperature, salinity, dissolved oxygen, nitrate, silicate, phosphate, chlorophyll-a, seamount age, and bathymetric position index [BPI]). We identified 55 unique invertebrate taxa and 66 unique fish taxa. Faunal community structure was highly dissimilar between and within subregions both for invertebrate (p < 0.001) and fish taxa (p = 0.022). For fishes, dogfish sharks (Squalidae) accounted for the greatest dissimilarity between subregions (18.27%), with mean abundances of 2.26 ± 2.49 at Desventuradas, an order of magnitude greater than at RN/SyG (0.21 ± 0.54). Depth, seamount age, broad-scale BPI, and nitrate explained most of the variation in both invertebrate (R2 = 0.475) and fish (R2 = 0.419) assemblages. Slightly more than half the deployments at Desventuradas (N = 14) recorded vulnerable marine ecosystem taxa such as corals and sponges. Our study supports mounting evidence that the Salas y Gómez and Nazca ridges are areas of high biodiversity and high conservation value. While Chile and Peru have recently established or proposed marine protected areas in this region, the majority of these ridges lie outside of national jurisdictions and are under threat from overfishing, plastic pollution, climate change, and potential deep-sea mining. Given its intrinsic value, this region should be comprehensively protected using the best available conservation measures to ensure that the Salas y Gómez and Nazca ridges remain a globally unique biodiversity hotspot.

First description of deep benthic habitats and communities of oceanic islands and seamounts of the Nazca Desventuradas Marine Park, Chile

Seamounts and oceanic islands of the Chilean Exclusive Economic Zone at the intersection of the Nazca and Salas y Gómez ridges lie within one of the least explored areas in the world. The sparse information available, mainly for seamounts outside Chilean jurisdiction and shallow-water fauna of the Desventuradas Islands, suggests that the area is a hotspot of endemism. This apparent uniqueness of the fauna motivated the creation of the large Nazca-Desventuradas Marine Park (NDMP, ~ 300,000 km2) around the small islands San Felix and San Ambrosio in 2015. We report for the first time a detailed description of benthic microhabitats (i.e., centimeter to meter scale), macrohabitats (i.e., meter to kilometer-scale) and associated megafauna within the NDMP. Descriptions were based on analysis of fauna collected by trawling and ROV video observations from ~ 50 to 370 m depth. Rocky, coarse sand and silty sediment bottom habitats were observed at island slopes. In contrast, rocky and coarse sandy bottom habitats with a predominance of rhodoliths, thanatocoenosis, and other biogenic components were observed at seamounts. Mobile fauna and predators dominated the oceanic islands and nearby seamounts, whereas seamounts farther from the islands were dominated by sessile and hemisessile fauna that were mainly suspension and deposit feeders. Based on the register of 118 taxonomic units, our results provide an expanded and updated baseline for the benthic biodiversity of NDMP habitats, which seemed pristine, without evidence of trawling or anthropogenic debris.

Complete mitochondrial genome of Carijoa riisei (Duchassaing & Michelotti, 1860) (Octocorallia: Alcyonacea: Stolonifera: Clavulariidae)

We report the first complete Stoloniferamitochondrial genome.Carijoa riisei(Duchassaing&Michelotti, 1860) isolate CLP2_A03was collected by scuba at 32 m on the USTS Texas Clipper (27° 53.7827' N, 93° 36.2702' W). The complete mitogenome has the ancestral octocoral gene order for its 14 protein-coding genes, two rRNA genes, and one tRNA gene. It is 18,714 bp (30.7% A, 15.8% C, 18.8% G, and 34.7% T). Of the Alcyonacea mitogenomes published to date, it is most genetically similar (94% uncorrected) to Sinularia ceramensisVerseveldt, 1977 (NC_044122).

Species boundaries in Zausodes-complex species (Copepoda:Harpacticoida:Harpacticidae) from the north-eastern Gulf of Mexico

Before 1999, the harpacticoid copepod species Zausodes arenicolus Wilson, 1932 was the subject of several ecological studies. Based on morphological evaluations of specimens from the north-eastern Gulf of Mexico, Bouck et al.’s (1999) taxonomic revision revealed three new species within what had been Z. arenicolus, making the ecological results suspect. Because harpacticoid copepods show convergent evolution and morphological stasis, Bouck et al.’s morphologically based approach may not have been sufficient. We have therefore re-evaluated their results using a combination of gene-sequencing and morphological methods. Partial mitochondrial cytochrome b (cytb) and 18S rRNA gene regions from individual Zausodes specimens found at five sites in the north-eastern Gulf of Mexico were separately analysed. Individuals of Zausodes septimus Lang, 1965 formed a single cytb gene-sequence clade, whereas Z. arenicolus individuals formed five. The uncorrected genetic divergences among these clades were 10 times those within them, providing evidence that each clade could be assigned to a different species. The 18S rDNA results support those from cytb. Subsequent morphological analysis revealed differences that will allow two clades of Z. arenicolus to be described as new species. Bouck et al. (1999) revealed some but not all of the species present.