Polychaetes from tropical ecosystems of the eastern Pacific have been poorly studied; thus, the aim of this study was to analyse their taxonomic composition in the southern Mexican Pacific shelf and to examine their biogeographic affinities. A total of 3741 specimens from 82 species, 52 genera, and 27 families were identified from 38 stations at 42–109 m depth. The Sedentaria group was more diverse (40 species, 48.8%) and abundant (1753 ind., 46.9%) compared to the Errantia (36 species, 43.9%; 346 ind., 9.2%) and the Basal Annelida groups (6 species, 7.3%; 1642 ind., 43.9%). The families Onuphidae (14 spp.), Spionidae (8 spp.), and Paraonidae (8 spp.) were the most diverse. The Amphinomidae and Spionidae accounted for 72.6% of the fauna; the remarkably high abundance of both families together is unusual in the tropical eastern Pacific. The polychaete species had high biogeographic affinities with the Mexican tropical Pacific ecoregion (45.1%), which has tropical conditions, and the Cortezian (29.3%), which has warm-temperate characteristics. Twelve amphiamerican species and ten with worldwide distribution were found. The tropical eastern Pacific is one of the world regions with the lowest number of polychaete records, thus underlining the importance of the taxonomic and biogeographic information provided here. The sampling effort should increase, since the non-parametric estimators indicated that 116–138 species were expected, instead of the 82 species actually found.

The Galapagos Islands lie within the oceanic ecoregion of the Tropical Eastern Pacific, which has a unique fish assemblage composition due to the influence of several ocean currents and El Niño Southern Oscillation (ENSO) events. In the El Niño phase of these events, water temperature changes facilitate the movement of fish species between oceanic ecoregions, as well as across the Eastern Pacific Barrier. Here, we present five new fish records for the Galapagos Marine Reserve based on underwater imagery. These include two rays (Mobula thurstoni and Myliobatis longirostris) and three bony fishes (Lobotes pacifica, Lutjanus colorado and Sphyraena stellata). Of these, the first species is proposed as potentially resident to the Galapagos, and the latter four as vagrant species in the Galapagos until further sightings can conclusively determine their status. The effects of ENSO, the use of underwater video technology, and the importance of up-to-date and accurate species listings to understand the impact of the climate crisis are discussed.

The Chilean torpedo Tetronarce tremens is recorded for the first time in the Mexican Pacific. A single male specimen was captured by artisanal fishermen using a bottom-set gillnet off San Agustinillo, Oaxaca. The specimen identification was based on morphology and confirmed by DNA barcoding of the cytochrome oxidase subunit I gene and its comparison with sequences available in online repositories. A phylogenetic analysis of Tetronarce resulted in the clustering of three species that inhabit the Pacific Ocean: Tetronarce tremens, Tetronarce californica and Tetronarce tokionis. This study provides the northernmost record of Tetronarce tremens in the Eastern Pacific Ocean, an atypical sighting beyond its native distribution range in tropical and temperate waters off South America.

The present research provides detailed information on the geographic and bathymetric distributional patterns of fishes and describes the main species assemblages of the continental shelf and upper slope off El Salvador. The sampling was based on 673 bottom-trawl tows taken during research surveys from April to November 2003. The data analysis was based on presence-absence matrixes and was conducted with PRIMER 6 software. A total of 148 fish species were recorded during the study period: the families with the highest number of species were Sciaenidae (13) and Carangidae (10), and the highest percentages of occurrence were registered for Porichthys margaritatus (40.6%), Pontinus sp. (34.8%) and Monolene dubiosa (33.1%). The cluster analysis by depth showed three faunistic associations: (1) on the inner and part of the mid continental shelf (20–60 m), (2) one bathymetric stratum on the mid continental shelf (80–100 m), and (3) on the outer continental shelf and upper slope (120–240 m). The cluster analysis by geographic zones showed separation between three zones: Western, Central and Eastern Zones off El Salvador. The Central zone is characterized by a different fish community of mixed habitat, while the main factor that determined the fish assemblages on the continental shelf and upper slope was depth.

The first records of Caranx ignobilis and Naso annulatus in the Galapagos Archipelago are reported based on several sightings from its northernmost island, Darwin. For C. ignobilis this also represents its first record from the Tropical Eastern Pacific region, considerably expanding its geographical distribution. Vagrant status is proposed for both species in the Galapagos shore fish list.

The spiny basket star Astrocaneum spinosum is an ophiuroid found in coastal waters of the tropical eastern Pacific. This paper presents a new record of this species from off the coast of Ecuador and an extension of its distribution range of some 1200 km to the south.

The presence of the Gorgona guitarfish, Rhinobatos prahli, in new zones of the Colombian Pacific coast is registered. The current unique Colombian record of the species corresponds to its description from Gorgona Island in 1995. This paper gives new information on the species on the tropical eastern Pacific coast; and contributes to the knowledge of the habitat used by this species in these zones.

Colonial invertebrates often mix sexual and asexual methods of propagation, and a comprehensive understanding of both is required for life history study. The asexual cloning of new colonies in cupuladriid bryozoans is much better studied than the formation of new colonies by sexual reproduction. As such, the relative investments of sexual and asexual modes of propagation remain uncertain. This preliminary study explores patterns of embryonic brooding as a measure of investment into sexual reproduction. We conduct a survey of quantity and arrangement of embryos in tropical eastern Pacific cupuladriid colonies and compare this to the frequency of cloning. Species populations show considerable variation in embryonic brooding. Patterns of brooding, both across and within species strongly support the hypothesis that as cloning increases, investment into sexual reproduction decreases. We find preliminary evidence that individual cupuladriid colonies that propagate sexually may senesce like solitary organisms, while species that regularly clone only appear to experience senescence at the level of the zooid.

Leptogorgia ignita is a new gorgonian species characterized by its conspicuous bright orange colour, irregular branching pattern and combination of sclerite types in the coenenchyme, all of the same orange colour, with abundance of capstans and blunt spindles, and less abundant acute spindles. The species was found in a shallow water coral community, 4–12 m deep in Samara Bay, Pacific Costa Rica. Morphologically, L. ignita belongs to the L. rigida-group comprising eight species for the group; 13 Leptogorgia species are known for Costa Rica, and 23 for the entire eastern Pacific. The new species is described, illustrated and compared to the other valid taxa of the group.