Search

Three new sea fan species of Leptogorgia were discovered during multiple scuba diving expeditions along the Gulf of California coast and islands. Leptogorgia iridis sp. nov. is distributed in the southern region of the gulf (Mexican Province), inhabiting tropical rocky reefs of the Islas Marías Archipelago (Nayarit) and Bahía Banderas (Jalisco). This species has small colonies (< 7 cm height) with at least five clearly distinct chromotypes. Leptogorgia martirensis sp. nov. was found exclusively on the rocky reefs of San Pedro Mártir and San Esteban Islands located in the northern region of the Gulf of California (northern region of Cortez Province). Leptogorgia enrici sp. nov. is distributed from the south to the northern region of the Gulf of California (Cortez Province), inhabiting substrates of rocky reefs, sandy and pebbly sea floors. Comprehensive ecological diving expeditions to identify and classify octocorals in the Mexican Pacific (1995–2019) indicate that L. iridis sp. nov. and L. martirensis sp. nov. are likely to be micro-endemics and L. enrici sp. nov. is endemic to the Gulf of California, which defines their currently known biogeographic distribution ranges.

Four adult females of a rare benthic/epiphytic harpacticoid copepod species of the genus Peltidium Philippi, 1839 were collected from insular zooplankton samples obtained at Revillagigedo National Park, Mexico. They were identified as Peltidium nayarit Suárez-Morales & Jarquín-González, 2013 with type location (and the single previously known distribution site) at Playa Careyeros (20°46'59.46"N, 105°30'35.48"W), Nayarit, Mexico. We provide a complementary description of this species including new details of antennules, caudal rami, legs 1 and 5, and cuticular ornamentation using scanning electron microscopy observations. Peltidium nayarit has a dark reddish-pink coloration allegedly mimicking the color of the macroalgae where they live, but specimens collected in the present study were obtained from sea surface zooplankton net tows. The record of Peltidium nayarit in the Revillagigedo Islands represents the southwestern-most record of the genus in the Americas and the second record for Mexico.

The description of diagnostic morphological characters and DNA barcoding of fish larvae from nine species of the carangid family are provided from specimens collected during a weekly zooplankton time-series (2016–2017) at Cabo Pulmo National Park, Gulf of California, Mexico. Five nominal species (Caranx sexfasciatus, C. caballus, Naucrates ductor, Selar crumenophthalmus, and Selene peruviana) and three morphotypes of Decapterus spp. and one of Caranx spp. were identified and separated based on morphological, meristic, and pigmentary diagnostic characters. All larvae were genetically sequenced for a fragment of the cytochrome c oxidase subunit I mitochondrial gene. Sequences of larval Caranx and Decapterus showed high genetic similarity (> 99%), low intraspecific divergence (< 1%), and an interspecific divergence between 6% and 11%, allowing the discrimination of diagnostic pigmentation patterns of fish larvae among three sibling species from each genus: Caranx (C. caballus, C. caninus, and C. sexfasciatus) and Decapterus (D. macarellus, D. macrosoma, and D. muroadsi). DNA barcoding supported the presence of Caranx caballus, C. caninus, C. sexfasciatus, Decapterus macarellus, D. muroadsi, Selar crumenophthalmus, and Selene peruviana, and for the first time Naucrates ductor and D. macrosoma at the CPNP. Abundance of these nine species (confirmed molecularly) was estimated throughout the 2016–2017 weekly time series. Decapterus macarellus and Caranx caninus were the most abundant species. The morphological and molecular taxonomic methods allowed us to infer the species number and abundance of these commercial species at the CPNP to improve conservation in protected areas and fishery management.

The prevalence of endoparasites associated with chaetognath abundance in the coastal waters of the Mexican Central Pacific was studied fortnightly from November 2010 to December 2011. A total of 35 (0.21%) out of 16,407 chaetognaths were found to be parasitized. Five out of twelve chaetognath species (Flaccisagitta enflata, F. hexaptera, Parasagitta euneritica, Serratosagitta pacifica, Zonosagitta bedoti) were found to be parasitized by nine endoparasitic taxa: Protists (two morphotypes), digenean metacercariae [Didymozoidae, Hemiuridae, Parahemiurus sp., Lepocreadiidae, Prosorhynchus sp. (Bucephalidae)], and cestodes (metacestodes) [Tetraphyllidea (two morphotypes)]. Parasagitta. euneritica and Z. bedoti were the most abundant chaetognath species, and Protist sp. 2 and Tetraphyllidea sp. 1 were the most abundant parasites. The highest prevalence for most of the endoparasite species occurred in June, and the values varied according to three hydroclimatic periods: stratified (S), semi-mixed (SM), and mixed (M). Eight non-infected chaetognath species, two parasitized chaetognaths (F. enflata and S. pacifica), and two parasites (Protist sp. 1 and Tetraphyllidea sp. 2) were associated with warm temperatures (S and SM periods); in contrast, P. euneritica, Z. bedoti, parasitized F. hexaptera, and the parasite Tetraphyllidea sp. 1 showed a strong local preference for cooler temperatures, high productivity, and high biomass conditions (M periods). We discovered the occurrence of the digenean Prosorhynchus sp. (Bucephalidae) parasitizing the chaetognath P. euneritica, and this is the first report of Prosorhynchus parasitizing chaetognaths worldwide. We also confirmed the presence of Lepocrediidae (metacercariae larval stage) infecting F. hexaptera, a parasite that had only been recorded infecting other chaetognaths of the Atlantic Ocean. The parasite diversity affecting the chaetognath populations of the Central Mexican Pacific coast likely differs between the offshore, outer slope areas, and the surveyed coastal system.

The influence of El Niño–Southern Oscillation (ENSO) on productivity at upwelling systems has been extensively studied. However, in recent decades, ENSO diversity has been documented; there are more frequent events with anomalies in the central Pacific (CP) causing ecological impacts that are different from the canonical events centered in the eastern Pacific (EP). We hypothesize that ENSO effects on upwelling intensity and its biological response are highly dependent on ENSO diversity. Wavelet coherence was computed for monthly standardized anomalies of Ekman transport and sea surface Chlorophyll-a (Chl-a) concentration from eight upwelling centers located along the west coast of the Baja California peninsula (1993–2022). Ekman transport (ET) showed a non-linear association with ENSO at interannual periodicities between 1.2 and 7 years, as well as semiannual scale variability. Coherence between ENSO and ET showed a reduction in upwelling intensity during CP ENSO events and an increased upwelling intensity after EP El Niño events with regional differences. Our results reveal an influence of northern Pacific circulation that subsequently influences ENSO events during its development and its peak. We detected an influence of SST and wind anomalies on the ENSO–Ekman transport connection associated with the northern Pacific Meridional Mode pattern. The CP shows an important role in sea surface Chl-a concentration anomalies (1998–2022). We highlight the conceptual relevance of distinguishing ENSO diversity, with influential ecological effects associated with CP ENSO events.

Twenty-one nominal species of Muricea have been reported in the Eastern Pacific with nine of them reported in the Mexican Pacific. We describe three new species of Muricea: Muricea ambarae sp. nov. and Muricea cacao sp. nov., from rocky reefs on the central and the northern Gulf of California and the Pacific coast of Baja California Sur, and Muricea molinai sp. nov., from the Pacific coast of Baja California Sur. Muricea ambarae sp. nov. and M. cacao sp. nov. are taxonomically allied to the nominal species Muricea fruticosa Verrill, 1869 due to the morphological similarity of colony growth patterns and the phylogenetic closeness based on the mitochondrial MutS gene (mtMutS); but differ mainly in the calyx form and composition of sclerites. The main morphological differences between the new Muricea species are in their sclerite forms and color; M. ambarae sp. nov. has orange-colored colonies, thin leaf spindles and tuberculated blunt spindles, while M. cacao sp. nov. has dark brown colored colonies, strong spinous spindles and an absence of tuberculated blunt spindles. Muricea molinai sp. nov. is phylogenetically close and morphologically similar to Muricea squarrosa Verrill, 1869 in the growth form of the colony and tubular calyces; but has dark brown colored colonies and has calyces from the base to the branch tips. With these three new species, the total number of Muricea species reported in the Mexican northwest region increases to twelve and a total of 24 nominal species in the Eastern Pacific.

A colonial ascidian of the genus Distaplia caused a mass mortality of the pen shell Atrina maura (Sowerby, 1835) during June 2016 in the southwest of the Gulf of California (Mexico), with a significant socio-economic cost. Tentatively identified in previous works as Distaplia cf. stylifera, a precise taxonomic determination was still lacking. In the present work, based on a detailed morphological study, it is confirmed that this aggressive species is Distaplia stylifera (Kowalevsky, 1874). Originally described from the Red Sea, the species currently has a wide circumtropical distribution (with the exception of the Eastern Pacific to date) and is reported as introduced in parts of its range. The present account thus represents an important range extension of this species. However, when revising the original description and later observations, the reported variability of several characters makes it likely that the binomen is in fact a complex of species, as is common in other ascidians with wide distributions. A complete morphological and genetic study including populations from the entire range of distribution would be necessary to settle the status of D. stylifera. Taxonomic uncertainties hinder a correct interpretation of biogeographical patterns and inference on the origin of the studied population. Nevertheless, the known introduction potential of the species, coupled with an explosive growth in an anthropized environment, and the lack of any previous reports in the Eastern Pacific, strongly suggest that the investigated population represents yet another instance of ascidian introduction. From the point of view of management, its invasive behavior is cause for great concern and warrants mitigation measures.

Plerocerci of the monotypic Paranybelinia otobothrioides were found parasitizing the subtropical neritic krill Nyctiphanes simplex in the Gulf of California, Mexico. The plerocerci were recovered from two microhabitats of the intermediate host, typically embedded inside the digestive gland (hepatopancreas) or rarely in the hemocoel. The morphology of the simple, single-layered blastocyst surrounding the entire scolex is unique within the Trypanorhyncha by having four large funnel-like pori or openings possibly with feeding and/or excretory function. One of the openings is located anteriorly and three at the posterior end. Scolex surface ultrastructure shows hamulate and lineate spinitriches covering the bothrial surface, capilliform filitriches at the anterior scolex end and on the scolex peduncle, and short papilliform filitriches on the long appendix. This pattern resembles that of species of the Tentaculariidae; but differs in that the hamulate spinitriches, which appear lineate at the bothrial margins, densely cover the entire distal bothrial surface. Tegumental grooves are present on the posterior bothrial margin, lacking spinitriches. Paranybelinia otobothrioides and Pseudonybelinia odontacantha share the following unique combination of characters: two bothria with free lateral and posterior bothrial margins, homeoacanthous homeomorphous armature, tegumental grooves, the distribution of the hamulate spinitriches, and the absence of prebulbar organs. Both genera infect euphausiids as intermediate hosts. Sequence data of the partial ssrDNA gene place Pa. otobothrioides sister to the family Tentaculariidae, and the Kimura two-parameters (K2P) distance between Pa. otobothrioides and species of the family Tentaculariidae ranged from 0.027 to 0.039 (44-62 nucleotide differences). These data suggest both species be recognized in a family, the Paranybeliniidae, distinct from, albeit as sister taxon to, the Tentaculariidae. High prevalence of infection (

The nearshore zooplankton species assemblage, identified per taxonomic groups (20) and per species for 12 selected groups, was analyzed from samples collected during November 2010 at four volcanic islands of the Islas Marías Archipelago (IMA), located 90-120 km offshore Nayarit, Mexico. From chlorophyll-a concentration and zooplankton biovolume perspective mesotrophic conditions prevailed in comparison with the Gulf of California during November. Crustaceans numerically dominated the zooplankton assemblage (92.3%) [Copepoda (79.2%), Decapoda larvae (4.7%), Cladocera (3.7%), Mysidacea (2.7%), and Euphausiacea (2.0%)]. The other 15 taxonomic groups (7.7% combined) accounted each one less than 1.5% of the relative abundance. Species richness of selected taxa (~56%>) included 259 taxa (121 identified to species, 117 to genus, and 21 not identified). Tropical species from neritic affinity clearly dominated zooplankton assemblage around IMA. Five tropical Copepoda species [Calanopia minor (Dana), Clausocalanus jobei Frost & Fleminger, Acrocalanus gibber Giesbrecht, Canthocalanus pauper (Giesbrecht), and Centropages furcatus (Dana)], a cladoceran Pseudevadne tergestina (Claus), and a Mysidacea species (Mysidium reckettsi Harrison & Bowman) dominated the zooplankton assemblage (accounting about 55% of total abundance of the identified species). Except C. furcatus, all these species are not abundant at oceanic regions of the central and northern Gulf of California. The similarity of multiple neritic and tropical species in the zooplankton assemblage from IMA and Cape Corrientes suggests strong coastal-insular plankton connectivity. Episodic current plumes associated with anomalous intense rivers discharge during rainy years, eddies generated by coastal upwelling event that move offshore, and northward regional oceanic circulation are the most likely mesoscale oceanographic processes that cause costal tropical zooplankton drift enhancing coastal-Archipelago species connectivity in this region.

The zooplankton community structure, including copepods, euphausiids, chaetognaths, and decapod larvae, was monitored during six circadian cycles using Bongo net (500 *m mesh net) samples from Bahía Magdalena, on the southwest coast of Baja California, México. Samples were obtained during three oceanographic surveys (March, July, and December 1996) to describe the changes in the zooplankton community structure throughout the main mouth of Bahía Magdalena. The zooplankton community structure showed strong changes with a close relation to environmental conditions. During March, a well-mixed water column with low temperature and salinity indicated an influence of the California Current water and local upwelling processes. During July, temperature increased a nd a wide salinity range was recorded. The stratification of the water column was intense during summer, enhancing the thermocline. The highest temperatures and salinity were recorded in December, related to the presence of the Costa Rica Coastal Current (CRCC). The thermocline deepened as water temperature increased. A typical temperate community structure with low specific richness dominated by Calanus pacificus, Nyctiphanes simplex, and Acartia clausi and high zooplankton biomass (average 9.3 and 5.5 ml 1000 m-3respectively) during March and July shifted to a more complex tropical community structure with a low zooplankton biomass in December (average 0.37 ml 1000 m-3). The mouth of Bahía Magdalena has a vigorous exchange of water caused by tidal currents. The zooplankton community structure was not significantly different between the central part of Bahía Magdalena and the continental shelf outside the bay for all months. The results suggest a more dynamic inside-outside interaction of zooplankton assemblages than first thought.La estructura de la comunidad de zooplancton, incluyendo copépodos, eufáusidos, quetognatos y larvas de decápodos, fue monitoriada por seis ciclos circadianos usando muestras de redes Bongo (red de 500 mm de poro) de bahía Magdalena, en la costa suroeste de Baja California, México. Las muestras se obtuvieron durante tres viajes oceanográficos (marzo, julio y diciembre de 1996) para describir los cambios en la estructura de la comunidad de zooplancton por toda la boca principal de la bahía Magdalena. La estructura de la comunidad de zooplancton mostró cambios fuertes con una relación cercana a las condiciones ambientales. Durante marzo, una columna de agua bien mezclada con baja temperatura y salinidad indicó una influencia del agua de la Corriente de California y de procesos de afloramiento local. Durante julio, la temperatura aumentó y se registró un ámbito de de salinidad amplio. La estratificación de la columna de agua fue intensa durante el verano, realzando la termoclina. Las temperatura y salinidad más altas fueron registradas en diciembre, relacionadas a la presencia de la Corriente Costera de Costa Rica (CRCC). La termoclina se hizo más profunda al aumentar la temperatura del agua. Una estructura de una comunidad templada típica con una riqueza específica baja denominada por Calanus pacificus, Nyctiphanes simplex y Acartia clausi y una biomasa de zooplancton alta (promedio 9.3 y 5.5 ml 1000 m-3 respectivamente) durante marzo y julio cambió a una estructura de una comunidad tropical más compleja con biomasa de zooplanton baja en diciembre (promedio 0.37 ml 1000 m-3). La boca de la bahía Magdalena tiene un intercambio vigoroso de agua causado por corrientes. La estructura de la comunidad de zooplancton no fue significantemente diferente entre la parte central de la bahía Magdalena y la plataforma continental afuera de la bahía en todos los meses. Los resultados sugieren una interacción de adentro hacia afuera más dinámica de los grupos de zooplancton que los antes pensado.