Pelagic amphipods (Crustacea: Amphipoda: Hyperiidea) in western Mexico. 7. Superfamily Platysceloidea. Family Oxycephalidae.

Twelve species of the family Oxycephalidae were collected during a deep-water survey off western Mexico: four species of Rhabdosoma, three species of Streetsia, two species of Oxycephalus, and one species each of Cranocephalus, Glossocephalus, and Leptocotis. In total, 321 specimens were collected, 114 males and 207 females, in 33 sampling localities in the Gulf of California (28) and off southwestern Mexico (5). Two species dominated in the samples and co-occurred in 17 of the 33 samples containing hyperiids: Oxycephalus clausi (24 localities, 152 specimens) and Rhabdosoma whitei (20 localities, 121 specimens). Considering this study and previous records, a total of 16 of the 18 described species of Oxycephalidae (89%) have been reported from western Mexico. Distribution of this new material off western Mexico is provided together with update data on species occurrence in the eastern Pacific.

Hyperiids (Amphipoda, Hyperiidea) collected during the TALUD cruises in western Mexico. 5. Family Amphithyridae, with the description of a new species of Amphithyropsis Zeidler.

In order to complete the information related to the little studied deep-sea planktonic fauna of western Mexico, samples from a wide depth range (surface to 1550 m depth) were obtained using different gear. Six species and 108 individuals of hyperiid amphipods of the family Amphithyridae were collected at 26 localities, including a new species of Amphithyropsis Zeidler, 2016, which is herein described based on an adult male and a gravid female. Other species include Amphithyrus bispinosus Claus, 1879, the most abundant and frequently collected species (70 specimens at 17 localities), A. muratus Volkov, 1982 (11 specimens at 8 localities), A. sculpturatus Claus, 1879 (14 specimens at 7 localities), Paralycaea gracilis Claus, 1879 (10 specimens from 6 localities), and P. hoylei Stebbing, 1888 (one specimen from one locality). Worldwide and regional distributions are provided for each species.

Pelagic amphipods (Crustacea: Amphipoda: Hyperiidea) in western Mexico. 3. Family Lestrigonidae.

Thirteen species belonging to five genera of pelagic amphipods of the family Lestrigonidae were collected during a deep-water survey off western Mexico: four species of Hyperietta, two species of Hyperioides, five species of Lestrigonus, and one species each of Phronimopsis and Themistella. This represents 93% of all known species of Lestrigonidae world-wide. A total of 1092 specimens were obtained in 40 sampling localities in the Gulf of California (35) and off southwestern Mexico (5). Although sampling methodology was rather heterogeneous, two species, Hyperioides sibaginis and Lestrigonus bengalensis, were particularly abundant (336 and 562 specimens) and frequent (present in 24 and 31 localities) in the samples, representing 82% of the total catch. The southernmost distribution limit of Hyperietta stebbingi is extended to off SW Mexico. Of the 13 species that were collected during this survey, 10 and 8 species co-occurred at two sampling localities in the SE Gulf of California.

Pelagic amphipods (Crustacea: Amphipoda: Hyperiidea) in western Mexico. 2. Family Eupronoidae.

During deep-water (0-1550m) sampling operations off western Mexico performed between 1989 and 2014, a series of 89 specimens of pelagic amphipods of the family Eupronoidae was obtained, including two genera and four species: Eupronoe armata, E. maculata, E. minuta, and Parapronoe parva. The most abundant species (50% of total number of individuals) and frequently collected species (in 65% of samples with eupronoids) was E. maculata. Worldwide and regional distributions are provided for each species. Notes on previously used names are provided.

Pelagic amphipods (Crustacea: Amphipoda: Hyperiidea) in western Mexico. 6. Superfamily Vibilioidea. Families Paraphronimidae and Vibiliidae.

Ten species belonging to the families Paraphronimidae and Vibiliidae were collected during a deep-water survey off western Mexico: two species of Paraphronima and eight species of Vibilia. This represents about 40% of all known species of these two genera world-wide. A total of 419 males and 607 females were obtained in 39 samples from localities in the Gulf of California (33) and off southwestern Mexico (6). Vibilia armata was by far the most frequently (32 localities) and most abundantly (687 specimens, 67% of the total) collected species, followed by V. longicarpus (231 specimens in nine localities) and P. crassipes (35 specimens in 9 localities). Co-ocurrence of species of Vibilioidea in our samples was very low, with maxima of seven and five species collected in the same sample, once each. Considering previous records, a total of 16 species of Vibilioidea (almost 70% of all known species) have now been reported from western Mexico: two species of Paraphronima and 14 species of Vibilia, including V. australis occasionally reported in the area as its junior synonym, V. wolterecki.

Species of Scina Prestandrea, 1833 (Amphipoda, Hyperiidea, Scinidae) from western Mexico with the description of a new species from the Gulf of California.

Only a few previous surveys of the deep-water planktonic fauna have been accomplished off western Mexico, in particular in the Gulf of California. Samples of pelagic amphipods were obtained between surface and as deep as 2394 m using different gear during an extensive survey in this area. Among these samples, nine species of the genus Scina were recognized, including 78 specimens: 27 males and 51 females. The genus Scina inhabits mesopelagic waters at depths over 200 m, a community that remains largely unknown. The material examined includes a new species, the first reported from the Gulf of California, which is described and compared with its closest congeners, S. setigera Wagler, 1926 and S. parasetigera Zeidler, 1990. These three species share the presence of a long bristle on the base of the dactylus of pereopods 5 and 6. Scina sp. nov. differs from these other two species mainly by: 1) the shape and proportions of pereiopods 1-7; 2) the presence of three inner spiniform elements on uropod 1; 3) the insertion of the exopod on distal 1/3 of uropods. Of the remaining species collected during the survey S. borealis was by far the most abundant and widely distributed, followed by S. wolterecki and S. marginata. The other five species, S. curvidactyla, S. nana, S. pacifica, S. setigera, and S. submarginata, were represented by one or two specimens only. Co-occurence of species of Scina in samples was low with a maximum of four species in a single sample, all associated with S. borealis, the most common species. The distribution of Scina species collected during this survey is briefly discussed.

Diet and stable isotope analyses reveal the feeding ecology of the orangeback squid Sthenoteuthis pteropus (Steenstrup 1855) (Mollusca, Ommastrephidae) in the eastern tropical Atlantic.

In the eastern tropical Atlantic, the orangeback flying squid Sthenoteuthis pteropus (Steenstrup 1855) (Cephalopoda, Ommastrephidae) is a dominant species of the epipelagic nekton community. This carnivore squid has a short lifespan and is one of the fastest-growing squids. In this study, we characterise the role of S. pteropus in the pelagic food web of the eastern tropical Atlantic by investigating its diet and the dynamics of its feeding habits throughout its ontogeny and migration. During three expeditions in the eastern tropical Atlantic in 2015, 129 specimens were caught by hand jigging. Stomach content analyses (via visual identification and DNA barcoding) were combined with stable isotope data (∂15N and ∂13C) of muscle tissue to describe diet, feeding habits and trophic ecology of S. pteropus. Additionally, stable isotope analyses of incremental samples along the squid's gladius-the chitinous spiniform structure supporting the muscles and organs-were carried out to explore possible diet shifts through ontogeny and migration. Our results show that S. pteropus preys mainly on myctophid fishes (e.g. Myctophum asperum, Myctophum nitidulum, Vinciguerria spp.), but also on other teleost species, cephalopods (e.g. Enoploteuthidae, Bolitinidae, Ommastrephidae), crustaceans and possibly on gelatinous zooplankton as well. The squid shows a highly opportunistic feeding behaviour that includes cannibalism. Our study indicates that the trophic position of S. pteropus may increase by approximately one trophic level from a mantle length of 15 cm to 47 cm. The reconstructed isotope-based feeding chronologies of the gladii revealed high intra- and inter-individual variability in the squid's trophic position and foraging area. These findings are not revealed by diet or muscle tissue stable isotope analysis. This suggests a variable and complex life history involving individual variation and migration. The role of S. pteropus in transferring energy and nutrients from lower to higher trophic levels may be underestimated and important for understanding how a changing ocean impacts food webs in the eastern Atlantic.

Time-calibrated molecular phylogeny of pteropods.

Pteropods are a widespread group of holoplanktonic gastropod molluscs and are uniquely suitable for study of long-term evolutionary processes in the open ocean because they are the only living metazoan plankton with a good fossil record. Pteropods have been proposed as bioindicators to monitor the impacts of ocean acidification and in consequence have attracted considerable research interest, however, a robust evolutionary framework for the group is still lacking. Here we reconstruct their phylogenetic relationships and examine the evolutionary history of pteropods based on combined analyses of Cytochrome Oxidase I, 28S, and 18S ribosomal rRNA sequences and a molecular clock calibrated using fossils and the estimated timing of the formation of the Isthmus of Panama. Euthecosomes with uncoiled shells were monophyletic with Creseis as the earliest diverging lineage, estimated at 41-38 million years ago (mya). The coiled euthecosomes (Limacina, Heliconoides, Thielea) were not monophyletic contrary to the accepted morphology-based taxonomy; however, due to their high rate heterogeneity no firm conclusions can be drawn. We found strong support for monophyly of most euthecosome genera, but Clio appeared as a polyphyletic group, and Diacavolinia grouped within Cavolinia, making the latter genus paraphyletic. The highest evolutionary rates were observed in Heliconoides inflatus and Limacina bulimoides for both 28S and 18S partitions. Using a fossil-calibrated phylogeny that sets the first occurrence of coiled euthecosomes at 79-66 mya, we estimate that uncoiled euthecosomes evolved 51-42 mya and that most extant uncoiled genera originated 40-15 mya. These findings are congruent with a molecular clock analysis using the Isthmus of Panama formation as an independent calibration. Although not all phylogenetic relationships could be resolved based on three molecular markers, this study provides a useful resource to study pteropod diversity and provides general insight into the processes that generate and maintain their diversity in the open ocean.

The rare deep-living hyperiid amphipod Megalanceoloides remipes (Barnard, 1932): complementary description and symbiosis.

A female ovigerous specimen of the rare deep-living hyperiid Megalanceoloides remipes (Barnard, 1932) was collected with a remotely operated submersible (ROV) at a depth of 2,094 m in the Farallon Basin, Gulf of California. The specimen was found to be symbiotically associated with the siphonophore Apolemia sp. Eschscholtz, 1829. Hitherto, this species was known only from two other specimens, one from the South Atlantic and another from the Indian Ocean; the present record is the first from the Pacific Ocean. Previous descriptions lacked morphological details of different appendages; these data are provided here. In addition, we present the first data on its symbiotic association from in situ observations. The colors of the hyperiid and of some parts of the Apolemid were very similar, thus supporting the notion that some hyperiids tend to mimic the color of its host.

A new species of Caligus Müller, 1785 (Copepoda: Siphonostomatoida: Caligidae) from coral reef plankton in the Mexican Caribbean.

During a survey of the zooplankton community of a protected reef system on the southern coast of the Mexican Caribbean, many female and male specimens of an undescribed species of Caligus Müller, 1785 were collected. The new species closely resembles C. wilsoni Delamare Deboutteville & Nunez-Ruivo, 1958 and C. belones (Krøyer, 1863) and has affinities with C. balistae Steenstrup & Lütken, 1861 and C. longipedis Bassett-Smith, 1898, all known from the Caribbean Sea and adjacent waters of the north-western Atlantic Ocean. Caligus ilhoikimi sp. nov., is described in full and illustrations of both sexes are also provided. The new species differs from C. wilsoni and C. belones in several features, including the shape of the sternal furca, the shape and proportions of the genital complex and abdomen, the lack of accessory processes on the distal elements of leg 1 exopod, and the presence of a lateral spine on the third exopodal segment of leg 2. This is the seventh species of Caligus known from waters of the Atlantic seaboard of Mexico and the 32nd species of the genus recorded in Mexican waters. The specimens were caught with a plankton light trap. The unusually high number of individuals captured and the fact that the sample was monospecific (i.e. only adults of this caligid species were collected) suggests that it is a chiefly planktonic form. This is a mode of life recently revealed as being more common among caligids than previously thought.

A new Lepeophtheirus (Copepoda: Siphonostomatoida: Caligidae) from Isla del Coco National Park, Costa Rica, Eastern Tropical Pacific / Un nuevo Lepeophtheirus (Copepoda: Siphonostomatoida: Caligidae) del Parque Nacional Isla del Coco, Costa Rica, Pacífico Tropical Oriental

Among the several groups of copepods that are teleost parasites, the siphonostomatoid family Caligidae is by far the most widespread and diverse. With more than 108 nominal species, the caligid genus Lepeophtheirus von Nordmann is one of the most speciose. There are no reports of this genus in Costa Rican waters. A new species of Lepeophtheirus is herein described based on female specimens collected from plankton samples in waters off Bahía Wafer, isla del Coco, an oceanic island in the Eastern Tropical Pacific. The new species, L. alvaroi sp. nov., has some affinities with other congeners bearing a relatively short abdomen, a wider than long genital complex and a 3-segmented exopod of leg 4. it differs from most of these species by the presence of an unbranched maxillular process and by the relative lengths of the terminal claws of leg 4, with two equally long elements. it is most closely related to two other Eastern Pacific species: L. dissimulatus Wilson, 1905 and L. clarionensis Shiino, 1959. it differs from these species by the proportions and shape of the genital complex, the shape of the sternal furca, the relative length of the maxillar segments, the absence of a pectiniform process on the distal maxillar segment, the length of leg 4 and the armature of leg 5. The new species represents the first Lepeophtheirus described from Costa Rican waters of the Pacific. The low diversity of this genus in this tropi- cal region is explained by its tendency to prefer hosts from temperate latitudes. Until further evidence is found, the host of this Lepeophtheirus species remains unknown.

Entre los varios grupos de copépodos que son parásitos de teleósteos, la familia sifonostomatoide Caligidae incluye los más dispersos y diversos. Con más de 108 especies nominales, el género de calígidos Lepeophtheirus von Nordmann es uno de los más diversos. No existen registros previos de este género en aguas de Costa Rica. Se describe una nueva especie de copépodo calígido del género Lepeophtheirus con base en especímenes femeninos recolectados a partir de muestras de plancton en aguas de Bahía Wafer, isla del Coco, una isla oceánica del Pacífico Tropical Oriental. La nueva especie, L. alvaroi sp. nov., tiene algunas afinidades con congéneres que poseen un abdomen relativamente corto, un complejo genital más ancho que largo y un exópodo de la pata 4 con 3 segmentos. Esta especie difiere de la mayoría de estas especies por la presencia de un proceso maxilular no ramificado y por el tamaño relativo de las garras terminales de la pata 4, con dos elementos igualmente largos. Está más cercanamente relacionada con otras dos especies del Pacífico Oriental: L. dissimulatus Wilson, 1905 y L. clarionensis Shiino, 1959. Difiere de estas especies por las proporciones y forma del complejo genital, la forma de la furca esternal, la longitud relativa de los segmentos maxilares, la ausencia de un proceso pectiniforme en el segmento maxilar distal, la longitud de la pata 4 y la armadura de la pata 5. La nueva especie representa el primer Lepeophtheirus descrito en aguas del Pacífico de Costa Rica. La baja diversidad del género en esta región tropical se explica por su tendencia a preferir hospederos de latitudes templadas. Hasta encontrar más evidencia, el hospedero de esta especie de Lepeophtheirus permanece desconocida.

Anfípodos hiperídeos (Crustacea: Peracarida) del Parque Nacional Isla del Coco, Costa Rica, Pacífico Tropical Oriental / Hyperiid amphipods (Crustacea: Peracarida) of the Parque Nacional Isla del Coco, Costa Rica, Eastern Tropical Pacific

Hyperiid amphipods are one of the most frequently encountered pelagic crustaceans and among the most diverse marine zooplankters. To determine the species composition of the hyperiid amphipods dwelling in the waters around Isla del Coco National Park, Pacific Costa Rica, we analyzad 12 zooplankton samples, collected by vertical and horizontals tows with plankton net with mesh sizes of 200 and 500 microns and 49cm mouth diameter. We recorded a total of 22 species belonging to 17 genera and 12 families. A faunistic list of this group is provided together with data on their taxonomy and their distribution both in the surveyed area and in general. Most of the species recorded in this zone have been reported in previous surveys in the Eastern Tropical Pacific region and particularly in oceanic waters of Costa Rica. We found eight species representing new records for Costa Rican waters, thus increasing by 26% (to 38) the number of hyperiid species known from Costa Rica. The most frequent species were Lestrigonus shoemakeri, L. bengalensis, Hyperiodes sibaginis, and Phronimopsis spinifera. We expect that additional samplings both from surface and deep waters will expand the knowledge of the diversity of the group in this important protected area.

Los anfípodos hiperídeos son uno de los grupos de crustáceos pelágicos más frecuentemente encontrados y están entre los más diversos del zooplancton marino. Para determinar la composición de especies de anfípodos hipéridos que habitan las aguas alrededor del Parque Nacional Isla del Coco, Costa Rica, se analizaron 12 muestras de zooplancton. Estas fueron recolectadas mediante arrastres verticales y horizontales con una red de plancton con mallas de 200 y 500 micras y 49cm de diámetro en la boca. Se encontró un total de 22 especies pertenecientes a 17 géneros y 12 familias. Se presenta el listado faunístico de este grupo junto con datos acerca de su taxonomía, su distribución en el área de estudio y su distribución general. La mayor parte de las especies registradas en esta zona han sido reportadas en estudios previos referentes a la región del Pacífico Tropical Oriental y en particular en aguas oceánicas de Costa Rica. Encontramos ocho especies que representan nuevos registros para aguas del Pacífico costarricense, lo que incrementa en un 26% (a 38) el número de especies de hipéridos conocidos en Costa Rica. Las especies más frecuentes fueron Lestrigonus shoemakeri, L. bengalensis, Hyperioides sibaginis y Phronimosis spinifera. Se espera que muestreos adicionales tanto de aguas superficiales como profundas expandan el conocimiento de la diversidad del grupo en esta área protegida.

[Euphausiids (Crustacea: Melacostraca) from the southern Mexican Caribbean Sea]. / Eufáusidos (Crustacea: Malacostraca) del centro y sur del Mar Caribe mexicano.

The composition, abundance and distribution of euphausiids from the southern part of the Mexican Caribbean Sea (August 1986) were sampled during the ARCOMM I cruise on board the R/V "Justo Sierra" of UNAM. Sampling was done using a Bongo-net (0.5 mm mesh size) performing oblique hauls from 200 m to the surface at 28 stations. Of the total euphausiid numbers, the most abundant species was Stylocheiron carinatum (49%), followed by Euphausia americana (9.8%) and E. tenera with (7.8%). The highest total density and that of the three most abundant species occurred during the night sampling, and probably was related to vertical migration patterns. The Bray-Curtis index revealed three station assemblages, related to the day-night variations of the euphausiid community. Species were distributed mainly in the oceanic area, and were absent in the neritic zones. The local fauna shows a strong affinity for the euphausiid community of the Gulf of Mexico and other areas of the Caribbean Sea. Four species are considered to be new records for the western Caribbean Sea.

Eufáusidos (Crustacea: Malacostraca) del centro y sur del Mar Caribe mexicano / Euphausiids (Crustacea: Melacostraca) from the southern Mexican Caribbean Sea]

The composition, abundance and distribution of euphausiids from the southern part of the Mexican Caribbean Sea (August 1986) were sampled during the ARCOMM I cruise on board the R/V "Justo Sierra" of UNAM. Sampling was done using a Bongo-net (0.5 mm mesh size) performing oblique hauls from 200 m to the surface at 28 stations. Of the total euphausiid numbers, the most abundant species was Stylocheiron carinatum (49), followed by Euphausia americana (9.8) and E. tenera with (7.8). The highest total density and that of the three most abundant species occurred during the night sampling, and probably was related to vertical migration patterns. The Bray-Curtis index revealed three station assemblages, related to the day-night variations of the euphausiid community. Species were distributed mainly in the oceanic area, and were absent in the neritic zones. The local fauna shows a strong affinity for the euphausiid community of the Gulf of Mexico and other areas of the Caribbean Sea. Four species are considered to be new records for the western Caribbean Sea.