Distribution of holoplanktonic typhloscolecids (Annelida-Polychaeta) in the eastern tropical Pacific Ocean

The distribution and composition of the holoplanktonic speciesof the family Typhloscolecidae are reported from 579 samplesobtained over an extensive area in the eastern tropical PacificOcean. The EASTROPAC Oceanographic Program collected the samplesin twelve cruises during five periods made between January–September1967 and January–April 1968. The 2105 specimens identifiedbelonged to three genera and four species. Typhloscolex muelleriand Sagitella kowalewski were dominant together, accountingfor 57–59% of the relative abundance and 36–49%of the occurrence. Travisiopsis dubia is recorded for the firsttime from the eastern tropical Pacific, and Travisiopsis lanceolatais reported in almost the same locality as its first recordin the surveyed region.     

Ptereleotris carinata, a new species of hovering goby (Perciformes: Microdesmidae) from the tropical eastern Pacific

A new hovering goby or dartfish is described from material collected in Mexico, Costa Rica and Panama. It is the only species of the cosmopolitan genus Ptereleotris known from the eastern Pacific. It is distinguished from its Western Atlantic and Indo-Pacific congeners by its low fin-ray counts, prominent median keel on the ventral margin of the head, lanceolate caudal fin with dusky lower half and dusky blue or lavender body in adults.     

Protemblemaria perla, a new species of tube blenny (Perciformes: Chaenopsidae) from the tropical eastern Pacific

Protemblemaria perla, from Isla del Rey, Islas Perlas, Panama, is distinctive in having a long unbranched cirrus on the posterior nostril, a U-shaped fleshy ridge bearing fleshy flaps and a pair of papillae on the nape, a relatively high number (18) of segmented dorsal-fin rays, and small rust-colored spots on the dorsal fin. Protemblemaria perla and P. punctata, from the southern Caribbean, share several morphological features and form a transisthmian species pair. Although the degree of color variation is unknown in P. perla, color varies greatly in P. bicirris and P. punctata, both of which have an orange morph.     

Spatial variability of mangrove fish assemblage composition in the tropical eastern Pacific Ocean

Mangroves in the tropical eastern Pacific (TEP) constitute a dominant coastal ecosystem that harbours diverse and economically important fish assemblages. We describe here regional scale patterns in the composition of this poorly documented mangrove ichthyofauna. A review of available studies (including own data) from five countries covering the entire region was performed. Species abundance distribution curves were constructed and compared among studies. Relative abundance data of fish species and families were analysed with classification and ordination techniques. Common species and families responsible for differences among localities were identified. Overall, 315 fish species associated to mangroves of the TEP were identified. Fifteen fish families accounted for 80 % or more of the relative abundance of all studies. Despite the use of different sampling techniques, common features arose for most of the mangrove fish assemblages. Clupeidae were numerically dominant throughout the region, while Gerreidae were particularly dominant in the northern mangroves. The catch mass contributions of families from studies where these data were available indicated a dominance of Ariidae, Centropomidae, Lutjanidae and Tetraodontidae. A relatively uniform composition at the family (and sometimes species) level supports recent claims to merge the Panamic with the Mexican province in the TEP according to the distribution of the shore fish fauna. Similarities found with other estuarine-mangrove ichthyofaunas in the Neotropics may be related to the connectedness of these regions in past geological times. Quantitative assessments of mangrove fish communities in four areas of the TEP would improve further zoogeographic analyses and facilitate the development of conservation strategies.     

A new species of Nezumia (Gadiformes: Macrouridae) from Fieberling Guyot, eastern North Pacific Ocean

A new species of the macrourine genus Nezumia is described from specimens collected from the crest of Fieberling Guyot in the eastern North Pacific Ocean. The new species is distinguishable from all other Nezumia species chiefly on the basis of a high number of pelvic fin rays, a relatively high number of first dorsal fin soft rays, a steep blunt snout lacking scales ventrally, a relatively weak suborbital ridge, and a moderately long, thin barbel. Although possibly endemic to the Baja California Seamount Province, the new species appears to lack close relatives among the other Nezumia species of the eastern North Pacific Ocean. It might have arrived there either from a disjunct Tethyan distribution, thus retaining close relatives among the Atlantic Ocean species of Nezumia, or by way of stepping-stone dispersal from the Indo-west Pacific Ocean.     

Reproductive biology of deep-sea catsharks (Chondrichthyes: Scyliorhinidae) in the eastern North Pacific

Apristurus brunneus, A. kampae, and Parmaturus xaniurus were caught by trawl and longline between Washington and southern California (48°N to 32°N latitude) from June 2001 through October 2004. In females, oviducal gland width increased with TL in all three species but remained within 4 to 6% of TL. Oocyte diameter increased with TL during reproductive development in all species, and continued to increase with size after reproductive maturity was reached. The weight-length relationships differed significantly among species but not between sexes of any species from the eastern North Pacific combined. Using logistic regression, it was determined that total length at 50% maturity (TL₅₀) of A. brunneus males was 514 mm TL and all A. brunneus males were mature at 547 mm TL. Female A. brunneus reached TL₅₀ at 501 mm TL and all female A. brunneus were mature at 581 mm TL. Apristurus kampae males and females reached TL₅₀ at approximately 485 mm TL and 490 mm TL, respectively. Parmaturus xaniurus males reached TL₅₀ at 444 mm TL and females at 501 mm TL. Gravid female A. brunneus were found in all months of the year, but gravid P. xaniurus were found primarily June through September. Adult A. kampae females were found only in July through November and there were gravid females in all these months. Based upon gonadosomatic indices, I _G, these species may mate within a defined period of time (April through June); however, A. brunneus appear to reproduce throughout the year and P. xaniurus reproduce within a defined season (approximately July through September).     

Reproductive biology of Zearaja chilensis (Chondrichthyes: Rajidae) in the south-east Pacific Ocean

Between 2000 and 2002, three artisanal landing sites were sampled in southern Chile, with data on population structure and reproductive development collected from 5477 yellownose skates Zearaja chilensis. Total length (L(T) ) ranged from 33 to 158 cm for females and 34 to 155 cm for males. No sexual dimorphism was evident in disc size (length or width) or in L(T)-mass relationships. The smallest mature female was 95 cm L(T) and the size at which 50% were mature (L(T50) ) was 109 cm. Males matured between 80 and 90 cm L(T) with a L(T50) of 88 cm. Although the largest Z. chilensis captured by the artisanal fishery was 155 cm L(T) , 89% of landings comprised relatively small, immature fish. This situation may compromise the stock integrity if intrinsic vulnerability and probable long-life span of Z. chilensis are considered. Consequences for the survival of the species and possible signs of a fishery collapse must be reviewed by management authorities by consideration of both artisanal and industrial landings in Chile.     

The eastern Pacific species of Bathygobius (Perciformes: Gobiidae)

The circumtropical gobiid genus Bathygobius Bleeker is defined and three Eastern Pacific species are redescribed, with first dorsal fin pattern and postorbital blotches being shown to be additional characters of diagnostic value. Two mainland species are recognised, the Mexican-Panamanian B. ramosus Ginsburg 1947 and the Panamanian B. andrei (Sauvage 1880). B. ramosus is now reported from Clarión Island, Revillagigedos, and also from Cocos Island. Meristic variation of ramosus is tabulated for local populations and PCA analysis of their morphometry suggests regional differentiation in this species, with Tres Marias and Revillagigedos populations clustering away from mainland and Montuosa material. An insular species, B. lineatus (Jenyns 1842) from the Galapagos is defined, with B. arundelii (Garman 1899) from Clipperton Island and B. l. lupinus Ginsburg 1947 from Lobos de Afuera, off Peru, placed as nominal subspecies of lineatus. This species resembles the Indo-west Pacific B. fuscus and Atlantic basin B. soporator more closely than it does ramosus and andrei and may be the product of transpacific dispersal. A similar origin for B. ramosus is discussed but it seems more likely that both B. ramosus and B. andrei have Caribbean sister species.     

Indo-Pacific echinoids in the tropical eastern Pacific

The existing literature reports that only one species of Indo-Pacific echinoid (Echinometra oblonga), occurs in the eastern Pacific. In this study we confirm the presence of this species at Islas Revillagigedo and also report the presence of two species ofEchinothrix (a genus hitherto unknown outside the Indo-Pacific) at Isla del Coco and at Clipperton Island. We also present evidence from isozymes and from mitochondrial DNA sequences indicating that at least one individual ofDiadema at Clipperton may belong to a maternal lineage characteristic of the west Pacific speciesD. savignyi. These data are consistent with the hypothesis that the observed populations of Indo-Pacific echinoid species are recent arrivals to the eastern Pacific, as opposed to the view that they are relicts of Tethyan pan-tropical distributions.Echinothrix diadema, in particular, may have arrived at Isla del Coco during the 1982-1983 El Nifio. In addition to Indo-Pacific species, Clipperton, Isla del Coco and the Revillagigedos contain a complement of eastern Pacific echinoids. The echinoid faunas of these islands should, therefore, be regarded as mixtures of two biogeographic provinces. Though none of the Indo-Pacific species are known to have reached the coast of the American mainland, their presence at the offshore islands of the eastern Pacific suggests that, for some echinoids, the East Pacific Barrier is not as formidable an obstacle to migration as was previously thought.     

Three new deep-sea species of Sphaerodoridae (Annelida,Polychaeta) from the eastern tropical South Pacific*

Three sphaerodorid species new to science are described from a manganese nodule area in abyssal depths of around 4150 m in the Peru Basin in the eastern South Pacific. Sphaerodoridium campanulata sp. n. is isolated within the genus, having, apart from spherical macrotubercles, additional dorsal stalked bell-shaped papillae, not previously described. Sphaerodoropsis discolis sp. n. is a species with four rows of dorsal macrotubercles and two pairs of lateral antennae. Sphaerodoropsis translucida sp. n. has six to seven rows of dorsal macrotubercles arrayed in two transverse rows per segment and two pairs of lateral antennae. A brief discussion points to the close relationship between Clavodorum and Sphaerodoridium, and to the present state of Sphaerodoropsis, being inhomogeneous in the characters of the arrangement of the dorsal macrotubercles and the numbers of the lateral antennae. An overview on the latter genus, with an attempt to subdivide it, is given.     

Vertical distribution of Pleuromamma (Copepoda: Metridinidae) across the eastern North Pacific Ocean

Vertical distributions of six species of Pleuromamma at ten stations across the eastern North Pacific Ocean from Honolulu to San Diego were determined from oblique Longhurst-Hardy Plankton Recorder tows to 650 m (350–450 m in the California Current). Vertical resolution was 20 m below 200 m and 5–10 m above. There was considerable overlap in surface layer distributions at night among all co-occurring species; daytime distributions showed less overlap. All species generally occurred deeper both day and night as distance offshore increased. The proportion of a species' population that remained at daytime depths during the night decreased with distance offshore. Warm water species penetrated into the California Current and nearshore region to a much greater extent than cool water species entered central gyre waters.     

Gordiichthys combibus, a new species of eastern Pacific sand-eel (Anguilliformes: Ophichthidae)

A new species of bascanichthyin ophichthid, Gordiichthys combibus, is described from shallow water along the Pacific coast of Colombia. It is the first known eastern Pacific species of Gordiichthys and is very similar to G. randalli from Puerto Rico. It differs from its other western Atlantic congeners in vertebral number and other characters. A key to the genus is provided.     

Redescription of Ammodytoides gilli, the tropical eastern Pacific sand lance (Perciformes: Ammodytidae)

Ammodytoides gilli (Bean, 1895) is the correct name for the tropical eastern Pacific sand lance. Its range is extended from Cabo San Lucas, Baja California south to Panama, Ecuador, and the Galapagos Islands. Ammodytes lucasanus Beebe and Tee-Van, 1938 is a junior synonym. Types of both nominal species were re-examined. The species is redescribed based on 50 specimens (42.3-115 mm SL) from 12 lots and is compared with other known species of Ammodytoides. Changes in ontogeny from the smallest known specimen (42.3 mm SL, illustrated) are detailed including reduction in the posterior dorsal fin lobe and development of branched dorsal and anal fin rays.     

Revision of the eastern Pacific species of Gobulus (Perciformes: Gobiidae), with description of a new species

Gobulus birdsongi is described as a new species from the Pacific coast of Panama. The two other known species of Gobulus from the eastern Pacific, Gobulus crescentalis and G. hancocki are redescribed. Gobulus birdsongi differs from other species in the genus in having more numerous second dorsal and anal rays. Gobulus hancocki differs from G. crescentalis in having a much smaller eye. The genus is distinctive in having reversed countershading, with the ventral surface of the body darker than the dorsal surface.     

Nitrite oxidation in the upper water column and oxygen minimum zone of the eastern tropical North Pacific Ocean

Nitrogen (N) is an essential nutrient in the sea and its distribution is controlled by microorganisms. Within the N cycle, nitrite (NO₂⁻) has a central role because its intermediate redox state allows both oxidation and reduction, and so it may be used by several coupled and/or competing microbial processes. In the upper water column and oxygen minimum zone (OMZ) of the eastern tropical North Pacific Ocean (ETNP), we investigated aerobic NO₂⁻ oxidation, and its relationship to ammonia (NH₃) oxidation, using rate measurements, quantification of NO₂⁻-oxidizing bacteria via quantitative PCR (QPCR), and pyrosequencing. ¹⁵NO₂⁻ oxidation rates typically exhibited two subsurface maxima at six stations sampled: one located below the euphotic zone and beneath NH₃ oxidation rate maxima, and another within the OMZ. ¹⁵NO₂⁻ oxidation rates were highest where dissolved oxygen concentrations were <5 μM, where NO₂⁻ accumulated, and when nitrate (NO₃⁻) reductase genes were expressed; they are likely sustained by NO₃⁻ reduction at these depths. QPCR and pyrosequencing data were strongly correlated (r²=0.79), and indicated that Nitrospina bacteria numbered up to 9.25% of bacterial communities. Different Nitrospina groups were distributed across different depth ranges, suggesting significant ecological diversity within Nitrospina as a whole. Across the data set, ¹⁵NO₂⁻ oxidation rates were decoupled from ¹⁵NH₄⁺ oxidation rates, but correlated with Nitrospina (r²=0.246, P<0.05) and NO₂⁻ concentrations (r²=0.276, P<0.05). Our findings suggest that Nitrospina have a quantitatively important role in NO₂⁻ oxidation and N cycling in the ETNP, and provide new insight into their ecology and interactions with other N-cycling processes in this biogeochemically important region of the ocean.     

A preliminary review of the eastern Pacific species of Elacatinus (Perciformes: Gobiidae)

Elacatinus limbaughi is described as new from the Gulf of California. Elacatimus digueti is redescribed and Elacatinus inornatus Bussing is synonymyzed with E. digueti. Data are presented on geographical variation in Elacatinus puncticulatus and E. digueti. Species of the genus Elacatimus are normally associated with coral reefs and several of the species clean parasites from other fishes. Elacatinus is regarded as distinct from Gobiosoma, based on vertebral and other characteristics.