What is the sex ratio of harpacticoid copepods in the deep sea?

The sex ratios of deep-sea harpacticoids have been thought to be greatly skewed toward females. The representation of males is notably more equitable (approximately 1:2) at three deep-sea sites (San Diego Trough: 32°52.4N, 117°45.5W, 1 050 m, January 1987; Porcupine Seabight: 51°36.85N, 12°57.30W, 1 369 m, August 1984; northwest Atlantic, 40°27N, 62°20W, 4 820 m, July 1982, June 1983). This ratio conceals extensive variation at the species level. For some species, males are unknown. For other species, males are more numerous than females. Sampling bias against males can occur and may explain the more extreme reports of male rareness in the literature.     

Ecological investigations of the late-stage phyllosoma and puerulus larvae of the western rock lobster Panulirus longipes cygnus

The distribution and abundance of the late-stage phyllosoma larvae of Panulirus longipes cygnus George and the distribution and densities of the final larval stage, the puerulus, both in the plankton and at settlement along the coast, were investigated. A total of 3,617 late-stage phyllosoma (Stages VI to IX) and 301 puerulus larvae were caught at 187 plankton stations during the July to November periods 1974, 1975 and 1976 off the west coast of Australia between 29°00 to 32°30S and 113°30 to 115°00E. The depth range sampled was 0 to 35 m on the continental shelf and 0 to 90 m off the shelf. During onshore/offshore cruises with similar sampling effort on and off the shelf, 1,169 late-stage phyllosoma larvae were taken, of which only 9 were caught on the shelf, and these near the outer edge. A series of cruises sampling two areas beyond the shelf near 29°30 and 32°00S yielded 2448 late-stage phyllosoma, with greater densities of larvae in the northern location. The settlement of puerulus-stage larvae along the coast in the same geographical range was also greater in the north than in the south. The data from the onshore/offshore cruises showed a definite effect of moon phase on numbers of puerulus larvae caught on the shelf, with higher catches near new moon. The low numbers of puerulus larvae (usually 0, 1 or 2 individuals) caught at all stations showed that the puerulus stage is sparsely distributed in the plankton. Fewer puerulus larvae were present at the surface than at lower depths, but it was not possible to determine a depth preference for the puerulus between 10 m and the lowest depths sampled because of the low catch numbers. No relationships were found between puerulus larvae density and surface-water temperature, salinity, or plankton biomass at each station. Data on the larval distributions indicate that, near the end of their planktonic existence, the majority of the late-stage phyllosoma larvae of P. longipes cygnus are not carried onto the shelf, where mixing of oceanic and continental shelf waters occurs only on the outer third, but are transported southward by oceanic circulation beyond the shelf. The puerulus moults from the last phyllosoma stage beyond the shelf and completes the larval cycle by swimming across the shelf and settling in the shallow reef areas.     

Small-scale pattern of a California current zooplankton assemblage

The small-scale vertical (10s of meters) and horizontal (100s to 1000s of meters) distribution of zooplankton in the California Current near Guadalupe Island, Baja California, Mexico was studied. Vertical distributions were sampled using a vertically-towed Longhurst-Hardy Plankton Recorder (LHPR) which gave a sequence of samples, each integrated over about 5 m, from 250 m to the surface. Because of the sampling biases of the LHPR, details in vertical structure of less than 15 to 20 m were not considered. The pattern of the vertical tows and the variability of the integrated counts of species were used to infer horizontal distribution. Four series of 8 tows each were taken around noon and midnight over a 2-day period. Four of the 8 tows in each series were randomly positioned within 2000 m of a parachute drogue (first day) or a fixed geographic position (second day); four were replicate tows taken at the drogue or the fixed position. Sixty-seven taxonomic categories were counted. The replicate tows, separated by no more than a few hundred meters, gave more similar vertical profiles for species than did the random tows, with separations of 100s to 1000s of meters. The night replicate tows showed less variability in depth distribution than did either the night random or any of the day tows, leading to the hypothesis that the vertical distributions observed were generated by interactions of the organisms' diel behavior with internal waves. Variability of abundance estimates using the integrated counts was the same for both replicate and random tows, indicating that horizontal patches may be smaller than 100 m. No evidence was found for a day-night change in patch size, or for a consistent overlapping of patches of different species. Replicate tows gave more similar estimates of community structure (relative proportions of species) than did random tows. Overall day community structure was more similar between tows than night structure. Similarities in species' proportions of any random tow to the replicate tows or to other random tows of a series decreased with increasing distance between the tows being compared. This decrease was greater for the night samples, suggesting that community structure is more heterogeneous at night.This study is based in part on a dissertation submitted in partial fulfillment of the requirements for the Ph.D. degree at the University of California, San Diego, and was supported by National Science Foundation Grant GB 12413 and the Marine Life Research Program of the Scripps Institution of Oceanography.     

Hyperiid amphipods in the eastern part of the South Pacific gyre

Studies were made of Amphipoda Hyperiidea collected in 1987 with a pelagic trawl in the South Pacific anticyclonic gyre in the vicinity of the Nazca and Sala y Gómez ridges (17°35 to 26°01S, 80°10 to 100°50W), at depths ranging from 50 to 300 or 600 m. Forty-three hauls contained 7 198 specimens, comprised of 119 species within 43 genera. Two of the species appeared to be new for science; two others were found in the Pacific Ocean for the first time. A comparison with hyperiid collections from other tropical Pacific regions revealed great stability of oceanic faunal composion. However, the collections differed considerably in their dominant species. Furthermore, comparison of Hyperiidea from various parts within the investigated area of the South Pacific gyre also reflected differences in dominant species. The degree of these mesoscale spatial differences was comparable to that among the central regions of the northern and southern anticyclonic gyres.     

Spatial mesoscale patterns of West Pacific picophytoplankton as analyzed by flow cytometry: their contribution to subsurface chlorophyll maxima

Vertical distributions of picophytoplankton (ppp) (<2 m) were studied by ship-board flow cytometry during two cruises in Western Pacific waters to Palau and to Australia in 1990. Weak red-fluorescing small ppp, supposed to be free-living prochlorophytes (Chisholm et al. 1988), were abundant in the area surveyed. These ppp, designated the prochlorophytes, were abundant in the surface waters (>10⁴ cells ml^-1) at the northern region (27°03N; 7°11N) in November, whereas in December at the southern tropical stations (0°23.54S; 9°20.30S; 13°50.6S), they formed subsurface maximum layers (>10⁵ cells ml^-1) on a nitracline at a depth of 3.5 to 5.4% surface irradiation. Their fluorescence intensity increased with depth below 10% surface irradiation. The prochlorophytes at a depth of 1% surface irradiation had ten times higher fluorescence than those at the surface layer. The total fluorescence intensity of the prochlorophytes accounted for 32 to 63% of the sum of the total fluorescence intensity of all fluorescing phytoplankton detected at subsurface chlorophyll maxima in the tropical area. These results suggest that distribution of the prochlorophytes is greatly affected by nitracline and by light intensity and that their chlorophyll is a major contributor to the subsurface chlorophyll maximum in the pelagic West Pacific Ocean.     

Identification of Amazon River water at Barbados,W. Indies,by salinity and silicate measurements

Salinity and silicate concentrations were studied at about fortnightly intervals for 21 months at a station near Barbados, W. Indies; latitude 13°15 N, longitude 59°42 W. A sensitive inverse correlation was found to exist at 5 and 25 m, but not at greater depths. Salinity near the surface varied between 33.5 and 36.0, and silicate between a little less than 1 and 4 g at/l. Low salinity water, rich in silicate, was found from February to July; salinity increased and silicate decreased from September to December. It is argued that the low salinity water at Barbados can be identified with the areas of reduced salinity found by Ryther et al. (1967) about latitude 8° to 10° N, longitude 50° to 55° W, and that this water originates from the Amazon River. Local precipitation does not seem to be a significant factor.     

Transformation of soft coral (Coelenterata: Octocorallia) terpenes by Ovula ovum (Mollusca: Prosobranchia)

The faecal pellets from specimens of the prosobranch mollusc Ovula ovum found feeding on the soft coral Sarcophyton sp. at Eclipse Island, Palm Island Group (18°46S; 146°33E) in November 1980 were analysed. The only terpene present in the faeces, 7,8-deoxysarcophytoxide, differed from the major constituent of the soft coral, sarcophytoxide, suggesting that the latter had been transformed into the former within the cowrie. This transformation is not trivial, and could not be produced simply by acid catalysis. Subsequent analysis of tissues dissected from different regions of O. ovum indicates that the transformation is probably effected by enzymes in the digestive diverticula stomach region of the prosobranch. The transformed compound is significantly less toxic to the mosquito fish Gambusia affinis Baird and Girard than the ingested compound.     

Response of gametophytes of Ecklonia radiata (Laminariales) to temperature in saturating light

Gametophytes of Ecklonia radiata (C.Ag.)J.Ag. from two New Zealand locations with different field temperature ranges were exposed to temperatures of 5° to 26°C in saturating light. Plants from Goat Island Bay (Lat. 36° 16S, Long. 174°48E) grew in 9.3° to 25°C and reproduced in 9.3° to 24°C. There was no growth at 8°C and plants died at 26°C. Plants from the cooler location, Houghton Bay (Lat. 41°20S, Long. 174°40E), grew from 8° to 24°C and reproduced up to 15°C but not at 21.5°C. The plants did not grow at 6°C and died at 26°C. The timing of the first cell division and subsequent growth rate were retarded close to the upper and lower tolerance limits. Reproduction was a broad optimum of roughly 12° to 20°C. Within this range, fertile female gametophytes grown at lower temperatures had fewer, larger cells and thus fewer potential ova than those grown at higher temperatures.     

Reproductive cycle of Golfingia margaritacea,a bipolar sipunculan,in subantarctic water

The reproductive cycle of the bipolar sipunculan Golfingia margaritacea collected from Ushuaia, Argentina (54°49 S; 68°13W) in 1986 and 1987 is reported. The population sampled showed a sex ratio of 1:1. Males, however, frequently outnumbered females. Measurements of coelomic oocytes delineated an annual reproductive cycle. Small oocytes were present in the coelom all year: a subpopulation began to increase size about the middle of spring and reached its maximum size in late summer. Spawns may occur from the end February to April. May is characterized by resorption of large oocytes. Monthy monitoring of the gonads revealed mitotic activity and a continuous release of gametocytes to the coelom. Parasites were detected in the gonads. Large coelomic oocytes were also present in the coelom during the same season in the Northern and Southern Hemispheres, but egg sizes were significantly larger in boreal populations.     

Response of a soft-bottom harpacticoid community to stingray (Dasyatis sabina) disturbance

The recolonization by harpacticoid copepods of patches disturbed by stingrays [Dasyatis sabina (LeSeur)] feeding in a subtidal (2–3 m depth) site off the Florida gulf coast (Lat. 29°54.55N, Long. 84°31.45W) was followed. Samples from disturbed patches could no longer be distinguished from control samples in terms of numbers of harpacticoids 29 h after disturbance. No species became significantly disproportionately abundant during the recovery suggesting that small-scale natural disturbances are not an important organizing force in this community.     

An instance of bacterial inhibition in oceanic surface water

Water from the 150 surface film 50 miles north of Puerto Rico at 19°30 N, 66°30W supported only a negligible microflora compared to that of adjacent stations. Bacteriostasis was indicated when a ten-fold dilution of the sample resulted in a ninety-fold increase in cultivable microorganisms. The surviving organisms, atypical pseudomonads, were biochemically inactive in comparison to isolates from the other stations. Net phytoplankters at this station were similar in relative composition and abundance to those at the adjacent station.     

Distribution of chlorophyll,carotenoids and phytoplankton in relation to certain environmental factors along the central west coast of India

Distribution of chlorophyll pigments, carotenoids and abundance of phytoplankton in relation to certain environmental factors of the nearshore waters off the central west coast of India (latitudes 15°30 to 18°30N) were studied monthly at 7 stations during 1970/1971. Changes in the hydrographical factors and the biological processes occurring in the region during different months appear to be influenced by the pattern of upwelling along the northern and southern parts of the west coast of India. The pigment concentration shows a marked decrease in October, but is followed by a slow but steady rise, which reaches its maximum in April/May. A slightly smaller maximum is noticed in December/January. The composition of various chlorophyll pigments and carotenoids indicated the physiological state of phytoplankton populations during different months in the region investigated. Abundance of specific phytoplanktonic elements, consisting mainly of diatoms, in space and time, characterises the waters of the central west coast of India, indicating a clear succession of species.     

Capillary supply and mitochondrial volume density in the axial muscles of the mesopelagic teleost Argyropelecus hemigymnus

Quantitative measurements have been made on the ultra-structure and capillary supply to the axial muscles of the mesopelagic hatchet fish Argyropelecus hemigymnus (Cocco, 1829). Fish were collected at Eastern North Atlantic Ocean Station 10244, 32°48N; 31°15W during November 1980, from a depth of 480 to 550 m. Mitochondria with densely packed cristae occupy 44.3% of slow-fibre volume. Each myofibril is in direct contact with a mitochondrion. Compared with other fishes studied, the capillary supply to A. hemigymnus slow fibres is poorly developed. The average number of capillaries per fibre is 0.9, such that each m of capillary contact supplies 0.011 m² of fibre cross-sectional area. The capillary surface area (m²) supplying 1 m³ of slow-fibre mitochondria is 0.17 in anchovy (Engraulis encrasicolus), 0.14 in rat-fish (Chimaera monstrosa), 0.14 in tench (Tinca tinca), 0.16 in catfish (Clarias mossambica), and only 0.025 for A. hemigymnus. It is suggested that, relative to the former species, some modifications in factors determining tissue oxygenation (e.g. myoglobin concentrations, blood flow, perfusion distribution or haemoglobin) and/or mitochondrial respiration rate are required in order to match oxygen supply and demand to the slow muscle in A. hemigymnus.     

Biremis blandi (Polychaeta: Terebellidae), new genus,new species,caught by D.S.R.V. “Alvin” in the Tongue of the Ocean,new providence,Bahamas

Biremis, n. gen., characterized by an enlarged cephalic lobe, achaetous thoracic segments, and abdominal bilobed uncinigerous pinnules, lacks eyes and branchiae and is, thus, grouped with the subfamily Polycirrinae of the Terebellidae. Biremis blandi, n. sp., has prominent longitudinal muscular ventral ridges, lacking ventral glandular scutes. The avicular uncini, arranged in a single row on each lobe of each abdominal pinnule, are very similar to those of Polycirrus. The new species, collected from D.S.R.V. Alvin, was observed resting on and swimming over the sloping walls of the Tongue of the Ocean (25° N; 77°35 W), at 600 m depth. Its ability to swim may be a requirement for survival on an unstable substratum.Contribution No. 2891 from the Woods Hole Oceanographic Institution.     

Feeding mechanism of Pelagia noctiluca (Scyphozoa: Semaeostomeae); laboratory and open sea observations

The behaviour of the oral arms of Pelagia noctiluca (Forsskål) has been investigated in open sea predation and in predation induced both in the laboratory and the natural environment. Specimens were first studied in the field and then collected from coastal aggregations in the Gulf of Trieste, North Adriatic Sea, in December 1985 (Lat. 13°40 E, Long. 45°42 N) and in June 1986 (Lat. 13°39 E, Long. 45°43 N). The results of laboratory experiments and in situ observations, recorded on videotapes and photographs, show that the marginal tentacles are utilized to: (1) paralyze the prey; (2) contract and bend inward towards the nearest oral arm. Occasionally the tentacle does not contract and the prey is released; thus prey selection may occur. The oral arms are therefore involved in the: (1) transport of prey from the tentacle to the gastric cavity; (2) catching of motionless prey; (3) anchoring the medusa to the substratum. A similar feeding pattern can explain the survival of several specimens of P. noctiluca near the bottom during the winter of 1985/1986 in the Gulf of Trieste (North Adriatic Sea) in spite of the severe climatic conditions.     

Benthic recruitment and manganese crust formation on seamounts

Hydrogenous ferromanganese crusts are a common feature of oceanic seamounts, forming slowly (predominantly at 1 to 5 mm/m.yr through precipitation from seawater, by a process that is poorly understood yet producing crusts of thicknesses up to 240 mm. It remains unexplained why crusts are not overwhelmed by more rapid biological processes occurring simultaneously. The present study of recruitment by sessile invertebrates to ferromanganese crusts and basalt on Cross Seamount (18°40N; 158°17W), North Pacific Ocean, from July 1988 to February 1990 supports the view that hydrogenesis alone may not adequately account for crust formation. Here, mediation of crust growth by benthic Foraminifera and inhibition of ferromanganese oxide precipitation by high abundances of sessile macrofauna are suggested as two interactive biological processes relevant to crust accretion. Larval supply is an important factor in the distribution of sessile macrofauna on oceanic seamounts.     

Ecdysial rhythms in megalopae and first instars of the Dungeness crab Cancer magister

Diel molting cycles of megalopae and first instar Dungeness crabs Cancer magister Dana captured in the Grays Harbor estuary (46° 55N; 124° 05 W) in May 1991 were studied under laboratory conditions. Sixtyone percent of the megalopae and 76% of the first instar crabs molted during periods of ambient darkness under a normal light — dark diel regime, and molting pattern was not affected by changes in the photoperiod (24 h daylight or 24 h darkness). Time until metamorphic molt increased as conspecific density increased. Habitat type (shell or mud) did not affect time until molt of megalopae and first instar crabs, nor did it affect daily molting rhythm of first instars. We hypothesize that nightly ecdysis of megalopae and first instar Dungeness crabs and density-dependent molting may be an adaptive response to predation and cannibalism among young-of-the-year.Contribution No. 875 from the School of Fisheries, WH-10, University of Washington, Seattle, Washington     

Deep-sea harpacticoid copepod diversity maintenance: The role of polychaetes

Several models to account for enhanced diversity in the deep sea have been proposed, but the available natural history information has been inadequate to distinguish among them. In particular, few data exist on patterns of co-occurrence among species. At 1220 m depth in the San Diego Trough (32°35.75N; 117°29.00W), harpacticoid copepod species covary significantly with polychaetes when the polychaetes are combined into functional groups on the basis of feeding type and mobility. In particular, harpacticoid species tend to avoid polychaetes which are sessile surface-deposit feeders. The results provide support for models in which disturbance/predation plays an important role in maintaining deep-sea diversity.Contribution No. 15 from Expedition Quagmire.     

Relationship of daily and circatidal activity rhythms of the fiddler crab,<Emphasis Type="Italic"> Uca princeps</Emphasis>, to the harmonic structure of semidiurnal and mixed tides

Intertidal organisms may employ circatidal rhythms to track the tidal cycle, but tidal patterns may vary within a species range and necessitate adaptation to the local tides. Circatidal rhythms were examined in populations of the eastern Pacific fiddler crab Uca princeps (Smith) from four sites with differing tidal characteristics, La Paz (24°10N; 110°21W), San Blas (21°33N; 105°18W) and Manzanillo (19°6N; 104°24W), Mexico (lower amplitude, mixed semidiurnal tides) and Mata de Limon, Costa Rica (9°55N; 84°43W) (high-amplitude, semidiurnal tides). Local tides were characterized by harmonic constants of M₂, S₂, K₁, and O₁, partial tides that largely determine their semidiurnal and diurnal features. Rhythmic structure in continuously recorded locomotor activity of individual crabs held under laboratory conditions was described by cosinor and periodogram methods of time-series analysis. Both daily and circatidal rhythms were found in crabs studied in light–dark cycles set to local conditions at the time of collection. Crabs at all four sites shared a tendency toward bimodality, with a mid-morning activity peak and varying degrees of nocturnal activity. Circatidal rhythms closely matching the period of the 12.42-h M₂ partial tide were consistently present at all sites except Manzanillo. At Mata de Limon, the circatidal rhythm clearly dominated locomotor activity, but was strongly modulated by a daily rhythm in a repeating pattern at a semilunar interval. In contrast, the amplitude of the daily rhythm was higher than that of the circatidal rhythm in crabs from the three mixed tide sites on the Mexican coast, where the tidal pattern is dominated by a diurnal inequality arising from the diurnal K₁ and O₁ partial tides. These results suggest that populations of U. princeps use both daily and circatidal timing systems to track local forms of the tide generated by their M₂, S₂, K₁, and O₁ geophysical counterparts.Communicated by J.P. Grassle, New Brunswick     

Community structure in Florida Escarpment seep and Snake Pit (Mid-Atlantic Ridge) vent mussel beds

Comparisons between invertebrate communities hosted by similar foundation species under different environmental conditions permit identification of patterns of species distributions that might be characteristic of the different ecosystems. Similarities and differences in community structure between two major types of chemosynthetic ecosystems were assessed by analyzing samples of invertebrates associated with Bathymodiolus heckerae Gustafson et al. mussel beds at the Florida Escarpment seep (Gulf of Mexico, 26°01.8N; 84°54.9W; October 2000) and B. puteoserpentis von Cosel et al. mussel beds at the Snake Pit vent (Mid-Atlantic Ridge, 23°22.1N; 44°56.9W; July 2001). Macrofaunal species richness was nearly twice as high in the seep mussel bed compared to the vent mussel bed, and only a single morphospecies, the ophiuroid Ophioctenella acies Tyler et al., was shared between the sites. Similarities between the two faunas at higher taxonomic levels (genus and family) were evident for only a small percentage of the total number of taxa, suggesting that evolutionary histories of many of these seep and vent macrofaunal taxa are not shared. The taxonomic distinctiveness of the seep and vent mussel-bed macrofaunal communities supports the hypothesis that environmental and oceanographic barriers prevent most taxa from occupying both types of habitats. Macrofaunal community heterogeneity among samples was similar in seep and vent mussel beds, indicating that spatial scales of processes regulating community variability may be similar in the two types of ecosystems. Suspension feeders were not represented in the macrofauna of seep or vent mussel beds. Primary consumers (deposit feeders and grazers) contributed more to the total abundance of macrofauna of seep mussel beds than vent mussel beds; secondary consumers (polychaetes and shrimp) were more abundant in the vent mussel beds.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-004-1304-z.Communicated by J.P. Grassle, New Brunswick