Egg size and reproductive adaptations among Arctic deep-sea copepods (Calanoida,<Emphasis Type="Italic"> Paraeuchaeta</Emphasis>)

Reproductive strategies of the four congeneric and sympatric calanoid copepods Paraeuchaeta glacialis, P. norvegica, P. barbata, and P. polaris were studied in the Arctic Greenland Sea. Females of all species produce egg sacs and carry their brood attached to the genital opening until the offspring hatch. However, egg size and lipid content as well as clutch size and the fraction of females carrying egg masses show characteristic differences among the four species. P. glacialis and P. norvegica produce large numbers (37 to more than 50) of relatively small eggs, whereas P. barbata and P. polaris rely on small numbers (10 to 19 and 4 to 6, respectively) of large eggs with a high energy content. There is no correlation between female body size and egg size or clutch size, respectively. Females of the smallest species, P. polaris, produce relatively large eggs and show the highest energetic investment per egg. In contrast, energetic investment per clutch is highest in P. glacialis. Reproductive adaptations appear to be strongly related to the depth range inhabited by the respective species. In the central Greenland Sea P. glacialis and P. norvegica occur in the epipelagial and upper mesopelagial, whereas the other two species inhabit lower mesopelagic to bathypelagic depths. Thus, egg size increases with depth of occurrence, whereas clutch size is inversely correlated with depth. This observation leads to the hypothesis that the evolution of large eggs in deep-sea copepods may enable hatchlings to rely on a lecithotrophic development and thus represents a successful adaptation to cope with the limited food supply at great depths, whereas high offspring numbers in epipelagic species compensate for higher predation risks in the euphotic zone.Communicated by H.-D. Franke     

Larval,megalopal and early juvenile development in Pagurus granosimanus (Stimpson, 1859) (Decapoda: Anomura: Paguridae) reared in the laboratory

Summary

The larval, megalopal and early juvenile stages of Pagurus granosimanus are described, illustrated and compared with other North Pacific species of the genus. Morphologically, the zoeae of P. granosimanus appear most similar to the Japanese P. brachiomastus in the majority of characters, but share the endopodal setation of the third maxilliped with a second Japanese species, P. pectinatus. The megalopae of P. granosimanus are unlike those of other North Pacific species in having 5+5 marginal setae on the telson, rather than the customary 4+4, or less frequent 3+3. Comparison of juvenile characters is limited to pleopodal changes among the regional species for which data are available. P. granosimanus is unusual in undergoing complete pleopodal loss at the second crab stage with return of left pleopods in the fourth stage.     

Molecular determination of kleptoplast origins from the sea slug Plakobranchus ocellatus (Sacoglossa,Gastropoda) reveals cryptic bryopsidalean (Chlorophyta) diversity in the Hawaiian Islands

The sacoglossan sea slug species complex Plakobranchus ocellatus is a common algivore throughout the tropical Pacific, including the Hawaiian Islands. Plakobranchus ocellatus is kleptoplastic—it sequesters and retains algal chloroplasts—a characteristic that can be exploited to molecularly characterize diminutive bryopsidalean algae that are typically difficult to locate, collect, and identify. Previous DNA barcode analyses of both P. ocellatus and its kleptoplasts have been conducted primarily in the western Pacific and have only minimally sampled the most eastern populations in the Hawaiian Islands. Using two chloroplast markers, rbcL and tufA, kleptoplast samples from an Oahu population of P. ocellatus were amplified and cloned to identify their algal sources. Plakobranchus ocellatus sequester chloroplasts from up to 11 bryopsidalean algal species, all but one being diminutive in thallus size. Notably, eight of the detected algal species were new records to the Hawaiian Islands. A sequestration preference study demonstrated that the O‘ahu population of P. ocellatus preferentially sequesters chloroplasts from diminutive, epilithic taxa. Using coxI barcoding of P. ocellatus, we showed the O‘ahu population to be part of a clade that includes sequences from the neighboring island Maui, Australia, and the Philippines. The use of P. ocellatus as a novel sampling tool allows the exploration of the green algal community diversity and composition at a fine scale.     

The ectoparasitic barnacle Anelasma (Cirripedia,Thoracica, Lepadomorpha) on the shark Centroscyllium nigrum (Chondrichthyes,Squalidae) from the Pacific sub-Antarctic

We report the occurrence of the ectoparasitic lepadomorph barnacle Anelasma sp. on the deep-sea squaloid shark Centroscyllium nigrum from the Pacific sub-Antarctic off southern Chile. Anelasma has previously been documented only from the northeast Atlantic on the squaloid shark Etmopterus spinax; this new record extends the known range of Anelasma into the Pacific Ocean and into the Southern Hemisphere, and documents a new host for this parasitic barnacle.     

Rhytisma polaris: morphological and molecular characterization of a new species from Spitsbergen Island,Norway

Rhytisma polaris, which causes tar spot disease on Salix polaris on Spitsbergen Island, is described. The most characteristic morphological feature of this new species are ascospores distinctly broader than those of other Rhytisma species. rDNA ITS and LSU sequence analysis also indicated that R. polaris is sufficiently distinct from other Rhytisma species to justify the new species status.     

Occurrence of the benthic trachymedusa Ptychogastria polaris Allman, 1878 (Cnidaria: Hydrozoa) off Northeast Greenland and in the northern Barents Sea

The trachymedusa Ptychogastria polaris Allman, 1878 has been identified in seabed photographs from high-Arctic shelves and upper continental slopes off Northeast Greenland and in the northern Barents Sea. It was found to be a common epifaunal element, being present at 34 of 57 stations in 40- to 495-m depth and at 7 of 11 stations in 70- to 330-m depth, respectively. All specimens recorded in the photographs either sat directly at, or hovered very closely (≤ about 1 cm) over, the sea bed, indicating a primarily epibenthic life style of this hydrozoan species. The small-scale (i.e. within-station) distribution of medusae was rather patchy, with frequencies along photographic transects – consisting of 35–73 pictures distributed over seabed strips of 150- to 300-m length – varying from 1 to 58% off Northeast Greenland and from 1 to 34% in the Barents Sea. Absolute maximum density was 6 ind m⁻², and station mean abundances ranged from 0.01 to 0.91 ind m⁻² and from 0.01 to 0.52 ind m⁻², respectively. Values tended to decrease with water depth, albeit significantly only off Northeast Greenland. Otherwise, no clear relationships to environmental conditions, such as geomorphology or near-bottom water hydrography, were detected. Circumstantial evidence suggests that seabed granulometry and potential food supply are important distribution determinants. However, further investigations are required to identify more stringently the key factors controlling the distribution of P. polaris. Received: 8 September 1997 / Accepted: 12 September 1997     

Diversity and distribution of Laurencia sensu stricto (Rhodomelaceae,Rhodophyta) from the Mexican Pacific,including L. mutueae sp. nov.

The alpha diversity of Laurencia sensu stricto, as well as the majority of the other algal groups along the Mexican Pacific, was underestimated because very few studies had incorporated the use of molecular markers in taxonomic studies, which would allow a more realistic estimation of diversity, incluing new records and new species. The records of Laurencia s.s. for the Eastern Pacific (California, USA to Chile) currently represent 23% of its richness worldwide. In this work, we proposed an updated census of the currently recognized species of Laurencia s.s. for the Mexican Pacific. This checklist reported the occurrence of 22 species that represent 16% of the 137 species worldly recorded. We further included taxonomic remarks, type localities, and a detailed distribution for each species. In addition, we proposed a new species for this region, Laurencia mutueae sp. nov., based on morphological observation as well as phylogenetic analyses. The distribution in the Mexican Pacific revealed that the highest records of species were for the sub‐temperate region, while the localities along the Mexican tropical Pacific were poorly recorded. The scarcity of floristic affinities between the eastern and the western and central parts of the North Pacific Ocean was hypothesized to be a consequence of a strong isolation and hard barriers, such as the water masses between these regions.     

Seasonal shift in factors controlling net ecosystem production in a high Arctic terrestrial ecosystem

We examined factors controlling temporal changes in net ecosystem production (NEP) in a high Arctic polar semi-desert ecosystem in the snow-free season. We examined the relationships between NEP and biotic and abiotic factors in a dominant plant community (Salix polaris–moss) in the Norwegian high Arctic. Just after snowmelt in early July, the ecosystem released CO₂ into the atmosphere. A few days after snowmelt, however, the ecosystem became a CO₂ sink as the leaves of S. polaris developed. Diurnal changes in NEP mirrored changes in light incidence (photosynthetic photon flux density, PPFD) in summer. NEP was significantly correlated with PPFD when S. polaris had fully developed leaves, i.e., high photosynthetic activity. In autumn, NEP values decreased as S. polaris underwent senescence. During this time, CO₂ was sometimes released into the atmosphere. In wet conditions, moss made a larger contribution to NEP. In fact, the water content of the moss regulated NEP during autumn. Our results indicate that the main factors controlling NEP in summer are coverage and growth of S. polaris, PPFD, and precipitation. In autumn, the main factor controlling NEP is moss water content.     

Clipperton Atoll (eastern Pacific): oceanography,geomorphology, reef-building coral ecology and biogeography

Coral reef geomorphology and community composition were investigated in the tropical northeastern Pacific during April 1994. Three areas were surveyed in the Revillagigedo Islands (Mexico), and an intensive study was conducted on Clipperton Atoll (1,300 km SW of Acapulco), including macro-scale surface circulation, sea surface temperature (SST) climatology, geomorphology, coral community structure, zonation, and biogeography. Satellite-tracked drifter buoys from 1979–1993 demonstrated complex patterns of surface circulation with dominantly easterly flow (North Equatorial Counter Current, NECC), but also westerly currents (South Equatorial Current, SEC) that could transport propagules to Clipperton from both central and eastern Pacific regions. The northernmost latitude reached by the NECC is not influenced by El Niño-Southern Oscillation (ENSO) events, but easterly flow velocity evidently is accelerated at such times. Maximum NECC flow rates indicate that the eastern Pacific barrier can be bridged in 60 to 120 days. SST anomalies at Clipperton occur during ENSO events and were greater at Clipperton in 1987 than during 1982–1983. Shallow (15–18 m)and deep (50–58 m) terraces are present around most of Clipperton, probably representing Modern and late Pleistocene sea level stands. Although Clipperton is a well developed atoll with high coral cover, the reef-building fauna is depauperate, consisting of only 7 species of scleractinian corals belonging to the generaPocillopora, Porites, Pavona andLeptoseris, and 1 species of hydrocoral in the genusMillepora. The identities of the one Pocilpopora species and one of the twoPorites species are still unknown. Two of the remaining scleractinians (Pavona minuta, Leptoseris scabra) and the hydrocoral (Millepora exaesa), all formerly known from central and western Pacific localities, represent new eastern Pacific records. Scleractinian corals predominate (10–100% cover) over insular shelf depths of 8 to 60m, and crustose coralline algae are dominant (5–40% cover) from 0.5 to 7m. Spur and groove features, constructed of alternating frameworks ofPocillopora andPorites, and veneered with crustose coralline algae, are generally well developed around most atoll exposures. Although crustose coralline algae predominate in the breaker zone (with up to 100% cover), a prominent algal ridge is absent with only a slight buildup (ca. 10 cm) to seaward. Frequent grazing by the pufferfishArothron meleagris results in the removal of large amounts of live tissue and skeleton fromPorites lobata. Acanthaster planci is present, but rare. The grazing of large diadematid sea urchins, (2 species each ofDiadema andEchinothrix) on dead corals cause extensive erosion in some areas. Large numbers of corals on the 15–18 m terrace had recently suffered partial (P. lobata, 60–70% maximum of all colonies sampled) or total (Pocillopora sp., 80% maximum) mortality. The lengths of regenerating knobs and the rates of linear skeletal growth inP. lobata, determined by sclerochronologic analysis, indicated a period of stress during 1987. Massive skeletal growth is significantly higher at intermediate (16–17 m) than shallow (6–8 m) depths with mean extension rates of 1.5 mm yr^–1 inP. lobata and 1.4 mm yr^–1 inP. minuta at intermediate depths. Skeletal growth inP. lobata was depressed during the 1987 El Nifio event at Clipperton. The branching coralPocillopora sp. demonstrated high and similar skeletal growth rates at both shallow (25.4 mm yr^–1) and intermediate (26.5 mm yr^–1) depths. The presence of widely distributed Indo-Pacific zooxanthellate corals at Clipperton and the Revillagigedo Islands indicates that these NE Pacific Islands probably serve as a stepping stone for dispersal into the far eastern Pacific region.     

AN ATLANTIC POPULATION OF PIKEA CALIFORNICA (DUMONTIACEAE,RHODOPHYTA)1

The marine red alga Pikea californica Harvey, previously known only from the east coast of Japan and the west coast of North America, was found in 1983 to be abundant in the surge zone throughout the Isles of Scilly archipelago, off SW England. Examination of herbarium material showed that the population was present in 1967. All plants observed in July 1983 and September 1984 were sterile, but reproductive male and female plants were collected in November 1983. The habitat and phenology of P. californica in the Isles of Scilly closely resemble those of Pacific populations. English plants are vegetatively and reproductively identical to the type and other California specimens. They can easily be distinguished from Sphaerococcus coronopifolius Stackhouse (Sphaerococcaceae, Gigartinales), the most similar species in the flora of the British Isles, by the presence in transverse sections of several lacunae, representing axial and whorl-branchlet filaments, in contrast to the single axial filament of S. coronopifolius. It is possible that the Isles of Scilly population of P. californica is a relict of a species once more widespread, but it seems more likely that it is another example of the well-established pattern of marine introductions into the British Isles from the North Pacific. The range of temperature regimes occupied by P. Californica in the Pacific suggests that the species could become more widespread in Europe, but at present it appears to be confined to the Isles of Scilly.     

Chlorogenic acid as an antiherbivore defence of willows against leaf beetles

In the leaves of 13 Finnish willow species, the content of a phenolic, chlorogenic acid, was found to vary from 0 up to 18 mg g^–1 D.W. Effects of pure chlorogenic acid on insect feeding behaviour were tested using four common leaf beetle species which are in the field mainly found on willows with low-chlorogenic acid leaves. One species, Lochmaea capreae L., was invariably deterred by pure chlorogenic acid applied in naturally occurring concentrations on the willow leaves. Accordingly, in 2-choice laboratory feeding trials L. capreae was found to prefer low-chlorogenic acid leaves of four willow species over high-chlorogenic acid leaves of Salix pentandra L. and S. myrsinifolia Salisb. When presented on the leaves of S. phylicifolia L, pure chlorogenic acid inhibited also the feeding by Phratora polaris Sp.-Schn. Instead, chlorogenic acid had no significant effect on Ph. polaris when it was presented on the leaves of another willow S. cinerea L. In laboratory, Ph. polaris did not show general preference for willow species with low chlorogenic acid content in their leaves. Thus, the response of Ph. polaris to chlorogenic acid seems to depend on the plant species. Apparently variation in other traits such as leaf hairyness may easily override the potential effect of chlorogenic acid content on Ph. polaris. To two other leaf beetle species, Galerucella lineola F. and Plagiodera versicolora Laich., chlorogenic acid is an ineffective deterrent even at unnaturally high concentrations. In laboratory, G. lineola and P. versicolora did not prefer willows with low chlorogenic acid content in their leaves. Thus, among four studied leaf beetle species, only L. capreae seems to be clearly affected by this phenolic. Therefore, overall importance of chlorogenic acid as a defence against willow-feeding leaf beetles appears to be very limited.     

Scymnodon plunketi (Waite, 1910): a junior synonym of Scymnodon macracanthus (Regan, 1906) (Somniosidae: Elasmobranchii)

The taxonomic status and validity of Scymnodon macracanthus (Regan, 1906) and Scymnodon plunketi (Waite, 1910) are revised in light of new material from the Southern Pacific and Indian Oceans. Despite being historically accepted as distinct taxa, recent studies suggested the possibility that these species could represent a single taxon. Morphometrics, meristics and morphology of dermal denticles show that S. plunketi is indeed a junior synonym of S. macracanthus. Previous distinctive characters proved to be the result of intraspecific variation. S. macracanthus is therefore redescribed including an updated comparative diagnosis for the genus Scymnodon in the family Somniosidae.     

On Gaussia Wolfenden (Copepoda,Calanoida, Metridinidae)

Aspects of the female genital segment with and without attached couplers and enclosed spermatophores are studied of Gaussia specimens collected in the SW Atlantic and SE Pacific. A new species found in the SW Atlantic, Gaussia asymmetrica, is proposed.     

Phylogeography of the Hypnea musciformis species complex (Gigartinales,Rhodophyta) with the recognition of cryptic species in the western Atlantic Ocean

Populations of the marine benthic red macroalgae Hypnea musciformis and Hypnea pseudomusciformis along the Atlantic and Pacific Oceans were tested for phylogeographic structure using the DNA barcode COI‐5P combined with rbcL for the construction of the phylogenetic tree. Strong patterns of genetic structure were detected across 210 COI‐5P DNA sequences, and 37 COI‐5P haplotypes were found, using multiple statistical approaches. Hypnea musciformis was found in the Northeast and Northwest Atlantic, the Mediterrean Sea, Namibia, and along the Pacific coast of Mexico. Two new putative species were detected, Hypnea sp. 1 in the Caribbean Sea and Hypnea sp. 2 in the Dominican Republic. Three distinct marine phylogeographic provinces were recognized in the Southern Hemisphere for H. pseudomusciformis: Uruguay, South‐Southeast Brazil, and Northeast Brazil. The degree of genetic isolation and distinctness among these provinces varied considerably. The Uruguay province was the most genetically distinct, as characterized by four unique haplotypes not shared with any of the Brazilian populations. Statistically significant results support both, isolation by distance and isolation by environment hypotheses, explaining the formation and mantainance of phylogeographic structuring along the Uruguay‐Brazil coast. Geographic, taxonomic and molecular marker concordances were found between our H. pseudomusciformis results and published studies. Furthermore, our data indicate that the Hawaiian introduced populations of H. musciformis contain Hypnea sp. 1 haplotypes, the current known distribution of which is restricted to the Caribbean.     

New deep-sea Nematoda (Enoplida,Thoracostomopsidae, Oncholaimidae,Enchelidiidae) from a manganese nodule area of the eastern South Pacific*

Five new nematode species are described from a mangancsc nodule area of the abyssal eastern South Pacific: Enoploides tyrannis sp. n., Paramesacanthion abyssorum sp. n., P. forcepssp. n. (all three Thoracostomopsidae), Phylloncholaimus immanis gen. et sp. n. (Oncholaimidac), and Eurystomina absoluta sp. n. (Enchelidiidae). They are characterized by large size (body length 5000–23000 μm), short tails (c = 17–33), and strongly cuticularizcd, barrel-shaped buccal cavities with large teeth. With the exception of one male of E. tyrannis from the surface of a manganese nodule, all other specimens were found in the sediment. The new species are sporadic in distribution and represented by few individuals.     

PseudocalanusSpecies (Copepoda: Calanoida) in Avachinskaya Bay,Southeastern Kamchatka

The species composition of copepods of the genus Pseudocalanusthat dominate the zooplankton in Avachinskaya Bay was studied from samples collected in 1988. Three species were identified: P. minutus(Kröyer), P. newmani(Frost), and P. acuspes(Giesbrecht). The latter species is the first record for the fauna of the northwestern Pacific Ocean. Synonymy and original figures are given; the seasonal variations in the morphometric features and characteristics of Pseudocalanusare discussed.     

A phylogeny of Pacific fiddler crabs of the subgenus Minuca (Crustacea,Brachyura, Ocypodidae: Uca) with the description of a new species from a tropical gulf in Pacific Costa Rica

The phylogeny of all Pacific fiddler crab representatives of the subgenus Minuca Bott, 1954 (sensu Beinlich and von Hagen, 2006) is reconstructed. For the molecular analysis, Cox1 mitochondrial and 28S ribosomal nuclear DNA sequences were used. According to these data, same transisthmian sister species relationships are confirmed and a new species of the genus Uca Leach, 1814, Uca osa sp. n., is described from Golfo Dulce, a tropical gulf in Pacific Costa Rica. Morphological as well as molecular data confirm distinctness of this species compared with all other members of the subgenus Minuca, to which it belongs. Distinctive morphological traits are presented to distinguish Uca osa sp. n. from its congeners in the Eastern Pacific.