Palau Islands Research Articles

Paleomagnetic Evidence from Land-Based and ODP Cores for Clockwise Rotation and Northward Translation of the Philippine Sea Plate: ABSTRACT

On-land and deep-sea core paleomagnetic data have been collected from around the Philippine Sea plate. Data from the Palau islands suggest 70{degree} of clockwise rotation and northward translation since the mid-Oligocene. The authors interpret this rotation as a rotation of the West Philippine Sea basin as a whole. New paleomagnetic data from Guam indicate 70{degree} of clockwise rotation and northward translation since the early Oligocene. Although Eocene results have been previously quoted, the new data suggest that there is no reliable Eocene data from Guam. New data from Saipan suggest 50-60{degree} of clockwise rotation since the Late Eocene and 20{degree} of clockwise rotation since the mid-Miocene, along with northward translation. During ODP Leg 126, a new technique utilizing the formation microscanner logging tool was employed to obtain orientated drill cores from the Bonin forearc basin. Preliminary results indicate that 70-110{degree} of clockwise rotation has occurred there since the mid-Oligocene. Inclination studies on cores from ODP Legs 125 and 126 along with the on-land paleomagnetic data support 15{degree} of northward translation of the Philippine Sea plate since the mid-Oligocene. The consistent clockwise rotations found around the Philippine Sea plate suggest that the entire plate, including the Bonin and Mariana arcs, hasmore » rotated more than 50{degree} since the mid-Oligocene. The similarity of Oligocene results from the Bonin forearc and Guam suggest that little or no relative rotation has occurred between these two points. This implies that the shape of the Mariana arc is probably not due to rotational deformation. The northward translation and clockwise rotation of the Philippine Sea plate established oblique subduction along the proto-Philippine margin, which could account for the 600 km of subducted slab beneath the eastern Celebes Sea.« less

Distinctions between Hypoglossum barbatum Okamura, H. minimum Yamada and H. simulans sp. nov. (Delesseriaceae, Rhodophyta)

Morphological criteria are provided to distinguish three superficially similar species of the genus Hypoglossum Kützing. Hypoglossum barbatum Okamura is known from the western Pacific (southern Japan, Korea, and the Palau Islands), and H. minimum Yamada is known only from Japan. A new species, H. simulans, is described, with a collection from Malendure, Guadeloupe, French West Indies, designated as holotype. The apical organization of the blades in the new species distinguishes it from the other two. In addition to its occurrence in the Caribbean, H. simulans is recorded from eastern Australia, the South Pacific, and Hawaii.

Coral Reef in Palau Islands

Coral Reef in Palau Islands

Paleomagnetic results from Palau, West Caroline Islands: A constraint on Philippine Sea plate motion

Paleomagnetic results from the Palau Islands indicate that the islands have undergone 60°-70° of clockwise rotation since mid-Oligocene time. This post-mid-Oligocene rotation is interpreted to represent the motion of the Philippine Sea plate and not a local rotation for the following reasons: (1) lack of morphologic expression of the differential rotation along the Palau-Kyushu Ridge, (2) similarity to predicted rotations obtained by using phase-shifted magnetic anomaly data, and (3) ubiquitous clockwise rotations seen in paleomagnetic data from around the Philippine Sea plate. This strong clockwise rotation of the Philippine Sea plate provides a mechanism for oblique subduction and related transcurrent motion along the margin of the Philippine archipelago.

THE DISPERSAL BARRIER IN THE TROPICAL PACIFIC: IMPLICATIONS FOR MOLLUSCAN SPECIATION AND EXTINCTION

Stretches of deep ocean constitute barriers to the dispersal of many shallow-water marine species in the tropical Pacific. The purpose of this study was to assess the selectivity of these barriers with respect to the habitat characteristics, adult size, and predation-related shell architecture of gastropods, and to explore the implications of this selectivity for macroevolutionary patterns of extinction and speciation. The dispersal barrier between continental islands (represented in my collections by species from eastern Indonesia, the southern Philippines, and the north coast of New Guinea) and the nearby oceanic Palau Islands was studied by evaluating the percentage of each architectural and habitat category that is present on the continental islands but missing in Palau. The barrier is significantly more effective against sand-dwelling species than against rock-dwellers, and among rock-dwellers it is most effective against aperturally unarmored taxa. Barriers between Palau and Guam, Guam and the Hawaiian Islands, and the Line Islands and the tropical Eastern Pacific are generally unselective with respect to substratum type and architecture. The fact that narrow-apertured species are less affected by the barrier between the continental islands and Palau than are other rock-dwelling gastropods is consistent with the interpretation that this group has been unusually resistant to extinction and highly susceptible to founder speciation when oceanic circulation is altered. These patterns of susceptibility and geographical distribution may explain why armored gastropods have increased in numbers relative to unarmored ones in the tropical Pacific during the Cenozoic.

Research Report on Tropical Environment, Especially on Mangrove Swamps in Palau Islands, Southern Pacific

Research Report on Tropical Environment, Especially on Mangrove Swamps in Palau Islands, Southern Pacific

"Their" Environmental Problems and Our Own: The United States and the Palau Islands

"Their" Environmental Problems and Our Own: The United States and the Palau Islands

Occurrence of a New Hermit Crab of the Genus Porcellanopagurus (Decapoda, Paguridae) in the Sea Adjacent to the Palau Islands

Occurrence of a New Hermit Crab of the Genus Porcellanopagurus (Decapoda, Paguridae) in the Sea Adjacent to the Palau Islands

Genotypic relationships between Prochloron samples from different localities and hosts as determined by DNA-DNA reassociations

Genotypic relationships between seven Prochloron samples isolated from different didemnid ascidian hosts collected at the Palau archipelago and Munda (Solomon Islands) and one cyanobacterial (Synechocystis) strain were determined by DNA-DNA reassociations. Thermal stability values of DNA-DNA hybrids indicate that all Prochloron samples involved are mutually very closely related and only slightly related with the Synechocystis strain. It is concluded that the Prochloron samples tested are representatives of one and the same species.

Words of the Lagoon: Fishing and Marine Lore in the Palau District of Micronesia

Words of the Lagoon is an account of the pioneering work of a marine biologist to discover, test, and record the knowledge possessed by native fisherman of the Palau Islands of Micronesia.

Sulfated flavonoids and leaf morphology of the Halophila ovalis—H. minor complex (hydrocharitaceae) in the Pacific Islands and Australia

Sulfated flavonoids showed a systematic pattern among Halophila populations of the Pacific and Australia. Large-leaved plants, typical of H. ovalis (R.Br.) Hook. f., in the Palau Islands (Belau) and in Australia contained sulfated flavonoids, but small-leaved plants that have received various treatments under H. ovalis, including ssp. bullosa (Setchell) den Hartog and ssp. hawaiiana (Doty & Stone) den Hartog, and under H. minor (Zoll.) den Hartog or H. ovata Gaud. in American Samoa, Western Samoa, Tonga, Fiji, Wallis I., New Caledonia, Yap, Guam, Hawaii and Australia lacked sulfated flavonoids. Plants collected in their natural habitats as well as those grown in experimental cultures showed the characteristic patterns of these secondary compounds. Although the large-leaved plants have the potential for producing the largest leaves in the complex, they are not separable from small-leaved plants in leaf dimensions or in number of pairs of cross veins under all environmental conditions. The production of sulfated flavonoids and the potential for greater leaf length are the characteristics that can be used to separate typical H. ovalis and ssp. australis (Doty & Stone) den Hartog from other members of the complex.

Comparison of δ13C values for seagrasses in experimental cultures and in natural habitats

For seagrasses of 11 genera, most species in experimental cultures had δ 13C values that were more negative than those in natural habitats. In the experimental cultures, 21 out of 25 species had values in the range from −12.0 to −16.9%, but in natural habitats 18 of the 25 species had values in the range from −3.6 to −12.5%. Zostera americana den Hartog from Washington had nearly identical values under both conditions, −15.3 and −16.3 (field) and −16.9 (laboratory), but Enhalus acoroides (L. f) Royle, Thalassia hemprichii (Ehrenb.) Aschers. and Cymodocea serrulata (R.Br.) Aschers. & Magnus from the Palau Islands (Belau) had values of −4.9, −5.7 and −8.0%, respectively, in the field and −12.3, −12.9 and −15.6% in the cultures. The values that were lowwer in the laboratory than in the natural habitats probably reflect differences in the isotopic composition of the inorganic carbon pools as well as differences in refixation of respired and photorespired carbon dioxide.

Galatheids and Pagurids of the Palau Islands (Crustacea: Anomura)(Zoological Result of the Expedition to the North Equatorial Current Areas : I Reef-Associated Fauna in the Palau and Yap Islands, Western Caroline Islands, during June-July, 1980)

Galatheids and Pagurids of the Palau Islands (Crustacea: Anomura)(Zoological Result of the Expedition to the North Equatorial Current Areas : I Reef-Associated Fauna in the Palau and Yap Islands, Western Caroline Islands, during June-July, 1980)

Brief introduction to the land crabs of the Palau islands: Stages in the transition to air breathing

Brief introduction to the land crabs of the Palau islands: Stages in the transition to air breathing

Morphological variation and isozymes under laboratory conditions in Cymodocea serrulata

Experimental cultures of Cymodocea serrulata (R.Br.) Aschers. & Magnus from the Indian Ocean and the western Pacific showed infraspecific differences in morphology. Plants from the Palau Islands (Belau), Micronesia, produced short shoots that were elevated above the sediment by as much as 7.5 cm, but plants from Kenya and from Thursday Island, Queensland, Australia, produced short shoots that remained near the sediment surface. The three collections did not differ in isozyme patterns for any of eight enzyme systems. The difference in orientation of the short shoots is probably of selective significance in local habitats differing in sediment type and/or depth of submergence.

Holocene sea-level changes in Palau, West Caroline Islands

14C ages supplemented by 230Th234U determinations have been obtained for calcareous deposits on Koror, Babelthuap, Auluptagel, and Adorius Islands in the Palau Group, West Caroline Islands. Test borings for a bridge between Koror and Babelthuap reveal shoreface terraces consisting largely of bioclastic sand, but resembling fringing reefs. The base of the shoreface terraces dates to between 7000 and 8000 14C yr B.P. and the upper surfaces are slightly younger than 4000 yr B.P. Spacing of the subsurface isochrons indicates that the rate of sedimentation increased up-section on Koror terrace and decreased up-section on Babelthuap terrace. The average rate of deposition in the terraces was 0.5 cm/yr. Isochrons in the Babelthuap shoreface terrace are 7 m higher than those in the Koror terrace. If deposition was sufficient to keep the surfaces of the terraces at low tide level, then the Babelthuap side was essentially stable and the Koror side was uplifted between about 8000 and 6300 yr ago, and then subsided until 4000 yr ago; since then there has been about 2 m of uplift. “Top hat” microatolls on Koror terrace indicate that relative sea level has dropped about 30 cm in the past 75 yr. In the absence of good evidence for changes of level in water ponded in a moat, it is likely that the microatolls indicate uplift of the terrace. On the other hand, if tectonic activity was minimal, then differences in the two terraces are due to differences in sedimentation with the Koror side of the channel being substantially subtidal between about 7000 and 5000 yr B.P. Taking the composite eustatic sea-level curve of Hawaii and elsewhere as a reference standard, it is deduced that Auluptagel Island has risen 0.8 m in the last 2900 yr, and Adorius Island has risen approximately 8 m in the last 5000–6000 yr.

Notes on the Taxonomy, Natural History, and Status of the Resident Birds of Palau

This paper reports observations made from 1976 to 1979 of the resident birds of the Palau Islands in western Micronesia. Comments on population status, distribution, and habitat are made for all species. Song descriptions and food habits are reported for many species. Nests are de- scribed for Megapodius laperouse, Ptilinopus pelewensis, Cettia (=Psama- thia) annae, Myiagra erythrops, Rhipidura lepida, Zosterops cinerea, My- zomela cardinalis, Aplonis opaca, and Artamus Zeucorhynchus. Taxonomic comments are made on Ptilinopus, Coracina, Psamathia, Myiagra, Colluri- cincla, and Megazosterops. The recommendation is made that Pyrrhoglaux podargina, Rhipidura lepida, and possibly Megapodius laperouse be declas- sified as Endangered Species, but that Palau populations of Rallina eurizo- noides, Gallinula chloropus, Porphyrio porphyrio, and Caprimulgus indicus be considered for such listing.

Flowering under controlled conditions by Cymodocea rotundata from the Palau Islands, Micronesia

Flowering of Cymodocea rotundata Ehrenb. & Hempr. ex Aschers. has been reported in natural seagrass beds only in 1871 and 1967. The production of staminate flowers on three separate occasions in 1977–1978 in experimental cultures transplanted from Kayangel Atoll suggests primarily temperature control.

日本産ゴキブリ分類ノート, XII. : モリゴキブリ群の種類, II(日本および関連台湾産を含む)

In this second part of this series of works a taxonomic revision was made regarding two genera of the Tribe Ischnopterites, Episymploce and Scalida, found in the Ryukyus and Taiwan. Genus Episymploce Bey-Bienko A redefined generic diagnosis of Episymploce, compared with those of Symploce s. str., is as follows : a. Male supraanal plate divided distally or asymmetrically formed, usually with a sharp median incision with ventral spinous projection (s). b. Male hypandrium definitely asymmetrical, its extreme base furnished with sharp spine (s) on each side. c. The lateral margin of 9th tergite covers the sides of hypandrium, sometimes provided with a small spine on this margin. d. In all the species examined left phallosome of males sickle-shaped, turning at right angle with the "handle" abruptly thickened. e. Female supraanal plate is, in general, slightly divided at the apex. 9. Episymploce sinensis (Walker) A remarkable reddish brown species with broad black marginal area in the wings. Shiraki (1931) misidentified one female of this species as a male Blattid, "Periplaneta apicalis Shiraki" together with a female of a Hebardina species! The type locality of sinensis (Walker) is "Hong Kong", then recorded from "Peking" and "Nanking". In Taiwan this species seems to be very rare. 10a. Episymploce formosana formosana (Shiraki) As stated in my previous Note, Shiraki (1931) synonymized this species with "Ischnoptera modestiformis Karny", but I found that this is a good species examining both the type materials. Perhaps not uncommon in Taiwan. Based on the description and type material Shiraki's "Ischnoptera asymmetrica" appears a synonym of this species. 10b. Episymploce formosana yoshinoe (Shiraki) In examining the type material of "yoshinoe" preserved in the National Taiwan University the prothorax and wings are much broader than those of "formosana". But since I could not recognize any distinct difference in the structure of male hypandrium I now lower yoshinoe on a subspecific level of formosana. In this connection I have never found Shiraki's "yoshinoe var. brevielytra" in the collection of National Taiwan University, there was, instead, a female labelled "makiana n. sp." (nom. nud.) which also appears to be a formosana yoshinoe. 11. Episymploce princisi nov. Karny (1915) misidentified this species to be Burmese "Ischnoptera multiramosa Brunner v. W." which seems quite different from ours at least in the absence of dark spots on the prothorax. Princis's new name "karnyi" is a nomen nudum, and since no reliable description has ever been made I gave it here based upon my new material taken in the mountains of Taiwan. 12. Episymploce amamiensis Asahina This slender species is allied to the preceeding one at least in the presence of paired dark stripes on the prothorax, but differs from princisi in the character of male hypandrium and female supraanal plate. Distributed from Amami Islands as far north as Yakushima. 13. Episymploce yashiroi (Shiraki) A small pale brownish species, first described from Okinawa and later found rather common throughout the other Ryukyu Islands south of Okinawa. I examined one male specimen taken in Taiwan (Baibara, in coll. Hokkaido Univ.), and believe that "Symploce taiwanica Bey-Bienko" (1969) is the same species. Several Episymploce specimens in the Micronesian collection (♂♂♀♀ Babeldaub, Palau Islands) seem also the same or very closely allied species, and I even suppose "Symploce vietnami Bey-Bienko" taken in Vietnam appear to be yashiroi if seen from the brief picture given by Bey-Bienko. 14. Episymploce taiheizana nov. A very slender species with a round dark spot on the prothorax. Confined to Taiheizan Mountains in North Taiwan. Genus Scalida Hebard Superficially these insects lo

Length and spacing of the tube feet in crinoids (echinodermata) and their role in suspension-feeding

The morphology of the primary tube feet in 15 species of comatulid (unstalked) crinoids from coral reefs in the Palau Islands and Lizard Island, Great Barrier Reef, was investigated using close-up underwater photographs of the tube feet taken in the natural habitat. Measurements of length of the tube feet and their spacing along the pinnule were taken from these photographs. Tube feet of species of the family Comasteridae have a mean length of 0.75 mm and a mean spacing of 6 tube feet mm-1. Tube feet of non-comasterid species occurring in the same environments have a mean length of 0.55 mm and a mean spacing of about 8 tube feet mm-1. The relationship between spacing and length of the tube feet is highty significant for both the Palau and Lizard Island samples (P<0.01). Species having longer and more widely spaced tube feet live partly concealed within the infrastructure of the reef and hold the arms and pinnules in a multidirectional posture. Species having shorter and more closely spaced tube feet perch on top of reef pinnacles or alcyonarians and form planar filtration fans normal to unidirectional currents or wave oscillations. Longer and more widely spaced tube feet in species dwelling within the reef infrastructure provide more efficient filtration in the slow, meandering flow prevailing there. Closer spacing of the tube feet in species exposed to near-mainstream flow provides a more efficient filtration mechanism at higher flow velocities. Reduced length of the tube feet in these species may be a consequence of closer spacing of the pinnules. Differentiation of these co-occurring species in spacing and length of the tube feet implies differentiation in food particles captured. This may in some cases constitute resource partitioning. Most species which overlap in living habits are significantly different in spacing and length of the tube feet.