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Field study on the habitat of Nautilus in the environs of Cebu and Negros Islands, the Philippines

Authors:
Shozo HAYASAKA
Shozo HAYASAKA
Shozo HAYASAKA
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Toshiro Saisho
Toshiro Saisho
Toshiro Saisho
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Yoshio Kakinuma
Yoshio Kakinuma
Yoshio Kakinuma
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Akihiko Shinomiya
Akihiko Shinomiya
Akihiko Shinomiya
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Abstract

On the basis of, and as a development of the preliminary survey in 1980, the main work of the present research project, entitled the "Marine Ecological Studies on the Habitats of Nautilus in the Environs of Cebu and Negros Islands, the Philippines" was carried out in 1981 for about a month from 26th August to 26th September, as a joint venture of Japanese and Philippine research workers. In this article the processes and the results of the field study in 1981 are reported with some remarks on the trapped specimens of nautilus pompilius from the area studied.
Hayasaka et al. 1982 (Mem. Kagoshima Univ. Res. Center S. Pacific) compress
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... Los datos usados los hemos reflejado en la siguiente página: BelauensisTanabe1995.html. [35] Para los ejemplares de Nautilus Pompilius D, E y F en Hayasaka et al. (1982) . Los datos podemos verlos en esta otra página: PompiliusKayasaka1982.html. ...
... Datos estadísticos del Nautilus pompilius (Hayasaka et al., 1982). [10] 0, 4964 0, 4926 0, 4938 ...
... 0, 4900 [10] 101 ...
Modelo matemático tridimensional uniforme del Nautilus
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  • Dec 2024
Libro que conforma la trilogía de este autor sobre el modelado matemático del Nautilus. Se da un salto dimensional que obvia la mirada plana en la que se centran los dos libros anteriores, asumiendo la escondida tridimensionalidad intrínseca de la concha de este molusco. Se plantea una perspectiva de crecimiento uniforme y se detalla el modelo de la concha y del callo umbilical.
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... During the day they either rest at depths of around 200 m or forage at depths up to 700 m, and during the night move almost continuously between depths of 130 and 700 m [1]. While foraging at depth animals encounter low concentrations of oxygen (oxygen partial pressure, PO 2 , approximately 50 mmHg or 30% of air-equilibrated surface water; [2].) The high capacity of the haemolymph for oxygen storage [3], the high affinity of haemocyanin for oxygen 2018 The Authors. ...
Swimming mechanics and propulsive efficiency in the chambered nautilus
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  • Feb 2018
The chambered nautilus (Nautilus pompilius) encounters severe environmental hypoxia during diurnal vertical movements in the ocean. The metabolic cost of locomotion (Cmet) and swimming performance depend on how efficiently momentum is imparted to the water and how long on-board oxygen stores last. While propulsive efficiency is generally thought to be relatively low in jet propelled animals, the low Cmet in Nautilus indicates that this is not the case. We measured the wake structure in Nautilus during jet propulsion swimming, to determine their propulsive efficiency. Animals swam with either an anterior-first or posterior-first orientation. With increasing swimming speed, whole cycle propulsive efficiency increased during posterior-first swimming but decreased during anterior-first swimming, reaching a maximum of 0.76. The highest propulsive efficiencies were achieved by using an asymmetrical contractile cycle in which the fluid ejection phase was relatively longer than the refilling phase, reducing the volume flow rate of the ejected fluid. Our results demonstrate that a relatively high whole cycle propulsive efficiency underlies the low Cmet in Nautilus, representing a strategy to reduce the metabolic demands in an animal that spends a significant part of its daily life in a hypoxic environment.
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... Tañon Strait, located between the islands of Negros and Cebu in the central Philippines ( Fig. 1) was found to have a considerably high diversity of cetaceans, given its relatively small area (Leatherwood et al. 1992;Dolar et al. 1994Dolar et al. , 2006, which has led to the establishment of a nationally protected seascape, Tañon Strait Protected Seascape (TSPS), in 1998. The strait is 220 km long and 27 km at its widest, with steep slopes on both sides that rapidly descend to >500 m deep in the middle section (Hayasaka et al. 1982). The shallow bathymetric sill in the southern opening of the strait (125 m deep) and the many small islands (Bantayan group of islands) in the shallow northern opening separate the strait from Bohol Sea and Visayan Sea. ...
The Indo-Pacific bottlenose dolphin (Tursiops aduncus) in Tañon Strait, central Philippines
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Previous sightings of bottlenose dolphins in Tañon Strait, central Philippines, in the late 1980’s to early 1990’s were limited to the southern section of the strait, in waters <500 m deep, and the species was formerly identified as Tursiops truncatus. Photo-identification surveys (n = 117) conducted in 2014 and 2015 in Tañon Strait resulted in 50 encounters of Indo-Pacific bottlenose dolphins Tursiops aduncus. No common bottlenose dolphin T. truncatus was seen. The Indo-Pacific bottlenose dolphin has only recently been confirmed to occur in coastal waters in the Philippines and thus very little is known of its local distribution and ecology. In Tañon Strait, the species was seen across a wide range of water depth (4–668 m, x̅ = 309 m) in groups ranging from 1 to ~60 individuals. We provide a photographic verification of this species and first evidence of a seemingly small population in a tropical protected seascape in the Philippines.
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... Tañon Strait, located between the islands of Negros and Cebu in the central Philippines ( Fig. 1) was found to have a considerably high diversity of cetaceans, given its relatively small area (Leatherwood et al. 1992;Dolar et al. 1994Dolar et al. , 2006, which has led to the establishment of a nationally protected seascape, Tañon Strait Protected Seascape (TSPS), in 1998. The strait is 220 km long and 27 km at its widest, with steep slopes on both sides that rapidly descend to >500 m deep in the middle section (Hayasaka et al. 1982). The shallow bathymetric sill in the southern opening of the strait (125 m deep) and the many small islands (Bantayan group of islands) in the shallow northern opening separate the strait from Bohol Sea and Visayan Sea. ...
The Indo-Pacific bottlenose dolphin (Tursiops aduncus) in Tañon Strait, central Philippines
Article
Full-text available
  • Oct 2016
Previous sightings of bottlenose dolphins in Tañon Strait, central Philippines, in the late 1980’s to early 1990’s were limited to the southern section of the strait, in waters <500 m deep, and the species was formerly identified as Tursiops truncatus. Photo-identification surveys (n = 117) conducted in 2014 and 2015 in Tañon Strait resulted in 50 encounters of Indo-Pacific bottlenose dolphins Tursiops aduncus. No common bottlenose dolphin T. truncatus was seen. The Indo-Pacific bottlenose dolphin has only recently been confirmed to occur in coastal waters in the Philippines and thus very little is known of its local distribution and ecology. In Tañon Strait, the species was seen across a wide range of water depth (4–668 m, x̅ = 309 m) in groups ranging from 1 to ~60 individuals. We provide a photographic verification of this species and first evidence of a seemingly small population in a tropical protected seascape in the Philippines.
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Isotopic evidence concerning the habitat of Nautilus macromphalus in New Caledonia
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Modern nautilids (Nautilus and Allonautilus) have often been studied by paleontologists to better understand the anatomy and ecology of fossil relatives. Because direct observations of these animals are difficult, the analysis of light stable isotopes (C, O) preserved in their shells has been employed to reveal their habitat and life history. We aim to (1) reconstruct the habitat depth of Nautilus macromphalus and (2) decipher the fraction of metabolic carbon in its shell by analyzing oxygen and carbon isotopes (δ¹⁸O, δ¹³C) in the septa of two specimens in combination with analyses of water samples from the area. Additionally, we investigate whether morphological changes during ontogeny are reflected in the isotopic values of the shells. Results reveal that the patterns of change of δ¹⁸O and δ¹³C in the septa of N. macromphalus pre- and post-hatching are consistent with previous studies. Values of δ¹⁸Owater range from 0.7 to 1.4‰ (VSMOW), with a maximum value coincident with a salinity maximum at ~150 m. We use the temperature and δ¹⁸Owater profiles to calculate equilibrium values of δ¹⁸Oaragonite with depth. Comparing these values with the measured δ¹⁸O of the septa shows that the habitat depth of N. macromphalus is ~140 m pre-hatching and ~370 m post-hatching. Using δ¹³C of shell carbonate and published data on metabolic carbon, the fraction of metabolic carbon is reconstructed as ~21% and 14% pre- and post-hatching, respectively. The reconstructed depth pre-hatching is slightly shallower than in N. pompilius from the Philippines and Fiji, but the post-hatching depth is similar. However, it is important to emphasize that these estimates represent average over time and space because nautilus is a mobile animal. Lastly, the changes in morphological parameters and the changes in δ¹³C and δ¹⁸O during ontogeny do not coincide except at hatching and at the onset of maturity.
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Survey of Nautilus pompilius Linnaeus, 1758 (Cephalopoda) from Siquijor Island and Dalaguete–Alcoy in the Philippines Using Baited Traps and Baited Remote Underwater Video Systems (BRUVS)
Article
Full-text available
  • Jun 2022
Nautilus fisheries throughout the Philippines supported a worldwide trade in the nautilus shell for decades, with little to no management. A consequence has been significant declines in catch rate and low population abundances. This survey took place in April 2014 at Siquijor Island (9°17′30.7″N 123°38′36.5″E) and Dalaguete–Alcoy (09°43′20.9″N, 123°35′52.8″E) sites using baited traps and baited remote underwater video systems (BRUVS). The last report of nautiluses at Siquijor Island was in the early 1980’s and although nautiluses inhabit areas near the Dalaguete–Alcoy area, this site has not been surveyed. At Siquijor Island, zero nautiluses were caught using 27 baited traps and zero nautiluses were recorded from nearly 20 h of BRUVS footage. At the Dalaguete–Alcoy site, one nautilus was caught using 120 traps and zero nautiluses were recorded from 12 h of BRUVS footage. These data are like other fished areas and suggest the populations of nautiluses at the Siquijor and Dalaguete-Alcoy sites are small.
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Morphological analysis of Nautilus pompilius. In: Hayasaka, S. (ed.) Marine ecological studies on the habitat of Nautilus pompilius in the environs of Viti Levu, Fiji
Article
Full-text available
  • Jan 1985
Based on the two population samples from the Suva and the Pacific Harbour areas, Viti Levu Island, Fiji Islands, morphological variation and relative growth of soft and hard tissues of Nautilus pompilius were analyzed. In both samples development of gonad begins at the stage of more than 130 mm in shell diameter. Soft tissue, gonad and shell of mature males are usually heavier and larger than those of mature females. Shell form ratios are slightly different between sexes, and most mature males have broader and higher whorl apertural area than females. Morphological comparison of the two samples with that from the Philippines shows a fairly large geographical variation not only in size and weight of the mature animals but also in the nepionic size between the two separated habitats.
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The role and status of Nautilus in its natural habitat: evidence from deep-water remote camera photosequences
Article
  • Jan 1984
Bottom site remote camera photosequences at depths of 73-538 m on forereef slopes in Palau show that Nautilus belauensis is a highly mobile, chemosensitive, epibenthic scavenger and opportunistic predator. The overall depth range of this species is 70-500 m, but photosequences indicate a preferred range of 150-300 m. Nautilus is active both nocturnally and diurnally, locating bait sites within 1-2 h. Nautilus exhibits a combination of characters that typify deep-sea strategy, including reproductive tactics, growth rate, and population dynamics. This and other evidence suggest that fossil Nautilidae may have been deep-water forms, in contrast to the typically shallower water ammonoids, and that Nautilus is a normal component of the deep forereef rather than a late Cretaceous refugee from shallow water. -from Author
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Isotope Signature of Ammonoid Shells
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Geochemical analyses of ammonoid shells provide an independent and objective data set to evaluate life and habitat of the animal. This uniformitarian consideration, in combination with functional morphology and physical evidence for ecology or physiology, potentially delivers a significant advantage for new insights in paleoecology. One difficulty is that ammonoids as a proxy carrier are assumed to be mobile organisms. In contrast to stationary proxy carriers like benthic bivalves, it is difficult to impossible to estimate absolute depth or locality in which a certain proxy was recorded. Although the temperature proxy is very informative, it could indicate alternative scenarios; shallower calcification depth or calcification in the warmer season. When the calcification temperature is calibrated against the thermal structure of the water column, the proxy records would be fully understood. Therefore, providing the external frame of references is significantly important for getting better insights from geochemical signatures on ammonoids.
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