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A neotenous dwarf-form of Capulus ungaricus (L.) (Gastropoda, Prosobranchia) commensalistic on Turritella communis Risso
144
Oceanographic Abstracts
area, while the southern ridge has extended itself into latitudes which are too warm and altitudes where moisture is insufficient to maintain an ice cap. The meteorological model, taken by itself, would not permit long interglacials, lsostasy, which moves the land surface up and down (in response to loading and unloading) over a vertical range of perhaps as much as 1.0 km., provides the necessary time lag. The meteorological model can operate effectively only on "" wide "' continents such as North America and Europe. Greenland and Antarctic ice sheets are, therefore, safe from the dangers of migrating into warmer areas, and hence will not melt until over-all glacial conditions have been terminated. Field evidence suggests that complete melting did not take place during any of the Pleistocene interglacials. The combined model can be used to predict that sea level will not return, in the near future, to its " n o r m a l " position, but rather that, in an interval on the order of 102-104 years, it will begin to drop again as the earth enters a new cold epoch. The precise timing will depend on the rate at which isostatic rebound re-elevates pertinent parts o f North America and Europe to the critical position, and perhaps also on the timing of an "extreme value" sequence of heavy-snowfall years. In the light of the rate at which North America has approached its polar position over the last 10a years, the over-all history of Pleistocene glaciation can be expected to last for approximately 10s years, interrupted by various interglacials as the ice sheets starve themselves. TAREEV B. A., 1965. Unstable Rossby waves and nonstationarity of the oceanic currents. (In Russian; English abstract). Fisika Atmosferi i Okeana., Izo Akad. Nauk, SSSR, I (4): 426-438. A problem of ocean current stability on a/3-plane is considered with some approximations. Friction, stratification and inertia terms are taken into account. The instability depends on the value of the vertical velocity shear. Many oceanic currents are unstable. The wave length o f the most unstable quasi-geostrophical disturbances equals about 300 km for typical Gulf Stream parameters.
TELLAI SALAH, 1964. R6partition g6ographique et saisonni6re du microplancton dans la Baie d'Alger. Pelagos, Bull. Inst. Oc~anogr., Alger, 2 (1): 5-50. During the four seasons of 1963 (January 12, March 15, July 4, November 2) water samples were collected in differents points in Algiers Bay. The quantitative analysis of the microplankton in these samples showed that the geographical distribution of Protista was relatively homogeneous, despite the peculiar characteristics of certain points. In comparing our results with those for earlier years, it appears that the biological properties of the Atlantic current were not modified. THIEL GUSTAV, 1964. Die Sturmflut der Nord- und Ostsee vom 16 und 17 Fcbruar 1962. Deutsche
Hydrogr. Zeits., 17 (4): 174-178. The great variations o f sea level in the North and Baltic seas are discussed and the gradient method used for the computation of the heights of sea level associated with storm surges in the North Sea is described. The track of the storm low that caused the storm surge in the North Sea on 16th and 17th February, 1962 is delineated and, an explanation is given of the height of the storm surge that occurred along the coasts of the German Bight and at Hamburg at that time. Furthermore, it is pointed out that the Russian high obstructed the track of the storm low and attention is drawn to tracks o f two corresponding storm lows that caused storm surges in the Baltic. THORSON GUNNAR, 1965. A neotenous dwarf-form of Capulus ungaricus (L.) (Gastropoda, Prosobranchia) commensalistic on Turritella communis Risso. Ophelia, 2 (1): 175-210. Capulus ungaricus is, in its typical form, a semi-commensalistic, protandric, brood-protecting prosobranch with a 15--40 mm long, cap-shaped shell. It is usually located near the shell margin o f certain large lamellibranchs of the suspension-feeding type, exploiting its host partially by profiting from the water current the latter creates, partially by introducing its long, muscular proboscis into the mantle cavity of the lamellibranch thus " stealing " its food. While the typical form of Capulus occurs infrequently in inner Danish waters, a dwarf-form of up to 11 mm length of shell and regularly sitting on shells of living Turritella communis proves to be common locally in the northern Kattegat in mud bottoms inhabited by an Amphiura-community. Since Turritella as a host can only offer conditions less favourable and strikingly different from those which Capulus may usually obtain when located on a large lamellibranch, an analysis was made to find out why it prefers Turritella on this bottom and of the ecological consequences for Capulus of inhabiting this unusual host - all in relation to its dwarfish appearance. Since Capulus is molded to the narrow last whorl of the Turritella so as to fit its curvature, at least the older specimens must be bound to that site for life, thus automatically giving them very restricted possibilities for growth. The dwarf-form has a strongly divergent shape o f shell, and the long proboscis, so important for the feeding activity of adults of the typical form, is at best rudimentary and often absent. In spite o f having retained such juvenile characters, 22 out of the 70 dwarf-form specimens examined were found brooding their egg-sacks under their foot, thus being sexually mature. This fact, together with the juvenile anatomy, designates the dwarf-form as neotenous. Since the dwarf population is mainly recruited by echinospira larvae of the typical form drifting in with the current from the Skagerrak and the North Sea, this neoteny must be ecologically determined. In many marine invertebrates growth will stop at the same time as the production o f eggs sets in. Here, the reciprocal process seems to take place; growth is stopped by the location on the
Oceanographic Abstracts
145
narrow shell of the host, and the nutritive surplus usually used for enlarging the shell and the body can be used for an early production o f eggs and sperm instead. Among the 70 dwarf-specimens examined, those with male-phase characters were far less numerous than female-phase ones. In four cases one male-phase and one female-phase animal were found together on the same Turritella, but all the rest were isolated specimens. A functional male of the Capulus dwarf-form isolated on its Turritella seems only to have a fairly small chance of copulating with another specimen. So, most female-phase specimens seem largely to be dependent on selffertilization, probably by spermatozoa stored in their own receptaculum seminis during an early male phase in which a copulatory organ may or may not be developed. The sparse and scattered occurrence of specimens of the typical form in Danish seas means that this must rely still more upon self-fertilization than the dwarf-form. Rough sketches of the larvae are given and their occurrence is discussed. THURBER DAVID L., WALLACES. BROECKER, RICHARD L. BLANCHARDand HERBERT A. POTRATZ, 1965. Uranium-series ages of Pacific atoll coral. Science, 149 (3679): 55-58. The thorium-230: uranium-234 method of dating corals and oolites has been evaluated in detail for reliability, and various criteria have been established. Reliable ages for extensive coral formations o f about 6000 and 120,000 years were obtained. A hiatus in the development of coral between 6000 and 120,000 years ago on the Pacific atoll o f Eniwetok implies that conditions did not permit coral growth during this period. The record prior to 120,000 years ago is not clear, probably because o f a lack o f unaltered samples. TOWNSEND A. A., 1965. Excitation of internal waves by a turbulent boundary layer. J. FluidMech. 22 (2): 241-252. In a barotropic fluid, a free turbulent flow induces a fluctuating potential flow which is determined by the instantaneous flow near the edge o f the turbulent flow. If the surrounding fluid is stably stratified, internal wave-motions are possible and, in general, wave-energy accumulates until it is sufficient to modify the turbulent flow. Here the growth o f wave-motion from rest is examined with particular reference to the atmospheric problem of wave excitation by the surface boundary layer. Wind shear is supposed negligible outside the turbulent flow and the disturbances from the boundary layer are assumed to travel with a convection velocity V relative to the upper air. For times large compared with {-- g/p (dp/dz)}-~ (p is the potential density), most of the wave-energy resides in components of phase-velocity near the convection velocity. For a model atmosphere with increased stability above a tropopause, this resonance mechanism leads the formation of wave-groups with crests at right-anglestotheconvectionvelocityandwavelengthsnear2~rV[--g/p(dp/dz)]-½. Using likely values for the surface disturbances, wave-amplitudes o f order 100 m can develop within several hours o f the initiation of the boundary layer but sufficient amplitude to produce overturning or breaking is unlikely within a reasonable time. TYLER JOHN E., 1965. In situ spectroscopy in ocean and lake waters. J. opt. Soc., Am., 55 (7): 800-805. In situ experimental measurements over the wavelength range 400-700 um have been made in Crater Lake and in Pacific coastal water to reveal their inherent absorption spectra. The measurements are reported as the ratio of the radiance observed in a horizontal direction underwater to the irradiance falling on the surface o f the water and, as such, are independent o f the spectral properties o f the source of flux as well as those of the detector. The instrument used is discussed briefly and a short theoretical analysis is given to illustrate the effect o f changes in absorption and scattering on the ratios obtained. UDINTSEV G. B., 1965. Topography and structure o f the Pacific floor. (In Russian; English abstract). Okeanolog. lssled., Rez. Issled. po Programme Mezhd. Geofiz. Goda, Mezhd. Geofiz. Komitet, Prezidiume Akad. Nauk, SSSR, No. 13: 143-147. On the "Tectonic chart o f the Pacific" compiled by the Institute o f Oceanology o f the Academy o f Sciences of the USSR an attempt was made to show the tectonics o f sea and ocean floors. The principles of representing the tectonics o f the ocean floor are somewhat different from those used in compiling tectonic maps for land areas. It is possible to distinguish areas with a folding o f various age under the water only within very limited limits. Of major importance is information about difference in the structure o f the Earth's crust, the morphology o f the ocean floor, the latest tectonics, volcanicity and the regime o f sedimentation. The chart shows distribution areas o f three main types o f the Earth's crust : continental, oceanic and transitional. From the point o f view o f tectonics the first two are areas o f a platform type, whereas the transitional area is characterized by a geosynclinal development. An area of the transitional type of the crust structure is also the area o f the midoceanic ridges, which tectonically is not analogous to the geosynelinal or platform areas but is a special development o f the crust and the upper mantle. Within the present geosynclinal zone, which occupies the peripheral part o f the Pacific Ocean, different stages o f geosynclinal development are recorded. Thus, in the development o f the present geosynclinal belt one observes the same regularities - difference in age - as in the geosynclinal belts o f the past in the land o f Eurasia. Within the Pacific oceanic platform an exceptional role o f block tectonics and volcanicity has been established, which reflects the development of a differential process in the subcrust and its effect on the formation
Oceanographic Abstracts
area, while the southern ridge has extended itself into latitudes which are too warm and altitudes where moisture is insufficient to maintain an ice cap. The meteorological model, taken by itself, would not permit long interglacials, lsostasy, which moves the land surface up and down (in response to loading and unloading) over a vertical range of perhaps as much as 1.0 km., provides the necessary time lag. The meteorological model can operate effectively only on "" wide "' continents such as North America and Europe. Greenland and Antarctic ice sheets are, therefore, safe from the dangers of migrating into warmer areas, and hence will not melt until over-all glacial conditions have been terminated. Field evidence suggests that complete melting did not take place during any of the Pleistocene interglacials. The combined model can be used to predict that sea level will not return, in the near future, to its " n o r m a l " position, but rather that, in an interval on the order of 102-104 years, it will begin to drop again as the earth enters a new cold epoch. The precise timing will depend on the rate at which isostatic rebound re-elevates pertinent parts o f North America and Europe to the critical position, and perhaps also on the timing of an "extreme value" sequence of heavy-snowfall years. In the light of the rate at which North America has approached its polar position over the last 10a years, the over-all history of Pleistocene glaciation can be expected to last for approximately 10s years, interrupted by various interglacials as the ice sheets starve themselves. TAREEV B. A., 1965. Unstable Rossby waves and nonstationarity of the oceanic currents. (In Russian; English abstract). Fisika Atmosferi i Okeana., Izo Akad. Nauk, SSSR, I (4): 426-438. A problem of ocean current stability on a/3-plane is considered with some approximations. Friction, stratification and inertia terms are taken into account. The instability depends on the value of the vertical velocity shear. Many oceanic currents are unstable. The wave length o f the most unstable quasi-geostrophical disturbances equals about 300 km for typical Gulf Stream parameters.
TELLAI SALAH, 1964. R6partition g6ographique et saisonni6re du microplancton dans la Baie d'Alger. Pelagos, Bull. Inst. Oc~anogr., Alger, 2 (1): 5-50. During the four seasons of 1963 (January 12, March 15, July 4, November 2) water samples were collected in differents points in Algiers Bay. The quantitative analysis of the microplankton in these samples showed that the geographical distribution of Protista was relatively homogeneous, despite the peculiar characteristics of certain points. In comparing our results with those for earlier years, it appears that the biological properties of the Atlantic current were not modified. THIEL GUSTAV, 1964. Die Sturmflut der Nord- und Ostsee vom 16 und 17 Fcbruar 1962. Deutsche
Hydrogr. Zeits., 17 (4): 174-178. The great variations o f sea level in the North and Baltic seas are discussed and the gradient method used for the computation of the heights of sea level associated with storm surges in the North Sea is described. The track of the storm low that caused the storm surge in the North Sea on 16th and 17th February, 1962 is delineated and, an explanation is given of the height of the storm surge that occurred along the coasts of the German Bight and at Hamburg at that time. Furthermore, it is pointed out that the Russian high obstructed the track of the storm low and attention is drawn to tracks o f two corresponding storm lows that caused storm surges in the Baltic. THORSON GUNNAR, 1965. A neotenous dwarf-form of Capulus ungaricus (L.) (Gastropoda, Prosobranchia) commensalistic on Turritella communis Risso. Ophelia, 2 (1): 175-210. Capulus ungaricus is, in its typical form, a semi-commensalistic, protandric, brood-protecting prosobranch with a 15--40 mm long, cap-shaped shell. It is usually located near the shell margin o f certain large lamellibranchs of the suspension-feeding type, exploiting its host partially by profiting from the water current the latter creates, partially by introducing its long, muscular proboscis into the mantle cavity of the lamellibranch thus " stealing " its food. While the typical form of Capulus occurs infrequently in inner Danish waters, a dwarf-form of up to 11 mm length of shell and regularly sitting on shells of living Turritella communis proves to be common locally in the northern Kattegat in mud bottoms inhabited by an Amphiura-community. Since Turritella as a host can only offer conditions less favourable and strikingly different from those which Capulus may usually obtain when located on a large lamellibranch, an analysis was made to find out why it prefers Turritella on this bottom and of the ecological consequences for Capulus of inhabiting this unusual host - all in relation to its dwarfish appearance. Since Capulus is molded to the narrow last whorl of the Turritella so as to fit its curvature, at least the older specimens must be bound to that site for life, thus automatically giving them very restricted possibilities for growth. The dwarf-form has a strongly divergent shape o f shell, and the long proboscis, so important for the feeding activity of adults of the typical form, is at best rudimentary and often absent. In spite o f having retained such juvenile characters, 22 out of the 70 dwarf-form specimens examined were found brooding their egg-sacks under their foot, thus being sexually mature. This fact, together with the juvenile anatomy, designates the dwarf-form as neotenous. Since the dwarf population is mainly recruited by echinospira larvae of the typical form drifting in with the current from the Skagerrak and the North Sea, this neoteny must be ecologically determined. In many marine invertebrates growth will stop at the same time as the production o f eggs sets in. Here, the reciprocal process seems to take place; growth is stopped by the location on the
Oceanographic Abstracts
145
narrow shell of the host, and the nutritive surplus usually used for enlarging the shell and the body can be used for an early production o f eggs and sperm instead. Among the 70 dwarf-specimens examined, those with male-phase characters were far less numerous than female-phase ones. In four cases one male-phase and one female-phase animal were found together on the same Turritella, but all the rest were isolated specimens. A functional male of the Capulus dwarf-form isolated on its Turritella seems only to have a fairly small chance of copulating with another specimen. So, most female-phase specimens seem largely to be dependent on selffertilization, probably by spermatozoa stored in their own receptaculum seminis during an early male phase in which a copulatory organ may or may not be developed. The sparse and scattered occurrence of specimens of the typical form in Danish seas means that this must rely still more upon self-fertilization than the dwarf-form. Rough sketches of the larvae are given and their occurrence is discussed. THURBER DAVID L., WALLACES. BROECKER, RICHARD L. BLANCHARDand HERBERT A. POTRATZ, 1965. Uranium-series ages of Pacific atoll coral. Science, 149 (3679): 55-58. The thorium-230: uranium-234 method of dating corals and oolites has been evaluated in detail for reliability, and various criteria have been established. Reliable ages for extensive coral formations o f about 6000 and 120,000 years were obtained. A hiatus in the development of coral between 6000 and 120,000 years ago on the Pacific atoll o f Eniwetok implies that conditions did not permit coral growth during this period. The record prior to 120,000 years ago is not clear, probably because o f a lack o f unaltered samples. TOWNSEND A. A., 1965. Excitation of internal waves by a turbulent boundary layer. J. FluidMech. 22 (2): 241-252. In a barotropic fluid, a free turbulent flow induces a fluctuating potential flow which is determined by the instantaneous flow near the edge o f the turbulent flow. If the surrounding fluid is stably stratified, internal wave-motions are possible and, in general, wave-energy accumulates until it is sufficient to modify the turbulent flow. Here the growth o f wave-motion from rest is examined with particular reference to the atmospheric problem of wave excitation by the surface boundary layer. Wind shear is supposed negligible outside the turbulent flow and the disturbances from the boundary layer are assumed to travel with a convection velocity V relative to the upper air. For times large compared with {-- g/p (dp/dz)}-~ (p is the potential density), most of the wave-energy resides in components of phase-velocity near the convection velocity. For a model atmosphere with increased stability above a tropopause, this resonance mechanism leads the formation of wave-groups with crests at right-anglestotheconvectionvelocityandwavelengthsnear2~rV[--g/p(dp/dz)]-½. Using likely values for the surface disturbances, wave-amplitudes o f order 100 m can develop within several hours o f the initiation of the boundary layer but sufficient amplitude to produce overturning or breaking is unlikely within a reasonable time. TYLER JOHN E., 1965. In situ spectroscopy in ocean and lake waters. J. opt. Soc., Am., 55 (7): 800-805. In situ experimental measurements over the wavelength range 400-700 um have been made in Crater Lake and in Pacific coastal water to reveal their inherent absorption spectra. The measurements are reported as the ratio of the radiance observed in a horizontal direction underwater to the irradiance falling on the surface o f the water and, as such, are independent o f the spectral properties o f the source of flux as well as those of the detector. The instrument used is discussed briefly and a short theoretical analysis is given to illustrate the effect o f changes in absorption and scattering on the ratios obtained. UDINTSEV G. B., 1965. Topography and structure o f the Pacific floor. (In Russian; English abstract). Okeanolog. lssled., Rez. Issled. po Programme Mezhd. Geofiz. Goda, Mezhd. Geofiz. Komitet, Prezidiume Akad. Nauk, SSSR, No. 13: 143-147. On the "Tectonic chart o f the Pacific" compiled by the Institute o f Oceanology o f the Academy o f Sciences of the USSR an attempt was made to show the tectonics o f sea and ocean floors. The principles of representing the tectonics o f the ocean floor are somewhat different from those used in compiling tectonic maps for land areas. It is possible to distinguish areas with a folding o f various age under the water only within very limited limits. Of major importance is information about difference in the structure o f the Earth's crust, the morphology o f the ocean floor, the latest tectonics, volcanicity and the regime o f sedimentation. The chart shows distribution areas o f three main types o f the Earth's crust : continental, oceanic and transitional. From the point o f view o f tectonics the first two are areas o f a platform type, whereas the transitional area is characterized by a geosynclinal development. An area of the transitional type of the crust structure is also the area o f the midoceanic ridges, which tectonically is not analogous to the geosynelinal or platform areas but is a special development o f the crust and the upper mantle. Within the present geosynclinal zone, which occupies the peripheral part o f the Pacific Ocean, different stages o f geosynclinal development are recorded. Thus, in the development o f the present geosynclinal belt one observes the same regularities - difference in age - as in the geosynclinal belts o f the past in the land o f Eurasia. Within the Pacific oceanic platform an exceptional role o f block tectonics and volcanicity has been established, which reflects the development of a differential process in the subcrust and its effect on the formation