Shallow-water Forms Research Articles

Clinal variation in the evolution of Ectenocrinus simplex

The crinoid Ectenocrinus has unusual trimeric columnals which make it instantly recognizable. In northern New York State such columnals first appear in the deep shelf facies of the lower Trenton Group (the Sugar River Limestone). In these strata the columnals display nearly triangular shapes with triangular lumina and represent a new species, E. triangulus. A small minority of the columnals of these early forms are round with five-pointed lumina.A definite cline had developed by middle Trentonian time. Deep-water columnals display the ancestral triangular form, whereas adjacent, shallow-water forms are rounder and have the five-pointed or pentagonal lumina. These round types came to be the beneficiaries of middle Trentonian facies changes. This was a time when the eastern bank margin steepened and narrowed. The deep shelf habitat shrank to the east and disappeared. Trapped in this shrinking sea floor setting, the populations of the deep-water members of the cline dwindled and disappeared before late Trentonian time. Only the round form with a pentagonal lumen survived. This form, Ectenocrinus simplex, was a great success; its numbers increased and its range expanded throughout the remainder of Trentonian time.The transition from Ectenocrinus triangulus to E. simplex is seamless. No boundary, other than an arbitrary one, can be recognized. A simple and gradual shift of phenotype abundance characterized the event.

Comparative light microscopic studies on the retina of some elasmobranch fishes.

Retinas of 11 species of elasmobranchs from 6 families including deep sea forms were examined by light microscopy. Variations in retinal structure were correlated with depth of capture. The retinas of shallow water forms had a well developed pigment epithelium, cone photoreceptors, numerous short rod outer segments and large horizontal cells with two or three layers. The retinas of deep sea species are characterized by possessing a reduced pigment epithelium, cone-free retinas and their rods have comparatively longer outer segments. No clear identification of bipolar, horizontal and amacrine cells was possible, but there are certainly no highly differentiated horizontal cells of the kind found in most shallow water fish retinas. However, the retinal structures of elasmobranchs are rather standardized and the dramatic variations of retinal structures which often occur in teleosts were not found in this observation.

Star-shaped feeding traces produced by echiuran worms on the deep-sea floor of the Bay of Bengal

Many star-shaped foraging traces were observed in bottom photographs of the deep-sea floor taken in the Bay of Bengal between the depths of 5025 and 2635 m. They were classified into 10 types according to their dimensions, aspect ratios (length/width) of their spokes, features of the central structure, and possible production mechanisms. The proboscis of a deep-sea bonellid echiuran worm was photographed at a depth of 2635 m in the act of producing one of the star-shaped foraging traces. On the basis of photographic observations and observations of shallow-water forms, several types of the feeding traces can be ascribed to the foraging of deep-sea echiuran worms on surface detritus. At least four types of the star-shaped trace are probably produced by deep-sea bonellid worms, and a linear correlation could be found between the aspect ratios of the spokes and maximum number of spokes around the central hole. A geometrical model experiment stimulating the feeding behavior of a bonellid worm suggested simple behavioral principles which afford maximum utilization of the surface area around a central hole with least expenditure of energy. The prediction of the maximum number of spokes for a given aspect of spokes by the model experiment agreed well with those observed, both utilizing about 76% of the fresh sediment surface within the span of the probiscis around a central hole. This efficient feeding pattern may have adaptive value in deep-sea environments such as the central part of the Bay of Bengal, where energy input is limited.

Miocene foraminiferal paleoecology of the basin of Vence, Southeast France

Two transgressive—regressive cycles occurred in the Basin of Vence during the Miocene. The sea transgressed the region from the southeast direction. The first cycle commenced in the Early Aquitanian and probably ended in the Burdigalian. A second minor cycle was terminated by Late- to post-Miocene tectonic activity related to the last phases of the Alpine Orogeny in the region. Benthonic and planktonic foraminiferal assemblages indicate that the Miocene deposits represent littoral to mesopelagic zones in the tropical to temperate Miocene sea in which turbidity currents were active. These assemblages, comprising characteristic shallow-water forms ( Cibicides lobatulus, Uvigerina peregrina, U. subperegrina, Nodosaria ovicula, Guttulina communis, Siphonodosaria nuttalli and Spiroplectammina carinata) and deep-water species like Hoeglundina elegans, Lagena striata, Marginulina glabra, Bulimina elongata, Melonis pompilioides, Sphaeroidina bulloides and Pullenia bulloides plus abundant planktonic foraminifera, in the western and eastern parts respectively, indicate that the sea shoaled progressively westwards. Lithology, macrofaunal content and sedimentary and biogenic structures support these conclusions. Renewed post-Miocene transgressions in the area extended only as far northwest as the Pliocene basin of the Var.

Spirorbidae (Polychaeta) collected by R. V. “Vitjas” from abyssal depths of the Pacific Ocean

Pileolaria levensteinae sp. nov. was represented by juvenile and presumably adult stages, attached to ferromanganese substrata. None bore embryos, but the larger individuals had deep opercular cups and the species is closely related to certain shallow water forms which incubate in such cups. A second species was dextrally coiling but represented by a single fragment too small to describe. Spirorbids would appear to be preadapted for abyssal life, by having a brief, lecithotrophic larval stage.

Fossils in mélanges

So-called ‘tectonic’ melanges in many parts of the world seem to contain a disproportionately high number of fossils relative to the enclosing rocks. This is particularly true of melanges in ‘greywacke type’ terrains, in particular the Esk Head Melange1 in the otherwise sparsely fossiliferous Torlesse Zone of the Alpine Assemblage2 in the New Zealand Geosyncline, the melange belts of the Franciscan Assemblage of California (M. C. Blake, jun., personal communication), and the Liptrap Formation of southern Victoria, Australia. In addition, the fossils contained in melange belts commonly contain shallow water forms, and in extreme cases even terrestrial fossils (D. L. Jones, personal communication).

Dolomite, Phosphorite, and Carbonate Diagenesis on a Caribbean Seamount

ABSTRACT Carbonate rocks consisting of micritic phosphorite, reefoid conglomerate, and calcarenite were dredged from a seamount on Aves Swell at 13°30 N, 63°10 W. The petrology of these rocks was investigated by optical, chemical, X-ray diffraction, and electron microprobe techniques in order to study the effects of diagenesis. Samples of micritic phosphorite were dense and hard, contained Oligocene-Miocene foraminiferal remains, and were composed dominantly of microcrystalline carbonate-apatite. The phosphorite was obtained from the slopes of the seamount at 620 to 730 m. It is considered to have formed as a result of replacement of an original calcareous ooze by phosphorous from sea water, according to mechanisms proposed by Kazakov (1937) and Ames (1959). Conglomerate composed of highly altered, reefoid detritus and containing fossils of probable Pleistocene to early Holocene age was collected in the depth range of 340 to 455 m. Etched and embayed calcareous structures show that the rock has been partially replaced by a microcrystalline matrix of carbonate-apatite and iron/manganese oxides, in which dolomite euhedra occur abundantly. Epitaxial rims of dolomite crystals around algal detritus suggest that fragments of high-magnesium calcite may have served as local nuclei for the development of dolomite within the rock. Because of its intimate association with Fe/Mn oxides, it does not appear likely that the dolomite formed at shallow depths in this open-ocean, unrestricted environment. Very coarse, porous calcarenite composed dominantly of unabraded foraminiferal tests and molluscan fragments and cemented by fibrous, high-magnesium calcite were collected from the top of the seamount, at 340 m. Abundant pelagic forms, uninverted aragonite grains, and the scarcity of shallow-water forms suggest that this rock has not been exposed to the effects of atmospheric water. Cementation has therefore probably taken place below sea level. A paragenesis involving changes in water depth over the seamount is proposed to explain the origin of these different rock types.

Miocene vertebrates and North Florida shorelines

Vertebrate fossils from ten localities, spread across northern Florida, give evidence of shorelines and deltas that have previously been established on geologic evidence or invertebrates alone. Terrestrial mammal remains, in association with shallow-water forms, indicate a deltaic assemblage and in several instances specific animals suggest restricted water depths at the time of sediment deposition. Fortunately diagnostic fragments of Miocene horses, Merychippus and Parahippus, are present in these beds, allowing for a rather close age evaluation of these sediments. Adequate fossil material has been collected from these localities to suggest the past environment and ecological conditions for the forms represented. By utilizing a suggested course of experiments with stream table apparatus it is possible to use the orientation of the fossil vertebrate remains as aids in determining past conditions of sediment accumulation.

From Shore to Abyss: Nearshore Transport, Slope Deposition and Erosion, Canyon Transport, and Deep-Basin Sedimentation: ABSTRACT

From Shore to Abyss: Nearshore Transport, Slope Deposition and Erosion, Canyon Transport, and Deep-Basin Sedimentation: ABSTRACT

The Makara faulted outlier and the age of Cook Strait

Abstract The lithology and foraminiferal content of a faulted outlier of Pliocene conglomerate, sandstone, and mudstone at Makara in the south of the Wellington Peninsula are evidence of an important marine transgression during the Opoitian, The beds have the characteristics of deposits in a wide-mouthed embayment, with a basal shallow-water conglomerate and, in the upper part of the sequence, mudstone deposited probably deeper than 50 fathoms. As the rocks are 200 ft thick, the relative rise of sea level was more than 500 ft. The abundance of delicate thin-shelled Foraminifera, and the absence of Miliolidae and thick-shelled shallow-water forms, which are being transported widely throughout Cook Strait sediments by strong turbulent currents at the present day, indicate that a strait was not then in existence. The deposit does, however, provide evidence that makes possible a correlation of the lime and mode of development of Cook Strait with the Manawatu Gorge.

Notes on the Biology of Some Pogonophora

Observations have been made on living pogonophores obtained from the continental slope to the south-west of the British Isles and from the continental shelf off the west coast of Ireland.The blood of five species examined contains haemoglobin in solution. The tube appears to be freely permeable to water, but less so to electrolytes and small molecules.The appearance and behaviour of living embryos is noted and the spermatozoon of one species figured. Possible feeding and other behaviour is discussed and it is concluded that the best line of future investigation lies with the shallow-water forms found in the Arctic Ocean.

Petrography of Northeastern Lake Michigan Bottom Sediments

ABSTRACT A direct relationship between sediment properties and their environment of deposition, source material, and post-glacial history was shown by textural and mineralogical studies of cores and dredge samples obtained from northeastern Lake Michigan. The lake bottom topography of the area, which may be characterized as a valley-and-ridge province, exerts a very strong control on the distribution of sediments. In general the coarse sediments are found on the ridges and their adjacent flanks and fine sediments are restricted to the hollows between ridges. There is a regular variation in size with depth, but no regular variation in size with relation to distance from shore. The majority of bottom sediments are well sorted, but most of the samples from the lower portion of the flanks of troughs show poor sorting, probably the result of slumpage of coarser sediments from the higher portions on the flanks. Evidence for the Lake Chippewa low-water stage is shown by the following: Core samples taken from depths of water less than 275 feet contain coarse sediment overlying, underlying, or included within a sequence of much finer grained silty clay or clayey silt. The presence of shells of shallow-water forms in some of these coarse sediment zones and a peat deposit found in association with this coarse sediment give additional evidence of a low-water condition. The similarity of the mineralogy of the detrital sand-sized material in the lake sediments to that of the glacial drift from the adjacent shore shows that the lake sediments were derived mainly from that source. The general order of abundance of clay minerals in both the lake sediments and glacial till material from the adjacent shore is illite, mixed-layer chlorite and illite materials, and chlorite. Little variation in the clay mineral composition with changes in depth of water, distance from shore, or depth of burial was observed. In general the carbonate content of the lake bottom samples increases with a decrease in the median diameter of the sediment. There is, however, a lower carbonate content in the dark-gray sediments found in the deep troughs and in Little Traverse Bay: this is attributed to the solution of calcium carbonate as a result of a decrease in the pH within the sediment. Pyrite, in association with calcareous shell material, was found in many core samples, but not in glacial till samples from the adjacent land areas. The pyrite is interpreted as secondary, resulting from local reducing conditions produced by the decay of soft parts of the shelled organisms.

POLYCHAETOUS ANNELIDS FROM THE SHALLOW WATERS AROUND BARBADOS AND OTHER ISLANDS OF THE WEST INDIES, WITH NOTES ON LARVAL FORMS

Thirty-four species of polychaetous annelids, belonging to 16 families, are reported. Most of them come from the West Indian Island of Barbados but some were collected also, or only, in Jamaica. All are coastal, shallow water forms. Observations on the life history and in particular on larval forms are included when pertinent. Zoogeographical implications are considered briefly.

Effects of DDT Mosquito Larviciding on Wildlife Part III. The Effects on the Plankton Population of Routine Larviciding with DDT

The use of DDT as an anopheline larvicide has caused considerable concern in some groups because of the potentialities of destruction of other, more desirable forms of life in ponds and lakes. A series of studies has been undertaken to determine the extent, if any, of such damage. Among the organisms under consideration, fish are of prime importance to wildlife and sportsman interests, and might be affected in any of several ways: direct damage by poisoning and killing, reduction or destruction of desirable food organisms, or ecological changes resulting in unfavorable environmental and growth conditions. Ecologically, there are three groups of important fish-food organisms in areas commonly larvicided: the fauna of the bottom, the plankton organisms, and the surface and shallow-water forms. The present paper, the third in a series reporting on the effects of DDT larviciding on wildlife, is a report on the plankton, which is the chief food source for several species of fish and most fish fry. The present study was begun in the spring of 1945 on ponds located in the vicinity of Savannah, Ga. The ponds were all shallow and small, being typical of ponds in which breeding of Anopheles quadrimaculatus occurs.

Reports of the Australian Antarctic Expedition

THE scientific results of the Australian Antarctic Expedition are being published with commendable promptitude. Of the five parts recently received the most generally interesting is the report on the Brachiopoda by Dr. J. Allan Thomson, Wellington, N.Z. The Brachiopods recorded, though not many in number, are relatively rich in species, a new genus, Amphithyris (family Terebratellidae), and new species of seven other genera being described. The author gives a summary of the known distribution of Brachiopods in South Temperate and Antarctic seas, and discusses the bearing of the facts on the theories of southern land connections, “which it is one of the aims of Antarctic expeditions to prove or disprove.” He points out that the known larvae of Brachiopods, with the exception of those of Lingula and Discina (sensu lato), have no mouth during the free-swimming stage, and that they soon settle down. Consequently, the deep oceans are barriers which Brachiopods, the majority of which live on the submarine slopes of continents and adjacent islands, and their larvae cannot cross, and therefore cases of discontinuous distribution of these shallow-water forms have an important significance.

The British Association: Section D—Biology

On the Cause of the extreme Dissimilarity between the Faunas of the Red Sea and Mediterranean notwithstanding their recent connection, by Prof. Edward Hull, LL.D., F.R.S.—The faunas of the Mediterranean and of the Red Sea are so unlike that if the beds of the two seas were upraised, and their contents examined, naturalists would probably refer them to distinct geological periods. The dissimilarity is greater than was formerly supposed. In Woodward's “Manual of the Mollusca” it is stated that seventy-four species of mollusks are common to the two seas, but Prof. Issel, of Genoa, places the number at eighteen, or about 2 per cent. Equal differences exist if we compare other great groups of life; in fact, as Prof. Haeckel well observes, the fauna of the Red Sea is related to that of the Indian Ocean, the fauna of the Mediterranean to that of the Atlantic. This extreme dissimilarity would not surprise us if it were not for the proofs of recent connection between the two seas. Evidence of old sea margins, up to about 220 feet above the present sea-level, are frequently found along the Nile and in the valleys and plains of Philistria. As many of the marine forms found in these deposits still exist, the date of the submergence may be safely referred to that of the Pliocene; but it continued to a later period, and (in the author's opinion) it to some extent remained to the time of the Pharaohs. The existing fauna probably date; back to Eocene times, when the ocean spread widely over the area in question. In the Miocene period the main outlines of land and sea as we now find them were marked out, the deposits of this age being here small and local. Under the extremely different conditions existing in the two areas, the fauna during and after the Miocene period became differentiated. The connection re-established during and after the Pliocene period was insufficient to destroy these differences, although it allowed a mingling of forms to some extent. The maximum submergence was about 220 feet; but as the summit level between the two seas is about 50 feet, the depth of water would only be about 170 feet at the maximum. Only littoral and shallow-water forms would cross in the adult state; but many forms inhabiting deeper water in the adult state might have crossed when in the free-swimming larval state. When the land again rose, and the marine straits were finally effaced, the different physical conditions of the two seas would again come into effect. The difference of temperature is now very considerable, and probably was much greater during the Glacial period, especially if, as appears probable, the eastern or Levant basin of the Mediterranean were separated from the others; for into this would flow the cold waters of the Black Sea and of Central Europe, whilst the Red Sea would receive warm water, and be itself exposed to the rays of a tropical sun. It would be an interesting subject of inquiry—Which of these faunas most closely resembles that of the original stock?

Chalk and The “Origin and Distribution of Deep-Sea Deposits”

IN a letter of Mr. Starkie Gardner's in the last number of NATURE (p. 192), he stated that my opinion as to the Chalk having been a shallow-water deposit was “based exclusively on the present habits of the very few genera of Mollusca that have survived from the Chalk period, and seems quite in contradiction to the far more important groups, the Sponges, Echinodermata, and the minute organisms of which the formation is so largely composed, while no opinion has yet found its way into the hands of geologists regarding the depth of water indicated by the Crustacea and the fishes of the Chalk.” Mr. Gardner appears to have overlooked that passage in my Address to the Biological Section of the British Association (to which he refers in his letter), wherein I added, “Mr. Woodward tells me that the Chalk Crustacea are shallow-water forms.” Dr. Woodward is certainly no mean authority on fossil Crustacea. As to the surviving genera of Chalk Mollusca being “very few” in number, I would refer him and my readers to the long list of genera given in my Address, which was furnished by our great palaeontologist, Mr. Etheridge, and to the exclusively littoral habits of some of those genera. And with respect to the Sponges, Echinodermata, and minute organisms being “far more important groups” than the Mollusca, I must leave that question to naturalists in general. Sponges (silicious as well as horny or ceratose), and Echinoderms are notoriously not restricted to deep water. Quite the contrary. They live at every depth from the shore between tide-marks to the abyssal and benthal zones. The “minute organisms” which enter so largely into the composition of the Chalk, for the most part, if not entirely, inhabit the surface of the sea.