Growth rates of pterobranchs and the lifespan of graptolites

Paleobiology ◽  
1993 ◽  
Vol 19 (4) ◽  
pp. 459-475 ◽  
Author(s):  
Susan Rigby ◽  
P. Noel Dilly
Keyword(s):  
Environmental Stress ◽  
Water Column ◽  
Growth Rates ◽  
Life Tables ◽  
Taxonomic Significance ◽  
Utica Shale ◽  
Minimum Age ◽  
First Time

Pterobranchs are the closest living relatives of graptolites. Their skeleton is constructed from the same material, and in a homologous manner. Growth rates of the pterobranch Cephalodiscus gracilis are described for the first time and, along with rhabdopleuran growth rates, they are used to estimate the amount of time invested by a graptolite colony in growing its rhabdosome. This is a measure of minimum age. The significance of age calculations is shown for individuals and large communities of graptoloids. Large individuals can be shown to be much older than the time it would have taken them to settle through seawater and so it is shown that graptoloids moved up, as well as down, through the water column. Life tables constructed for biserial graptoloids from the Utica shale in Quebec, Canada, suggest that these graptoloids died from constant environmental stress. Graptoloid length can thus be a function of environment and should only cautiously be considered to be of taxonomic significance.

A population birth-and-mutation process, I: explicit distributions for the number of mutants in an old culture of bacteria

1974 ◽  
Vol 11 (03) ◽  
pp. 437-444 ◽  
Author(s):  
Benoit Mandelbrot
Keyword(s):  
Growth Rate ◽  
Mutation Rate ◽  
Growth Rates ◽  
Random Variable ◽  
Mutation Process ◽  
Limit Condition ◽  
Rate Of Growth ◽  
Mathematical Techniques ◽  
First Time

Luria and Delbrück (1943) have observed that, in old cultures of bacteria that have mutated at random, the distribution of the number of mutants is extremely long-tailed. In this note, this distribution will be derived (for the first time) exactly and explicitly. The rates of mutation will be allowed to be either positive or infinitesimal, and the rate of growth for mutants will be allowed to be either equal, greater or smaller than for non-mutants. Under the realistic limit condition of a very low mutation rate, the number of mutants is shown to be a stable-Lévy (sometimes called “Pareto Lévy”) random variable, of maximum skewness ß, whose exponent α is essentially the ratio of the growth rates of non-mutants and of mutants. Thus, the probability of the number of mutants exceeding the very large value m is proportional to m –α–1 (a behavior sometimes referred to as “asymptotically Paretian” or “hyperbolic”). The unequal growth rate cases α ≠ 1 are solved for the first time. In the α = 1 case, a result of Lea and Coulson is rederived, interpreted, and generalized. Various paradoxes involving divergent moments that were encountered in earlier approaches are either absent or fully explainable. The mathematical techniques used being standard, they will not be described in detail, so this note will be primarily a collection of results. However, the justification for deriving them lies in their use in biology, and the mathematically unexperienced biologists may be unfamiliar with the tools used. They may wish for more details of calculations, more explanations and Figures. To satisfy their needs, a report available from the author upon request has been prepared. It will be referred to as Part II.

A Revision of the Subfamily Microscaphidiinae (Platyhelminthes, Digenea, Microscaphidiidae) Parasitic in Marine Turtles (Reptilia, Chelonia)

1986 ◽  
Vol 34 (2) ◽  
pp. 241 ◽  
Author(s):  
D Blair
Keyword(s):  
Green Turtle ◽  
Chelonia Mydas ◽  
Nomen Nudum ◽  
Taxonomic Significance ◽  
Marine Turtles ◽  
As Species ◽  
First Time ◽  
Species Inquirendae

A revision of the subfamily Microscaphidiinae Looss, 1900 is presented and characters of taxonomic significance discussed. The genus Microscaphidium Looss, 1900, contains M. reticulare (van Beneden, 1859) Looss, 1901 (synonyms M. japonicum Oguro, 1941; M. caballeroi Groschaft, 1977); M. aberrans Looss, 1902 (synonym M. reticulare in part); and M, warui, sp. nov. Confusion in the literature over the identities of M. reticulare and M. aberrans is discussed. A neotype is selected for the former species and a lectotype for the latter. Polyangium linguatula (Looss, 1899) Looss, 1902 (synonyms P. miyajimai Kobayashi, 1921; P. colymbi Poche, 1925; P. longiseminale Chattopadhyaya, 1972) is the sole species in Polyangium Looss, 1902. The genus Angiodictyum Looss, 1902 contains A. parallelum (Looss, 1901) Looss, 1902; A. posterovitellatum Chattopadhyaya, 1972; A. longum, sp, nov.; A. glossoides, sp. nov. Polygorgyra, gen. nov., is proposed for P. cholados, sp. nov. Microscaphidium chelonei Chattopadhyaya, 1972 nec Mehrotra, 1973 and Angiodictyum anteroporum Chattopadhyaya, 1972 are regarded as species inquirendae. Microscaphidium chelonei Mehrotra, 1973 nec Chattopadhyaya, 1972 is a nomen nudum. The following species are recorded for the first time from the green turtle, Chelonia mydas (L.) in Australian waters: Microscaphidium reticulare; M. aberrans; M. warui; Angiodictyum posterovitellatum; A. longum; Polygorgyra cholados.

scholarly journals Coriolis effects on the elliptical instability in cylindrical and spherical rotating containers

2007 ◽  
Vol 585 ◽  
pp. 323-342 ◽  
Author(s):  
M. LE BARS ◽  
S. LE DIZÈS ◽  
P. LE GAL
Keyword(s):  
Growth Rates ◽  
Close Agreement ◽  
Unstable Mode ◽  
Quantitative Agreement ◽  
Fixed Rate ◽  
Elliptical Instability ◽  
Normal Mode Theory ◽  
Set Up ◽  
First Time ◽  
Selection Of

The effects of the Coriolis force on the elliptical instability are studied experimentally in cylindrical and spherical rotating containers placed on a table rotating at a fixed rate $\tilde{\Omega}^G$. For a given set-up, changing the ratio ΩG of global rotation $\tilde{\Omega}^G$ to flow rotation $\tilde{\Omega}^F$ leads to the selection of various unstable modes due to the presence of resonance bands, in close agreement with the normal-mode theory. No instability occurs when ΩG varies between −3/2 and −1/2 typically. On decreasing ΩG toward −1/2, resonance bands are first discretized for ΩG<0 and progressively overlap for −1/2 ≪ ΩG < 0. Simultaneously, the growth rates and wavenumbers of the prevalent stationary unstable mode significantly increase, in quantitative agreement with the viscous short-wavelength analysis. New complex resonances have been observed for the first time for the sphere, in addition to the standard spin-over. We argue that these results have significant implications in geo- and astrophysical contexts.

scholarly journals HISTORY OF ANTHROPOLOGICAL RESEARCHES OF BELARUSIAN CHILDREN, TEENAGERS AND YOUTH (the end of 19th– the beginning of the 21st century)

2018 ◽  
Vol 63 (3) ◽  
pp. 317-328
Author(s):  
O. V. Marfina
Keyword(s):  
Growth Rates ◽  
Physical Development ◽  
Acceleration Process ◽  
Historical Aspect ◽  
Somatic Development ◽  
Anthropological Study ◽  
History Of ◽  
Important Direction ◽  
The 19Th Century ◽  
First Time

The work purpose is to present history of anthropological study of physical development of the Belarusian children, teenagers and youth. This story originates at the end of the 19th century, at that time the anthropological science endured the period of the formation. In 1920 one of national objectives was health protection of younger generation; systematic study of physical development of the children’s population of BSSR began to be carried out. In the same time uniform methodical approaches were developed, mathematical data processing was introduced. Standards of physical development of the Belarusian children were for the first time created. In 1950 mass researches of health and physical status of children and teenagers in our republic were conducted by forces of doctors and hygienists. Results of their work allowed to establish dynamics and to reveal the main regularities of formation of a children’s organism. New age and sex standards of physical development of school children were created. Since 1970, the staff of department of anthropology of Institute of history NAN of Belarus conducts systematic complex researches of physical development of children, teenagers and youth. Researches include studying of intra group distinctions taking into account growth rates and definition like somatic development. Researches include studying of intra group distinctions taking into account growth rates and definition like somatic development. Thanks to this work in our republic the results illustrating the most important epoch-making regularities of physical development of newborns, preschool children, pupils of schools including acceleration process were received. In historical aspect the most important direction of anthropological researchers at the present stage is monitoring of physical development of the children’s population of Republic of Belarus. Reduction of massiveness of a skeleton was observed in consequence of which a thinner constitution of modern children at the age of 7–17 years is noticed. 

scholarly journals The Waterston’s evaporatorium of Ceraphronidae (Ceraphronoidea, Hymenoptera): A morphological barcode to a cryptic taxon

2021 ◽  
Vol 85 ◽  
pp. 29-56
Author(s):  
Jonah M. Ulmer ◽  
István Mikó ◽  
Andrew R. Deans ◽  
Lars Krogmann
Keyword(s):  
Phylogenetic Analysis ◽  
Potential Function ◽  
Parasitoid Wasp ◽  
Species Level ◽  
Exocrine Gland ◽  
Dorsal Vessel ◽  
Taxonomic Significance ◽  
Character Set ◽  
Males And Females ◽  
First Time

The Waterston’s evaporatorium (=Waterston’s organ), a cuticular modification surrounding the opening of an exocrine gland located on metasomal tergite 6, is characterized and examined for taxonomic significance within the parasitoid wasp family Ceraphronidae. Modification of the abdominal musculature and the dorsal vessel are also broadly discussed for the superfamily Ceraphronoidea, with a novel abdominal pulsatory organ for Apocrita being discovered and described for the first time. Cuticular modification of T6, due to the presence of the Waterston’s evaporatorium, provides a character complex that allows for genus- and species-level delimitation in Ceraphronidae. The matching of males and females of a species using morphology, a long standing challenge for the group, is also resolved with this new character set. Phylogenetic analysis including 19 Waterston’s evaporatorium related characters provides support for current generic groupings within the Ceraphronidae and elaborates on previously suggested synapomorphies. Potential function of the Waterston’s organ and its effects on the dorsal vessel are discussed.

Updating the International Seafarers' Code: Recent Developments

1997 ◽  
Vol 12 (3) ◽  
pp. 341-363 ◽  
Author(s):  
George P. Politakis
Keyword(s):  
State Control ◽  
Private Placement ◽  
Hours Of Work ◽  
Recent Developments ◽  
Labour Standards ◽  
Minimum Age ◽  
Changing Practices ◽  
Working And Living Conditions ◽  
First Time ◽  
Core Issues

AbstractMaritime labour matters have traditionally been of particular importance as far as the ILO's standard-setting function is concerned. To date, the ILO has adopted a total of 39 conventions and 30 recommendations-a body of labour standards known as the International Seafarer's Code-addressing the specific problems related to the working and living conditions of seafarers. The 84th (Maritime) session of the International Labour Conference, held in October 1996, undertook to revise core issues of this body of standards in the light of rapidly changing practices and needs of the maritime sector. This article traces briefly the negotiating history and highlights some of the most salient aspects of the new conventional instruments such as the setting of the minimum age for seafarers at 16 years, the adoption of a convention for the first time on labour inspection, the establishment of daily and weekly limitations on hours of work, the extension of port state control (as provided for in ILO Convention 147) in matters concerning hours of work and manning, or the recognition of private placement services for seafarers.

scholarly journals Morphology of the sporophyte and gametophyte of the swamp fern, Blechnum serrulatum (Blechnaceae, Pteridophyta)

2010 ◽  
Vol 58 (6) ◽  
pp. 508 ◽  
Author(s):  
C. H. Rolleri ◽  
C. Prada ◽  
J. M. Gabriel y Galán ◽  
L. M. Passarelli ◽  
M. M. Ciciarelli
Keyword(s):  
Spore Germination ◽  
Cell Walls ◽  
Taxonomic Significance ◽  
Comprehensive Description ◽  
First Time ◽  
The Relationship ◽  
Blechnum Serrulatum

In the present paper, we provide a revised, comprehensive description of the sporophyte and gametophyte of the swamp fern, Blechnum serrulatum Rich., from neo- and paleotropical localities. External and internal characters of the sporophyte were analysed, including axes, laminae, pinnae, indusia and spores. Intercellular pectic connections of the parenchyma of the rhizomes are reported for the first time. In stipes, cell walls of the aerenchyma tissue contain filamentous protuberances that are composed primarily of cellulose but contain also fatty substances. The morphology of the gametophyte, from spore germination to gametangia formation, is discussed. The taxonomic significance of the characters is considered, especially in regard to the relationship between B. serrulatum and the closely related B. indicum.

Ernietta from the late Edicaran Nama Group, Namibia

2016 ◽  
Vol 90 (6) ◽  
pp. 1017-1026 ◽  
Author(s):  
David A. Elliott ◽  
Peter W. Trusler ◽  
Guy M. Narbonne ◽  
Patricia Vickers-Rich ◽  
Nicole Morton ◽  
...  
Keyword(s):  
Water Column ◽  
Body Length ◽  
Type Species ◽  
Body Wall ◽  
Original Description ◽  
The Body ◽  
Dorsal Part ◽  
Taxonomic Significance ◽  
Field Site ◽  
On Farm

AbstractErnietta plateauensis Pflug, 1966 is the type species of the Erniettomorpha, an extinct clade of Ediacaran life. It was likely a gregarious, partially infaunal organism. Despite its ecological and taxonomic significance, there has not been an in-depth systematic description in the literature since the original description fell out of use. A newly discovered field site on Farm Aar in southern Namibia has yielded dozens of specimens buried in original life position. Mudstone and sandstone features associated with the fossils indicate that organisms were buried while still exposed to the water column rather than deposited in a flow event. Ernietta plateauensis was a sac-shaped erniettomorph with a body wall constructed from a double layer of tubes. It possessed an equatorial seam lying perpendicular to the tubes. The body is asymmetrical on either side of this seam. The tubes change direction along the body length and appear to be constricted together in the dorsal part of the organism.

Immature stages of Calycopis bellera (Hewitson) and C. janeirica (Felder) (Lepidoptera, Lycaenidae, Theclinae, Eumaeini): Taxonomic significance and new evidence for detritivory

Zootaxa ◽  
2009 ◽  
Vol 2325 (1) ◽  
pp. 39-61 ◽  
Author(s):  
MARCELO DUARTE ◽  
ROBERT K. ROBBINS
Keyword(s):  
Morphological Characters ◽  
Sexually Dimorphic ◽  
Immature Stages ◽  
Taxonomic Significance ◽  
Larval Instars ◽  
Species Groups ◽  
Males And Females ◽  
First Time ◽  
New Evidence

Details of egg, larval, and pupal morphology are described and illustrated for Calycopis bellera (Hewitson) and C. janeirica (Felder), with a special emphasis on larval chaetotaxy. Wild-caught Calycopis females laid eggs on dead leaves in the laboratory, and the caterpillars successfully completed development on an artificial agar diet to which no leaves were added. Males and females of the sexually dimorphic C. bellera had been previously placed in different genera or different species groups. Calycopis janeirica had been chronically misidentified (and misspelled C. jeneirica). Males and females of this species appear to be correctly associated for the first time. Whereas C. bellera has five larval instars—as reported previously for C. caulonia—C. janeirica has four. Morphological characters of the immatures of C. bellera and C. janeirica are summarized in a table and compared with those of other reared Calycopis species.

Life history of a small form of the plethodontid salamander Desmognathus quadramaculatus

2003 ◽  
Vol 24 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Christopher Beachy ◽  
Richard Bruce
Keyword(s):  
Growth Rates ◽  
Frequency Distributions ◽  
Plethodontid Salamander ◽  
Plethodontid Salamanders ◽  
Body Sizes ◽  
Minimum Age ◽  
History Of ◽  
Desmognathus Quadramaculatus ◽  
Gravid Females ◽  
Age At Maturation

AbstractWe sampled Desmognathus quadramaculatus, one of the largest species of plethodontid salamanders in eastern North America, from a population exhibiting extremely small adult body sizes in the Bald Mountains of North Carolina (USA). In order to test the hypothesis that miniaturization in desmognathine salamanders is due to early metamorphosis and maturation, we estimated ages and sizes at metamorphosis and maturation. Analysis of size-frequency distributions suggests that most larvae metamorphose after 24 months, with the remainder metamorphosing after 36. The minimum age of sexually mature individuals in the summer months is estimated to be 4 years in males and 5 years in females; some may mature 1 year earlier. This is earlier than other reliable estimates of age at maturation in D. quadramaculatus, and appears to account for the small size of the species at this locality. Larval and juvenile growth rates are within the range of growth rates of other populations. As in other populations of D. quadramaculatus, males are smaller than females at maturation, but grow to larger sizes. Estimates of clutch sizes based on dissection of gravid females are relatively low. The other species of salamanders in this community do not appear to be miniaturized.

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