Morphometric variability in larvae of the Antarctic fly, Belgica antarctica (Diptera: Chironomidae)

1979 ◽  
Vol 57 (12) ◽  
pp. 2311-2318 ◽  
Author(s):  
William R. Atchley ◽  
Larry R. Hilburn
Keyword(s):  
Sexual Dimorphism ◽  
Head Capsule ◽  
Free Living ◽  
Holometabolous Insect ◽  
Limited Success ◽  
Belgica Antarctica ◽  
Ecological Parameters ◽  
Western Side ◽  
The Antarctic

Morphometric variability is examined in the larval head capsule of the midge Belgica antarctica Jacobs (Diptera: Chironomidae). This species is the southernmost free-living holometabolous insect and occurs over about a 650-km range on the western side of the Antarctic Peninsula. Highly significant differences were found between samples and between sexes for nine larval head capsule characters. No morphometric effect was found due to chromosomal inversion heterozygosity. The expression of sexual dimorphism was found to vary greatly between samples. Some samples exhibited no sexual dimorphism whereas others exhibited highly complex patterns of sexual dimorphism. Attempts to relate morphometric variability to geographic and ecological parameters met with only limited success. No correspondence was noted between the classification of samples based on inversion heterozygosity and that based on larval morphology.

RHYNCHOLITES AND THE PROBLEM OF NARROW AND BROAD CONCEPTION OF TAXONS

2018 ◽  
pp. 12-17 ◽  
Author(s):  
I. R. Khuzina ◽  
V. N. Komarov
Keyword(s):  
Sexual Dimorphism ◽  
Morphological Characteristics ◽  
Mass Scale ◽  
Individual Variability ◽  
Point Of View ◽  
The Other ◽  
New Taxon ◽  
Artificial System ◽  
Broad Understanding

The paper considers a point of view, based on the conception of the broad understanding of taxons. According to this point of view, rhyncholites of the subgenus Dentatobeccus and Microbeccus are accepted to be synonymous with the genus Rhynchoteuthis, and subgenus Romanovichella is considered to be synonymous with the genus Palaeoteuthis. The criteria, exercising influence on the different approaches to the classification of rhyncholites, have been analyzed (such as age and individual variability, sexual dimorphism, pathological and teratological features, degree of disintegration of material), underestimation of which can lead to inaccuracy. Divestment of the subgenuses Dentatobeccus, Microbeccus and Romanovichella, possessing very bright morphological characteristics, to have an independent status and denomination to their synonyms, has been noted to be unjustified. An artificial system (any suggested variant) with all its minuses is a single probable system for rhyncholites. The main criteria, minimizing its negative sides and proving the separation of the new taxon, is an available mass-scale material. The narrow understanding of the genus, used in sensible limits, has been underlined to simplify the problem of the passing the view about the genus to the other investigators and recognition of rhyncholites for the practical tasks.

Life history traits of adults and embryos of the Antarctic midge Belgica antarctica

Polar Biology ◽  
2014 ◽  
Vol 37 (8) ◽  
pp. 1213-1217 ◽  
Author(s):  
Eri Harada ◽  
Richard E. Lee ◽  
David L. Denlinger ◽  
Shin G. Goto
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Belgica Antarctica ◽  
The Antarctic

scholarly journals Application of Three Dimensional Geometric Morphometric Analysis for Sexual Dimorphism of Human Skull: A Systematic Review

2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Abdelnasser Ibrahim ◽  
Aspalilah Alias ◽  
Mohamed Swarhib Shafie ◽  
Faridah Mohd Nor
Keyword(s):  
Systematic Review ◽  
Sexual Dimorphism ◽  
Morphometric Analysis ◽  
Meta Analysis ◽  
Positive Contribution ◽  
Inclusion Criteria ◽  
Geometric Morphometric ◽  
Human Skull ◽  
Geometric Morphometric Analysis

The present systematic review explores the most sexually dimorphic parameters by using geometric morphometric analysis of human skull. An extended search was conducted in Google Scholars and PubMed (published between 2005 and 2017). The main inclusion criteria were research articles published in English, and studies that used geometric morphometric analysis for classification of human skull. The literature search identified 54 potential relevant articles whereby, five had met the inclusion criteria. Most studies reported positive contribution of geometric morphometric as an alternative and accurate tool for classification of unknown human crania. Geometric morphometric method resulted in a high classification accuracy of sexual dimorphism among different populations. Further studies are required to approach the best method used for varied types of postcranial bones equipped with a more advanced meta-analysis of the results.

Description of new chiactine-bearing sponges provides insights into the higher classification of Calcaronea (Porifera: Calcarea)

Zootaxa ◽  
2019 ◽  
Vol 4615 (2) ◽  
pp. 201
Author(s):  
ADRIANA ALVIZU ◽  
JOANA R. XAVIER ◽  
HANS TORE RAPP
Keyword(s):  
New Species ◽  
Phylogenetic Reconstruction ◽  
Molecular Data ◽  
Phylogenetic Study ◽  
Two New Species ◽  
Close Relationship ◽  
New Material ◽  
Relationship Of ◽  
The Antarctic

A recent phylogenetic study revealed a close relationship between chiactine-bearing (family Achramorphidae, order Leucosolenida) and pugiole-bearing (order Baerida) calcaronean sponges as well as new putative taxa within Achramorphidae. In this study, we present a revision of chiactine-bearing sponges based on morphological re-examination of type material and recently collected specimens, in addition to new molecular data for the ribosomal 18S and C-region of the 28S. We provide re-descriptions for all known chiactine-bearing species, and further describe two new species from the Antarctic (Achramorpha antarctica sp. nov. and Megapogon schiaparellii sp. nov.) and two new species and a new genus from the Nordic Seas (Achramorpha ingolfi sp. nov. and Sarsinella karasikensis gen. nov. sp. nov.). The new phylogenetic reconstruction based on ribosomal 18S and C-region of the 28S confirms previous findings about the close relationship of some members of Baerida and the family Achramorphidae of the order Leucosolenida. However, new material and the addition of molecular data from the type species of both taxa would be required to formally propose changes at (sub-)ordinal levels within the classification of Calcaronean sponges. 

Sexual Dimorphism in the Adipose Fin of Pacific Salmon (Oncorhynchus)

1983 ◽  
Vol 40 (11) ◽  
pp. 2019-2024 ◽  
Author(s):  
Terry D. Beacham ◽  
Clyde B. Murray
Keyword(s):  
Sexual Dimorphism ◽  
Chinook Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
Relative Size ◽  
Correct Identification ◽  
Actual Amount ◽  
Adipose Fin

Male adipose fins of Oncorhynchus species were 30–50% larger than those of same-sized females, the actual amount depending on the species. Accuracy of classification of the standards ranged from 87% in chinook salmon (O. tshawytscha) to 98% in pink salmon (O. gorbuscha). Testing the method on new samples usually resulted in an accuracy of at least 90% correct identification of sex for any species. Relative size of the adipose fin should allow for easy and accurate external identification of the sexes of silver-bright Oncorhynchus.

Sleep Thresholds in Depression

1962 ◽  
Vol 108 (455) ◽  
pp. 466-473 ◽  
Author(s):  
Irene Martin ◽  
Brian M. Davies
Keyword(s):  
Limited Success ◽  
Series Of Experiments ◽  
Biochemical Features

There are conflicting psychiatric opinions about the value of separating depressive illnesses into several syndromes on clinical grounds, and so far experimental attempts to reach a classification of depression by distinguishing physiological or biochemical features which characterize one group rather than another have had only limited success. One interesting series of experiments in this area has been that of Shagass and his colleagues on the sedation threshold (Shagass et al., 1956, Shagass and Naiman, 1956, Shagass, 1954); they report that neurotic and psychotic depressions can be differentiated by means of EEG and other reactions to sodium amytal (amylobarbitone sodium) neurotics requiring greater amounts of the drug to reach the sedation threshold.

New free-living marine nematode species (Nematoda: Desmodoridae) from the coast of New Zealand

Zootaxa ◽  
2010 ◽  
Vol 2611 (1) ◽  
pp. 45
Author(s):  
D. LEDUC ◽  
D. A. WHARTON
Keyword(s):  
New Zealand ◽  
Sexual Dimorphism ◽  
Nematode Species ◽  
Marine Nematode ◽  
Head Region ◽  
Free Living ◽  
Intertidal Sand

Pseudochromadora reathae n. sp. is described from intertidal sand in Otago Harbour (southern New Zealand), and Pseudodesmodora lacrima n. sp. is described from subtidal sediment in the Firth of Thames (northern New Zealand). Pseudochromadora reathae n. sp. differs from other species of the genus through the combination of the following characters: sexual dimorphism in the shape of the apertura amphidialis, no interdigitation of body annuli at level of lateral alae, presence of eight longitudinal rows of somatic setae, and conspicuous pre-cloacal supplements consisting of star-shaped projections flanked by two cuticularised pieces. Pseudodesmodora lacrima n. sp. is characterised by the presence of large unispiral amphids on amphidial plates, conspicuous ducts in the head region, low a values, and short cephalic setae.

scholarly journals Environmental factors influencing fine-scale distribution of Antarctica’s only endemic insect

Oecologia ◽  
2020 ◽  
Vol 194 (4) ◽  
pp. 529-539
Author(s):  
Leslie J. Potts ◽  
J. D. Gantz ◽  
Yuta Kawarasaki ◽  
Benjamin N. Philip ◽  
David J. Gonthier ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Spatial Scales ◽  
Abiotic Factors ◽  
Ecological Factors ◽  
Biotic Interactions ◽  
Species Distributions ◽  
Biotic Factors ◽  
Belgica Antarctica ◽  
Abiotic And Biotic Factors ◽  
The Antarctic

AbstractSpecies distributions are dependent on interactions with abiotic and biotic factors in the environment. Abiotic factors like temperature, moisture, and soil nutrients, along with biotic interactions within and between species, can all have strong influences on spatial distributions of plants and animals. Terrestrial Antarctic habitats are relatively simple and thus good systems to study ecological factors that drive species distributions and abundance. However, these environments are also sensitive to perturbation, and thus understanding the ecological drivers of species distribution is critical for predicting responses to environmental change. The Antarctic midge, Belgica antarctica, is the only endemic insect on the continent and has a patchy distribution along the Antarctic Peninsula. While its life history and physiology are well studied, factors that underlie variation in population density within its range are unknown. Previous work on Antarctic microfauna indicates that distribution over broad scales is primarily regulated by soil moisture, nitrogen content, and the presence of suitable plant life, but whether these patterns are true over smaller spatial scales has not been investigated. Here we sampled midges across five islands on the Antarctic Peninsula and tested a series of hypotheses to determine the relative influences of abiotic and biotic factors on midge abundance. While historical literature suggests that Antarctic organisms are limited by the abiotic environment, our best-supported hypothesis indicated that abundance is predicted by a combination of abiotic and biotic conditions. Our results are consistent with a growing body of literature that biotic interactions are more important in Antarctic ecosystems than historically appreciated.

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