Search results for "VIPER"
showing 10 items of 23 documents
Comments on Guimarães & Sawaya. Pretending to be venomous: is a snake's head shape a trustworthy signal to a predator?
2011
Several species of non-venomous snake are known to flatten their heads when disturbed, and this behaviour has been suggested to be a mimicry of vipers (Arnold & Ovenden 2002, Hailey & Davies 1986, Young et al. 1999). Using plasticine models, Guimaraes & Sawaya (2011) tested the antipredatory function of a triangular head shape in snakes. Their article presents the first published empirical experiment testing the adaptive significance of vipers’ triangular head shape. Guimaraes & Sawaya (2011) found no support for the viper mimicry hypothesis. Accordingly, they concluded that ‘the shape of [the] head seemed not to confer advantage itself’. Although the use of plasticine models is a generally…
Vipera aspis hugyi (Southern Italian Asp) Coloration
2020
We report the first observation of concolor coloration in Vipera aspis hugyi
Significance of the dorsal zigzag pattern of Vipera latastei gaditana against avian predators
2005
Summary 1. Aposematism is an antipredatory strategy in which prey animals conspicuously signal their noxiousness to potential predators. This successful strategy is based on avoidance learning of predators. 2. Most species in the viperid genus Vipera have a characteristic dorsal zigzag pattern. It has previously been suggested that the dorsal zigzag pattern of Vipera berus (the adder) has a cryptic function and thus makes the snake less conspicuous to avian predators. However, a recent experiment suggested that the pattern may function as an aposematic signal rather than being cryptic, and therefore induces active avoidance in avian predators. 3. We conducted a field experiment in Donana na…
First helminthological data on Iberian vipers: Helminth communities and host-parasite relationships
2006
AbstractEuropean vipers are ambush predators with sporadic feeding events, thereby maintaining the digestive tract empty for long periods. According to previous studies relating lizards’ dietary habits and their helminth faunas, we predict poor gastrointestinal helminth communities in vipers. To test this hypothesis, we have examined the digestive tract of 86 specimens of Vipera aspis (L., 1758) and V. latastei Boscá, 1878, from several localities of the Iberian Peninsula. We found adults of only two nematode species Kalicephalus viperae (Rud., 1819) and Ophidascaris sp. and cysts adhering to the external wall on the stomach in case of two other nematode species Ascarops strongylina (Rud., …
Amino acid sequence and homology modeling of obtustatin, a novel non-RGD-containing short disintegrin isolated from the venom of Vipera lebetina obtu…
2003
Disintegrins represent a group of cysteine-rich peptides occurring in Crotalidae and Viperidae snake venoms, and are potent antagonists of several integrin receptors. A novel disintegrin, obtustatin, was isolated from the venom of the Vipera lebetina obtusa viper, and represents the first potent and selective inhibitor of the binding of integrin alpha(1)beta(1) to collagen IV. The primary structure of obtustatin contains 41 amino acids and is the shortest disintegrin described to date. Obtustatin shares the pattern of cysteines of other short disintegrins. However, in contrast to known short disintegrins, the integrin-binding loop of obtustatin is two residues shorter and does not express t…
Protective coloration of European vipers throughout the predation sequence
2020
Antipredator adaptations in the form of animal coloration are common and often multifunctional. European vipers (genus Vipera) have a characteristic dorsal zigzag pattern, which has been shown to serve as a warning signal to potential predators. At the same time, it has been suggested to decrease detection risk, and to cause a motion dazzle or flicker-fusion effect during movement. We tested these hypotheses by asking whether (1) the zigzag pattern decreases detection risk and (2) the detection is dependent on the base coloration (grey or brown) or the snake's posture (coiled, basking form or S-shaped, active form). Additionally, (3) we measured the fleeing speed of adders, Vipera berus, an…
Resembling a Viper: Implications of Mimicry for Conservation of the Endangered Smooth Snake
2014
The phenomenon of Batesian mimicry, where a palatable animal gains protection against predation by resembling an unpalatable model, has been a core interest of evolutionary biologists for 150 years. An extensive range of studies has focused on revealing mechanistic aspects of mimicry (shared education and generalization of predators) and the evolutionary dynamics of mimicry systems (co-operation vs. conflict) and revealed that protective mimicry is widespread and is important for individual fitness. However, according to our knowledge, there are no case studies where mimicry theories have been applied to conservation of mimetic species. Theoretically, mimicry affects, for example, frequency…
iOS lietotņu arhitektūras risinājumi
2018
Viena no būtiskākajām programmatūras izstrādes daļām ir arhitektūras izvēle. Ja programmatūras izstrādes ciklā šim aspektam nav pievērsta liela uzmanība, projekts paliek grūti uzturams un ieviest jaunu funkcionalitāti paliek arvien grūtāk. Bakalaura darbā tiek apskatītas iOS lietotņu arhitektūras, to labās prakses un nepieciešamās tehnoloģijas, lai tās praktiski ieviestu. Darba praktiskajā daļā esoša laika projektā, kur arhitektūras izvēle bijusi neefektīva, vienā no moduļiem tiek ieviesti trīs arhitektūras tēli – MVVM, MVP un VIPER. Arhitektūras tēli tiek salīdzināti pēc to darbietilpības, izmantotajām tehnoloģijām, kā arī tika veikts ekspertu novērtējums, kurā nozares eksperti vērtēja izs…
Suomalaisten pörssiyhtiöiden irtisanomiset : kannattavuusseuraukset lyhyellä aikavälillä
2016
Kollektiiviperusteiset irtisanomiset ovat vakiinnuttaneet paikkansa liikkeenjohdollisena perustoimenpiteenä kannattavuuden parantamiseksi. Tämä tutkimus paneutuu asiaan taloudellisten seurausten näkökulmasta. Menetelmällisesti tutkimus pohjautuu De Meusen, Vanderheidenin ja Bergmannin vuonna 1994 julkaistuun artikkeliin ”Announced Layoffs: Their Effect on Corporate Financial Performance”. Tutkimusongelmina on selvittää, onko kollektiiviperusteisilla irtisanomisilla vaikutusta suomalaisten pörssiyhtiöiden kannattavuuteen, ja eroaako irtisanoneiden yhtiöiden taloudellinen suorituskyky yhtiöistä, jotka eivät irtisanoneet. Yhtiöiden kannattavuutta tarkasteltiin vuosilta 2010-2014, ja irtisanomi…
Antipredatory function of head shape for vipers and their mimics.
2011
Most research into the adaptive significance of warning signals has focused on the colouration and patterns of prey animals. However, behaviour, odour and body shape can also have signal functions and thereby reduce predators' willingness to attack defended prey. European vipers all have a distinctive triangular head shape; and they are all venomous. Several non-venomous snakes, including the subfamily Natricinae, commonly flatten their heads (also known as head triangulation) when disturbed. The adaptive significance of this potential behavioural mimicry has never been investigated. We experimentally tested if the triangular head shape typical of vipers offers protection against predation.…