The snake head-shape signal: a reply to Valkonen & Mappes

2011 ◽  
Vol 28 (1) ◽  
pp. 125-126 ◽  
Author(s):  
Murilo Guimarães ◽  
Ricardo J. Sawaya
Keyword(s):  
Head Shape ◽  
Plasticine Models

It has already been suggested that snake head triangulation might be related to mimicry of the head shape of vipers (Greene & McDiarmid 2005, and references therein). Until very recently, this hypothesis has never been experimentally tested. We first tested the hypothesis of snakes’ head shape as a dangerous signal to predators by use of plasticine models (Guimarães & Sawaya 2011). We suggested in that study that shape of the head does not confer advantage itself but may work in synergy with a set of traits including colour and behavioural displays that warn and discourage predator attacks.

Comments on Guimarães & Sawaya. Pretending to be venomous: is a snake's head shape a trustworthy signal to a predator?

2011 ◽  
Vol 28 (1) ◽  
pp. 123-124 ◽  
Author(s):  
Janne K. Valkonen ◽  
Johanna Mappes
Keyword(s):  
Prey Species ◽  
Adaptive Significance ◽  
Predation Pressure ◽  
Olfactory Cues ◽  
Head Shape ◽  
Venomous Snake ◽  
Avian Predators ◽  
Empirical Experiment ◽  
Plasticine Models

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, Guimarães & 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. Guimarães & 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 accepted method of testing predation pressure on snakes, we argue that the experiment may have failed to find the antipredatory function of triangulation due to the pooling of attacks by mammalian and avian predators. Mammals generally rely on olfactory cues during foraging. Plasticine has a strong odour which does not resemble the odour of any prey species. It is thus unlikely that mammals would treat snake replicas as true snakes.

3D-Measuring for Head Shape Covering Hair

2011 ◽  
Vol 131 (12) ◽  
pp. 2082-2088 ◽  
Author(s):  
Tsukasa Kato ◽  
Koosuke Hattori ◽  
Takuya Nomura ◽  
Ryo Taguchi ◽  
Masahiro Hoguro ◽  
...  
Keyword(s):  
Head Shape

scholarly journals Variation in pleiotropic hub gene expression is associated with interspecific differences in head shape and eye size in Drosophila

2021 ◽  
Author(s):  
Elisa Buchberger ◽  
Anıl Bilen ◽  
Sanem Ayaz ◽  
David Salamanca ◽  
Cristina Matas de las Heras ◽  
...  
Keyword(s):  
Natural Variation ◽  
Compound Eye ◽  
Genetic Manipulation ◽  
Morphological Evolution ◽  
Morphological Diversity ◽  
Network Evolution ◽  
Head Shape ◽  
Eye Size ◽  
Recurrent Mutations ◽  
Repeated Evolution

Abstract Revealing the mechanisms underlying the breath-taking morphological diversity observed in nature is a major challenge in Biology. It has been established that recurrent mutations in hotspot genes cause the repeated evolution of morphological traits, such as body pigmentation or the gain and loss of structures. To date, however, it remains elusive whether hotspot genes contribute to natural variation in the size and shape of organs. Since natural variation in head morphology is pervasive in Drosophila, we studied the molecular and developmental basis of differences in compound eye size and head shape in two closely related Drosophila species. We show differences in the progression of retinal differentiation between species and we applied comparative transcriptomics and chromatin accessibility data to identify the GATA transcription factor Pannier (Pnr) as central factor associated with these differences. Although the genetic manipulation of Pnr affected multiple aspects of dorsal head development, the effect of natural variation is restricted to a subset of the phenotypic space. We present data suggesting that this developmental constraint is caused by the co-evolution of expression of pnr and its co-factor u-shaped (ush). We propose that natural variation in expression or function of highly connected developmental regulators with pleiotropic functions is a major driver for morphological evolution and we discuss implications on gene regulatory network evolution. In comparison to previous findings, our data strongly suggests that evolutionary hotspots are not the only contributors to the repeated evolution of eye size and head shape in Drosophila.

Radiographic Measurements of the Affected and Unaffected Feet in Patients with Unilateral Hallux Limitus

2016 ◽  
Vol 106 (3) ◽  
pp. 172-181
Author(s):  
Andrew F. Knox ◽  
Alan R. Bryant
Keyword(s):  
Metatarsal Head ◽  
Radiographic Evaluation ◽  
Head Shape ◽  
Intrinsic Factors ◽  
Hallux Limitus ◽  
First Metatarsal ◽  
Radiographic Measurements ◽  
Angle Data ◽  
Significant Difference ◽  
First Ray

Background: Controversy exists regarding the structural and functional causes of hallux limitus, including metatarsus primus elevatus, a long first metatarsal, first-ray hypermobility, the shape of the first metatarsal head, and the presence of hallux interphalangeus. Some articles have reported on the radiographic evaluation of these measurements in feet affected by hallux limitus, but no study has directly compared the affected and unaffected feet in patients with unilateral hallux limitus. This case-control pilot study aimed to establish whether any such differences exist. Methods: Dorsoplantar and lateral weightbearing radiographs of both feet in 30 patients with unilateral hallux limitus were assessed for grade of disease, lateral intermetatarsal angle, metatarsal protrusion distance, plantar gapping at the first metatarsocuneiform joint, metatarsal head shape, and hallux abductus interphalangeus angle. Data analysis was performed using a statistical software program. Results: Mean radiographic measurements for affected and unaffected feet demonstrated that metatarsus primus elevatus, a short first metatarsal, first-ray hypermobility, a flat metatarsal head shape, and hallux interphalangeus were prevalent in both feet. There was no statistically significant difference between feet for any of the radiographic parameters measured (Mann-Whitney U tests, independent-samples t tests, and Pearson χ2 tests: P > .05). Conclusions: No significant differences exist in the presence of the structural risk factors examined between affected and unaffected feet in patients with unilateral hallux limitus. The influence of other intrinsic factors, including footedness and family history, should be investigated further.

Examining Head-shape Differences and Ecology in Morphologically Similar Salamanders at Their Zone of Contact

Copeia ◽  
2016 ◽  
Vol 104 (1) ◽  
pp. 233-242 ◽  
Author(s):  
Jennifer Deitloff ◽  
Claire Floyd ◽  
Sean P. Graham
Keyword(s):  
Head Shape

Disorders of Head Shape and Size

2020 ◽  
pp. 957-999
Author(s):  
Essam A. Elgamal ◽  
Mustafa A. M. Salih
Keyword(s):  
Head Shape ◽  
Shape And Size

A mutation study of sperm head shape and motility in the mouse: lessons for the clinic

Andrology ◽  
2014 ◽  
Vol 3 (2) ◽  
pp. 174-202 ◽  
Author(s):  
P. de Boer ◽  
M. de Vries ◽  
L. Ramos
Keyword(s):  
Sperm Head ◽  
Head Shape
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