Does allometric growth explain the diminutive size of the fangs of Scytodes (Araneae: Scytodidae)?

Suter, Robert B.; Stratton, Gail E.

doi:10.1636/b10-10.1

Cited by 7 publications

(5 citation statements)

References 15 publications

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“…In spiders the common reference character is carapace width [ 92 ]. However, to study the comparative allometry of fang size in three spider species ( Scytodes thoracica , Loxosceles reclusa , and, Varacosa avara ), Suter and Stratton [ 70 ] opted to use sternum width as a proxy for size. The authors contended that use of carapace width was inappropriate, as it has been targeted by selection to a greater extent in Scytodes (indirectly due to venom gland hypertrophy [ 101 ]) than in other species.…”

Section: Discussionmentioning

confidence: 99%

“…The optimal scenario is to use a reference character that correlates with size, is independent of nutritional state[ 67 ], and is itself non-dimorphic[ 63 ]. However, the choice of an appropriate reference character can be fraught with difficulty [ 62 , 63 , 68 – 70 ], and may require the measurement of numerous body components. Choice of a reference character for body size can profoundly affect the assessment of dimorphism and its interpretation.…”

Section: Introductionmentioning

confidence: 99%

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The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism, Sexual Body Component Dimorphism, and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

2015

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Sexual differences in morphology, ranging from subtle to extravagant, occur commonly in many animal species. These differences can encompass overall body size (sexual size dimorphism, SSD) or the size and/or shape of specific body parts (sexual body component dimorphism, SBCD). Interacting forces of natural and sexual selection shape much of the expression of dimorphism we see, though non-adaptive processes may be involved. Differential scaling of individual features can result when selection favors either exaggerated (positive allometry) or reduced (negative allometry) size during growth. Studies of sexual dimorphism and character scaling rely on multivariate models that ideally use an unbiased reference character as an overall measure of body size. We explored several candidate reference characters in a cryptically dimorphic taxon, Hadrurus arizonensis. In this scorpion, essentially every body component among the 16 we examined could be interpreted as dimorphic, but identification of SSD and SBCD depended on which character was used as the reference (prosoma length, prosoma area, total length, principal component 1, or metasoma segment 1 width). Of these characters, discriminant function analysis suggested that metasoma segment 1 width was the most appropriate. The pattern of dimorphism in H. arizonensis mirrored that seen in other more obviously dimorphic scorpions, with static allometry trending towards isometry in most characters. Our findings are consistent with the conclusions of others that fecundity selection likely favors a larger prosoma in female scorpions, whereas sexual selection may favor other body parts being larger in males, especially the metasoma, pectines, and possibly the chela. For this scorpion and probably most other organisms, the choice of reference character profoundly affects interpretations of SSD, SBCD, and allometry. Thus, researchers need to broaden their consideration of an appropriate reference and exercise caution in interpreting findings. We highly recommend use of discriminant function analysis to identify the least-biased reference character.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism, Sexual Body Component Dimorphism, and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

2015

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“…For each trial, we selected a cricket based on its size relative to the spider. After euthanizing spiders, we were able to take more precise measurements of relative prey size, using spider sternum width as a proxy for spider body size (Lee, Somers, & Chown, ; Suter & Stratton, ). A spider's sternum is a single sclerotized plate, and unlike other measurements, like mass or body length, sternum width does not change based on how recently or how much a spider has eaten.…”

Section: Methodsmentioning

confidence: 99%

Ontogenetic approach reveals how cognitive capability and motivation shape prey‐searching behavior in Pholcus phalangioides cellar spiders

2018

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An important part of understanding the evolution of behavior is understanding how and why behavior develops and changes throughout ontogeny. Patterns of behavior are shaped by an animal's capabilities as well as its motivations, both of which are subject to selection. We ran an experiment to see how spiders' efforts to recover lost prey change with age and to determine the relative contributions of shifts in capability and motivation. We found that as spiders mature, they spend less time searching to recover lost prey, and they discriminate less between prey of different sizes. We also found that even the youngest, least experienced spiders are cognitively equipped to search for lost prey. Thus, predatory behavior in spiders fluctuated primarily with each age group's motivations to capture and consume prey, and did not seem to be hindered by behavioral or cognitive limitations at young ages.

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“…Subsequently, to ascertain growth patterns, I transformed the raw data by log 10 and calculated Pearson's correlation coefficient (r) and the slope of the least squares regression curves ± their 95% confidence intervals (CI) for 8 parameters relative to carapace width, a commonly used size standard for spiders (Hagstrum 1971). As reviewed recently by Suter & Stratton (2011), spider growth is only loosely related to passage of time or developmental stage, so it is appropriate to use a sclerotized carapace dimension as an independent variable to assess if growth is allometric or isometric.…”

Section: Growth Of Immature Spidersmentioning

confidence: 99%

“…Growth patterns and rules in spiders, the largest group of invertebrate predators, are poorly studied, but in general they follow a geometric progression, known as Dyar's rule (Kleinteich & Schneider 2011;Suter & Stratton 2011). The smooth log-log regression curves actually cloak the discontinuous nature of spider growth mandated by molting of the cuticle from one instar to another.…”

Section: Nest Hole Size Preference In Immature Spidersmentioning

confidence: 99%

Growth and Nest Hole Size Preferences in Immature Southern House Spiders (Araneae: Filistatidae): Are They Constrained Consumers?

Carrel¹

2015

Florida Entomologist

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Does allometric growth explain the diminutive size of the fangs of Scytodes (Araneae: Scytodidae)?

Cited by 7 publications

References 15 publications

The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism, Sexual Body Component Dimorphism, and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism, Sexual Body Component Dimorphism, and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

Ontogenetic approach reveals how cognitive capability and motivation shape prey‐searching behavior in Pholcus phalangioides cellar spiders

Growth and Nest Hole Size Preferences in Immature Southern House Spiders (Araneae: Filistatidae): Are They Constrained Consumers?

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