Ontogenetic change in survival value of leg autotomy in a wolf spider, Gladicosa pulchra (Keyserling) (Araneae: Lycosidae), during scorpion attacks

1994 ◽  
Vol 72 (12) ◽  
pp. 2133-2135 ◽  
Author(s):  
Paul D. Klawinski ◽  
Daniel R. Formanowicz Jr.
Keyword(s):  
Body Size ◽  
Wolf Spider ◽  
Ontogenetic Change ◽  
Relative Body Size ◽  
Predatory Tactics

The survival value of leg autotomy during attacks by scorpions (Vaejovis waueri Gertsch and Soleglad, 1972 (Scorpiones: Vaejovidae)) was assessed in three successive instars of the wolf spider Gladicosa pulchra (Keyserling, 1877) (Araneae: Lycosidae). During the first three instars after hatching, spiders were subjected to predatory encounters with adult scorpions. Spider survival due to leg autotomy decreased and the tendency of scorpions to use the sting to subdue the spiders increased with increasing size of wolf spider instars. As spider instar size increased, more scorpion attacks were directed at the cephalothorax and abdomen, resulting in decreased opportunity for larger spiders to utilize leg autotomy as an escape tactic. The decrease in survival and change in scorpion predatory tactics with increasing instar size reflect an increase in the relative body size of the spiders. Therefore, the survival value of an antipredator mechanism may vary with the degree of opportunity to use the mechanism.

scholarly journals Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics

2012 ◽  
Vol 8 (4) ◽  
pp. 660-664 ◽  
Author(s):  
K. T. Bates ◽  
P. L. Falkingham
Keyword(s):  
Body Size ◽  
Feeding Behaviour ◽  
Ontogenetic Change ◽  
Positive Allometry ◽  
Musculoskeletal Models ◽  
Terrestrial Animal ◽  
Body Dynamics ◽  
Mode Of Life ◽  
Scaling Analyses ◽  
Multi Body

Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a modest bite mechanically limited T. rex to scavenging, while others argue that high bite forces facilitated a predatory mode of life. We use dynamic musculoskeletal models to simulate maximal biting in T. rex . Models predict that adult T. rex generated sustained bite forces of 35 000–57 000 N at a single posterior tooth, by far the highest bite forces estimated for any terrestrial animal. Scaling analyses suggest that adult T. rex had a strong bite for its body size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour in T. rex , associated with an expansion of prey range in adults to include the largest contemporaneous animals.

scholarly journals Contest interactions and outcomes: relative body size and aggression independently predict contest status

2019 ◽  
Vol 157 ◽  
pp. 43-49 ◽  
Author(s):  
Lisa D. Mitchem ◽  
Reena Debray ◽  
Vincent A. Formica ◽  
Edmund D. Brodie
Keyword(s):  
Body Size ◽  
Relative Body Size

scholarly journals Phylogenomic Variation at the Population-Species Interface and Assessment of Gigantism in a Model Wolf Spider Genus (Lycosidae, Schizocosa)

2021 ◽  
Vol 5 (5) ◽  
Author(s):  
James Starrett ◽  
Ashley Bui ◽  
Rowan McGinley ◽  
Eileen A Hebets ◽  
Jason E Bond
Keyword(s):  
Body Size ◽  
Size Variation ◽  
Wolf Spider ◽  
Similar Species ◽  
Machine Learning Approach ◽  
Population Structuring ◽  
Phylogenetic Framework ◽  
Genetic Clustering ◽  
Close Relatives ◽  
And Behavior

Abstract Animal body size has important evolutionary implications. The wolf spider genus Schizocosa Chamberlin, 1904 has developed as a model for studies on courtship, with visual and vibratory signals receiving attention; however, body size has never been carefully evaluated. Although species of Schizocosa can be distinguished from their close relatives by differences in genitalic structures, male ornamentation, and behavior, some species are morphologically similar, making diagnosis, and identification difficult. Evaluation of species boundaries using genetic data across Schizocosa is limited. The similar species S. maxima Dondale & Redner, 1978 and S. mccooki (Montgomery, 1904) are separated predominantly on the basis of size differences, with S. maxima being larger. We evaluate the evolution of size in these two Schizocosa species distributed in western North America, where gigantism of S. maxima is hypothesized to occur, particularly in California. We sampled subgenomic data (RADseq) and inferred the phylogeny of S. mccooki, S. maxima, and relatives. We apply a variational autoencoder machine learning approach to visualize population structuring within widespread S. mccooki and evaluate size within the context of a comparative phylogenetic framework to test the hypotheses related to genetic clustering of populations and gigantism. Our data show S. mccooki populations are not genealogically exclusive with respect to S. maxima. Likewise, S. maxima individuals are not recovered as a lineage and do not form an isolated genetic cluster, suggesting that the observed differences in size cannot be used to accurately delimit species. The cause of gigantism in S. maxima remains unexplained, but provides a framework for future studies of size variation and speciation.

Impacts of leg loss and regeneration on body condition, growth, and development time in the wolf spider Schizocosa ocreata

2007 ◽  
Vol 85 (7) ◽  
pp. 823-831 ◽  
Author(s):  
K.M. Wrinn ◽  
G.W. Uetz
Keyword(s):  
Body Size ◽  
Body Condition ◽  
Growth And Development ◽  
Development Time ◽  
Wolf Spider ◽  
Limb Loss ◽  
Lower Body ◽  
Schizocosa Ocreata ◽  
Trade Offs ◽  
Subsequent Regeneration

Autotomy (self-amputation) of appendages and subsequent regeneration is common to many taxa. These processes are known to affect foraging abilities, growth, and development time in many taxa. However, little is known about their effects in arachnids. We addressed the effects of autotomy and regeneration on body condition, growth (size and mass), and development time (molt interval) for the wolf spider Schizocosa ocreata (Hentz, 1844) in the field and laboratory. Frequency of autotomy in the field was high (11%–19%). Field-caught individuals with missing or regenerating legs had significantly lower body size, mass, and condition. To test the effects of regeneration on size, mass, and molt interval in the laboratory, we induced autotomy of one or both forelegs. Spiders regenerating two legs had reduced molt intervals, were smaller, and weighed less than spiders that were intact or regenerating one leg. Field-caught spiders that had undergone autotomy and regeneration in the laboratory exhibited reduced size, mass, and molt interval. In contrast, laboratory-reared spiders exhibited increased molt intervals but no difference in mass after regeneration. These results reveal that limb loss via autotomy is common (but potentially costly) in S. ocreata, and that environmentally mediated trade-offs between growth and development time may occur during regeneration.

The Role of Relative Body Size in a Predator-Prey Relationship between Dragonfly Naiads and Larval Anurans

Oikos ◽  
1985 ◽  
Vol 45 (1) ◽  
pp. 59 ◽  
Author(s):  
Joseph Travis ◽  
W. Hubert Keen ◽  
John Juilianna
Keyword(s):  
Body Size ◽  
Predator Prey ◽  
Larval Anurans ◽  
Relative Body Size
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