scholarly journals Influence of body size and level of cooperation on the prey capture efficiency of two sympatric social spiders exhibiting an included niche pattern

2011 ◽  
Vol 25 (4) ◽  
pp. 859-867 ◽  
Author(s):  
Jennifer Guevara ◽  
Leticia Avilés
1995 ◽  
Vol 198 (5) ◽  
pp. 1161-1171 ◽  
Author(s):  
P Wainwright ◽  
B Richard

We present the first analysis of scaling effects on the motor pattern of a feeding vertebrate. Data are presented for the effects of body size on the pattern of activity in four head muscles during prey capture in the largemouth bass, Micropterus salmoides. Electromyographic (EMG) recordings were made from three expansive-phase muscles (the epaxialis, the sternohyoideus and the levator arcus palatini) and one compressive-phase muscle (the adductor mandibulae), during the capture of small fish prey. Recordings were made of 181 prey-capture events from 19 bass that ranged in size from 83 to 289 mm standard length. We measured seven variables from the myogram of each capture to quantify the temporal pattern of muscle activation, including the duration of activity in each muscle and the onset time of each muscle, relative to the onset of the sternohyoideus muscle. Regressions of the mean value of each variable for the 19 individuals on standard length revealed that only the onset time of the adductor mandibulae changed with fish body size. The increase in onset time of the adductor muscle appears to reflect the longer time taken to open the mouth fully in larger fish. Other research shows that the kinematics of the strike in this species slows significantly with increasing body size. The combined results indicate that the duration of the EMG signal is not directly correlated with the duration of force production in muscles when compared between fish of different sizes. The lack of scaling of burst duration variables suggests that the reduced speeds of prey-capture motion are explained not by changes in the envelope of muscle activity, but rather by the effects of scale on muscle contractile kinetics. These scaling effects may include changes in the relative resistance of the jaw and head structures to movement through water and changes in the intrinsic contractile properties of the muscles of the feeding apparatus.


Author(s):  
Fernanda Carolina da Silva ◽  
Mateus Moleta ◽  
Camila Alves Dos Anjos ◽  
Gabriel Marra Schade ◽  
Gabriel Staichak ◽  
...  

1981 ◽  
Vol 26 (3) ◽  
pp. 461-466 ◽  
Author(s):  
Michael C. Swift ◽  
Richard B. Forwarder.

Author(s):  
Ronald Osinga ◽  
Sanne Van Delft ◽  
Muhammad Wahyudin Lewaru ◽  
Max Janse ◽  
Johan A.J. Verreth

In order to determine optimal feeding regimes for captive corals, prey capture by the scleractinian coral Galaxea fascicularis was determined by measuring clearance of prey items from the surrounding water. Colonies of G. fascicularis (sized between 200 and 400 polyps) were incubated in 1300 ml incubation chambers. Nauplii of the brine shrimp Artemia sp. were used as the prey item. A series of incubation experiments was conducted to determine the maximal capture per feeding event and per day. To determine maximal capture per feeding event, total uptake of nauplii after one hour was determined for different prey item availabilities ranging from 50 to 4000 nauplii per polyp. To determine maximal capture per day, the corals were subjected to four repetitive feeding events at three different prey item densities (50, 100 and 150 nauplii per polyp). Alongside these quantitative experiments, it was tested to what extent the feeding response of corals is triggered by chemical cues. One hour after food addition, extract of Artemia nauplii was added to the incubation chambers to test its effect on subsequent prey capture rates. In all experiments, prey capture was expressed as the number of nauplii consumed per coral polyp. Total capture of Artemia nauplii by G. fascicularis after a single feeding event increased linearly up till a prey item availability of 2000 nauplii per polyp. Maximal capture per feeding event was estimated at 1200 nauplii per polyp, which is higher than rates reported in previous studies. It became apparent that at high densities of Artemia nauplii, the clearance rate method does not discriminate between active capture and passive sedimentation. Repetitive feeding with 50 nauplii per polyp resulted in a constant total prey capture per feeding event. At a supply of 100 nauplii per polyp, total capture decreased after the first feeding event, and remained constant during the subsequent feeding events at a level comparable to the lower food availability. However, at a supply of 150 nauplii per polyp, total capture per event was higher throughout the entire four-hour incubation period, which obfuscates an accurate estimation of the maximal daily food uptake. In all incubations, a decrease in capture efficiency was observed within the course of the feeding event. In all repetitive feeding experiments, capture efficiency increased immediately upon addition of a new batch of food. This increase in efficiency was not caused by a priming effect of extract of Artemia. The inconsistencies in the data show that estimates of prey capture based on clearance rates should be interpreted with caution, because this method does not take into account potential dynamics of prey capture and release.


2019 ◽  
Author(s):  
Edmund R. Hunt ◽  
Brian Mi ◽  
Rediet Geremew ◽  
Camila Fernandez ◽  
Brandyn M. Wong ◽  
...  

AbstractGroups of social predators capture large prey items collectively, and their social interaction patterns may impact how quickly they can respond to time-sensitive predation opportunities. We investigated whether various organizational levels of resting interactions (individual, sub-group, group), observed at different intervals leading up to a collective prey attack, impacted the predation speed of colonies of the social spider Stegodyphus dumicola. We found that in adult spiders overall group connectivity (average degree) increased group attack speed. However, this effect was detected only immediately before the predation event; connectivity two and four days before prey capture had little impact on the collective dynamics. Significantly, lower social proximity of the group’s boldest individual to other group members (closeness centrality) immediately prior and two days before prey capture was associated with faster attack speeds. These results suggest that for adult spiders, the long-lasting effects of the boldest individual on the group’s attack dynamics are mediated by its role in the social network, and not only by its boldness. This suggests that behavioural traits and social network relationships should be considered together when defining keystone individuals in some contexts. By contrast, for subadult spiders, while the group maximum boldness was negatively correlated with latency to attack, no significant resting network predictors of latency to attack were found. Thus, separate behavioural mechanisms might play distinctive roles in determining collective outcomes at different developmental stages, timescales, and levels of social organization.Significance statementCertain animals in a group, such as leaders, may have a more important role than other group members in determining their collective behavior. Often these individuals are defined by their behavioral attributes, for example, being bolder than others. We show that in social spiders both the behavioral traits of the influential individual, and its interactions with other group members, shape its role in affecting how quickly the group collectively attacks prey.


2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Tharaka Wijerathna ◽  
Dilini Tharanga ◽  
Inoka C. Perera ◽  
Mayuri R. Wijesinghe

We compare web properties and fitness of the Giant wood spider Nephila pilpes within and outside its natural rainforest habitat in Sri Lanka. The nonforest habitats comprised rural home gardens and plantations. We hypothesize that marked differences would be evident between the two habitats in (i) web properties and (ii) fitness of the female spiders. Web architectural and silk thread properties were measured in 25 webs of adult female spiders in each of the two habitats, while female abdomen size was used as the proxy for fitness. Findings support both hypotheses. The nonforest webs were more closely knit (smaller mesh spaces) and the hub was placed at higher position on the web than that in the forest webs both altering prey capture efficiency. Also, females in nonforest habitats were significantly smaller than those in the forest, indicating lowered fitness. The disparities in web characteristics and fitness are impressive given that the forest and nonforest habitats are located in close proximity, suggesting that rainforest orbweaver spiders such as Nephila pilpes may suffer population declines if the extents of natural forest continue to shrink.


2007 ◽  
Vol 21 (6) ◽  
pp. 623 ◽  
Author(s):  
Miquel A. Arnedo ◽  
Pedro Oromí ◽  
Cesc Múrria ◽  
Nuria Macías-Hernández ◽  
Carles Ribera

The spider genus Dysdera Latreille is an excellent model for the study of the evolution of cave life: ten species are known to exist exclusively in the subterranean environment of the Canary Islands, where the genus has undergone local diversification. In the present paper, two new troglobitic species (Dysdera madai, sp. nov. and D. sibyllina, sp. nov.) and the previously unknown sex of five additional species are described and illustrated: the males of D. gollumi Ribera & Arnedo, 1994, D. hernandezi Arnedo & Ribera, 1999 and D. labradaensis Wunderlich, 1991; and the females of D. andamanae Arnedo & Ribera, 1997 and D. gibbifera Wunderlich, 1991. The first direct evidence of troglobitic members of Dysdera in micro- and mesocaverns are reported. The evolution of cave life as hypothesised following a combined morphological and molecular phylogeny is investigated. Troglobitic Canarian Dysdera species have colonised the underground on eight independent occasions. The Dysderidae groundplan represents a preadaptation to cave life and has facilitated the colonisation of caves. Canarian members of Dysdera have a predominantly parapatric mode of speciation, although postspeciation changes in distribution may have obscured allopatric processes. Eye regression and, to a lesser extent, larger body size and appendage elongation characterise troglobitic species. The different levels of troglobiomorphism are interpreted as local adaptations to heterogeneous subterranean conditions. The high levels of sympatry among troglobites are explained by trophic segregation and changes in prey capture strategy were involved in the single identified case of subterranean speciation in the group.


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