# 2.1 To eat or to mate? sexual cannibalism in mantodea and arachnid  (Page 9/15)

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Economic models are also readily applied to the behavior of Australian redback spiders. Experiments consistently show that when a male somersaults into the female’s mouth (thus inducing cannibalism), the length of the copulation period doubles (Andrade 2003). Male redbacks, like many organisms, can sexually function long after females start to consume them. While females are occupied with their meal, the male profits from 15-20 minutes extra insemination time. Studies show that cannibalized males usually insert emboli twice, and in one experiment, self-sacrificing redbacks fertilized twice the number of eggs as non-eaten males (Andrade 1996). Self-sacrifice also gives males an advantage in terms of sperm competition , because females tend to spurn other males directly after they copulate with, and cannibalize, their first mate (Andrade 2003). In economic terms, the male redback reaps high paternity benefit from increasing the proportion of offspring he sires in the female’s brood. Meanwhile, the cost inherent in redback self-sacrifice is extremely low, because males live in a hostile environment that often precludes them from second matings. In fact, there is an 85% mortality rate for males after they leave natal webs [Chart 1], so each male is destined to encounter very few females during his lifetime (Andrade 2003). Therefore, the fitness benefit to post-copulation survivorship is low (Andrade 1997). Based on economic models, male complicity in redbacks makes sense.

Economic models are further verified by evidence from the orb-weaving spider. Males of the genus Argiope often die directly after copulation, regardless of female cannibalism (Sasaki and Iwahashi 1995). In the species Argiope aurantia , mating triggers the inflation of the male’s second palp when increased haemolymph pressure causes its distal bulb to expand. Palp swelling catalyzes a cascade of reactions that culminates in the male’s death 15 minutes later (Foellmer and Fairbairn 2003). Since the male willingly engages in mating and evolution has not selected against the spontaneous death mechanism, terminal reproductive investment appears ultimately beneficial. It is unusual to think of dying as a prime fitness strategy, but two morbid processes actually benefit males. The first is familiar: the male soma provides nutrients to the female and increases the quantity and quality of her offspring. Additionally, the dead male can prevent female polyandry. Several male spiders often wrestle vigorously for access to a mate, and even try to dislodge males already in the copulatory position. If the mating male’s pedipalp is in the inflated state, he is more difficult to remove, so his corpse serves as a genital plug to block his rivals’ access to the female (Foellmer and Fairbairn 2003). Thus, evidence from the orb-weaving spider indicates that the costs of foregoing future mating opportunities can be overcome by the direct benefit of increased female nutrition and the male’s confidence in paternity .

#### Questions & Answers

where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
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