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Does a male ever really present himself to be eaten? In fact, such complicity is blatantly displayed in Australian redback spider mating, wherein the male grabs the female and somersaults directly into her mouthparts (move this up to the non compliance section). Without halting his acrobatics, the redback transfers his sperm into female storage organs by inserting one or both emboli into her (Andrade 1996). As a result, 65% of redback mating interactions end in sexual cannibalism (Andrade 2003). The male Australian redback’s biomass is miniscule, so his sacrifice has no apparent impact on the female spider’s reproductive output.

Discussion question:

Why could males have evolved such exaggerated willingness for self-sacrifice?

The tradeoffs: economic models for sexual cannibalism

In an attempt to develop an adaptionist description of sexual cannibalism, several researchers have devised mathematical cost-benefit models that address both the foraging strategy hypothesis and observations of redback self-sacrifice.

The male perspective

Male complicity in sexual cannibalism is interpreted by the economic model of Buskirk et al. Buskirk posits that a male should permit himself to be eaten only if he increases his inclusive fitness more in that manner than by surviving to inseminate other females (Buskirk et al. 1984). Two factors impact the male’s inclusive fitness in sexual cannibalism: the number of times a male may be expected to mate during his lifetime and the proportional increase in the male’s offspring resulting from self-sacrifice. The first factor is based on several conditions, including the ability of males to locate other females (often through the use of pheromones), as well as the time and effort required to court and defend the female. Other constraints are posed by male morphology, such as the length of reproductive lifetime, the time and energy needed to produce sperm, and (in spiders) the detrimental loss of pedipalpal tips to previous mates (Schneider and Lubin 1998). The second factor, offspring increase, is dependent on the female’s food supply and the male’s confidence of paternity . In turn, confidence of paternity is contingent on the extent of a female’s polyandrous behavior, as well as copulation duration, sperm storage methods, and the nearness of copulation to oviposition ( [link] ) (Buskirk et al. 1984).

Based on these parameters, the adaptive value of cannibalism for males can be mathematically modeled ( [link] ).

graph showing the evolution of sexual cannibalism
Buskirk et al.’s model for the evolution of sexual cannibalism, based on the mathematical formula A P > E NC 1 - 1 - C ENC - 1 C
This theoretical graph shows the relationship of A/P to C for different values ENC. For organism X, C=0.5 and A/P=2.5, and ENC=4. That is, if a male has a 50% chance of being cannibalized and can produce 2.5 times more offspring by being cannibalized than not, then self-sacrifice is advantageous until the male’s expected number of lifetime matings exceeds four (in other words, until being cannibalized causes him to forgo three or more matings). The graph suggests that, as the number of expected matings increases, male self-sacrifice must greatly enhance his mate’s fecundity in order to offset his cost of neglecting future mates (Buskirk et al. 1984).

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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