week 2 - emasculation gloves off strategy enhances eunuch spider endurance LEE ET AL 2012

Question 1

Background

what is the eunuch phenomenon

Answer 1

complete emasculation of males genitalia

males of sexually cannibalistic spiders commonly mutilate parts of their paired gentilas (palps) during copulation

Question 2

what are palps?

Answer 2

male spiders genitalia

Question 3

what is the study species of lee et al 2012?

Answer 3

orb web nephilid spider

Question 4

author

Answer 4

lee et al 2012

Question 5

describe what happens to male nephilid spiders during sex?

Answer 5

75% of males fall victim to sexual cannibalism

surviving males become half or full eunuchs

Question 6

what has been shown about male eunuch spiders compared to intact males?

Answer 6

they are better fighters but the exact proximate mechanisms are not known

Question 7

what is the gloves off hypothesis?

Answer 7

one of the hypotheses as to why eunuch spiders are better fighters
attributes eunuchs enhanced locomotor endurance to the reduction in total body weight caused by genital mutilation

Question 8

what did lee et al 2012 do?

Answer 8

tested whether the gloves off hypothesis could account for the greater fighting ability in eunuchs. By comparing the time until exhaustion (ie endurance) of intact males with half and full eunuchs created experimentally

Question 9

what did lee et al 2012 find?

Answer 9

found that by reducing body weight up to 4% in half eunuchs and 9% in full eunuchs through emasculation endurance increased significantly in half eunuchs (32%) and greatly in full eunuchs (80%)

Question 10

what are the impact of lee et al 2012 results?

Answer 10

corroborate gloves off hypothesis

adaptive significance of male emasculation

Question 11

what does theory predict about monogamous males?

Answer 11

that they secure their paternity either by out competing rivals in sperm competition or by limiting the probabilty of a female remating ie mate guarding, copulatory plugs, genital mutilation, mechanisms increase quantity of sperm transferred

Question 12

in spiders male genital mutilation is common in ____/_____ and highly _____ species, what does it typically involve?

Answer 12

monogynous / bigynous
cannibalistic
breaking of palp parts that remain lodged in female genitalia

Question 13

what do mating plugs do?

Answer 13

increase male paternity and reduce sperm competition

Question 14

why is male emasculation maldaptive?

Answer 14

because eunuchs are effectvely sterile

Question 15

there are hypotheses as to why the eunuch phenomenon has evolved which include the gloves off hypotheses. what have some studies shown about eunuchs?

Answer 15

eunuch males are better fighters than intact males but the proximate mechanisms behind the better fighting abilities are unknown

Question 16

what did lee et al 2012 find? (4)

Answer 16

after palp removal both palps on average represented 9% of body weight
full eunuchs exhibited a significantly larger weight change than intact or half eunuchs
the number of palps significantly affected fighting ability
full eunuchs had significantly higher endurance than half eunuchs and intact males and half eunuchs had significantly higher endurance than intact males

Question 17

what are the implications of lee et al 2012 results? (2)

Answer 17

support for the gloves off hypotheses as to why males are better fighters when eunuchs
palp weight poses a significant physical cost to males

Question 18

palp removal produced significant reduction in male ___ —— and significantly enhanced ___ ____ thus increasing endurance capacity

Answer 18

body weight

physical stamina

Question 19

what does increased endurance enable eunuchs to do?

Answer 19

enables them to perform better in contests with intact males

Question 20

what is the functional conflict of the palps?

Answer 20

larger palps are favourable for reproduction but hinder locomotion.