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Stegodyphus lineatus

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Stegodyphus lineatus
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Arachnida
Order:
Araneae
Suborder:
Araneomorphae
Family:
Eresidae
Genus:
Stegodyphus
Species:
S. lineatus
Binomial name
Stegodyphus lineatus
(Latreille, 1817)
Synonyms

Eresus lineatus
Eresus acanthophilus
Eresus unifasciatus
Eresus adspersus
Eresus fuscifrons
Eresus lituratus
Stegodyphus adspersus
Stegodyphus molitor
Eresus arenarius
Stegodyphus quadriculatus

Stegodyphus lineatus is the only European species of the spider genus Stegodyphus.

Description

Males can grow up to 12 mm long, females up to 15 mm. The colour can range from whitish to almost black. In most individuals the opisthosoma is whitish with two broad black longitudinal stripes. Males and females look similar, but the male is generally richer in contrast and has a bulbous forehead.[1] The species name refers to the black lines on the back of these spiders (not present in all individuals).

Behaviour

These spiders build a web between twigs, mostly of low thorny shrubs. The web has a diameter of about 30 cm and is attached to a retreat made out of silk and covered with debris and food remains. Retreat is a cone-shaped structure about 5 cm long, which has an entrance at one end. The spiderlings hatch in this retreat, being released from their cocoon by their mother and then protected by her for a further two weeks. Web building behavior uses up time and energy, but provides an advantage in the ability to catch prey. For Stegodyphus lineatus fixing and constructing webs occurs only at night, but prey capture can occur during the day or at night. Both males and females can make webs to capture prey, but males may leave their web in search of mates.[2] Adult males can be found in spring. Males are known to exhibit infanticide, by killing the offspring of mated females. Offspring are matriphagous meaning they eat their own mother.[3]

Mating Behavior

Polyandrous Behavior

Females can mate with several males (polyandry). Females can mate with as many as five males, but unnecessary matings waste time and energy.[4] Polyandry may provide a potential for outbreeding if females preferentially bias paternity towards unrelated males.[5] Polyandry can occur when males cause female spiders to mate again because it is in their own interest even though it is against the female’s interests, or if the benefits of mating more than once are greater than the costs.[4] Males often stay 2 to 3 days in a females nest, but have been known to stay up to 18 days.[6]

Fitness Consequences of Polyandrous Behavior

While females may gain some benefits from multiple matings,[7] overall polyandry is costly [8] and mated females are often aggressive towards males (also see below). An increase in the number of mating for an individual is bad for a female’s health because it decreases the number of offspring they can have.[9] Having a male in their web also causes females to catch less prey because they fix their web less and forage less while the male is present and the male eats some of the captured prey.

Infanticide from Female Perspective

Infanticide occurs when males attempt to increase their fitness by disposing eggs sacs of females fertilized by other males. [10] Krish707 (talk) Female fitness is greatly reduced by the loss of their young, with the female being less likely to survive until her next lot of offspring can hatch, as well as having fewer eggs the second time. Their offspring also hatch later in the season and are less likely to thrive themselves. With this in mind, it comes with little surprise that females aggressively attend to their nest, chasing off around half the males that come nearby. This is also why females who have already mated are more likely to be aggressive toward a male entering their nest than females who have not mated yet.[10] Males can sustain injuries in these battles with the larger females, and in some cases the female not only kills, but eats the male intruder. For males however there is little option but to take this risk, resulting in sexual conflict that sees around 8% of egg sacs destroyed.[11]

Fitness Benefits of Polyandrous Behavior

One reasoning for why polyandry remains despite it's negative effect on female's health is because it is very beneficial to males. Males may chance upon only one or two mates in their entire lifetime. Before mating male spiders sometimes shake the webs of female spiders creating vibrations. The function of these vibrations before mating in Stegodyphus lineatus is likely to make the females more willing to mate.[12]

Infanticide from Male Perspective

Infanticide increases males ability to force females who have already mated to mate again with them.[6] Krish707 (talk) Egg sacs are lost quite frequently due to predation by ants and females are able to lay another clutch if they lose their first. This represents an opportunity for males, however, who can secure themselves a mate by simply disposing of her offspring (this can occur because some males are still seeking mates when most females have already laid). Males go about this by detaching the egg sac with their chelicerae, moving it to the entrance, then simply tossing it to the ground.[10] Females take longer to replace egg sacs lost by infanticide than egg sacs lost due to other reasons.[13] Stegodyphus lineatus eggs are unusual compared to normal spiders because they have a small number of small eggs relative to the body size of the mother, whereas most other spiders either have a small number of large eggs or a large number of small eggs.[14]

Mate Search and Reproductive Success

The desert spider shows low rates of polygamy,[5] but sexual selection and environmental cues play an important role during mate search and reproductive success.

Sexual Selection

The high rates of sexual selection allow phenotypes to change, which allow populations of these spiders to evolve. The selected traits during sexual selection helped males since the ones who could find females faster were at an advantage in contrast to those males lacking those traits acquired through sexual selection.[5] Sexual selection allows males to receive receptivity signals from females, in the form of pheromones which are detected by the males. Mature females let off a pheromone to reduce their attractiveness towards males due to the high costs of re-mating for the egg sac (infanticide mentioned above).[15] Mature females are aggressive towards males because loss of eggs is costly, although multiple mating increases genetic variation the offspring. Male receive 50% success of fertilizing eggs in mature females than virgin females who may have not reached maturation yet.[15] Since males mature on average 16 days earlier than females, they encounter virgin females frequently, but these immature females are not mature enough to allow the egg sac to mature.[16]

Environmental Cues

Environmental cues, for example the seasons progressing, decrease the rate at which a male encounters virgins and increases high paternity gain through encounters with mature females.[15] Since males mature earlier than the females, they migrate to other nests to look for females in order to fertilize eggs and increase paternity, this allows genetic variation to take place in populations, alongside inbreeding which also takes place amongst this species.[5] Cost of inbreeding are low, and females show no avoidance to this behaviour. If inbreeding avoidance mechanisms would increase, it would be the result from kin mating to increase and this pattern has not been observed amongst individuals in this species.[16] Since inbreeding does occur, but at low rates, random mating allows genetic diversity to occur.

Maternal Care

The act of reproduction, regarding the female, leads to an increase of digestive enzymes, allowing her to eat more prey and to stock more nutrients. Digestive enzymes start to digest the inside of the organism, except for the heart, the guts, and mostly the ovaries. Once the offspring are born, and until the mother dies, the mother regurgitates for two weeks the inside stocked fluids as really nutritive food for the progeny. 95% of the mother's mass is digested by the offspring. They will grow three times their size between their birth and their dispersion.[17] During the period when female spiders are caring for their hatched offspring the mothers do not eat, and their offspring only eat the food that the mother regurgitates along with the mothers’ body at the end of this time.[18]

Genetic Variation and Mating

Evidence of multiple mating is found for this species, and genetic variation is likely due to multiple fathers alongside male infanticide rates being high and re-mating in a natural population. The species allow random mating due to the single females colonizing new nesting sites and male migration from other nests.[19] Female dispersal has shown to have more impact when enhancing genetic differences amongst offspring in a population. Environments of spiders should be taken into consideration when studying the structure of a population, especially with S.lineatus that reside in stable and unstable conditions. In some instances, populations of spiders interbreed due to movement of juveniles.[19] Juveniles settle in the maternal nests where they later mate, introducing clusters of siblings in a nest.

Migration although, can counteract the costs of interbreeding by males from other nests. This in turn promotes genetic differentiation. It is observed that amongst populations, philopatry and founder events allows some individuals to live and others to go extinct, in result enhancing genetic variance among mating groups. When siblings, males or females disperse to nearby nests, this allows for random mating to occur which will enhance the differentiation amongst spiders in the following generation.[20]

Distribution

S. lineatus occurs in Europe only in the southern Mediterranean region (south of Barcelona, southern Greece including Crete) and stretches up to Tajikistan.

Footnotes

  1. ^ Bellmann 1997
  2. ^ Ward, David; Lubin, Yael (1993-04-01). "Habitat Selection and the Life History of a Desert Spider, Stegodyphus lineatus (Eresidae)". Journal of Animal Ecology. 62 (2): 353–363. doi:10.2307/5366.
  3. ^ Salomon, M.; Aflalo, E. D.; Coll, M.; Lubin, Y. (March 4, 2015). "Dramatic histological changes preceding suicidal maternal care in the subsocial spider Stegodyphus lineatus (Araneae: Eresidae)". Journal of Arachnology. 43 (1): 77–85. doi:10.1636/B14-15.1. ISSN 0161-8202. Retrieved 10 May 2015.
  4. ^ a b Maklakov, Alexei A.; Lubin, Yael (2004-05-01). "Sexual conflict over mating in a spider: increased fecundity does not compensate for the costs of polyandry". Evolution; International Journal of Organic Evolution. 58 (5): 1135–1140. ISSN 0014-3820. PMID 15212394.
  5. ^ a b c d Ruch, Jasmin; Heinrich, Lisa; Bilde, Trine; Schneider, Jutta M. (2009-12-01). "The evolution of social inbreeding mating systems in spiders: limited male mating dispersal and lack of pre-copulatory inbreeding avoidance in a subsocial predecessor". Biological Journal of the Linnean Society. 98 (4): 851–859. doi:10.1111/j.1095-8312.2009.01322.x. ISSN 1095-8312.
  6. ^ a b Erez, Tamar; Schneider, Jutta M.; Lubin, Yael (2005-07-01). "Is Male Cohabitation Costly for Females of the Spider Stegodyphus lineatus (Eresidae)?". Ethology. 111 (7): 693–704. doi:10.1111/j.1439-0310.2005.01090.x. ISSN 1439-0310.
  7. ^ Maklakov & Lubin 2006
  8. ^ Maklakov et al. 2005
  9. ^ Maklakov, Alexei A.; Bilde, Trine; Lubin, Yael (2005-05-01). "Sexual conflict in the wild: elevated mating rate reduces female lifetime reproductive success". The American Naturalist. 165 Suppl 5: S38-45. doi:10.1086/429351. ISSN 1537-5323. PMID 15795860.
  10. ^ a b c Schneider & Lubin 1996
  11. ^ Arnqvist & Rowe 2005
  12. ^ Maklakov, Alexei A.; Bilde, Trine; Lubin, Yael (2003-10-01). "Vibratory courtship in a web-building spider: signalling quality or stimulating the female?". Animal Behaviour. 66 (4): 623–630. doi:10.1006/anbe.2003.2245.
  13. ^ Schneider, null; Lubin, null (1997-08-01). "Infanticide by males in a spider with suicidal maternal care, Stegodyphus lineatus (Eresidae)". Animal Behaviour. 54 (2): 305–312. doi:10.1006/anbe.1996.0454. ISSN 0003-3472. PMID 9268461.
  14. ^ Schneider, Jutta M. (1996-01-01). "Differential Mortality and Relative Maternal Investment in Different Life Stages in Stegodyphus lineatus (Araneae, Eresidae)". Journal of Arachnology. 24 (2): 148–154.
  15. ^ a b c Tuni, Cristina; Berger-Tal, Reut (2012-05-01). "Male preference and female cues: males assess female sexual maturity and mating status in a web-building spider". Behavioral Ecology. 23 (3): 582–587. doi:10.1093/beheco/ars001. ISSN 1045-2249.
  16. ^ a b Bilde, Trine; Lubin, Yael; Smith, Deborah; Schneider, Jutta M.; Maklakov, Alexei A. "THE TRANSITION TO SOCIAL INBRED MATING SYSTEMS IN SPIDERS: ROLE OF INBREEDING TOLERANCE IN A SUBSOCIAL PREDECESSOR". Evolution. 59 (1). doi:10.1554/04-361.
  17. ^ Salomon 2015 Israel Cohen Institute For Biological Control
  18. ^ Salomon, Mor; Mayntz, David; Toft, Søren; Lubin, Yael (2010-12-29). "Maternal nutrition affects offspring performance via maternal care in a subsocial spider". Behavioral Ecology and Sociobiology. 65 (6): 1191–1202. doi:10.1007/s00265-010-1132-8. ISSN 0340-5443.
  19. ^ a b "Saint Louis University Libraries | Saint Louis University" (PDF). www.jstor.org.ezp.slu.edu. Retrieved 2015-10-21.
  20. ^ Johannesen, Jes; Lubin, Yael (1999-06-01). "Group founding and breeding structure in the subsocial spider Stegodyphus lineatus (Eresidae)". Heredity. 82 (6): 677–686. doi:10.1046/j.1365-2540.1999.00528.x. ISSN 0018-067X.

References

  • Schneider, J.M. & Lubin, Y. (1996): Infanticidal male eresid spiders. Nature. 381: 655-656.
  • Bellmann, Heiko (1997): Kosmos-Atlas Spinnentiere Europas. Kosmos. ISBN 3-440-10746-9
  • Arnqvist, G. & Rowe, L. (2005): Sexual conflict. Princeton University Press, Princeton ISBN 0-691-12217-2
  • Maklakov, A.A. & Lubin, Y. (2006): Indirect genetic benefits in a spider with direct costs of mating. Behavioural Ecology and Sociobiology. 61: 31-38.
  • Maklakov, A.A. et al. (2005): Sexual conflict in the wild: elevated mating rate reduces female lifetime reproductive success. American Naturalist. 165: S38-S45.
  • Erez, T. et al.(2005):Is Male Cohabitation Costly for Females of the Spider Stegodyphus Lineatus (Eresidae)? Ethology 111.7: 693-704.
  • Schneider, J. & Lubin, Y. (1997): Infanticide by males in a spider with suicidal maternal care, Stegodyphus lineatus(Eresidae). Animal Behavior. 54: 305-312
  • Schneider, J. (1996): Differential mortality and relative maternal investment in different life stages in stegodyphus lineatus (Araneae, Eresidae). The Journal of Arachnology. 24: 148-154
  • Maklakov, A. et al. (2003) Vibratory courtship in a web-building spider: signaling quality or stimulating the female? Animal Behavior. 66: 623-630
  • Salomon, M. et al. (2010): Maternal nutrition affects offspring performance via maternal care in a subsocial spider. Behavioral Ecology and Sociobiology. 65: 1191-1202
  • Ward, D. & Lubin, Y. (1993): Habitat selection and the life history of a desert spider Stegodyphus lineatus (Eresidae). Journal of Animal Ecology. 62: 353-363
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