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FINAL MATRIPHAGY PAGE: edit

Matriphagy is the consumption of the mother by her offspring.[1][2] The behavior generally takes place within the first few weeks of life and has been documented in some species of insects, nematode worms, scorpions, and other arachnids as well as in caecilian amphibians.[3][4][5]

 
Desert Spider, Stegodyphus lineatus, one of the best described species that participates in matriphagy

The specifics of how matriphagy occurs varies among different species, but the process is best described in the Desert spider, Stegodyphus lineatus, where the mother harbors nutritional resources for her young through food consumption. The mother is able to regurgitate small portions of food for her growing offspring, but between 1-2 weeks after hatching the progeny capitalize on this food source by eating her alive. Typically, offspring only feed on their biological mother as opposed to other females in the population. In other arachnid species, matriphagy occurs after the ingestion of nutritional eggs known as trophic eggs (e.g. Black lace-weaver Amaurobius ferox, Crab spider Diaea ergandros) and involves different techniques for killing the mother, such as transfer of poison via biting and sucking to cause a quick death (e.g. Black lace-weaver) or continuous sucking of the hemolymph, resulting in a more gradual death (e.g. Crab spider). The behavior is less well described but follows a similar pattern in species such as the Hump earwig, pseudoscorpions, and caecilians.

Spiders that engage in matriphagy produce offspring with higher weights, shorter and earlier moulting time, larger body mass at dispersal, and higher survival rates than clutches deprived of matriphagy. In some species, matriphagous offspring were also more successful at capturing large prey items and had a higher survival rate at dispersal. These benefits to offspring outweigh the cost of survival to the mothers and help ensure that her genetic material is passed to the next generation, thus perpetuating the behavior.[6][7][8][9]

Overall, matriphagy is an extreme form of parental care but is highly related to extended care in the Funnel-web spider, parental investment in caecilians, and gerontophagy in social spiders. The uniqueness of this phenomenon has led to several expanded analogies in human culture and contributed to the pervasive fear of spiders throughout society.[10][11]

Etymology edit

Matriphagy can be broken down into two components:

  • Matri (mother)
  • Phagy (to feed on)

Description of behavior edit

Matriphagy generally consists of offspring consuming their mother; however, different species exhibit different variations of this behavior.

Spiders edit

Black lace-weaver: Amaurobius ferox edit

 
This Black lace-weaver (Amaurobius ferox) female adult will eventually be consumed by her offspring.

In many Black lace-weavers, Amaurobius ferox, offspring do not immediately consume their mother. A day after offspring emerge from their eggs, their mother lays a set of trophic eggs, which contain nutrition for the offspring to consume.[12] Matriphagy commences days later when the mother begins communicating with her offspring through web vibrations, drumming, and jumping.[12][13][7] Through these behaviors, offspring are able to detect when and where they can consume their mother. They migrate towards her and a couple of the spiderlings jump onto her back to consume her.[12] In response, the mother jumps and drums more frequently to keep her offspring off of her, however, they relentlessly continue attempting to get onto her back.[12] When the mother feels ready, she presses her body onto her offspring and allows them to consume her via sucking on her insides.[12] As they consume her, they also release poison into her body, causing a quick death.[12] The mother’s body is kept for a few weeks as a nutritional reserve.[12]

Interestingly, matriphagy in this species is dependent on the developmental stage that the offspring are currently at.[12] If offspring, older than four days, are given to an unrelated mother, they refuse to consume her.[12] However, if younger offspring are given to an unrelated mother, they readily consume her.[12] Additionally, if a mother loses her offspring, she is able to produce another clutch of offspring.[12]

Crab spider: Diaea ergandros edit

 
Crab spider, Diasea ergandros

Mothers of one particular species of the crab spider, Diaea ergandros, are only able to lay one clutch, unlike the Black lace-weaver.[9] They invest a significant amount of time and energy into storing nutrients and food into large oocytes, known as trophic eggs, similar to the Black lace-weaver.[9] However, these trophic eggs are too large to physically leave her body.[9] Some of the nutrients from the trophic eggs are liquefied into haemolymph, which can be consumed through the mother’s leg joints by her offspring.[9] She gradually shrinks until she becomes immobile and dies.[9][12]

In this species, it has been shown that this behavior may contribute to reducing cannibalism by siblings.[9]

Desert Spider: Stegodyphus lineatus edit

Right after hatching, desert spider, Stegodyphus lineatus, hatchlings rely solely upon their mother to provide them with food and nutrients. Their mother does this by regurgitating her bodily fluids, which contain a mixture of nutrients for them to feed on.[13][7]

This behavior begins during mating. Mating causes an increase in the mother’s production of digestive enzymes to better digest her prey. Consequently, she is able to retain more nutrients for her offspring to consume later. The mother’s midgut tissues start to slowly degrade during the incubation period of her eggs. After her offspring hatch, she regurgitates food for them to feed on with the help of her already-liquefied midgut tissues. Meanwhile, her midgut tissues continue to degrade into a liquid state to maximize the amount of nutrients from the mother’s body that her offspring will be able to obtain. As degradation continues, nutritional vacuoles form within her abdomen to amass all of the nutrients. Consumption begins when her offspring puncture her abdomen to suck up the nutritional vacuoles. After approximately 2-3 hours, the mother’s bodily fluids are completely consumed, and only her exoskeleton remains.[13]

This species is only able to have one clutch, which might explain why so much time and energy is spent on taking care of offspring. Furthermore, matriphagy can also occur between offspring and mothers who have recently laid eggs that are not related.[13]

Hump earwig edit

Anechura harmandi edit

Anechura harmandi is the only species of Earwigs that has been currently documented to exhibit matriphagy. Mothers in this particular species of Earwigs have been found to reproduce during colder temperatures.[14] This is mainly for the purpose of avoiding predation and maximizing their offspring's survival, since females are unable to produce a second clutch.[14] Due to the cold temperature, there is a scarcity of available nutrients when the offspring hatch, which is why the offspring end up consuming their mother.[14]

 
A group of pseudoscorpion (Paratemnoides nidificator) adults, the females of which will eventually be subject to matriphagy.

Pseudoscorpions edit

Paratemnoides nidificator edit

Matriphagy in this species of Pseudoscorpions is usually observed during times of food scarcity.[15] After their offspring hatch, mothers exit their nests and await to be consumed.[15] Offspring follow their mothers out of the nest where they grab onto her legs and proceed to feed through her leg joints, similar to that of Diaea ergandros.[15]

Females of this species are able to produce more than one clutch of offspring if their first clutch was unsuccessful.[15]

Matriphagy in this species has been predicted to prevent cannibalism between siblings as well.[15]

Vertebrates edit

 
Boulengerula taitanus, a species of Caecilians known to exhibit matriphagy.

Caecilians edit

Caecilians are the only vertebrate animals with well-documented matriphagous behaviours. In viviparous caecilians, the young consume the mother's oviduct lining by scraping it off with their teeth. In at least two species, Boulengerula taitana and Siphonops annulatus, the young feed on the mother's skin by tearing it off with their teeth, which then regenerates within a few days.[5] Because neither are closely related, either this behaviour is more common than currently observed or it evolved independently.[16]


Evolution edit

The adaptive value of matriphagy is based on the benefits provided to the offspring and the costs borne by the mother [2]. Functionally analyzing matriphagy in this manner sheds light on why this unusual and extreme form of care has evolved and been selected for.

Benefits to offspring edit

  • Consuming the mother is a source of nutrition which is important for growth and development.[12]
  • The body mass and opisthosoma length of spiderlings increases after matriphagy compared to before (opisthosoma is the posterior part of the body in spiders, analogous to the abdomen). Additionally, body mass tends to be higher for spiderlings that engage in matriphagy as compared to those that do not.[8][12]
  • Matriphagy advances molting time. Molting is the growing of a larger exoskeleton and shedding the old one. Advancement of molting time means that the spiders are able to grow at a faster rate.[12]
  • Matriphagous spiderlings tend to experience significantly greater survival rates and fitness compared to non-matriphagous offspring at dispersal.[7][12][14]
  • Matriphagous spiderlings hunt larger prey and show much more complete prey consumption than non-matriphagous spiderlings.[12]
  • Matriphagy improves sociality in spiders, primarily by reducing sibling cannibalism.[9]

Costs to the mother edit

Unlike other milder forms of parental care, matriphagy ends with the life of the mother, the gravest of all costs. So, why has it evolved? In order to answer this, it is important to look at costs to the mother in terms of reproductive output, egg sac development, and number of young reared (i.e. are offspring more successful if the mother evades matriphagy and reproduces again or if she engages in matriphagy and produces only one clutch?).

  • In the Black lace-weaver, Amaurobius ferox around 80% of females separated prior to matriphagy produce second egg sacs and only approximately 40% of these develop completely (compared to the >90% development of egg sacs in the first brood).[12]
  • Additionally, number of spiderlings in the second brood tend to be significantly lower than in the first brood. These individuals are also smaller than the spiders in the first brood.[12]
  • Females that successively lay two egg sacs have a lower expected output of dispersing offspring than females that are victims of matriphagy and produce only a single clutch.[12]

Summary edit

In conclusion, offspring that engage in matriphagy benefit more than those that do not engage in this behavior. Furthermore, the progeny of females that escape matriphagy to lay a second brood are significantly less successful than those that ate their mother. Hence, enhanced fitness of the mother accounts for the evolution of this unusual and extreme form of parenting.

Forms of parental care similar to matriphagy edit

Matriphagy is one of the most extreme forms of parental care observed in the animal kingdom. However, in some species such as the Funnel-web spider Coelotes terrestris, matriphagy is only observed under certain conditions and extended maternal protection is the main method by which offspring receive care. In other organisms such as the African social velvet spider, Stegodyphus mimosarum and Caecilian amphibians, parental behavior closely related in form and function to matriphagy is used.

Extended care in a Funnel-web spider: Coelotes terrestris edit

The ‘maternal social’ spider, Coelotes terrestris (Funnel-web spider) uses extended maternal care as a reproductive model for its offspring. Upon laying the egg sac, a C. terrestris mother stands guard and incubates the sac for 3 to 4 weeks. She stays with her young from the time of their emergence until dispersal approximately 5 to 6 weeks later. During the offsprings’ development, mothers will provide the spiderlings prey based on their levels of gregariousness.[17]

 
Image of a Funnel-web spider (Coelotes terrestris)

Protecting the egg sacs from predation and parasites yields a high benefit to cost ratio for the mothers. Fitness of the mother is highly correlated to offspring developmental state—a mother in better condition yields larger young that are better at surviving predation. The presence of the mother also protects the offspring against parasitism. In addition, the mother can keep feeding while guarding her progeny without any weight loss, allowing her to collect sufficient food for both herself and her offspring.[17]

Overall, costs of protecting the egg sac are low. Upon separation from egg sacs, 90% of females have the energy sustenance to lay new sacs, although it does induce a time loss of several weeks that could potentially affect reproductive success.[17]

In experimental conditions, costs arose if maternal care was not provided, with egg sacs drying out and developing molds, thus illustrating that maternal care is essential for survival. Experimental food-deprived broods reared by the mother induced matriphagy, where 77% of offspring consumed their mother upon birth. This suggests that matriphagy can exist under nutrient-limited conditions, but the costs generally outweigh the benefits when mothers have sufficient access to resources.[17]

Parental investment by skin-feeding in Caecilian amphibians   edit

Caecilian amphibians are worm-like in appearance, and mothers have thick epithelial skin layers. The skin on a caecilian mother is used for a form of parent-offspring nutrient transfer.

 
The ringed caecilian is an example of an oviparous caecilian that exhibits parental investment through skin-feeding of the oviduct lining.

The Taita African caecilian Boulengerula taitana is an oviparous (egg-laying) caecilian whose skin transforms in brooding females to supply nutrients to growing offspring. The offspring are born with specific dentition that they can use to peel and eat the outer epidermal later of their mother’s skin. Young move around their mother’s bodies, using their lower jaws to lift and peel the mother’s skin while vigorously pressing their heads against her abdomen. To account for this, the epidermis of brooding females can be up to twice the thickness of non-brooding females.[18]

Viviparous (developing in the mother) caecilians on the other hand, have specialized fetal dentition which can be used for scraping lipid-rich secretions and cellular materials from the maternal oviduct lining. The ringed caecilian Siphonops annulatus, an oviparous caecilian, exhibits characteristics similar to viviparous caecilians. Mothers have paler skin tones than non-attending females, suggesting that offspring feed on glandular secretions on the mother’s skin—a process that resembles mammalian lactation. This scraping method is different from the peeling actions performed by oviparous caecilians.[18]

For both oviparous and viviparous caecilians, delayed investment is a common benefit. Providing nutrition through the skin allows for redirection of nutrients, yielding fewer and larger offspring than caecilians who only provide their offspring with yolk nutrients.[18] Rather than the mother sacrificing herself and solely being used for the offspring’s nutrition, caecilian mothers supplement their offspring’s growth; they provide enough nutrients for the offspring to survive, but not at the cost of their own life.

Gerontophagy in social spiders, Genus Stegodyphus edit

 
An example of social spiders (Stegodyphus dumicola) that have been found to participate in gerontophagy as a form of parental care.

Stegodyphus mothers liquefy their inner organs and maternal tissue into food deposits. The African social velvet spider Stegodyphus mimosarum and the African social spider Stegodyphus dumicola are two social spider species that eat their mothers and other adult females, which is unique since social spiders do not tend to exhibit cannibalistic life history traits. In these specific spiders, deceased females are often found shriveled with shrunken abdomens. Offspring suck nutrients primarily from the dorsal part of the adult female's abdomen, and she may still be alive during this process.[19]

This behavior is not quite the same as matriphagy because Stegodyphus spiderlings are perfectly tolerant to other offspring, healthy conspecifics, and members of other species, suggesting that ordinary cannibalism is suppressed. Instead, the parental care exhibited is known as "gerontophagy", or the “consumption of old individuals” (geron = old person, phagy = to feed on). Gerontophagy is the final act of care for the offspring, and some offspring are found larger than others. This implies that some young spiders are already able to feed on prey by themselves and gerontophagy as a source of nutrition is supplemental rather than necessary. Thus, there exists the ‘cannibal’s kin-dilemma’, which reveals a form of kin selection in social spiders. In this scenario, kin selection should counteract cannibalism of related individuals in social spiders, but any designated victim should prefer to be eaten by available close relatives.[19]

Cultural significance edit

Although matriphagy is not a widely circulated term in society, there are specific instances where it has been used to represent or symbolize specific ideas. For instance, Dr. Luke Winslow from San Diego State University dubbed the concept "rhetorical matriphagy" in 2017 in connection with critiques of increasing online higher education offerings.[10] In this analogy, higher education assumes the role of the mother, neoliberalism assumes the role of the hatchlings, and online education discourse assumes the role of the mother’s symbolic resources, which are used to attract hatchings and eventually lead them to engage in matriphagy for these resources.[10] The theory behind the existence of matriphagy is similar to that of higher education. Matriphagy is a less than ideal survival mechanism in response to an environment with poor conditions and few natural resources, but it persists because of guaranteed survival of the mother’s genes via her hatchlings.[10] Similarly, online education does not consider itself at the same level as traditional forms of higher education but does provide an equal opportunity for all to attain such education in a cost-effective way that satisfies most stakeholders in the process.[10]

Those who have been exposed to matriphagy may be frightened by such a seemingly strange and bizarre natural behavior, especially since it is mainly observed in already feared organisms. Thus, matriphagy is often posed as perpetuation of a long held fear of arachnids in human society.[20]

In contrast, others may look to matriphagy as a leading example of purity, as it represents an instinctive form of altruism. Altruism in this case refers to an "intentional action ultimately for the welfare of others that entails at least the possibility of either no benefit or a loss to the actor," and is a highly popularized and desirable concept in many human cultures.[11] Matriphagy can be viewed as altruism, insofar as participating mothers "sacrifice" their survival for the welfare of their offspring.[11] Although participation in matriphagy is not truly an intentional action, mothers are nevertheless driven by natural selection pressures based on offspring fitness to engage in such behavior.[11] This in turn creates a cycle that perpetuates altruistic matriphagous behavior through generations. Such an example of altruism on a purely biological level differs severely from human standards of altruism, which are tainted by moral virtues such as rationality, trust, and reciprocity.[11]

List of species that engage in matriphagy edit

Spiders edit

Earwigs edit

  • Anechura harmandi

Strepsiptera edit

Pseudoscorpions

  • Paratemnoides nidificator

Vertebrates edit

References edit

  1. ^ "Zoologger: The baby spiders that munch up their mum". New Scientist. Retrieved 2017-03-23.
  2. ^ a b POLLOCK, D. A.; NORMARK, B. B. (2002). "The life cycle of Micromalthus debilisLeConte (1878) (Coleoptera: Archostemata: Micromalthidae): historical review and evolutionary perspective". Journal of Zoological Systematics and Evolutionary Research. 40 (2): 105–112. doi:10.1046/j.1439-0469.2002.00183.x. ISSN 0947-5745.
  3. ^ "Watch Baby Spiders Eat Their Mothers Alive". 2017-09-20. Retrieved 2018-03-22.
  4. ^ Engelhaupt, Erika (2014-02-06). "Some animals eat their moms, and other cannibalism facts". Science News. Retrieved 2018-03-22.
  5. ^ a b Kupfer, Alex; Muller, Hendrik; Antoniazzi, Marta M.; Jared, Carlos; Greven, Hartmut; Nussbaum, Ronald A.; Wilkinson, Mark (2006). "Parental investment by skin feeding in a caecilian amphibian". Nature. 440 (7086): 926–929. doi:10.1038/nature04403. PMID 16612382.
  6. ^ Toyama, Masatoshi (2003). "Relationship between reproductive resource allocation and resource capacity in the matriphagous spider, Chiracanthium japonicum (Araneae: Clubionidae)". Journal of Ethology. 21: 1–7. doi:10.1007/s10164-002-0067-6 – via Springer Link.
  7. ^ a b c d Salomon, Mor; Schneider, Jutta; Lubin, Yael (2005–2006). "Maternal investment in a spider with suicidal maternal care, Stegodyphus lineatus (Araneae, Eresidae)". Oikos. 109 (3): 614–622. doi:10.1111/j.0030-1299.2005.13004.x. ISSN 0030-1299.{{cite journal}}: CS1 maint: date format (link)
  8. ^ a b Toyama, Masatoshi (March 1999). "Adaptive advantages of maternal care and matriphagy in a foliage spider,Chiracanthium japonicum (Araneae: Coubionidae)". Journal of Ethology. 17 (1): 33–39. doi:10.1007/bf02769295. ISSN 0289-0771.
  9. ^ a b c d e f g h Evans, Theodore A.; Wallis, Elycia J.; Elgar, Mark A. (July 1995). "Making a meal of mother". Nature. 376 (6538): 299–300, author reply 301. doi:10.1038/376299a0. ISSN 0028-0836. PMID 7630393.
  10. ^ a b c d e Winslow, Luke (28 Apr 2017). "Rhetorical Matriphagy and the Online Commodification of Higher Education". Western Journal of Communication. 81 (5): 582–600. doi:10.1080/10570314.2017.1316418.
  11. ^ a b c d e Montayne, James A. (2016). "Review of 'Does Altruism Exist? Culture, Genes, and the Welfare of Others'". The Independent Review. 20 (3).
  12. ^ a b c d e f g h i j k l m n o p q r s t Kim, Kil-Won; Horel, André (2010-04-26). "Matriphagy in the Spider Amaurobius ferox (Araneidae, Amaurobiidae): an Example of Mother-Offspring Interactions". Ethology. 104 (12): 1021–1037. doi:10.1111/j.1439-0310.1998.tb00050.x. ISSN 0179-1613.
  13. ^ a b c d Salomon, M.; Aflalo, E. D.; Coll, M.; Lubin, Y. (2014). "Dramatic histological changes preceding suicidal maternal care in the subsocial spiderStegodyphus lineatus(Araneae: Eresidae)". Journal of Arachnology. 43 (1): 77–85. doi:10.1636/b14-15.1. ISSN 0161-8202.
  14. ^ a b c d Suzuki, Seizi; Kitamura, Masashi; Matsubayashi, Kei. "Matriphagy in the hump earwig, Anechura harmandi (Dermaptera: Forficulidae), increases the survival rates of the offspring" (PDF). Journal of Ethology. 23 (2). doi:10.1007/s10164-005-0145-7.pdf. ISSN 0289-0771.
  15. ^ a b c d e Tizo-Pedroso, Everton; Del-Claro, Kleber (2005). "MATRIPHAGY IN THE NEOTROPICAL PSEUDOSCORPION PARATEMNOIDES NIDIFICATOR (BALZAN 1888) (ATEMNIDAE)". Journal of Arachnology. 33 (3): 873–877. doi:10.1636/s03-61.1. ISSN 0161-8202.
  16. ^ Mark Wilkinson; et al. (June 2008). "One hundred million years of skin feeding? Extended parental care in a Neotropical caecilian (Amphibia: Gymnophiona)". Biology Letters. 4 (4): 358–61. doi:10.1098/rsbl.2008.0217. PMC 2610157. PMID 18547909.
  17. ^ a b c d Gundermann, Jean-Luc; Horel, André; Roland, Chantal (2010-04-26). "Costs and Benefits of Maternal Care in a Subsocial Spider, Coelotes terrestris". Ethology. 103 (11): 915–925. doi:10.1111/j.1439-0310.1997.tb00133.x. ISSN 0179-1613.
  18. ^ a b c Kupfer, Alexander; Müller, Hendrik; Antoniazzi, Marta M.; Jared, Carlos; Greven, Hartmut; Nussbaum, Ronald A.; Wilkinson, Mark (2006). "Parental investment by skin feeding in a caecilian amphibian". Nature. 440 (7086): 926–929. doi:10.1038/nature04403. ISSN 0028-0836.
  19. ^ a b "Gerontophagy versus cannibalism in the social spiders Stegodyphus mimosarum Pavesi and Stegodyphus dumicola Pocock". Animal Behaviour. 35 (6): 1903–1905. 1987-12-01. doi:10.1016/S0003-3472(87)80087-8. ISSN 0003-3472.
  20. ^ Barness, Sarah (2 Jan 2014). "Spider Babies Eat Their Mother From The Inside Out, Giving Us Another Reason To Be Terrified Of Arachnids". HuffPost.
  21. ^ Kim, Kil Won; Roland, Chantal; Horel, André (25 December 2001). "Functional Value of Matriphagy in the Spider Amaurobius ferox". Ethology. 106 (8): 729–742. doi:10.1046/j.1439-0310.2000.00585.x.
  22. ^ Koyanagi, Chie; Abé, Hiroshi (2016-08-07). "Offspring discrimination by female parents of the matriphagous spiderCheiracanthium japonicum(Araneae: Eutichuridae)". Journal of Natural History. 50 (41–42): 2573–2583. doi:10.1080/00222933.2016.1210689. ISSN 0022-2933.
  23. ^ Nuwer, Rachel (2015). "Mother, May I … Eat You?". Scientific American. 313 (4): 19. doi:10.1038/scientificamerican1015-19.

Category:Predation Category:Carnivory Category:Biology terminology

Introduction

Matriphagy is the consumption of the mother by her offspring.[1][2] The behavior generally takes place within the first few weeks of life and has been documented in some species of insects, nematode worms, scorpions, and other arachnids.[3][4]

The specifics of how matriphagy occurs vary among different species, but the process is best described in Stegodyphuts lineatus, where the mother harbors nutritional resources for her young through food consumption. The mother is able to regurgitate small portions for her growing offspring, but between 1-2 weeks after hatching the progeny capitalize on this food source by eating her alive. Typically, this behavior only acts on the biological mother of the young.

Spiders that engage in matriphagy produce offspring with higher weights, shorter and earlier moulting time, larger body mass at dispersal, and higher survival rates than clutches deprived of matriphagy. In some species, matriphagous offspring were also more successful at capturing large prey items and had a higher survival rate at dispersal. These benefits to offspring outweigh the cost of survival to the mothers and help ensure that her genetic material is passed to the next generation, thus perpetuating the behavior.

Overall, matriphagy is an extreme form of parental care that stands in stark contrast to other forms such as extended parental care and protection found in arachnids and other insects. The uniqueness of this phenomenon has led to several expanded analogies in human culture and contributed to the pervasive fear of spiders throughout society.

Etymology

  • This section, although brief in manner, is necessary to highlight the literal translation of the word, which therefore brings enhanced meaning to the term.
  • Matriphagy can be broken down into two components:
  • Matri- (mother)
  • -phagy (to feed on) (“matriphagy - Wiktionary”)

Description

  • This section will give a detailed description of matriphagy behavior in different species (how it happens, what changes within the body of the mothers, and what circumstances that led to the development of this behavior).
  • Matriphagy behavior generally consists of offspring consuming their mother; however, different species exhibit different versions of this behavior and this section will describe these variations.
  • Amaurobius ferox (subsection) - (Salomon et al., 2015) and (Kim, K. W., & Horel, A., 1998)
    • This matriphagy behavior is initiated by communication through web vibrations between the mother and her offspring. These web vibrations tell the offspring to go towards her abdomen
    • 1 day after the emergence of her offspring, the mother produces a second batch of eggs. These eggs are known as trophic eggs. Her offspring consumes these eggs immediately after they have been lain.
    • Then for the first 3 days after laying the trophic eggs, the mother keeps to herself, away from her offspring, until after the fourth day, when the mother begins pulling at the web while approaching her offspring.
    • 2-3 hours before the mother is consumed, she increases her activity by drumming on the web, brushing her offspring off of her back, and jumping.
    • This drumming may “activate” the young, while jumps may “inhibit” them.
    • During her last 20-30 minutes alive, her activity increases even more (more drumming and more jumping) and more of the offspring climb onto her.
    • At the very end, she presses her body onto her offspring and then relaxes her whole body and allows her offspring to consume her. The offspring actually move collectively towards her abdomen (opisthosoma) to begin consumption through sucking. This initial feeding takes up to 1 hour. The mother’s body is then kept for several weeks for the offspring to continually go back to for nutrients.
    • Pressing her body might act as a suggestion to the offspring to consume her.
    • 3-4 days after consummation of the trophic eggs, the offspring experience their first post emergence moult and afterwards consume their mother a day later.
    • Offspring older than 4 days have been found to unwillingly participate in matriphgay. This shows that the behavior in this species is very dependent on time of development of the offspring.
    • Interestingly, if the mother loses her brood, then she is able to produce another clutch. Also, a mother can be eaten by offspring that is not her own, however this does not apply for a virgin female.
    • All of the drumming and jumping indicate communication between the mother and her offspring, which may be how the offspring know when and where to consume their mother.
  • Anechura harmandi (subsection) - (Suzuki et al., 2005)
    • Offspring eat their mothers
    • It has been shown that the removal of mothers reduces survival in these hump earwig offspring, however few are able to survive and end up dispersing the nest earlier than those who were able to gain nutrients from their mother’s body.
    • Mothers of this species cannot produce a second brood.
    • Usually, when mothers of this species decide to reproduce, they reproduce early in the season at low temperatures mainly to avoid predation (especially since if they lose their one brood, then they will not be able to produce another). However, during this time, there isn’t much food available, which makes the mother the next best choice for nutrients.
  • Diaea ergandros (subsection) - (Evans et al., 1995)
    • Mothers of this species store nutrients and food in trophic eggs that are not laid. The nutrients are then converted into haemolymph, which can now be consumed by her offspring through her leg joints. During consumption, the mother loses the ability to move and her abdomen shrinks. The rest of the egg is then consumed during the consumption of the mother’s whole body.
    • These trophic eggs are actually unusually large oocytes that are only found in mothers that have already lain their single clutch (after laying eggs, their ovaries shrivel, but then they develop into ovaries with these larger and fewer oocytes). They are so large, that they cannot physically get through the mother’s oviducts, which explains why they can never be lain.
    • These mothers only lay one clutch.
    • Depending on the body mass of the mother, cannibalism within the offspring may occur earlier or later. (This study also suggests that matriphagy may reduce cannibalism within siblings).
  • Paratemnoides nidificator (subsection) - (Tizo-Pedroso, E., & Del-Claro, K., 2005)
    • The mother exits the nest and waits to be consumed during periods of food deprivation.
    • Her offspring follow her out of the nest to gather around her and then grab her legs. They feed through her leg joints.
    • Upon finishing consumption, the mother’s exoskeleton is thrown out of the tree bark (where they are living) and then the offspring begin hunting together.
    • If the mothers live in a group, they are able to produce more than one clutch during her lifetime.
    • Matriphagy behavior in this species may prevent cannibalism for occurring.
  • Stegodyphus lineatus (subsection) - (Salomon et al., 2015)
    • Offspring of this species, when first emerged, are too young to catch and ingest their own prey no their own, so they rely on their mother’s regurgitated fluid for feeding. Without this fluid, they would die.
    • Mothers’ midgut tissues begin slowly degrading during the middle of egg incubation period of their offspring. Even before that, mating might actually trigger an increase in the production in digestive enzymes to better digest the mother’s prey for the sake of helping her retain more nutrients for the offspring to consume later.
    • Mothers first regurgitate food for their offspring for a short period of time, while their midgut tissues continue to gradually degrade and, as a result, completely liquefy. This degradation is done in such a way that maximizes the amount of nutrition of the mother’s body in the liquid.
    • Her liquified midgut tissues are used to help regurgitation by acting as the regurgitation fluid, which ends up accelerating this degradation/liquifying process.
    • A mother’s abdomen fills with liquid containing nutritional vacuoles and their offspring are actually able to attain this liquid by puncturing into their mother’s abdomen.
    • These nutritional vacuoles are made after digesting prey with enzymatic digestive fluid from a previous meal and then sucking up the degraded tissues of their prey.
    • After approximately 2-3 hours, the offspring completely consume all of their mother’s body fluids. Only her exoskeleton remains.
    • By the end, ~95% of a mother’s body mass will be consumed by her offspring.
    • This intense maternal care can also be explained on why mothers of this species spend so much effort, time, and other resources into a single reproductive event. In the end, she only has one clutch, unless her previous clutch is lost or taken by others.
    • This behavior will only occur between mothers and their own offspring and in mothers who had recently just laid her eggs with offspring that are not her own. Virgin females will not aid in this feeding, indicating importance of reproductive stage even before matriphagy behavior occurs.

Evolution

  • This section is going to focus on the adaptive value of matriphagy in terms of the benefits provided to the offspring and the costs borne by the mother. This functional analysis of matriphagy will help shed light on why this unusual and extreme form of care has evolved and been selected for.
  • Benefits to Offspring (subsection) - Study conducted by Kim et al. (2000) in Amaurobius Ferox.
    • Consuming the mother is a source of nutrition which is important for growth and development.
    • The body mass and opisthosoma length of spiderlings increased (2.5 fold) after matriphagy compared to before (opisthosoma is the posterior part of the body in spiders, analogous to the abdomen). Additionally, body mass was higher for the group of spiderlings that engaged in matriphagy as compared to the group that did not (similar results were found by Toyoma et al., 1999).
    • Matriphagy also advanced molting time. Molting is the growing of a larger exoskeleton and shedding the old one. Advancement of molting time means that the spiders are growing at a faster rate.
    • The matriphagy group of spiderlings experienced significantly greater survival rates compared to the no-matriphagy group at dispersal (Suzuki et al., 2005). The spiders that engaged in matriphagy also had a larger body mass/size at dispersal, indicative of higher fitness (Salomon et al., 2005).
    • Predation started earlier in the no-matriphagy group (around the time matriphagy was expected to occur) because the spiderlings needed food to survive. However, the no-matriphagy spiderlings only hunted small prey whereas the spiders that engaged in matriphagy were successful at hunting larger prey, and this group also showed more complete prey consumption.  
    • Evans et al. 1995, also argue that matriphagy improves sociality in spiders, primarily by reducing sibling cannibalism.
  • Costs to mother (subsection) - (Kim et al., 2000)
    • Unlike other milder forms of parental care, matriphagy ends with the life of the mother, the gravest of all costs. So, why has it evolved? In order to answer this, we need to look at costs to the mother in terms of reproductive output, egg sac development and number of young (i.e. are offspring more successful if the mother evades matriphagy and reproduces again?).
    • Only 79% of the females who were separated prior to matriphagy produced second egg sacs and only 42% of these developed completely (compared to the >90% development of egg sacs in the first brood).
    • Number of spiderlings in the second brood were significantly lower than in the first brood. Additionally, these individuals were also smaller than the spiders in the first brood.
    • Females that were offered the opportunity to successively lay two egg sacs had a lower expected output of dispersing offspring than females that were victims of matriphagy which produced only a single clutch
  • In conclusion, these results show that spiderlings that engage in matriphagy benefit a lot more than spiderlings that do not engage in this behavior. Further, the progeny of females that escape matriphagy to lay a second brood are significantly less successful than those that ate their mother the first time around. Together, these results shed light on why this unusual and extreme form of parenting has been selected for and has evolved.

Other forms of Parental Care

  • Here we will compare matriphagy to other parental care methods in similar species and other arachnids; as a result, the audience will be able to realize the costs and benefits of other maternal parenting styles and realize the reasons for matriphagy in certain situations.
  • (will divide into SUBSECTIONS, by the parental care methods & by species)
  • Extended Care in Coelotes terrestris (subsection) - (Gunderman et. al, 1997);  This section will take a look at spider parental care that differs from matriphagy and involves extended care for the young
    • Detail the costs and benefits of maternal care in a subsocial spider Coelotes terrestris as an example of extended care toward its progeny
    • The mother guards its egg sac for 3-4 weeks and stays with its young from the time of emergence until dispersal approximately 1 month later
    • Comparisons of fitness of females performing care versus females separated from their egg sac will be analyzed
    • Benefits exist in that protection of egg sacs from predation and parasites as well as supplying the young with food will allow for increased survival rate and development of many of the spiderlings
    • Costs include decreased ability to produce a second clutch (similar to species that exhibit matriphagy) but this is variable according to the stage in the reproductive cycle; guarding of the egg sac has a low cost when comparing it to benefits
  • Mother-Offspring aggregation in the European earwig (subsection) - (Gomez et al, 2013)
    • Coadaptation of Forficula auricularia (European earwig) parents and offspring are age-dependent; similar to A. ferox and other species in the sense that timing of parental care affects how offspring will react
    • Offspring and parents interact repeatedly over time of parental care and their behavior is adjusted dynamically and adaptively depending on the time of interaction
    • Maternal care is beneficial, but not vital, for their offsprings survival
    • Care is most intense during the first larval instar as opposed to later points in development, as measured by a stability in aggregation levels between the parent and the offspring at early points, with a steep decline in aggregation levels over time or with different families
    • Nymph survival and female-offspring aggregation have a positive correlation when care is at its highest stages, which is often in the early stages of development
  • Parental care and production in Euscorpius flavicaudis (subsection) - (Dumke, 2017)
    • Maternal care in the scorpion Euscorpius flavicaudis is primarily involved for predation protection as opposed to food foraging
    • Differs in the sense that presence or absence of the mother does not have an effect on juvenile survival, assuming that conspecific scorpions were kept from other scorpions
    • If scorpions had access to other scorpions in a group, the presence of the mother prevented predation, but absence suggest extremely high brood mortality rates averaging 99%
    • Thus, avoidance of predation is the primary selective advantage in parental care
    • (This section will focus on the fact that this is true; research used as supplement)
  • Extended care in the Australian crab spider (subsection) - (Benton, 1991)
    • Maternal care is extended in Xysticus bimaculatus; here the crab spiders are subsocial species, and produce extremely small clutches
    • Potential that this reveals that there is a limit in how many offspring they are capable of caring for
    • Offspring obtain crucial benefits beyond nutritional independence and still require extensive maternal food provisioning
    • Prey-sharing occurred regardless of maternal presence; exploitative feeding behavior is involved and reflects a communal feeding style

Cultural Significance

  • This section will connect the biological behavior of matriphagy to human behavior, rhetoric, and pop culture. Information on cultural significance will broaden our target audience and highlight the importance of the evolution of this behavior beyond the species specific, biological level.
  • Rhetorical matriphagy is a concept dubbed by Dr. Luke Winslow in connection with critiques of online higher education offerings. (Winslow, 2017)
  • Higher education assumes the role of the mother, neoliberalism assumes the role of the hatchlings, and online education discourse assumes the role of the mother’s symbolic resources, which are used to attract the hatchings and eventually cause them to eat her alive for these resources.
  • Matriphagy is a less than ideal survival mechanism in response to an environment with poor conditions and few natural resources, but it does ensure the survival of the mother’s genes via her hatchlings. Similarly, online education does not consider itself at the same level has traditional forms of higher education but does provide an equal opportunity for all to attain such education in a cost-effective way that purports to satisfy most stakeholders in the process.
  • Matriphagy perpetuates a long held fear of arachnids in human society. (Barness, 2014)
  • Matriphagy serves as an instinctive form of altruism, a highly popularized and desirable concept in many human cultures. (Wilson, 2016)        
  • Altruism defined as “intentional action ultimately for the welfare of others that entails at least the possibility of either no benefit or a loss to the actor”
  • Matriphagy “intentional” behavior, insofar as the mother is programmed by natural selection to behave in such a way (only participating mothers have offspring that survive, thus perpetuating cannibalistic behavior through generations)
  • Human standard for altruism tainted by moral virtues such as rationality, trust, and reciprocity – concepts that are not seen in purely biological interactions.

List of species

  • Theridion impressum, Eresidae: Cheiracanthium japonicum

Category:Predation Category:Carnivory Category:Biology terminology

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