Pardosa pseudoannulata
Pardosa pseudoannulata, part of a group of species referred to as wolf-spiders, is a non-web-building spider belonging to the family Lycosidae. They are wandering spiders that track and ambush prey and display sexual cannibalism. They are commonly encountered in farmlands across China and other East Asian countries. Their venom has properties that help it function as an effective insecticide and therefore is a crucial pesticide control agent. [1]
| Pardosa pseudoannulata | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Desidae |
| Genus: | Phryganoporus |
| Species: | P. candidus
|
| Binomial name | |
| Phryganoporus candidus (L. Koch, 1872)
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| |
Description
Pardosa pseudoannulata has significant sexual dimorphism in terms of size. Females are, on average, 1.3 times larger than the males. This spider can be recognized from the ring markings on its legs and the dark bands on its carapace. The underside of the spider has six black dots. They are easy to detect, as most females will have an egg sac attached to their spinnerets. They have three rows of eyes, the front one having four and the other rows having two eyes each. [1]
Habitat and Distribution
Distribution
Pardosa pseudoannulata is widely spread across China, India, Korea, Japan and other countries in East Asia. It is most commonly populating farm fields throughout China. These spiders are commonly seen in rice fields and are mainly the dominant predator. [1]
Habitat
Pardosa pseudoannulata commonly inhabits arable farm fields and similar open habitats. It is one of the most common surface-dwelling spider species in Central China and plays an important role as a control agent against pests and insects within the crop fields. The spider is also found near fields with ponds and has the ability to move swiftly over bodies of water. Due to the nature of agriculture, the fields will remain cropless for several months, decreasing the density of prey that migrate into the field to take advantage of nutrients in the crops. This causes Pardosa pseudoannulata to starve for multiple months at times, explaining why it is so well adapted to survive in environment with insufficient resources. [2]
In order to produce the maximum number of eggs and the highest rate of successful hatchings, Pardosa pseudoannulata prefers temperatures between 20 to 30 oC, the optimal temperature being 25 oC. If the temperature is lower than 10 oC, the spiders will stop eating and as a result will not grow or develop. In temperatures above 40 oC, the spiders will move slowly and remain hidden in burrows. [3]
Diet
Pardosa pseudoannulata commonly starved and have a hard time foraging sufficient nutrients. Therefore, the occurrence of sexual cannibalism is accepted an adaptive strategy for female survival, along with its reproductive benefits. Pre-copulation cannibalism is commonly observed in females who have already mated, using the male spider solely as food. The consumption of conspecifics makes up a quarter of the female’s diet. Male spiders are especially a good source of nutrition because of their large size (females are 1.3 times larger) when compared to natural prey, which are insects that are several times smaller than the females. [2]
The natural preys of Pardosa pseudoannulata are rice field pests, the most common one being the rice brown planthopper, Nilaparvata lugens. They are very abundant in rice fields and are detrimental to the growth of rice plants. Pardosa pseudoannulata has been seen to show preference for the rice brown planthopper over other pests, with the planthopper making up around 30% percent of an average spider’s diet. [2][4]
Abdomen Size
Pardosa pseudoannulata’s abdomen width is an important indicator of its hunting abilities and starvation resistance. It is seen that there is a trade-off between the hunting abilities and the period of time the spider can withstand hunger. Spiders with larger abdomens are seen to withstand starvation for longer periods of time, whereas spiders with smaller abdomen were seen to be better and more agile hunters. [5]
Reproduction
Pardosa pseudoannulata males and females differ in terms of sexual behavior. Females are monandrous, which means the female will have only one mate at a time. This feature is a motivational factor for males in terms of sexual cannibalism, as the male will parent all of the female’s offspring, making the paternal investment worthy. On the other hand, males are polygynous if not cannibalized. [6]
Females are able to store sperm from a copulation and produce multiple egg sacs using it. This prevents them from being motivated to remate. This causes the higher aggression rates in female spiders who have previously mated. [1]
Females will carry their sac filled with eggs connected to their spinnerets. This will detach when it is time for the offspring to be born. The new offspring will craw onto the mother’s abdomen and stay there for 5 days. During this time, they will feed off of the remains of their yolk from the mother’s eggs. After this period, they will move into the leaf litter and live detached from the mother. [1]
Copulation duration for Pardosa pseudoannulata ranges from 19 to 93 minutes. The duration of copulation was significantly higher with males that were cannibalized. Copulation duration is independent of the sperm count of the male. Male spiders will need up to 7 days in order to replenish their sperm count. For females, reproducing with a male that has recently mated and has a low sperm count will lead to a lower chance of reproductive success. The sperm count of the male has no impact on copulation duration or intensity, so it is currently believed that females are unable to distinguish males with high sperm counts from males with low sperm counts. [6]
Life Cycle
Pardosa pseudoannulata will have on average have two and a half generations per year. Similar to other Pardosa species, sub-adults and adults overwinter in order to conserve energy and survive the cold winter months. The adults that are overwintering will be inactive from November to March, saving up body mass. They will burrow into the soil or use litter in their natural habitat as shelter. They will reach their reproductive peak in early May, and this peak is usually comprised of the overwintering generation. A second reproductive peak is observed in early July with the second generation, and a third one in late September with the next. [1]
Behavior
Sexual Cannibalism
Pardosa pseudoannulata engages in sexual cannibalism as a foraging strategy. Conspecific prey can make up 25% of the female’s diet. The female spider uses sexual cannibalism as a way to attain nutrition and increase offspring survival. There are instances where the female spider will attack and cannibalize the male before or after copulation, the latter being observed more frequently. The rate at which females attack males is dependent on the female’s hunger level and mating history. Spiders that are well-fed and virgins are less likely to attack males and perform pre-copulative cannibalism. The reason why starved females are more aggressive is apparent, as they have more motivation to acquire nutrition. Interestingly, the rate of cannibalization occurring did not change with the female’s sexual history or hunger state. Aside from this, male size is also a significant factor in cannibalization rates. As mate size dimorphism, the difference between the sizes of mates, increased, sexual cannibalism occurs more frequently. [1]
Sexual cannibalism increases offspring survival in Pardosa pseudoannulata. This is mainly due to the mother’s ability to care for them as a result of being well-fed through cannibalism. The presence of sexual cannibalism does not have any influence on fecundity, as cannibalistic and non-cannibalistic females produce the same amount if offspring. Another obvious benefit of sexual cannibalism to the female is the increase in body mass through the nutrients in the male body. [1]
Male Benefit in Sexual Cannibalism
From the male spider’s perspective, sexual cannibalism proves to be beneficial as well, given that cannibalism occurs after copulation. Each copulatory approach is a risk taken by the male, as there is always a chance that the female might cannibalize the male pre-copulation. In this scenario, the male loses all its future opportunities to reproduce. Additionally, being cannibalized before copulation increases the survival rates of rival males’ offspring. On the other hand, if copulation is successful, the male benefits. The male gets an opportunity to propagate his genes through his offspring by sacrificing his body in the form of paternal investment. As the females are monandrous, the male is guaranteed to father all offspring produced by the female.[6]
Courting Behavior
Pardosa pseudoannulata males display interesting courting behavior. This display includes pounding the floor with the first pair of legs. This courting behavior is sustained until the female acts on the male. If the male senses a lunge, or aggressive behavior from the female, it will attempt to escape. Most males are able to avoid cannibalism through escaping the female. Although, if the lunge of the female is successful and the male is caught, the female almost always cannibalizes the male. [1]
Webs
Pardosa pseudoannulata do not weave webs, but instead will ambush, or chase their prey in order to capture them. Upon genomic inspection, it is observed that they are significantly lacking in genes responsible for silk web production when compared to the genes they house for neurotoxic venom production. [1]
Venom
Pardosa pseudoannulata uses an immobilizing venom rather than a web. It’s venom has been effective against numerous pest than infest arable crop fields. Due to this, there is a lot of research that focuses on using the venom of Pardosa pseudoannulata as a pesticide in order to maximize crop yields in rice farms. The studied venom is shown to be very selective in its target and will only immobilize certain species that Pardosa pseudoannulata comes in contact with. Its venom is generally harmless for humans, although it could cause rashes or minor allergic reactions. [7]
- ^ a b c d e f g h i j Wu, Lingbing, and Huaping Zhang. “Factors Influencing Sexual Cannibalism and Its Benefit to Fecundity and Offspring Survival in the Wolf Spider Pardosa Pseudoannulata (Araneae: Lycosidae).” Behavioral Ecology and Sociobiology, vol. 67, 2013, doi:https://doi.org/10.1007/s00265-012-1440-2.
- ^ a b c Chesson, J.., et al. “Prey Preference of the Wolf Spider, Pardosa Pseudoannulata (Boesenberg Et Strand).” Population Ecology, Springer-Verlag, 1 Jan. 1978, link.springer.com/article/10.1007/BF02513547.
- ^ Xiao, Rong, and Liang Wang. “Transcriptome Response to Temperature Stress in the Wolf Spider Pardosa Pseudoannulata (Araneae: Lycosidae).” Ecology and Evolution, vol. 6, no. 11, 20 Apr. 2016, doi:https://doi.org/10.1002/ece3.2142.
- ^ Preap, Visarto, and Myron Zalucki. “Effectiveness of Brown Planthopper Predators: Population Suppression by Two Species of Spider, Pardosa Pseudoannulata (Araneae, Lycosidae) and Araneus Inustus (Araneae, Araneidae).” Journal of Asia-Pacific Entomology, vol. 4, no. 2, Nov. 2001, doi:https://doi.org/10.1016/S1226-8615(08)60122-3.
- ^ Iida, Hiroyuki. “Trade-off between Hunting Ability and Starvation Tolerance in the Wolf Spider, Pardosa Pseudoannulata (Araneae: Lycosidae).” Applied Entymology and Zoology, vol. 40, no. 1, 2005, doi:https://doi.org/10.1303/aez.2005.47.
- ^ a b c Gong, Deyong. “Mating Experience Affects Male Mating Success, but Not Female Fecundity in the Wolf Spider Pardosa Pseudoannulata (Araneae: Lycosidae).” Behavioral Processes, vol. 167, Oct. 2019, doi:https://doi.org/10.1016/j.beproc.2019.103921.
- ^ Yu, Na. “Genome Sequencing and Neurotoxin Diversity of a Wandering Spider Pardosa Pseudoannulata (Pond Wolf Spider).” Biorxiv, 29 Aug. 2019, doi:https://doi.org/10.1101/747147.