Schizocosa ocreata

During the process of molting, old outer layers of an animal are shed to allow for new growth to occur. This molting process is an important element for the animal to become sexually developed as well, and it was found to be an important process for the S. ocreata.[12]

In addition, the process of molting, gonad development, and reproductive timing in females is all impacted by the female spiders’ feeding history. There is much variation in the number of instars, the time for development, the width of the cephalothorax, and mass varied with different dietary patterns. Instars refer to the phases between two molting periods when an invertebrate animal develops into sexual maturity. The females that were well-fed actually needed more moltings to become sexually mature, needed less time for sexual development and were found to be heavier than those that were starved long-term.

A common behavior for S. ocreata spiders is self-amputation in order to regenerate a damaged limb. However, the spiders that had regenerating legs needed about an additional 3.7 days to molt. Although the spiders that had regenerating legs need additional time to molt, when talking about the number of additional moltings that are needed, these spiders usually only need one more molting.

The development of the S. ocreata spiders closely resembles most spiders; they start as an egg and develop physically into mini versions of their parents and live for a couple of years. They undergo multiple shedding of their skin throughout development and eventually undergo sexual development in order to reproduce and lay eggs. However, the eggs that the females lay are very much affected by the females’ diet history too. The number as well as the diameter of eggs was compared between well-fed females and food-limited females. It was found that the females treated with a low diet had lower egg numbers and both smaller egg diameter and volume than the well-fed females.[11]

Cuticular hydrocarbons, which cover the cuticles on insects and are waterproof, have been discovered to play a major role as a sex pheromone in spiders. The chemical cues that the female S. ocreata uses contain information that is species-specific and are able to communicate their own mating status. This signal is also able to reveal the history of what they have eaten in order to present their honest states. Although the chemical cues tell a lot about the state of the female, there is no current research done to conclude that the male chemical cues can exhibit signals.[13]

Female S. ocreata spiders were more receptive to the males they were more familiar with. Since males are the only ones that have tufts, which is the area on the forelegs covered in bristles, the usage of the multifactorial approach revealed how the female preferences are decided. The male’s tuft size phenotype is a significant factor that predicts how females will choose. Hence, females that were more exposed to the small-tufted males were more likely to be receptive to the small-tufted males. But, females that were more exposed to large-tufted males were more likely to be receptive to the large-tufted males. But, females are slightly more selective in that, in general, they have increased preferences for the large-tufted males more than the small-tufted male.[14] For the species S. ocreata, the males that are smaller in size tend to be at more risk to be attacked and cannibalized. Additionally, the species' females will attack the males with smaller tufts. The males with the larger leg tufts are able to have increased chances of mating as well.

In addition to the effects of exposures on the choosiness of female during mating, the rate of courtship may also be attributed to males' eavesdropping behaviors. Males are more likely to exhibit courtship behaviors when there is a video showing another male also exhibiting courtship activities. These courting behaviors are not exhibited by S. ocreata spiders when the video is of a male that is simply walking (or non-courting). The male spiders are able to know where the females are simply by eavesdropping on the males that are close-by. However, these findings are only suggesting a possible eavesdropping behavior by the male spiders since the other male being eavesdropped on was only on a video screen.[15]

There are two main types of approaches to copulation between the male and female spiders. The two types are either coercive or cooperative. The males would sometimes use their fang-like teeth to scar and mark the females during copulation. Scar tissues were detected in the area below the cephalothorax, but above the coxa of the leg in females. This scarred area was consistent with the part of the female’s body that the males attached their fangs on. The control, the group where virgin females were studied, showed no scar tissues on the area below the cephalothorax.[16]

The S. ocreata females can exhibit aggressive behavior towards the male after copulation. But, if they become too aggressive, the male spiders will inject them with venom in order to reduce the possibility of post-mating cannibalism, where the females would attack and eat the males.

Even though it’s unknown how much impact the venom injections have on the females, there is a possibility that there is a cost for the male’s future reproductive success as well. The death of a female due to the injection of the male venom could impact them in some way that we do not yet know about.[16]

Some of the predators of the S. ocreata are organisms that are very visually keen and able to come from above the spiders, such as various bird species. The American toad (Anaxyrus americanus) and other large organisms also prey on the S. ocreata as well.[13]

When various pathogens enter the S. ocreata, they have immunological mechanisms within their system to fight them off. However, it is still unclear the mechanism with which the S. ocreata is able to reduce the immunological inflammation and responses. In order to test whether the S. ocreata has immune functions, bacterial derivatives like lipopolysaccharide (LPS) were injected to elicit immune responses. But, an issue with studies like these is that most spiders actually are exposed to various bacteria through oral ingestion. Spiders also digest their food externally, so therefore enzymes are being secreted externally, which causes the food to be broken down outside of their body. Much of the research studies reveal that a lot of spiders have antimicrobial peptides (AMPs) to the gram-negative bacteria, gram-positive bacteria, and fungi. These AMPs are found mainly in hemocytes and sub-esophageal nerves.

When male S. ocreata spiders ingested around 600 Colony Forming Units/microliter, it was found that the spiders only had 291 Colony Forming Units in 3 microliters of their hemolymph. Hence, this suggested that there potentially is an immune system that works to prevent the ingested pathogens from getting into the hemolymph, which is the blood equivalent in most invertebrates. The CFU count in the hemolymph system shows that the spiders’ immune functions are working in some aspects to reduce the pathogens. However, further research needs to be done to determine the definite mechanism for how this occurs.[13]

It was also found that adult males that had experience with a bacterial infection in their juvenile days, actually had a stronger response to encapsulation when measured as an adult. Encapsulation is a type of immune response that is dependent on phenoloxidase; it’s widely used as a defense against macro-parasites. However, encapsulation response strength was found to be significantly higher in males who had previous juvenile exposure. But this does not mean that all immune responses are stronger.[13]

The spiders that are courting move down a more winding path and also utilize their abdomens to move as well as use their legs. Although both the courting and walking spiders move in a similar way, the courting spiders tend to spend more time moving than the walking spiders. The courting spiders’ forelegs are also almost always constantly in motion. But, when there is loss of haemolymph fluids, that could also lead to reduced mobility.[16]

These spiders use an external digestive system; they secrete the enzymes to digest the food, not within their gut, but outside themselves. These spiders have an exoskeleton, but when they have damage to their exoskeleton, there is a loss of haemolymph which can end up being consequential. A constant supply of blood volume will be needed for hydraulic locomotion, which is the process through which increased pressure in fluids from their cephalothorax stretch out their legs, and may cause reduced mobility.[16]

The only spiders that are found to have medically significant bites in the United States are the black widow and the brown recluse. Allergic reactions may still occur or develop from any spider bites. National Institute for Occupational Safety and Health.[18]

Prompt medical care should be sought if one is unsure whether the bite was from a venomous spider or not and if severe pain develops, or if problems with breathing occurs.[19]