Araneus ventricosus

Araneus ventricosus is a nocturnal orb-weaver spider found primarily in China, Japan, and Korea that has been involved in numerous research studies and is easily identified by its nocturnal web-building behavior. Araneus ventricosus' venom is effective against invertebrate prey, but it's venom is ineffective in vertebrates. This arachnid's silk has been researched extensively and has several unique properties. For instance, Araneus ventricosus is able to produce flagelliform silk, and full genomes have been established for its TuSp1 (tubuliform spidroin) and AcSp1 (aciniform spidroin) genes. The spider also has unique eyes that are affected by their circadian rhythm and imply the existence of an efferent optic nerve within the species' central nervous system.



General description
Araneus ventricosus is commonly brown, black, or gray. It is also identifiable by its unique behavior surrounding web-building, as the arachnid is known to build a web throughout the night before destroying it in the morning. The spider is also known to perform mating dances as a courtship ritual.

The spider feeds on other animals in Arthropoda, primarily insects as an adult, and is not dangerous to humans, but has been reported to bite pets and other animals. The venom of Araneus ventricosus has different effects on spider bite victims depending on the bitten animal's taxonomy. While the venom has been found to be inactive in vertebrates, it is easily capable of killing insects. De novo sequencing of the Araneus ventricosus venom was even able to find evidence of glutamic acid methylation, which had not been found in animal venom before, while a local venom protein database (LVPD) recognized 130 protein chains related to toxins.

Taxonomy
This species has several unique classifications taxonomically. Excluding the information provided in the chart, Araneus ventricosus is also included in the Entelygynae subgroup of Araneomorphae, as well as Orbicularae, which is a group branching from Entelygynae. The complete mitochondrial genome (mitogenome) of Araneus ventricosus was established and published in 2020, from which it was determined that the spider's codon arrangement was almost the same as Argiope bruennichi. This was able to then solidify that the Arachnida class is monophyletic.

Distribution and habitat
The spider primarily resides in garden, fields, and forest ecosystems. When considering the spider's global distribution, it is commonly found in East Asia. Specific countries in which it is primarily spotted include China, North and South Korea, and Japan.

Flagelliform silk production
Araneus ventricosus is able to produce flagelliform silk, also known as dragline silk, which has been found to be the most elastic of all spider silk types. However, this highly valuable silk type is very difficult to create through artificial means. Since spider silk has a variety of potential uses, including in fabrics and biomedical technologies, the sequence motifs for genes coding for this silk in the species have been studied to examine the potential for artificial production. In the study by Lee et al., clones of the genes for this silk were produced and injected into insect cells to determine if future cells would also contain these genetic motifs. Since the later generations of this strain of cells were able to maintain the AvFlag tag, it was discovered that the species could potentially be used to produce large quantities of this dragline spider silk.

Spidroins
The spidroins that make up all types of spider silk are produced by glands. In orb-weaving spiders, like Araneus ventricosus, there are typically seven or fewer of these glands. The silk proteins created by the glands include flagelliform spidroins, called Flag; tubuliform spidroins, called TuSp; aciniform spidroins, called AcSp; aggregate spidroins, called AgSp; pyriform spidroins, called PySp; and major and minor ampullate spidroins, respectively called MaSp and MiSp. Of these proteins, AcSp and TuSp help to create egg coverings, while the other five are involved in the spider silk's structure. However, thanks to recent analysis of the Araneus ventricosus genome, it has been discovered that there may be more than these seven spidroin types.

Tubuliform silk, which may also be called cylindriform silk, is used to develop egg coverings, so it is only produced by glands in female spiders. One specific tubuliform spidroin gene in Araneus ventricosus, TuSp1, has been studied using a long distance polymerase chain reaction. Through this study, it was found that 1921 amino acid residues with 9 collective repeats can be coded for by the gene's main component.

Aciniform silk, on the other hand, is involved in prey-wrapping behaviors along with creating egg coverings. With these two uses, this form of spider silk is much stronger and more flexible than most other silk types, making it a valuable research subject. For instance, similarly to the TuSp1 gene, a long distance PCR was performed on the gene for the aciniform spidroins in Araneus ventricosus, AcSp1. This procedure found that AcSp1 produces a protein with 3445 amino acids and contains 10338 base pairs.

Eye cells and sensitivity
Orb-weavers' anterior median eyes have three types of eye cells - blue, ultraviolet, and green. In noct-diurnal spiders, meaning those active during both the day and night, the blue eye cells have been found to be most responsive to circadian systems. In the nocturnal Araneus ventricosus, it has then been found that their anterior median eyes are able to change sensitivity in accordance with their circadian rhythm, meaning that the spider likely has an efferent optic nerve. Additionally, their eyes are unable to find differences in color and have only one type of photoreceptor.

Central nervous system
The central nervous system of Araneus ventricosus contains fused supraesophageal ganglia, which are then composed of substantially-sized clusters of neurons. These supraesophageal ganglia eventually lead to the spider's four pairs of eyes through the optic nerve. The leading portion of the nerve cord then consists of the subesophageal ganglia, including the ventral subesophageal mass. The subesophageal ganglia, unlike the supraesophageal ganglia, are responsible for the nerves tied to the spider's appendages and pedipalps. Furthermore, the Araneus ventricosus subesophageal mass and brain both lack soma, or cell bodies, in the neurons of their central fibrous masses.