The six-spotted fishing spider (Dolomedes triton) is an aquatic arachnid in the Pisauridae family. Living primarily throughout North America, these critters thrive in wetland habitats such as ponds and lakes. They are often called dock spiders because they can quickly scurry away into boat docks’ crevices when disturbed or threatened.
Six-Spotted fishing spider: Description
Easily distinguished by its noticeable features, the spider has impressive size and distinctive markings. With a grey-to-brown body, eight eyes for optimal vision, and a white-to-cream-colored stripe along each side of the cephalothorax – this species is unmistakable.
Furthermore, many small light spots embellish the abdomen alongside delicate lines that trail down either side. When viewed from below, six dark spots are visible on the bottom of said cephalothorax – hence its popular name. Like most arachnids today, this specific type exhibits sexual dimorphism characteristics as well.
The female Six-spotted fishing spider is considerably more significant than the male, measuring around 2.5 inches in length, including legs; her body alone spans 0.6-0.8 inches, while the males only reach a maximum of 0.50 inches long when fully grown. Young spiders look similar to adults but are much smaller – they undergo several molts throughout their lifetime, which helps them grow and eventually become full-sized adults!
The Six-spotted fishing spider is remarkable in its variety of distinct features and behavior – male specimens, for instance, can be identified by the rounded tibial apophysis, which extends past their tibia apex.
Meanwhile, females are distinguishable due to a specific pattern consisting of three pairs of dark sternal spots and several light spots on the abdominal dorsum; additionally, an anterior half within their epigynous area houses loose fertilization tubes alongside the seminal valve part of their copulatory apparatus.
The Six-spotted fishing spider: Distribution and habitat
Six-spotted fishing spiders are native to the North and South American continents, usually thriving in the Eastern parts of the US from Maine to Florida and south down through Texas. Additionally, they have been spotted up north into Ontario, Canada, and Alaska’s southern panhandle area. Despite this broad range, reports on them coming out of most southwestern states remain rare.
Semi-aquatic in nature, Six-spotted fishing spiders make their home among wetlands—ranging from lake shores and ponds to slow-moving streams. They can be found amongst emergent plants, rocks, or other structures near the body of water, such as docks or jetties.
Their domain extends further into the coastal zones of both lakes and ponds, along with pools at a more sluggish pace lying at the edge zone of rivers & creeks.
Six-spotted fishing spiders: Diet
The Six-spotted fishing spider can take down prey up to five times their body size thanks to a potent venom that quickly immobilizes and kills its target. Active during the day, they have been known to wait for hours until an unsuspecting victim happens – this could be aquatic insects or neuston organisms as well as terrestrial bugs that fell into the water and even tiny frogs and fish!
Yes, you read correctly: these spiders are one of the few species on Earth that feeds on vertebrate creatures!
Prey is usually captured alive by Six-spotted fishing spiders, as they aren’t scared away by the sclerotization and metasternal secretions of potential targets.
However, young Six-Spotted fishing spiders consume more minor victims than mature ones, particularly females who show a notable absence in capturing small game due to their intense energy needs for yolk production.
Prey detection is hypothesized to be established through two distinct strategies – tactile stimuli on the water surface and visual perceptions.
The first strategy involves resting the anterior legs across the water surface, where they detect ripples to identify prey. Many observe these insects with their limbs spread out, hovering by the edge of a body of water as they wait for their next meal.
These Six-spotted fishing siders can walk on the water’s surface and dive up to 7 inches below with impressive visual acuity, which is critical in their prey-catching ability. As a result, they can easily snag underwater creatures and those that remain or traverse the surface, such as a water strider.
However, while vision plays an important role here, other sensory cues are less prominent for these hunters.
Six-spotted fishing spider: Use of webbing and silk.
For avid hunters that pursue and catch aquatic prey, Six-spotted Fishing Spiders do not rely on webs to trap their victims. Instead, silk plays an integral role in enabling them to survive in their aquatic habitats. As they traverse bodies of water, they use these draglines made out of silk as a safety anchor; this allows them increased mobility without putting themselves at risk.
After spiders reach sexual maturity, they employ web construction for various purposes – females utilize draglines to transport pheromones that draw in potential mates. At the same time, males construct sperm webs and nuptial gifts with silk. In addition, female spiders use their silken threads to wrap eggs into spherical sacs and craft nursery webs where spiderlings can be sheltered after hatching.
Six-spotted fishing spiders: Mating and reproduction.
The six-spotted fishing spider courting ritual begins with the female releasing silk pheromones that can signal over long distances. Intriguingly, these dragline hormones remain in place when exposed to wet surfaces and water – allowing males to locate them by following a trail of scents as they would if on land or rowing along while pulling it across bodies of water.
Males Six-spotted fishing spiders can escape after mating, allowing them to mate with multiple females. However, females rarely seek out a second partner and become hostile towards males who attempt further copulation. Moreover, while males do not discriminate between virgins and non-virgins when trying courting behaviors, female aggression is heightened when they are not freshly mated.
After pheromones have been released, male Six-spotted fishing spiders begin their pre-copulatory behavior by performing an “announcement display,” including leg-waving and jerking. This method of communication is known as palpation and serves to kick off the mating process.
The male six-spotted fishing spider makes a beeline for the female, using his dragline to arrive quickly and signaling with rapid tapping of his legs. These “jerks” consist of alternating leg extensions that result in double bursts of surface waves radiating from him–likely vibratory signals meant to alert her presence. She responds by “drumming” on whatever ground is nearby before beginning her own slower version of waving her limbs around. This forms an extended period where both parties wave their legs about until copulation occurs.
Virgins of the female persuasion are apt to run toward potential mates if they catch wind of their vibratory signals. Yet, mated females tend to feign aloofness by waiting for males to approach before pouncing.
Six-spotted fishing spiders are known for an incredibly aggressive type of intersexual conflict – pre-copulatory cannibalism, wherein females prey on males before copulation. Shockingly, mating trials show that almost a third of the pairings result in a female attack and up to 40% end with successful predation. Not only does this mean male individuals become part of their mates’ diets, but also it leads to a decrease in male population density once the female generation emerges.
Six-Spotted fishing spider reproduction.
For the typical Six-spotted female spider, egg sac production typically begins between April and September. After producing their eggs, these spiders carry them around in their mouths for up to two weeks before constructing a secure web where they carefully guard until their brood is ready to venture into nature.
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