Photo StoryPublished : Mar 15, 2021Updated : Sep 24, 2023
A rare peek into the world of this semi-aquatic nursery web spider in a secluded seasonal swamp in Cooch Behar where it catches fish and hunts for other invertebrates in the dead of night
Text by: Divya Candade Photos by: Ripan Biswas
A rare peek into the world of this semi-aquatic nursery web spider in a secluded seasonal swamp in Cooch Behar where it catches fish and hunts for other invertebrates in the dead of night
Gossamer webs and silken threads are what most of us associate with spiders. But that is just part of their story. The wonderful world of spiders is as complex as their webs. Interestingly, not all spiders have eight eyes, not all spiders build webs or wait to ambush their prey. Some of these highly skilled and diverse creatures, like fishing spiders, even catch fish and other invertebrates.
In Cooch Behar, West Bengal, wildlife photographer Ripan Biswas captured some rare and stunning images of a species of fishing spider (Nilus albocinctus). Every monsoon evening, Biswas went to a seasonal swamp near his home to photograph insect life. On one such walk he came across a peculiar spider poised on top of vegetation. It had a fish almost as large as itself in its mouth. What Biswas saw was a fishing spider or fish-eating spider in action (Nilus species, earlier classified as Thalassius). A semi-aquatic spider, the Nilus albocinctus belongs to the Pisauridae family commonly known as nursery web spiders. Pisauridae spiders closely resemble wolf spiders, and are also called hunting spiders.
The swamp area he visited was used for paddy cultivation during the summer, and come monsoon it brims with insect life. Biswas hadn’t seen these water-loving spiders before. Over the next three years that he documented their lives, he managed to photograph them hunting fish only three or four times. “There are several species of fishing spiders but sighting them while they are actually eating a fish is extremely rare,” he says.
This spider is often found near water, preferring shallow water sources like forest streams, swamps, and wetlands. Running water contains more dissolved oxygen than still water because more contact with the air allows more oxygen to mix into the water. In swamps and ponds, these opportunistic hunters have been observed taking advantage of the low oxygen levels which require fish to come up to the surface in search of oxygen-rich water. “This could also explain why I have often seen these spiders hunt at night,” Biswas adds, “At night the oxygen levels reduce even more.” Dissolved oxygen levels tend to drop at night as aquatic photosynthesis is light dependent.
According to the World Spider Catalogue, India has 18 known spiders in the Pisauridae family and Nilus albocinctus is distributed from India to Philippines. This striking hunter can be recognised by the long, black glossy band bordered by white on either side of its upper body.
In this seasonal swamp, the leaves are usually large, like those of the water hyacinth or the white waterlily. The fishing spider tends to latch onto large leaves with its back legs and stretch its front legs into the water, as seen in the images above. It stays very still and waits to pick up signals and sense prey, so that when the prey comes close enough it can strike. The surface tension of the water prevents the spider from sinking. Biswas notes that he has even seen this spider crawl on the surface of the water. In these images, the spider has caught a young snakehead fish (top) and an Indian barbed fish (above). These fish are usually around 1.5-3 inches long, roughly similar to the size of the spider.
These unique spiders sense their prey by feeling vibrations carried through the water. Like other spiders that feel vibrations in a web by means of tiny, extremely sensitive hair called trichobothria on their legs, the fishing spider detects these vibrations in water. On sensing prey, the spider quickly pounces, injecting the catch with neurotoxin and paralysing it. The victorious hunter then retreats to the vegetation or a nearby rock to consume its catch. “The entire process of eating its catch takes around 40 minutes,” notes Biswas. The passing prey could also include insects like striders which are a large art of their diet and other invertebrates like tadpoles and frogs.
Observation in this swamp suggests that the monsoon is possibly their breeding season. The female fishing spider wraps herself between leaves and carries her egg sacs. All female spiders of the nursery web family usually carry their egg sacs under their body with their chelicerae (pair of pincer-like appendages in front of their mouths). This is a key difference between these spiders and the similar looking wolf spiders. Female wolf spiders carry their egg sacs behind them using their silk-spinning organs (spinnerets).
When the eggs are about to hatch, the female spider builds a “nursery tent” web. This is a typical trait that gives the Pisauridae family of spiders their name, “nursery web spiders”. The female fishing spider places her egg sac inside the web. Females usually guard their nests. While the main prey of fishing spiders is aquatic insects and fish, during this phase female spiders are opportunistic eaters and will consume anything suitable that happens to be within range. Once the monsoon ends and the swamp begins to dry up, the fishing spider once again retreats to its secret universe.
is a social anthropologist who works in the area of communication for sustainable development. She loves nature and slow travel, and is most content in the wilderness.
