When we think of animals that produce milk, mammals like cows and humans come to mind. But as it turns out, a tiny jumping spider native to Southeast Asia, Toxeus magnus, is rewriting the rules. This unique spider mother has found a way to nourish her young with a milk-like fluid, giving her babies a jumpstart in life.
Researchers discovered that Toxeus magnus mothers produce a creamy, nutrient-rich liquid for their young. Unlike typical spider juveniles that fend for themselves or go hungry, these spiderlings rely on this “milk” in the earliest days of life. Surprisingly, the milk-like secretion contains four times as much protein as cow’s milk and is essential for their growth.
Clues From Clinging Spiderlings
One evening, biologist Zhanqi Chen from the Chinese Academy of Science observed something unusual: a baby spider clinging to its mother’s belly. This observation led to a groundbreaking revelation—spiders might be feeding their offspring directly. To test this, Chen and his team gently pressed the spider mother’s abdomen and discovered a milky fluid, confirming their suspicions.
Essential for Survival
The “milk” isn’t just a boost for these spiderlings; it’s crucial for their survival. When researchers blocked the mother’s ability to produce milk, the young spiders died within ten days. This finding highlights how essential this milk is, especially in the critical early stages of development. While young T. magnus spiders start hunting for food around 20 days old, they continue drinking their mother’s milk until they reach about 40 days. This pattern resembles the way human babies rely on milk supplemented with solid foods as they grow. The presence of both milk and insects in their diet helps the young spiders thrive.
The Value of Maternal Presence
Removing the mother spider during this milk-feeding phase proved to be detrimental, with a 40% drop in survival rates among the orphaned young. Those with their mother nearby fared significantly better, underscoring the importance of maternal care.
Rethinking Milk Production in Nature
Milk secretion is generally a mammalian trait, but this spider has evolved a similar process to sustain its young. Researchers speculate that the spider’s milk could be made from unfertilized eggs that are “recycled” by the mother to nourish her offspring, a strategy seen in some other invertebrates.
A Surprising Influence on Gender
The presence of the mother spider seems to affect the gender balance among her offspring. With the mother around, more females tend to survive, which benefits the species, as a higher female population means more potential offspring. Interestingly, adult daughters are allowed back into the nest, while sons are driven away.
Maternal Care Rarely Seen in Invertebrates
Extended maternal care, such as allowing adult daughters to return to the nest, is rare among invertebrates. This type of ongoing care is usually seen in social animals like elephants and humans. Why T. magnus mothers devote so much time and energy to their young remains a mystery.
A Mother’s Tough Love
Life in the wild can be challenging, and it’s possible these spider mothers are preparing their young to be resilient. Extended maternal care may provide spiderlings with essential survival skills, ensuring they’re equipped to handle the demands of life on their own. The discovery of milk-producing spiders reveals the complexity and diversity of maternal care in the animal kingdom, showing that even the tiniest creatures have their own unique ways of nurturing their young.
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