Krill
Table of Contents
The krill are tiny crustaceans living in the ocean, found everywhere around the world. The name of the species is derived from the identically sounding Norwegian word, meaning „young fry of fish”, fry being the stage of life when the animal already looks like a mature fish and is able to feed on its own, but it still has no fins and scales.
Krill vary in terms of sizing: most of them are small, about 1-2 cms long at mature age, but there are a few species that grow to about 6-15 cms. They all have an exoskeleton that consists of three distinct parts: the head, the thorax and the abdomen. Most species feature compound eyes that adapt quickly and easily to the changing light conditions of the waters. As an appendage to the head, most animals also have antennae.
Different species have different numbers of legs. All species have five pairs of legs used for swimming and other leg pairs attached to the thoracic part of the animal’s body.
These tiny animals are filter feeders. Their mouth-like organs at the front of their heads form a very dense comb used for filtering nutrients out of the water. The food they are looking for include mainly phytoplanktons. Most of these creatures are omnivorous, meaning that they feed on zooplanktons as well as very small fish.
After these creatures emerge from the eggs, they go through several stages of development as larvae. They also go through several sessions of moulting, that is, shedding their exoskeletons when they become too tight – smaller species shed more often than larger ones and the frequency of moulting decreases as the animal advances in age. The length of inter-moult periods depends on the climate, on the species and on the availability of food as well, some species being able to moult even when food is scarce and their body size shrinks, making their exoskeleton too large.
Male krill deposit their sperm in the female’s body through an orifice called thelycum. The female then carries the sperm sack in her ovaries until the eggs are ready to be delivered. The number of eggs carried can reach several thousand, with the sack growing until it reaches about one third of the animal’s body.
These tiny, frail-looking animals are in fact very resilient and relatively long-lived. Some species live for as long as 6 years, while the majority of krill species live for about two years.
The Essential World of Krill: Nature’s Tiny Titans
Krill may not be the first thing that pops into your mind when you think about the ocean’s marvels, but these small crustaceans are fundamental to the marine food web. Despite their diminutive size, krill play a pivotal role in the ecological balance and health of oceanic ecosystems around the globe. Euphausia superba, the scientific name for Antarctic krill, is just one of the 85 known species that inhabit our oceans, illustrating the diversity and widespread nature of these organisms.
Krill’s Role in Marine Ecosystems
The Nutritional Powerhouse
Krill are more than just tiny specks in the ocean; they’re a mega source of nutrients for a variety of marine life. These crustaceans are packed with omega-3 fatty acids, proteins, and other essential nutrients that make them a key part of the diet for whales, seals, penguins, and fish. The biomass of Antarctic krill alone is estimated to be around 379 million tonnes, showcasing their abundance and importance as a food source in the marine ecosystem.
The Great Migrators
Krill are known for their daily vertical migration, which is one of the largest biomass movements on the planet. During the day, they swim to deeper waters to avoid predators, and at night, they return to the surface to feed on phytoplankton. This behavior not only helps them survive but also plays a crucial role in the ocean’s carbon cycle. By feeding on carbon-rich phytoplankton at the surface and excreting waste in deeper waters, krill help sequester carbon dioxide, thus contributing to the regulation of our planet’s climate.
Krill Harvesting and Human Use
Sustainable Krill Fishing
The harvesting of krill, particularly for their omega-3 fatty acids and as a feed in aquaculture, has grown into a significant industry. Sustainable krill fishing practices are crucial to ensure that this does not negatively impact the marine ecosystems. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) regulates krill harvesting to maintain ecological balance and ensure that krill populations remain healthy and abundant for their natural predators.
Krill in Nutraceuticals and Pharmaceuticals
Krill oil, extracted from these crustaceans, has gained popularity in the nutraceutical industry due to its high concentration of omega-3 fatty acids, which are more bioavailable than those found in fish oil. This makes krill oil a sought-after supplement for human consumption. Additionally, krill’s unique properties are being studied for potential applications in pharmaceuticals, offering promising avenues for medical research and development.
Understanding Krill Behavior and Physiology
The Complex Life Cycle
Krill’s life cycle is fascinating and complex, involving multiple stages of development from eggs to adulthood. This cycle is intricately linked with the seasonal dynamics of the ocean, where the availability of phytoplankton influences their growth and reproductive rates. Understanding these cycles is crucial for scientists to predict population changes and assess the health of marine ecosystems.
Krill’s Adaptations to Extreme Environments
Krill have evolved remarkable physiological adaptations that allow them to thrive in some of the planet’s most extreme marine environments. Their ability to produce antifreeze glycoproteins prevents their bodily fluids from freezing in icy waters, and their highly efficient filtering apparatus enables them to feed on tiny phytoplankton. These adaptations underscore the resilience and ecological significance of krill in the ocean’s food web.
In conclusion, krill, though small, are mighty contributors to the marine ecosystem. Their role in the food web, their unique behaviors and physiological adaptations, and their significance to human industries underscore the importance of these tiny crustaceans. Sustainable practices and further research are essential to ensure the health of krill populations and, by extension, the health of the oceans.
FAQs About Krill
1. What do krill eat, and how do they feed? Krill primarily feed on phytoplankton, which are microscopic plants that float in the ocean’s surface waters. They use their small, hair-like appendages to filter these tiny organisms from the water. This feeding strategy allows them to consume large quantities of phytoplankton, supporting their large populations.
2. How large can krill populations get? Krill populations can be vast, particularly in the Antarctic, where the biomass of Antarctic krill (Euphausia superba) is estimated to be between 300 and 500 million tonnes. Such large populations are crucial for supporting a wide array of marine species that rely on krill as a primary food source.
3. How do krill contribute to the carbon cycle? Krill play a significant role in the carbon cycle through their feeding and migration behaviors. By consuming carbon-rich phytoplankton at the ocean’s surface and then releasing carbon in deeper waters through their waste, krill help transport carbon from the surface to the deep ocean, effectively sequestering it and contributing to the reduction of atmospheric carbon dioxide levels.
4. What are the main threats to krill populations? The main threats to krill populations include climate change, which affects the availability of their phytoplankton food sources, and unsustainable fishing practices that can deplete krill numbers faster than they can reproduce. Maintaining ecological balance and sustainable harvesting practices are essential for krill conservation.
5. How are krill used in human industries? Krill are harvested for their omega-3 fatty acids, which are used in dietary supplements like krill oil. They are also used as feed in aquaculture and for extracting chitin, a substance used in various medical and biotechnological applications. Sustainable harvesting practices are crucial to ensure that krill remain a viable resource for both marine ecosystems and human use.
