Ctenophores: The Comb Jelly Wonders
The ocean is home to some of the most mesmerising and alien-looking creatures on the planet, and comb jellies, or ctenophores, are no exception. These gelatinous marine animals captivate with their bioluminescence and unique feeding habits, making them both fascinating and beautiful inhabitants of the underwater world. This article will explore the mesmerising bioluminescence and feeding habits of comb jellies and provide insights into their care in a reef aquarium.
What Are Comb Jellies?
Comb jellies, belonging to the phylum Ctenophora, are gelatinous marine organisms found in oceans worldwide. Despite their jelly-like appearance, they are distinct from jellyfish and belong to a completely different phylum. Comb jellies are known for their rows of ciliary plates, called comb rows, which they use for locomotion.
Key Characteristics:
• Appearance: Comb jellies have a transparent, gelatinous body with eight rows of ciliary plates, or comb rows, running along their sides. These cilia refract light, creating a mesmerizing, rainbow-like effect.
• Size: Depending on the species, comb jellies can range from a few millimetres to over a meter in length.
• Bioluminescence: Many species of comb jellies exhibit bioluminescence, emitting a blue or green light that can be seen in the dark depths of the ocean.
Mesmerising Bioluminescence
One of the most enchanting features of comb jellies is their ability to produce bioluminescence. This natural light emission occurs through chemical reactions within specialised cells called photocytes.
1. How It Works:
• Bioluminescence in comb jellies is produced by the reaction of luciferin (a light-emitting molecule) with oxygen, catalysed by the enzyme luciferase. This reaction emits light, which can be seen as a glowing trail in the water.
2. Functions of Bioluminescence:
• Predator Evasion: Bioluminescence can confuse or startle potential predators, giving comb jellies a chance to escape.
• Attracting Prey: The light may attract small prey organisms, making them easier to capture.
• Communication: Bioluminescence can be used to communicate with other comb jellies, particularly during mating.
Unique Feeding Habits
Comb jellies have developed several unique feeding strategies to capture their prey, which consists mainly of small planktonic organisms.
1. Tentacles:
• Many comb jellies possess long, sticky tentacles that trail behind them. These tentacles are lined with colloblasts, specialised cells that release a sticky substance to trap prey. Once captured, the prey is transported to the mouth by the tentacles.
2. Ciliary Action:
• Some species, such as those in the order Cydippida, use their ciliary comb rows to create water currents that draw plankton towards their mouths.
3. Direct Engulfment:
• Larger comb jellies can directly engulf prey with their mouths. This feeding method is more common in species that lack long tentacles.
Role in Marine Ecosystems
Comb jellies play a crucial role in marine ecosystems, contributing to the balance and health of oceanic environments.
1. Plankton Control:
• As voracious predators of plankton, comb jellies help regulate plankton populations, which in turn affects the entire marine food web.
2. Prey for Larger Species:
• Comb jellies themselves serve as a food source for larger marine animals, such as fish, sea turtles, and other jellyfish.
3. Indicators of Ocean Health:
• The presence and abundance of comb jellies can be indicators of ocean health and changes in marine ecosystems, as they are sensitive to environmental fluctuations.
Care and Maintenance in Reef Aquariums
Keeping comb jellies in a reef aquarium is a challenging but rewarding endeavour that requires specific conditions and careful attention to their needs.1. Tank Setup:
• Comb jellies require a large, open aquarium with gentle water flow to mimic their natural pelagic environment. A cylindrical tank or a tank with rounded corners is ideal to prevent them from getting trapped or damaged.
2. Water Parameters:
• Maintain water temperatures between 72-78°F (22-26°C), salinity levels of 1.023-1.025 specific gravity, and a pH of 8.1-8.4. Stable water quality and regular monitoring are essential, as comb jellies are sensitive to changes in their environment.
3. Feeding:
• Provide a constant supply of small planktonic food, such as copepods, rotifers, and baby brine shrimp. Target feeding may be necessary to ensure they receive adequate nutrition.
4. Lighting:
• While comb jellies do not require intense lighting, a moderate light cycle that mimics their natural environment can help maintain their biological rhythms.
5. Compatibility:
• Comb jellies are best kept in species-specific tanks or with other non-aggressive, small plankton feeders. Avoid housing them with larger, predatory fish that may harm or eat them.
Benefits of Keeping Comb Jellies
For aquarists who can meet their care requirements, comb jellies offer several unique benefits:
1. Stunning Visual Display:
• The bioluminescence and iridescent ciliary movements of comb jellies create a captivating and otherworldly display in the aquarium.
2. Educational Value:
• Observing comb jellies provides valuable insights into marine biology, bioluminescence, and the diversity of life in the ocean.
3. Biodiversity:
• Adding comb jellies to a reef tank enhances its biodiversity and promotes a more complex and dynamic ecosystem.
