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232. A few Banggai Cardinalfish (Pterapogon kauderni) are finding refuge within the tentacles of an Upside-down jellyfish (Cassiopea sp.)



Subject:

Several small Banggai Cardinalfish (Pterapogon kauderni) are seeking protection within the tentacles of an Upside-down Jellyfish (Cassiopea sp.).


The beautiful Banggai Cardinalfish is probably the most stunning member of the large cardinalfish family (Apogonidae). This cardinalfish stands out from its relatives due to its exquisite and distinctive anatomy. Unfortunately, the little fish are overfished and caught to supply the aquarium trade, resulting in this cardinalfish becoming endangered.


Originally, the Banggai Cardinalfish was an endemic species of the Banggai Archipelago on Sulawesi’s eastern coast in Indonesia. Nowadays, they are found in other locations such as the Lembeh Strait in Sulawesi and Gilimanuk Bay in Bali, where this video was filmed. The exact cause of this distribution is unclear, but voluntary or involuntary introduction by aquarium traders is the most likely reason.


Cardinalfish are often rather small in size, and therefore, they often fall prey to predatory fish like groupers (Epinephelinae) and frogfish (Antennariidae). One efficient way they protect themselves from predation is by sheltering amongst the spines of sea urchins, within the branches of cnidarians (see vlog post 113), or within the tentacles of jellyfish, as seen in this short underwater video clip.


The Upside-down Jellyfish provides enough protection to the cardinalfish that they are reluctant to leave the safety of the jelly’s stinging tentacles.


Unlike most jellyfish species, the upside-down jellyfish is a group of jellies that spend their lives in an upside-down position on or near the bottom of the seabed. They are often found on sandy or muddy substrates and frequently provide protection for various vertebrate and invertebrate life forms. Some crabs (Ethusa sp.) carry the jellyfish as a form of deterrent on their backs, with the jellyfish held in place by the crab’s last pair of walking legs.


The Upside-down Jellyfish lives in symbiosis with different shrimp species and with zooxanthellae, a photosynthetic dinoflagellate algae that reside on the underside of the adult’s bell. These zooxanthellae require sunlight to photosynthesise nutrients. Therefore, these medusas are mainly found in shallow waters like bays and lagoons where sunlight is abundant.


The shrimps that live amongst the creamy green, yellowish, and grey oral arms (tentacles) receive protection from the jelly’s nematocysts (stinging cells), and in return, the shrimps keep the medusa free from parasites. It is unclear if the Banggai Cardinalfish have a similar mutualistic relationship with the jelly or if the cardinals are just there taking temporary advantage of the jellyfish’s offered security.


Technique:

Filmed in the murky and slightly greenish water with a lot of suspended particles of Secret Bay (Gilimanuk Bay/Bali), this underwater footage needed a lot of colour correction. To achieve the desired colours, I used the white balancing tool in my editing software for the initial correction. With many light and near-white areas with various hues, I clicked with the white-balance pointer on different points to achieve the desired palette. The key is to experiment until the image becomes acceptable, then fine-tune with your colour wheels to remove or desaturate a certain hue.


Filming location:

This short underwater videoclip has been filmed in Bali, Indonesia 🇮🇩


More about this topic:

For other in-depth descriptions about fish protecting themselves from predation by sheltering within the branches of cnidarians please visit vlog post number 113 or click https://www.beyondscuba.com/post/hell-s-fire-anemone-actinodendron-arboreum


Watch it on YouTube:

You can watch it directly on YouTube by clicking the following link: https://www.youtube.com/watch?v=Za_V1ZdM2mQ


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