Wet Beast Wednesday: clownfish
Welcome to Wet Beast Wednesday: Pride edition. Today I'm covering a little fish that looks at the concept of a sex binary and says "nah". Clownfish are famous for their association with anemones and are sometimes even called anemonefish. Come on and I'll show you how Finding Nemo was not that scientifically accurate.
(Image: a pair of ocellaris clownfish (Amphiprion ocellaris) swiming among the tentacles of a large, purple anemone. The fish are small and orange, with three large, vertical, white lines going down the body, one behind the head, one in the moddle, and one before the tail. The fins have black borders. End ID)
Clownfish are 29 species in the genus Amphiprion. Their closest relatives are the damselfish. Clownfish are small, with the largest being the maroon clownfish Amphiprion biaculeatus at up to 17 cm (6.7 in) and the smallest being the orange clownfish Amphiprion percula at 8 cm (3.1 in). Clownfish vary in body shape from ovoid to more cylindrical. The lack scales between the upper lip and eyes and have saw-shaped edges on the gill flap which is the source of their scientific name. Amphiprion means "saws on both sides". Clownfish appear in a number of colors, usually with a red, orange, yellow, brown, or black background and between zero and three vertical lines on the side that are white with black outlines. The number of vertical lines seems to be correlated with the species of anemones the clownfish species is specialized in living within. Those with multiple lines tend to live in anemones with long tentacles and use their nines at camouflage. The species with one or no lines tend to live in anemones with short tentacles that the fish cannot full hide in. These fish seem to be using a unique form of aposematism. Aposematism is when an animal is brightly colored to warn potential predators that it isn't safe to eat. In the case of these fish, their aposematism is warning predators about the anemone, not the fish itself, which is not seen in other aposematic species. Clownfish may also use their lines to distinguish between different species in places where their ranges overlap.
(Image: the sebae clownfish Amphiprion sebae. It has a black body with three white lines similar tot he above description. The front of the face is yellow. Ed ID)
Clownfish live in warm, shallow water in the Indian and western Pacific Oceans. They are onmivores who mostly eat drifting algae and plankton. Clownfish are known for their mutualistic relationship with species of anemones. There are ten species of anemone known to host clownfish and all are large with long tentacles. Clownfish require anemones to survive. Meanwhile the anemones are aided by having clownfish occupants, but do not need them to survive. Clownfish can either be generalists that can live in many anemone species or specialists that only live on one or two. When multiple species in an area need the same anemone species to survive, they will often partition off territory for each species to inhabit. More rarely, you may sometimes find multiple species of clownfish occupying the same individual anemone. Mutualism is a form of symbiotic relationship where all parties benefit. The clownfish use the anemone for protection from predators and in turn, they protect the anemone from its own predators, fan water over the tentacles, remove parasites, and their feces attracts algae useful for the anemone. Clownfish typically spend their time within the tentacles of the anemone, with larger individuals being more likely to venture outside. When a clownfish comes to a new anemone, with will take time to acclimate itself by rubbing itself against the tentacles. This is believed to give it protection from the anemone's stingers. It is theorized that the mucus secreted from the clownfish's skin protects it either through being very thick or containing proteins or bacteria that tells the anemone's stinging cells not to activate.
(Image: the red saddleback clownfish Amphiprion ephippium. It is a clownfish with no lines. It has a red-orange body with a dark, saddle-like patch on the back. End ID)
Clownfish are social animals who live in small groups that consist of a female, a breeding male, and one or more non-breeding males. A male's position in the hierarchy depends on his size, with the largest male being the breeding male. A male large enough may attempt to challenge the breeding male for his position. Clownfish communicate through touch and a variety of sounds described as chirps, pops, clicks, and grunts. Most communication appears to be dedicated to maintaining the hierarchy through dominance displays. The dominant pair will kick out fish if the population gets too big and will attempt to defend their anemone from potential rivals. Notably, should the female leave or die, the breeding male will transition into a female and the next larges male will become the new breeding male. This is known as protandrous sequential hermaphroditism, protandrous meaning the fish starts as a male and sequential meaning they change sex during their lives instead of producing both male and female gametes at the same time. If Finding Nemo was accurate, Nemo's dad should have become his mom and hooked up with one of his wife's side pieces.
(Image: a group of five pink skunk clownfish (Amphiprion perideraion) swimming above an anemone. They are light pink with yellowish undersides, a think white line behind the head, and a while line running down the back. Two of them are noticeably larger, being the female and breeding male. End ID)
Clownfish mate in spring and summer in temperate water and year-round in tropical water. Mating usually happens during the full moon and is preceded by several days of courtship in which the breeding male will follow the female around and raise his fins at her. When it is time to mate, the pair will clean a rock near the anemone. The female then lays up to a thousand eggs, which are sticky and attach to the rock. The male the fertilizes them and will watch over the eggs, defending them from predators, cleaning them, and fanning water over them, until they hatch, which takes about a week. The larvae are planktonic and are carried off by the current, sometimes for hundreds of kilometers. Once the juveniles finish their larval stage, they will descend to the bottom and look for an anemone to live in. Clownfish are born with both testicular and ovarian tissue on their gonads, but they will not produce gametes until rising to become a breeding male or female. Once a fish gets to become a breeding male, the testicular tissue will expand and begin producing sperm. Should he then transition to female, the testicular tissue will shrink and stop functioning while the ovarian tissue expands and starts producing eggs. Clownfish can live for up to 30 years, which is very long for a fish of their size.
(Image: a male ocellaris clownfish (see first description) guarding his eggs. The eggs look like tiny, orange gumdrops and are coating the surface of a rock that the male is swimming above. End ID)
Of the 26 species of clownfish, 24 are classified as least concern, one as vulnerable, and one as data deficient by the IUCN. The greatest threat to clownfish is anemone bleaching. This is when an anemone expels its symbiotic algae, usually in response to heat stress, and it is usually fatal. Anemone bleaching is increasing as a result of global warming. There is some evidence that clownfish can help anemones recover from bleaching. Mass die-offs of anemones cause clownfish to leave the area. Clownfish are extremely popular in the aquarium trade due to their bright colors. Several species of clownfish are among the most traded aquarium fish and while there is a captive breeding industry, a lot of pet clownfish were taken from the wild. Some places have seen pretty huge reductions in the clownfish population due to overharvesting. Coastal development, sedimentation, and pollution also harm clownfish populations.
(Image; a Clark's anemonefish (Amphiprion clarkii) swiming among aemone tentacles with its mouth open. It has a black body with an orange underbelly, face, and fins. There are three white lines going down the body, one behind the eye, one in the middle, and one around the tail. End ID)
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