Pseudanthias cooperi – Red-bar Anthias
Pseudanthias cooperi, commonly known as the Red-Bar Anthias, was first described by Regan in 1902. This name refers to the vertical red stripe on the flank that can occasionally be seen.
The genus name Pseudanthias translates to “false anthias.” This name reflects the fact that the species currently classified under this genus were once categorized under the genus Anthias for many years. The species name “cooperi” honors Clive Forster Cooper (1880-1947), who was involved in the expedition to the Maldives and Laccadives, where the type specimen was collected.
Synonyms: Anthias cooperi, Leptanthias kashiwae, Anthias kashiwae, Pseudanthias kashiwae, Planctanthias preopercularis.
Description
Pseudanthias cooperi has an oval body that typically reaches an average total length of 12 centimeters, with a maximum length of 14 centimeters. Its coloration varies based on sex and age. Males primarily exhibit a red body color, featuring a short vertical red stripe down the middle of their flank. A silvery stripe often runs beneath the eye and over the gill covers. The caudal fin is red, with elongated upper and lower rays that are frequently light blue. The anal fin is usually pale yellow to yellow-green. In contrast, females display a body color that ranges from orange to pink, with a silvery belly and a red caudal fin. Juveniles have a coloration similar to that of females.
Difference between males and females (Sexual Dimorphism)
There are distinct physical differences between males and females. Adult males are larger and exhibit a more vibrant red color, featuring a characteristic vertical red band. In contrast, females typically range from orange to pink and lack the vertical red band. Additionally, males have longer fins than females.
Sex change
Pseudanthias cooperi are protogynous hermaphrodites, meaning they are born as females and can later change to males. This typically occurs when the dominant male dies, allowing the largest female in the group to transition to male.
The sex change in Pseudanthias cooperi offers several evolutionary advantages:
- Reproduction assurance: In a harem system consisting of one dominant male and multiple females, the potential for a female to change sex ensures that reproduction can continue even if the male dies. The largest female can take the place of the male, thereby guaranteeing that the group’s reproductive capacity remains uninterrupted. This is an important adaptive strategy, particularly in environments where locating a new mate may be challenging.
- Maximal reproductive output: The ability to change sex allows an individual to fulfill both male and female reproductive roles throughout its lifetime. This maximizes the individual’s reproductive output, as it can produce both eggs and sperm.
- Social stability: The sex change contributes to social stability within the harem. It prevents the group from becoming unstable after losing the dominant male, and ensures a smooth transition to a new leader.
- Competition and selection: The possibility of sex change may also play a role in competition between individuals. Larger and stronger females have a greater chance of replacing the dominant male, leading to a form of sexual selection.
In conclusion, protogynous hermaphroditism in Pseudanthias cooperi is an evolutionarily successful strategy that enhances the species’ reproduction, social stability, and reproductive output. It represents a fascinating example of adaptive plasticity in nature.
Behavior and Temperament
Pseudanthias cooperi is a species that lives in schools, typically found near the bottom of coral reefs. They are diurnal, meaning they are active during the day, and they primarily feed on plankton. While they are generally peaceful, males can be territorial and may exhibit aggression towards other males of the same species. However, they usually tolerate the presence of non-territorial fish. For optimal care, it is advisable to keep them in groups, consisting of one dominant male and several females. In an aquarium, they tend to swim in the midwater column.
Habitat and Ecology
Pseudanthias cooperi is a species found in the tropical Indo-Pacific region, including areas such as East Africa, Samoa, the Line Islands, southern Japan, and the Great Barrier Reef. These fish inhabit coral reefs, reef slopes, drop-offs, and, at times, shallow coastal reefs.
The natural habitat of these fish includes coral reefs and rocky areas, typically found at depths ranging from 10 to 91 meters, though they can also inhabit other depths. These reefs are often subject to currents. The seabed features open substrate with low reefs and isolated bommies, which are small, standalone reefs. While coral and rocks are present, they are not found in abundance. The fish tend to prefer open areas where there are currents.
Dieet en Reef Safety
Diet in the Wild: Pseudanthias cooperi is a planktonic hedgehog, meaning that in the wild, it feeds primarily on plankton, including small crustaceans and other microscopic organisms that it filters from the water.
Aquarium Diet: In an aquarium, they can be fed a varied diet of high-quality, commercially available frozen foods such as mysis shrimp, brine shrimp, cyclops, and other small crustaceans. Live foods such as brine shrimp nauplii can also be offered but should form a small portion of the diet. Feeding small amounts several times a day is important as they have a high metabolism and eat frequently.
Foods to Avoid: It is advisable to avoid foods high in fats and oils as this can lead to health problems. Also, one should be careful about feeding large amounts of food at once as this can affect the water quality.
Reef Safe: Pseudanthias cooperi is generally considered reef safe. It does not feed on coral, polyps, or shrimp. Its diet consists of plankton, so it poses no threat to the invertebrates in a reef tank.
The Aquarium
For a small group of Pseudanthias cooperi, such as one male and a few females, an aquarium of at least 500 liters is recommended. However, a larger aquarium of 800 liters or more is preferable, especially if you plan to keep multiple fish. The tank should be decorated with rocks and hiding places, as these fish are naturally found in coral reefs. A sandy substrate is ideal, although gravel can also be used. It’s essential to provide ample swimming space, particularly in the upper water layers. While coral is not strictly necessary, it can enhance the natural environment of the aquarium.
Water conditions: The ideal water conditions for Pseudanthias cooperi are a temperature between 22°C and 27°C, a specific gravity (sg) of 1.020-1.025, a pH of 8.1-8.4 and moderate water flow.
Introduction to the aquarium: It is advisable to let the aquarium mature well before introducing Pseudanthias cooperi. This ensures that the water quality is stable and sufficient algae and other micro-organisms are present. The exact maturation time depends on various factors, but waiting at least a few weeks is advisable.
Compatibility with other inhabitants: Pseudanthias cooperi can be kept well with other peaceful reef inhabitants, as long as they are not too aggressive. However, it is important to remember that males of the same species can be very territorial. Suitable tankmates can be: other peaceful reef fish, such as certain gobies, cardinalfish and small clownfish. However, keeping them together with aggressive fish or fish that exhibit similar behavior is not advisable.
Breeding Pseudanthias cooperi
I could not find any information about breeding Pseudanthias cooperi in the aquarium.
Video
Author
John de Lange
Copyright images
Mark Rosenstein – CC BY-NC-SA 4.0
Francois Libert (Zsispeo) – CC BY-NC-SA 2.0
John Turnbull – CC BY – NC-SA 2.0
