Bring on the Clowns: Blennies of the genus Ecsenius
The Blenny family is large and diverse. While some are useful in the home aquarium for helping control microalgae growth and exhibit interesting behaviors, many of these small, bottom-dwelling fishes are not blessed with spectacular colors. But, there some members of the family that exhibit very pleasing chromatic characteristics. One such group is the genus Ecsenius. This genus, whose members are collectively referred to as Clown Blennies, is the largest in the family.
While several members of the genus are “regulars” in local aquarium stores, the genus is greatly underutilized by home aquarists. While I feel they are typically amazing aquarium inhabitants, there are a few caveats to keeping Ecsenius blennies. For example, there are several species that have been known to nip at stony coral polyps. They are also not as effective at algae control as some other members of the family (e.g., Salarias spp.). That said, the overall grade as a reef-friendly aquarium inhabitant is high! In this 3-part article series, we will look at the biology and aquarium care requirements of the Clown Blennies.
But before I go any further, a quick word about the common name. I chose to use the vernacular name Clown Blenny for the genus because of their comical demeanors and the bright colors many species sport. The name Combtooth Blenny has also been used for the group specifically, but is more regularly applied to the entire subfamily Salariinae. All the members of this subfamily have a blunt head profile with a wide mouth equipped with comb-like teeth.
As aquarists become more aware of these fishes and their popularity increases, I hope we will see more species of Ecsenius showing up in the aquarium trade. There are certainly many very attractive members of the group that I believe would become very popular if they were available.
The Natural History of Clown Blennies
The genus Ecsenius is comprised of approximately 53 small species, many of which are brightly colored or attractively marked. Dr. Victor Springer of the American Museum of Natural History is the authority on the group. In 1988, he named 20 species in the genus and has since named many others. The Clown Blennies are limited in distribution to coral reef ecosystems. In fact, it is one of a few genera of blenniids that is almost always found among stony corals. Most occur in shallow reef habitats (less than 50 feet), like fringing coastal reefs, reef flats, and outer reef faces.
Many of the Ecsenius spp. have very limited distributions. This is probably a function of their being strongly tied to coral reefs and their having a short larval stage. Because of these two factors, populations are more likely to become isolated over time and begin to change from one another as slight genetic differences begin to concentrate since there is no interchange in genetic material between the “mother” population and “satellite” populations (in the case of the Ecsenius spp., these changes to which I refer are usually limited to alterations in the color pattern).
In some cases, speciation may occur and distinct species may be present on different reef tracts separated by a coral-less area of only 50 miles. As ichthyologists investigate more isolated areas of the western Pacific, they are discovering more new Clown Blenny species. In fact, five species of Ecsenius have been described since the year 2000 as a result of such explorations.
Like most other Blennies, the majority of the Ecsenius spp. spend most of their time at rest on hard substrate. When they seek shelter, they usually back into small holes in the reef. They will remain in the holes with only their heads protruding until they are sure “the coast is clear.” Like all Blennies, the members of this genus lack a swim bladder. When they enter the water column, they have to scull frenetically with their pectoral fins to avoid sinking.
The majority of Ecsenius spp. derive the majority of their nutrients by rasping unicellular algae and some detritus from hard substrates. However, at least some species will consume the polyps of small-polyped stony corals. Those that are known to include coral polyps in their natural diets include the Bicolor Blenny (Ecsenius bicolor) and the Red Sea Mimic Blenny (E. gravieri). There are also a few species (e.g., Midas Blenny, Ecsenius midas) that regularly feed on zooplankton.
Many of the Clown Blennies occur singly and are territorial. There territories can be quite small as it is not uncommon to see several conspecifics on the same coral head or small patch reef. There are at least a few species that do live in small groups (e.g., Ecsenius lividanalis E. ops, and E. tricolor). While fighting is rarely observed in the field, in the confines of the aquarium many of the species will fight. These Blenny battles are ritualized, with serious injuries rarely occurring if space is not to limited. Like most fishes, these Blennies engage in threat displays before they attack conspecifics. If bluffing doesn't cause one individual to back down, fighting ensues. Individuals will bite and ram each other, directing their attacks toward the head and front of the body. Escalated aggression also includes jaw-locking with subsequent wrestling, or swimming in head-to-tail circles.
While seeking shelter in small holes is the most common antipredation tactic employed, there is at least one species that mimics a harmful family member in order to dissuade predators from attempting to eat them. The Red Sea Mimic Blenny mimics the Blackline Fang Blenny (Meiacanthus nigrolineatus). This is an example of Batesian mimicry, that is, when a “non-nasty” species mimics a “nasty one!” The “nasty one” in this case, has venomous fangs that it uses to bite the inside of the mouths of predators that ingest it. Predators quickly learn to avoid the venomous Blenny, and as result, this provides some degree of predatory immunity for the species that mimics it.
The Midas Blenny (E. midas) engages in social mimicry. This form of mimicry is often exhibited by solitary fish that swim among social species that form schools or shoals. While there is safety in numbers, an individual that stands out from the school will be more vulnerable to predation than group members of the same species. In order to take advantage of the “dilution of risk” that occurs when living in homogenous groups, some solitary reef fishes adopt or mimic the coloration of the schooling or shoaling species with which they associate.
Such is the case with the Midas Blenny. When it feeds, this solitary species will adopt the color pattern and live within groups of Anthias. In the Line Islands, the livery of the Midas Blenny resembles that of the Bartlett’s Anthias (Pseudanthias bartlettorum), Dispar Anthias (P. dispar), and Whitley’s Slender Anthias (Luzonichthys whitleyi). In the Indian Ocean, there is a purplish-gray color form that appears to mimic Evan’s Anthias (P. evansi). Over much of its range, E. midas mimics and hovers among groups of Lyretail Anthias (Pseudanthias squamipinnis).
The sexuality mode of the Ecsenius blennies has yet to be determined. It is likely that they are protogynous hermaphrodites. In at least some species, males are larger, on average, than females – this type of dimorphism is common in protogynous species. However, further research is required to verify this. In some species (e.g., E bicolor) males may also have more segmented dorsal fin and/or anal fin rays on average than females or have long filaments extending from the caudal fin (e.g., Aron’s Clown Blenny (Ecsenius aroni)). Some species also exhibit sexual differences in the number of incisor teeth.
The Clown Blennies lay demersal eggs in a nest (usually a hole or shell). In at least some species (e.g., E. bicolor) the fish eggs are attached to the sides or roof of a shelter hole by tiny threads that extend from the sides of the eggs. The fish eggs are approximately 0.75 mm long and 0.5 mm high. The male does not tend the fish eggs, until they are ready to hatch, at which time he vigorously fans them with his fins. In E. bicolor, the eggs hatch in nine days when kept at a temperature of 80 degrees Fahrenheit. At hatching, the larvae are 3.5 mm in length.
Clown Blennies in the Home Aquarium
The Ecsenius spp. make fascinating aquarium inhabitants. The colorful livery that many display, as well as their interesting behavior, makes them my favorites in the blenny clan. Even so, relatively few are common in the aquarium trade. Because of their small size, they can be kept in small or large aquariums. They can be kept in a nano-reef setting, but they may suffer from malnutrition in a smaller aquarium environment because there is likely to be less algae present for them to feed on than in a larger aquarium (if this is the case, the aquarist must make sure to aggressively supplement their diet).
When keeping Clown Blennies in the home aquarium, it is essential to provide them with plenty of hiding places. Members of this genus prefer tight spaces, like the calcareous tubes of serpulid worms, larger snail shells, or holes in the live rock. You can use an electric drill and a masonry bit to create appropriate-sized hiding places in the live rock. Depending on the size of the Blenny, holes that are approximately 0.5 to 1.0 cm in diameter are perfect for these fishes.
It is important that these Blennies are fed vegetable matter, like frozen foods that contain the blue-green algae, Spirulina. They typically will not thrive unless some microalgae (e.g., diatoms and unicellular green algae) is present in the aquarium. For this reason, it is a good idea to let microalgae grow on the sides and back of the aquarium to provide them with a constant food supply. The amount of supplemental feeding will be based in part on the amount of natural food present. If lots of algae is available in the aquarium, feed once a day. If plant matter is in short supply, feed them at least three times a day. Keep a close eye on the Blenny’s girth and if your Ecsenius appears to be losing weight, feed it more. The Midas (Ecsenius midas) and Tailspot Blenny (E. stigmatura) spend much of their time swimming in the water column feeding on zooplankton. These two species should be fed a couple of time a day to ensure their nutritional needs are met (E. stigmatura will feed on algae as well).
While the Ecsenius spp. are not normally highly belligerent, they may respond aggressively toward other Blennies or small, benthic fishes that invade their territories. Conspecifics will fight if crowded (males are most likely to quarrel). While in nature, subordinate individuals simply avoid more aggressive conspecifics, in the aquarium it can be difficult if space is limited. A Clown Blenny that is being picked on will typically end up hiding in the upper corners of the aquarium or under the reef décor. A dominant Ecsenius may preclude a subordinate from preferred hiding places and may also prevent it from getting enough to eat. If you have two quarreling Ecsenius spp., it is prudent to remove one of the combatants. If the aquarium is large enough (e.g., 135 gallon), it is possible to keep more than one Ecsenius (even two males) in the same setup (make sure there are plenty of suitable hiding places that are situated at each end of the aquarium).
There are some species in the genus that regularly occur in small groups in the wild (e.g., Ecsenius lividanalis E. ops, and E. tricolor) and may be kept in a similar social unit in the home aquarium. All individuals should be placed in the aquarium simultaneously and if persistent fighting occurs, sparing individuals may have to be separated. If you want to keep more than one Ecsenius in the same setup, your best bet is to house a male and female together. But how do you tell the sexes apart? There are a couple of ways to increase the odds of getting a male and a female. First of all, males tend to be larger than females (this has been shown in at least some members of this genus and is thought to be true for most). Therefore, selecting two conspecifics that differ significantly in size could increase the likelihood that you will acquire a heterosexual pair. The second way is to select two smaller conspecifics. If they have yet to sexually mature, one is likely to become a female, while the other may transform into a male (that is, if initial observations prove to be true and these are protogynous hermaphrodites).
While the Clown Blennies typically do not go out of their way to chastise heterospecific fish tankmates, there are occasions when they may behave aggressively toward small fishes that invade their territories. For example, I have seen adult bicolor blennies pick on tiny Gobies, Firefishes, and Dart Gobies that moved too close and have had this same species fight for a favorite hole with small Dottybacks, and a Royal Gramma. They usually chase or display at intruders, but if the interloper does not “get the message,” they may end-up nipping the other fish. They may even bite the fins of larger herbivores that pass through their territories. Clown Blenny aggression rarely results in serious injury unless the aquarium is so small that the other fish cannot avoid the Ecsenius sp.
It is more common that Clown Blennies are recipients of aggressive behavior often the target of specific tankmates. They are most likely to be harassed by other benthic reef-dwellers, like Dottybacks, Hawkfishes, and larger Blennies (e.g., Atrosalarias, Cirripectes and Salarias spp.). Clown Blennies that were incessantly chased have been known to jump completely out of the aquarium or leap into the overflow box. They are also likely to hide incessantly and stop feeding.
The Clown Blennies are typically wonderful reef aquarium fishes. You should be aware that some individuals will nip at corals and clam mantles. There are two species, the Bicolor Blenny (Ecsenius bicolor) and the Red Sea Mimic Blenny (E. gravieri), that have been implicated in feeding on small-polyped stony corals, although this is not a common occurrence. There are also species that will rasp slime off of large-polyped stony corals, which can cause the polyps to retract. This undesirable feeding behavior is more likely to occur if suitable algae is in short supply and they are not fed enough.
The Clown Blennies can live for at least 6 years in the home aquarium. They lack scales, which may lead you to conclude that they are more susceptible to parasitic infection. But the Ecsenius spp. are fairly disease resistant. This may be due to the fact that they protect themselves by producing excessive amounts of slime. When they are stressed (or at night) many adopt a more subdued color pattern that includes lines or bands on the body.
Scott Michael
Scott W. Michael is an internationally-recognized writer, underwater photographer, and marine biology researcher specializing in reef fishes, and was the Banquet Speaker at our 2007 and 2008 Coral Conference and Frag Swap. He is a regular contributor to Aquarium Fish Magazine, Freshwater and Marine Aquarium Magazine, SeaScope, and is the author of Reef Fishes Vol 1, Vol 2, and Vol 3, Vol 4, and Vol 5., A Pocket Expert Guide Marine Fishes, A Pocket Expert Guide to Reef Aquarium Fishes, 101 Best Saltwater Fishes: How to Choose and Keep Hardy, Brilliant, Fascinating Species That Will Thrive in Your Home Aquarium, Reef Sharks & Rays of the World, and Aquarium Sharks & Rays. Having studied marine biology at the University of Nebraska, Scott has served as a scientific consultant for National Geographic Explorer, the Discovery Channel, and French educational television.