There are a few egg-layers that are even stranger than some of the strange fish you may already be familiar with, such as Anableps, four-eyed fish and Dwarf Egyptian Mouthbrooder. No, these are even stranger aquarium fish including the Spraying Characin that lay, care for and hatches their eggs outside of the water, the Bitterling that lay their eggs inside a live mussel, and even though the eggs hatch in the mussel does not seem to notice and the strange courtships behaviors of certain cichlids.
The Spraying Characin
A member of a family that includes the feared Piranha—probably the most rapacious of all fresh-water fish. Otherwise, the Characin family of fish is made up of mostly small and peaceful species, many of which are familiar Aquarium fish. Fish like the Neon Tetra, Glowlight Tetra, Black Skirt Tetra, and Buenos Aires Tetra to name a few.
The Spraying Characin is also peaceable as well as colorful and attractive. Its mating behavior makes The Spraying Characin also called the Splashing Tetra an unusually interesting aquarium inhabitant. During the mating ritual, the female jumps out of the water and onto the leaves or stems of water plants that extend above the surface of the water. There she deposits her eggs, a few at a time, and is followed by the male jumping out of the water after her to fertilize the eggs each time she lays another small batch.
In this unique but rather exhausting manner, the several hundred eggs a pair of this species commonly produces in a single spawning are laid and fertilized. The female’s job is then done; the male, however, is far from having completed his part of the reproductive cycle. He remains near the eggs and guards them, even though they are above the water’s surface. To prevent drying out from the air, he sprays water over them from time to time with flips of his caudal fin. When the eggs finally hatch, the male directs a final, especially heavy spray at them, and so washes them down into the water. Only then is his task complete, and he goes about his own business without paying further attention to his offspring.
The strange behavior of the Splashing Tetra or Spraying Characin, which has given the species its common name, is unique even among the Characin’s immediate group; as far as we know, no other member of the Characin family behaves in this manner. A closely related fish of the same genus, for instance, deposits its eggs in a pit dug in sand or gravel, others breed normally in amongst the fine-leaved plants, still, others prefer moss or debris. We still have not found a really convincing reason why the Spraying Characin evolved its spawning activities into such a difficult and unique chore.
Another fish with interesting habits as well as beautiful coloring is the Bitterling which is native to the streams of Europe and Eastern North America. This tiny relative of the carp family is usually a rather undistinguished-looking greenish-yellow fish. But during the breeding season, the male turns into a glittering golden creature whose metallic hues would make the traditional goldfish appear dull in comparison. The female during the breeding season develops a special tube-like ovipositor with which she injects her eggs into certain kinds of fresh-water mussels; it is there where the male fertilizes them.
Strangely, the eggs do not seem to even bother the mussel at all, nor do the young that hatch in the mantle of the mollusk and continue to live there, well protected from enemies, for several days. Finally, the mussel seems to get tired of its uninvited tenants and expels them with the wastewater. However, by that time, the young are large enough to fend for themselves.
Without the mussel, the Bitterling could not breed. Again, no one so far has advanced a good explanation why this fish alone of all its relatives has evolved the peculiar habit of selecting an involuntary babysitter for its young during the critical first few days of their lives. What caused this species to develop the ability to inject the eggs into the mussel? Why do the Mussels not digest the eggs or the fry, so many questions, no answers?
Then there is the unusual case of the wrasses, some of which go through the first part of their lives as sexually mature females, and later undergo a sex change that turns them into functional males. We know that in at least two species of Wrasse, one female becomes a male upon the death of the last surviving male of any particular school. In that way, there is never any danger of the eggs not getting fertilized because any female can turn into a male whenever it becomes necessary.
Courtship and Lasting Love Among Certain Species
It is interesting to note that almost all fish, with intricate and complex courtship habits also engage in some type of brood care, in which either one or both parents take part. There is a clear relationship between territorial fights, courtship rituals, and brood care in the majority of instances, and extreme territorial possessiveness usually indicates some advanced form of care for the young.
By and large, the serious business of preparing a nest site for their future offspring is the first concern of the prospective parent or parents after the territorial problem has been settled. In some species, such as the Angel Fish, a mated pair will form a true partnership, and share in everything from preparing the nest site to guarding and protecting the young until they can fend for themselves. Often such a pair remains together in a lasting attachment long after the breeding season.
Fish Are Closer to Birds than Reptiles in Breeding Behaviors
It is interesting to note that in their breeding behavior and especially in their brood care, such fish are reminiscent of birds much more than of their much closer evolutionary kin, the reptile. No reptile, for example, practices any type of brood care even remotely resembling that of some of the fish we have given as examples. The great majority pay no attention at all to their offspring once the eggs have been laid.
The few exceptions among reptiles that fashion a nest of sorts lose all interest in their young once the eggs have hatched; there is not a single known case where reptile guards and protects its young against enemies. The fierce protectiveness of their nest and offspring displayed by many fish, on the other hand, is strikingly like the parental devotion that is a familiar feature of bird or avian behavior.
One Final Word
Out of the bewildering array of fish that we have most unscientifically classified under the heading of “unusual egg layers” are many old favorites and a few new importations of what we hope was of some interest. The amateur’s choice is limited only by their pocketbook, his accessibility to pet shops, and their susceptibility to the advertisements of fish dealers. If you read the magazines devoted to the subject, you will find yourself each month wanting to pick up a new kind of fish for your aquarium. If you are like me, your enthusiasm, once aroused, will be difficult to hold in check. But to maintain the ideal “show tank” it is important that you exercise restraint. Remember, do not overcrowd your aquarium, read here to make sure what you have chosen is compatible with the rest of your aquarium community, and pay attention to your pet's environmental and dietary needs. If you spend as much time studying your fish and their needs as you do discover new fish that you want to own, you will be a success in this great hobby of ours.