URL: 
http://cdserver2.ru.ac.za/cd/011120_1/Aqua/Ichthyology/Ichthyology/reproductive%20behaviour.htm

                      <h>Reproductive Behaviour of Fishes

   <p>Did you know that fishes embark upon courtship behaviour that leads to
   pairing and spawning? Many people are totally unaware of this. The
   courtship of fishes in not as complex nor as varied as that of men and
   women, and the courtship of fishes is not complicated by innuendos,
   hidden meanings and cryptic signals as in Homo sapiens. Rather,
   courtship in fishes, as with birds, mammals and other animals,
   comprises sets of recognisable signals, following set sequences which
   for fishes, provided the partners are physiologically ready, culminate
   in spawning. Courtship behaviour of fishes might be a simple set of
   signals and answers or it might be very elaborate and complex,
   depending on the type of fish. However, the signals are always easy
   for potential mates to read. Indeed, it is easy for biologists to read
   and interpret these signals.

   <p>Among the most interesting and best known to aquarists is the
   elaborate courtship of cichlid fishes. Typically a male develops a
   territory which he defends from all intruders. Many species also build
   nests, which might be elaborate sand castles, or excavations with
   tunnels or burrows, or may simply be a cleaned part of the rocky or
   sandy area in which the territory is held. Once the tasks of
   developing a territory and building a nest are complete the male is
   ready to invite females to his nest to spawn. Eager males may attempt
   to do this even before the nest is complete, but they are nearly
   always refused as the female does not get all the correct messages if
   the nest is not there. One of the reasons for this is that part of the
   courtship ritual includes the nest, and each nest type is
   species-specific; it is a characteristic of the species that is
   important to mate recognition and the acceptance of the correct
   partner.

   <p>The initial invitation is `side-shake' during which the male
   approaches a female, extends his fins and flexes so that the anal fin,
   which usually has attractive spots and colours on it, towards the
   female. If the female is interested the male then turns away and
   facing the spawning site beats its tail in a movement inviting the
   female to follow (`follow-shake'). If the female is still interested,
   then with exaggerated, undulating movements the male leads the female
   to the spawning site (lead-swim). Once in the nest or spawning site,
   the couple circle each other, perform a variety of shakes (nest shake,
   vertical nest shake etc) and gently nudge each other till the female
   lays eggs. The female then picks up the eggs in her mouth, sometimes
   doing so before the male has had time to fertilise them. This would be
   a waste of eggs, so to solve the problem the males of many species
   have dummy eggs on the anal fin. This fin is spread out in front of
   the female to display the egg dummies and curled slightly to hold
   spermatozoa that he will release. The female tries to pick the egg
   dummies from the male anal fin and in doing so collects spermatozoa,
   that fertilise the eggs in her mouth. The need to collect the eggs
   before they are fertilised arose from the fact that eggs are often
   stolen almost as soon as they appear by other fishes which feed upon
   them. Another problem is that males that do not have territories, and
   were not chosen as mates by the female, try to sneak spawnings by
   darting down between the spawning couple and fertilising eggs that are
   exposed. By collecting the eggs promptly, the efforts of robbers and
   sneakers are largely circumvented.

   <p>Once in the mouth the eggs develop into young fish that remain there
   until they are ready to feed for themselves. Most cichlids will then
   look after their young for sometime (a few days to four or more
   weeks), taking them into their mouths when there is a threat from
   predators. The fry are also taken into the mouth at night for
   safekeeping. Once the fry are independent they leave the care of the
   mother. Some cichlids behave as cuckoos; they give their fry to
   another species to care for. It seems that the foster parent can
   recognise the foreign young, but she is unable to chase them away or
   swallow them as both activities will endanger her own brood. Chasing
   foreign fry that are mixed tightly in a school with ones own fry is
   not possible without chasing away the own fry too. Similarly, how does
   the mother swallow foreign fry and not her own?

   <h>Submitted by: Dr Tony Ribbink

   <h>Email:
   A.Ribbink@ru.ac.za


