reproduction) are available for even fewer species, and information on
longevity is sketchy at best. Ironically, behavioral data (i.e., reproductive and
parental behavior) are perhaps most nearly complete, partly as a result of the
popularity of these fish with aquarists, and for interest in them as represen-
tative of some of the most specialized parental and social behavior among
fishes (Balon 197513; Maynard Smith 1977 ;Keenleyside 1979). Consequently,
we summarize data for generalized guarders and bearers, as representative
of the two alternative life history styles, altricial and precocial, while acknowl-
edging that these data may at times be drawn from different species in a
variety of circumstances, including non-tilapiine species in some cases (Balon
1959a, 195913; Noakes and Barlow 1973a, 1973b; Noakes 1978a, 197813,
1979; Lowe-McConnell, this volume).
Parental Roles and the Evolution of Parental Care Patterns
in Tilapiine FishesThere is convincing evidence from different sources (e.g., Fishelson 1966a,
196613; Fryer and Iles 1972; Trewavas 1973a; Barlow 1974; Balon 197513)
that mouthbrooding tilapias (bearers) evolved from substrate-spawning
(guarder) species (see Oppenheimer 1970 for a general discussion of mouth-
brooding in fishes). As Keenleyside (1979) has noted, tilapias are remarkable,
not so much for their welldeveloped parental care (which is in fact universal
among the Cichlidae), but for the fact that uniparental custodial care (of
whatever type) is almost invariably carried out by the female. This, paradox-
ically, resembles the pattern commonly encountered in birds and mammals,
but is opposite that found in most other fishes which show custodial (paren-
tal) care. The typical pattern among teleosts is that the male is the
responsible parent (Barlow 1974; Blumer 1979). In fact, this has given rise
to a number of efforts (Dawkins and Carlisle 1976; Maynard Smith 1977;
Baylis 1978, 1981; Barlow 1978; Ridley 1978; Perrone and Zaret 1979;
Werren et al. 1980) to suggest why the male should so often be the respon-
sible teleost parent.
The tilapias clearly differ from this pattern, and so require either a differ-
ent, or an extended explanation. All guarding tilapias are biparental, the
pattern typical for cichlids in this guild (Barlow 1974, Keenleyside 1979).
The bearers are remarkable. All bearing (mouthbrooding) species have been
assigned to the genus Sarotherodon (Trewavas 1973a, 1978, this volume) a
designation we might question, as we have already mentioned, although the
generic status is not critical to our discussion, as will become apparent. A
few bearer species (e.g., S. galilaeus) are biparental (i.e., both male and
female parent carry developing young in their buccal cavities) (Iles and
Holden 1969; Fryer and Iles 1972). In a few others (e.g., S. melanotheron),
the male is the sole custodial parent (Aronson 1949; Barlow and Green
1970; Ridley 1978). All other Sarotherodon forms are maternal bearers (i.e.,
only the female carries the developing young).
Various proposals (e.g., Trewavas 1978) have been suggested as possible
alternative evolutionary pathways for the different bearer strategies from the
guarding ancestral condition. We do not propose to resolve that controversy,