Georgina Jones is a Senior Naturalist of the Southern Underwater Research Group (SURG). For almost 20 years, Georgina has been a passionate scuba diver with a lasting and ever-increasing passion for the underwater life of False Bay and the Cape Peninsula. Georgina has published several well-respected resources used by divers and marine scientists to identify species found below the waves, and has made some of her own new discoveries along the way. We can think of few people with as much first-hand experience with South Africa's underwater ocean heritage, and are pleased to share her insight into the unique parenting styles of our marine animals.
Fish tend to be thought of as relatively casual parents. Many female fish lay their eggs into the water and the males, just as casually, do the same with their sperm. Usually, the two actions coincide in time and space and some of the eggs are successfully fertilised and go on to develop into larvae. The parents provide no care and rely on the huge numbers involved for a fraction of the successful larvae to develop into adult fish. But there are also fish parents that provide somewhat better for their offspring.
The twobar clownfish, a larger and darker version of the now-famous Nemo, lay their eggs on a hard surface near their home anemone. They then guard their eggs against predators on the lookout for an egg snack, as well as aerating them, until the tiny clownfish larvae hatch out.
The ferociously grumpy-looking rocksucker also guards its eggs.
Two-eyed blennies lay their purple-yolked eggs in abandoned red fanworm tubes, and remain on guard in the tube while the eggs develop. The eggs are laid in batches so that there is a staggered hatching, possibly so that overall the chances of the larvae hatching at just the right time, temperature and sea conditions are spread over a period of time, rather than the brood all hatching at once and possibly right into the maw of a hungry beast.
Seahorse and pipefish parents go a bit further. In both groups, the father broods the eggs. There are several groups of pipefish, some of which simply attach the eggs to their abdomens and brood them that way -- these are the fastest moving and most agile pipefish -- where other groups may tuck the fertilised eggs into folds of skin so they are protected from snatch and grab passers-by.
Seahorse dads have an actual brood pouch in which the developing larvae grow, the young finally emerging as miniature adults.
Ghost pipefish, despite looking very similar to both seahorses and pipefish, have a rather different way of looking after their broods. The females clasp their pectoral fins together to make a pouch and they will then swim with the developing eggs in their clasped fins, occasionally aerating the eggs, for as long as it takes for the babies to hatch.
There are also quite a few fish that give birth to live young. The klipfish family has internal fertilization and the females can be seen to get markedly bigger as the embryos inside them develop and grow. Eventually, they give birth to miniature versions of themselves. These tiny fishes may have protective camouflage coloration but are more able to fend for themselves than the externally fertilised fish larvae, having more developed bodies and senses.
Though they don't internally fertilise, cardinalfish are also committed parents, given that the males brood the eggs in their mouths, protecting and aerating them for as long as it takes for them to hatch. The female releases her batch of eggs near the male who then takes them into his mouth for brooding, periodically partially spitting the brood out and sucking it back to ensure the eggs are kept properly clean and aerated. Crucially, the father must starve for the duration of the brooding, although some observers suggest that at least some of the eggs are accidentally eaten.
Which brings us to another feature of heritage. In some species, the best heritage parents can give their children is a disguise. Adult emperor angelfish are territorial and will attack any interlopers to their ranges. They will particularly go for same species competitors. And this is why juvenile emperor angelfish look so different from their parents. It means they can live, as juveniles, in the kind of habitat that will be most advantageous to them as adults and also avoid being eaten by their fond but forgetful parents. When they get larger and more able to flee or fight, they start to develop adult coloration.
Heritage, as in the human world, can mean many different things in the marine world. But one thing is certain - whether you're a sea slug or a South African, ocean heritage affects us all!