Order ANGUILLIFORMES
Introduction and Key to Families by P.H.J. Castle
Eels
Eels are long-bodied, snake-like fishes with low dorsal
and anal fins (absent in a few species) generally long, continuous with caudal fin and supported by soft-rays ; gill
openings restricted to a slit or hole on each side (on underside of head in some species) ; pelvic fins absent. No spines
in fins. Scales usually absent; if present they are small and
embedded in the skin . Pectoral fins absent in many eel
groups, and the median fins are sometimes reduced or absent, especially in burrowing species.
These structural features are associated with a crevicedwelling or sediment-burrowing mode of life, although
some eels are pelagic in the open ocean . Generally good
swimmers, most eels are rather sedentary and rely on a welldeveloped sense of smell and large teeth to capture food,
mainly crustaceans and small fishes.
Although they occur in all parts of the ocean , eels are
more typical of warm waters and are abundant on coral
reefs , where they are greatly diverse : there are some 100
genera and about 250 species in the western Indian Ocean,
with 52 genera and 101 species in the waters of southern
Africa. Perhaps the most familiar of these are freshwater
eels (Anguillidae) and the many species of morays
(Muraenidae ).
All eels , even the freshwater species, breed in the open
ocean and spend their early lives in the upper waters as flat ,
transparent, delicate larvae (leptocephali) which look quite
unlike their adults.
A few species grow quite large (the largest being the
slender giant moray, Thyrsoidea macrura, at 4 m) , but most
eels are moderate to small-sized fishes . Some , including the
freshwater species , make good eating, but eels are not
generally regarded as food-fish . Indeed, the flesh of some
morays can be poisonous in certain circumstances, but
poisoning in this way has not been recorded in southern
Africa. Morays and other eels, especially large ones, can be
dangerous when cornered, and can inflict nasty wounds
with their sharp teeth, but their bite is not in itself venomous.
It is foolish to probe with the hands into rocky or coral
crevices where morays abound , or to attempt to spear large
individuals. An unpleasant experience is likely!
This large and diverse group of fishes is divided into 16
families of which 13 occur in southern Africa. As might be
expected of a group in which there has been reduction and
convergence in many external features, identification of
eels is often not easy . Body proportions, presence or absence of fins , position of fin origins , nature of nostrils and
158
Palings
gill openings and number of vertebrae are some of the features by which different species are distinguished. The extended pelagic life as a leptocephalus favours wide dispersal
of species, and many of our eels are known throughout the
Indo-Pacific. For this reason , continuing additions to our
eel fauna are to be expected as their special habitat is
explored and collected more fully by scientists and divers,
especially offshore in deep water and along the coast of
Natal and Mozambique.
KEY TO EEL FAMILIES
(Southern African representatives only)
1a LL pores reduced to 1-5 above and before
gill opening ; gill openings lateral slits or holes;
head profile moderately arched above and behind eye .... . 2
Ib LL pores present, though sometimes minute , covered
with mucus or restricted to front part of body ; gill
openings semicircular slits that are lateral , ventrolateral,
ventral or even confluent below throat ; head profile
gently sloping, weakly arched above and behind eye .. ..... 3
2a Rear nostril a simple hole or tube near
anterodorsal edge of eye; P absent. MURAENIDAE (No . 41)
~ ~ ' --~------------41
2b Rear nostril opening ventrally through upper
lip , covered by a flap ; P present or
absent .. ...... ... ..... .... .... .. XENOCONGRIDAE (No . 43)
43
3a A origin well behind anus ...... MORINGUIDAE (No . 44)
44
3b A origin immediately behind anus .. ............ .. ........ .. .. ... 4
Introduction and Key to Families by P.H.J. Castle
Eels
Eels are long-bodied, snake-like fishes with low dorsal
and anal fins (absent in a few species) generally long, continuous with caudal fin and supported by soft-rays ; gill
openings restricted to a slit or hole on each side (on underside of head in some species) ; pelvic fins absent. No spines
in fins. Scales usually absent; if present they are small and
embedded in the skin . Pectoral fins absent in many eel
groups, and the median fins are sometimes reduced or absent, especially in burrowing species.
These structural features are associated with a crevicedwelling or sediment-burrowing mode of life, although
some eels are pelagic in the open ocean . Generally good
swimmers, most eels are rather sedentary and rely on a welldeveloped sense of smell and large teeth to capture food,
mainly crustaceans and small fishes.
Although they occur in all parts of the ocean , eels are
more typical of warm waters and are abundant on coral
reefs , where they are greatly diverse : there are some 100
genera and about 250 species in the western Indian Ocean,
with 52 genera and 101 species in the waters of southern
Africa. Perhaps the most familiar of these are freshwater
eels (Anguillidae) and the many species of morays
(Muraenidae ).
All eels , even the freshwater species, breed in the open
ocean and spend their early lives in the upper waters as flat ,
transparent, delicate larvae (leptocephali) which look quite
unlike their adults.
A few species grow quite large (the largest being the
slender giant moray, Thyrsoidea macrura, at 4 m) , but most
eels are moderate to small-sized fishes . Some , including the
freshwater species , make good eating, but eels are not
generally regarded as food-fish . Indeed, the flesh of some
morays can be poisonous in certain circumstances, but
poisoning in this way has not been recorded in southern
Africa. Morays and other eels, especially large ones, can be
dangerous when cornered, and can inflict nasty wounds
with their sharp teeth, but their bite is not in itself venomous.
It is foolish to probe with the hands into rocky or coral
crevices where morays abound , or to attempt to spear large
individuals. An unpleasant experience is likely!
This large and diverse group of fishes is divided into 16
families of which 13 occur in southern Africa. As might be
expected of a group in which there has been reduction and
convergence in many external features, identification of
eels is often not easy . Body proportions, presence or absence of fins , position of fin origins , nature of nostrils and
158
Palings
gill openings and number of vertebrae are some of the features by which different species are distinguished. The extended pelagic life as a leptocephalus favours wide dispersal
of species, and many of our eels are known throughout the
Indo-Pacific. For this reason , continuing additions to our
eel fauna are to be expected as their special habitat is
explored and collected more fully by scientists and divers,
especially offshore in deep water and along the coast of
Natal and Mozambique.
KEY TO EEL FAMILIES
(Southern African representatives only)
1a LL pores reduced to 1-5 above and before
gill opening ; gill openings lateral slits or holes;
head profile moderately arched above and behind eye .... . 2
Ib LL pores present, though sometimes minute , covered
with mucus or restricted to front part of body ; gill
openings semicircular slits that are lateral , ventrolateral,
ventral or even confluent below throat ; head profile
gently sloping, weakly arched above and behind eye .. ..... 3
2a Rear nostril a simple hole or tube near
anterodorsal edge of eye; P absent. MURAENIDAE (No . 41)
~ ~ ' --~------------41
2b Rear nostril opening ventrally through upper
lip , covered by a flap ; P present or
absent .. ...... ... ..... .... .... .. XENOCONGRIDAE (No . 43)
43
3a A origin well behind anus ...... MORINGUIDAE (No . 44)
44
3b A origin immediately behind anus .. ............ .. ........ .. .. ... 4