FAUNA AND FLORA O F MANGROVE SWAMPS
225
It may be significant that the eight or so species of mangrove which
have become established on the coasts of Africa, Madagascar, the
Mascarene Islands and Melanesia as well as other South Pacific islands
are all species which in Malaya and Indonesia have been shown to reach
their optimum development in areas of near normal salinity.
Insufficient is known of the life histories of the animals listed as
being ubiquitous to account for their wide distribution.
1. Division 1. The western Indian Ocean
The fauna of the first division, i.e. the western Indian Ocean and its
associated seas and channels, contains only a small number of endemic
species. Sesarma catenata is an outlier of its genus which extends along
the southern African coasts from the Bay of Lourengo Marques where
it is uncommon. Southwards it becomes more abundant and it is the
dominant salt marsh crab from Pondoland to Knysna and extends
westwards along the southern African coast to the Brede river mouth at
approximately long. 21"W. Sesarma ortrnanni and 8. eulimene are two
species which have only recently been distinguished from one another
(Crosnier, 1965). Both occur at or near high water mark but the latter
penetrates more deeply into the barringtonia racemosa association,
upstream in an estuary, while the former prefers waters of higher
salinity. S. guttata and 8. longipes are species common within the
mangal. All four have their centre of distribution in eastern Africa and
Madagascar and only S. longipes reaches Indian waters-it has been
recorded from the Andaman Islands.
Uca uraillei is purely African and Malgache, and U . inversa ranges
from southern Africa to the vicinity of Karachi.
Eurycarcinus natalensis ranges from Natal to India and is recorded
from Madagascar, the Red Sea and the Nicobar Islands. (I wonder if
this last specimen is in fact E. natalensis species of this genus are not
easily distinguished from one another.)
Cerithidea decollata is the only representative of its genus to be found
in most of eastern Africa and Madagascar. Dautzenberg (1929) records
C. obtusa, a widespread but eastern species, from Madagascar.
Certain species are endemic t o the Red Sea, such as Sesarmajousseaurnei .
The Malabar coast and the rest of the Arabian Sea's Indian shores
have been colonized by the " central fauna " ; Sesarrna rnederi is present and Chhapgar (1957) also records S. quadrata, S. oceanica and S.
minuta, all typical Malayan species. Eurycarcinus orientalis replaces
E. natalensis and continues eastwards.
Several gastropods become common. Terebralia sulcata and Tele-
225
It may be significant that the eight or so species of mangrove which
have become established on the coasts of Africa, Madagascar, the
Mascarene Islands and Melanesia as well as other South Pacific islands
are all species which in Malaya and Indonesia have been shown to reach
their optimum development in areas of near normal salinity.
Insufficient is known of the life histories of the animals listed as
being ubiquitous to account for their wide distribution.
1. Division 1. The western Indian Ocean
The fauna of the first division, i.e. the western Indian Ocean and its
associated seas and channels, contains only a small number of endemic
species. Sesarma catenata is an outlier of its genus which extends along
the southern African coasts from the Bay of Lourengo Marques where
it is uncommon. Southwards it becomes more abundant and it is the
dominant salt marsh crab from Pondoland to Knysna and extends
westwards along the southern African coast to the Brede river mouth at
approximately long. 21"W. Sesarma ortrnanni and 8. eulimene are two
species which have only recently been distinguished from one another
(Crosnier, 1965). Both occur at or near high water mark but the latter
penetrates more deeply into the barringtonia racemosa association,
upstream in an estuary, while the former prefers waters of higher
salinity. S. guttata and 8. longipes are species common within the
mangal. All four have their centre of distribution in eastern Africa and
Madagascar and only S. longipes reaches Indian waters-it has been
recorded from the Andaman Islands.
Uca uraillei is purely African and Malgache, and U . inversa ranges
from southern Africa to the vicinity of Karachi.
Eurycarcinus natalensis ranges from Natal to India and is recorded
from Madagascar, the Red Sea and the Nicobar Islands. (I wonder if
this last specimen is in fact E. natalensis species of this genus are not
easily distinguished from one another.)
Cerithidea decollata is the only representative of its genus to be found
in most of eastern Africa and Madagascar. Dautzenberg (1929) records
C. obtusa, a widespread but eastern species, from Madagascar.
Certain species are endemic t o the Red Sea, such as Sesarmajousseaurnei .
The Malabar coast and the rest of the Arabian Sea's Indian shores
have been colonized by the " central fauna " ; Sesarrna rnederi is present and Chhapgar (1957) also records S. quadrata, S. oceanica and S.
minuta, all typical Malayan species. Eurycarcinus orientalis replaces
E. natalensis and continues eastwards.
Several gastropods become common. Terebralia sulcata and Tele-