214
WILLIAM MACNAE
ocypodids do not pump water through the gill chamber for breathing
purposes but only for feeding.
e. Burrowing
Crustacean burrowing subserves three distinct functions : (1) provision of a refuge, ( 2 ) as a centre of territorial behaviour and so as an
accessory to mating, and (3) as an accessory to feeding. Any burrow
may be used for each or all of these purposes.
The use of a burrow as a refuge is presumably the primitive use of a
burrow. As has been shown by Verwey (1930) and noted by Macnae
(1957) and by Macnae and Kalk (1962a) burrows of all crustaceans on
mud banks (and this includes mangrove swamps) extend down t o the
water table. At this level the single burrows of crabs widen t o form a
chamber where the crab can turn. This burrow is important to Uca as
a centre of activity in territory defence. But when the crabs are not in
the territorial phase the burrow is merely used as a refuge, and when
used thus may be occupied by several crabs after an alarm.
Special behaviour of this sort has not been described for any other
genus of mangrove crabs, but preliminary work strongly suggests that
Xesarma meinerti does use its burrow as a centre of territorial defence
and display.
The use of the burrow as an accessory for feeding has not been
described for any crab but it has been shown to be important in the
thalassinidean genera Upogebia and Callianassa (see MacGinitie, 1930,
1934) and the same probably applies to Thalnssina anomala (see above).
Another curious use of the burrow has been described by Tweedie
(1935a,b). He recorded that from a burrow occupied by Xquilla choprai
he obtained eleven larvae apparently all of the same brood, and that he
obtained several specimens, many immature and some mature, of
Ilyoplax delsmani from. another burrow. These records suggest that
some mangrove crabs pass their whole life cycle close to the burrow of
their birth and possibly even indicate some parental care such as
defence of the brood in the nursery.
f. Scylla serrata
Xcylla serrata (Forsk%l) (Fig. 73) is the only portunid crab characteristically found in the mangal. It lives in burrows and is rarely seen
'away from them. These burrows are almost always elliptical in cross
section ; they are usually long, up to 5 m, and slope gently down to the
water table. They are most commonly found on the banks of creeks to
the level of low water in the creeks, but they may also be found on the
floor of the bruguiera,and rhizophora forests or among the roots of
Avicennia and Sonneratia in the seaward fringe ; an occasional burrow
WILLIAM MACNAE
ocypodids do not pump water through the gill chamber for breathing
purposes but only for feeding.
e. Burrowing
Crustacean burrowing subserves three distinct functions : (1) provision of a refuge, ( 2 ) as a centre of territorial behaviour and so as an
accessory to mating, and (3) as an accessory to feeding. Any burrow
may be used for each or all of these purposes.
The use of a burrow as a refuge is presumably the primitive use of a
burrow. As has been shown by Verwey (1930) and noted by Macnae
(1957) and by Macnae and Kalk (1962a) burrows of all crustaceans on
mud banks (and this includes mangrove swamps) extend down t o the
water table. At this level the single burrows of crabs widen t o form a
chamber where the crab can turn. This burrow is important to Uca as
a centre of activity in territory defence. But when the crabs are not in
the territorial phase the burrow is merely used as a refuge, and when
used thus may be occupied by several crabs after an alarm.
Special behaviour of this sort has not been described for any other
genus of mangrove crabs, but preliminary work strongly suggests that
Xesarma meinerti does use its burrow as a centre of territorial defence
and display.
The use of the burrow as an accessory for feeding has not been
described for any crab but it has been shown to be important in the
thalassinidean genera Upogebia and Callianassa (see MacGinitie, 1930,
1934) and the same probably applies to Thalnssina anomala (see above).
Another curious use of the burrow has been described by Tweedie
(1935a,b). He recorded that from a burrow occupied by Xquilla choprai
he obtained eleven larvae apparently all of the same brood, and that he
obtained several specimens, many immature and some mature, of
Ilyoplax delsmani from. another burrow. These records suggest that
some mangrove crabs pass their whole life cycle close to the burrow of
their birth and possibly even indicate some parental care such as
defence of the brood in the nursery.
f. Scylla serrata
Xcylla serrata (Forsk%l) (Fig. 73) is the only portunid crab characteristically found in the mangal. It lives in burrows and is rarely seen
'away from them. These burrows are almost always elliptical in cross
section ; they are usually long, up to 5 m, and slope gently down to the
water table. They are most commonly found on the banks of creeks to
the level of low water in the creeks, but they may also be found on the
floor of the bruguiera,and rhizophora forests or among the roots of
Avicennia and Sonneratia in the seaward fringe ; an occasional burrow