'Gazetteer of the Persian Gulf. Vol I. Historical. Part II. J G Lorimer. 1915' [‎2223] (740/1262)

2228
Qaie about Chiru, at the islands of Das, Qarnain and Zirko, and
ogtie coast of Euus-al-Jibal between Ras-al-Khaimah and Ghnbbat
Grhazirah; in its habitat the Sadaifiyah resembles the Zanniyah, for it
.frequents hard muddy or shelly bottoms in the same depth of water.
The SadaiHyah does not often yield pearls, but those which it produces
are ordinarily large and of fine quality.
The laws which govern the growth of the oyster and the fluctuation Growth and
of oyster colonies in the Persian Gulf The historical term used to describe the body of water between the Arabian Peninsula and Iran. are by no means ascertained and ▼ariation of
the causes in accordance with which the yield of pearls varies from Ilum ^ er6,
season to season have not been investigated there as they have been in
Ceylon.
It is believed that the Mahharah increases steadily in horizontal
diameter until the end of the second year, when it measures about 2
inches, and that thereafter the rate of its growth diminishes; if
1 The^following facts in relation to the Ceylon pearl oyster, nearly all taken from
Profesfior W. A. Herdman's Report on the Pearl Oyster Fisheries of the Gulf of
Mmar, 1903-06, may be of interest to the general reader; it is, of course, uncertain
how far they hold good of the pearl oyster of the Persian Gulf The historical term used to describe the body of water between the Arabian Peninsula and Iran. .
The pearl oyster is not hermaphroditic, and the sex of the individual, whether
male or female, is permanently the same. The number of males and females is
approximately equal, but there may be a slight preponderance of males. The oyster
is gregarious without {distinction of sex, and reproduction takes place by the emission
of the generative products of male and female into the surrounding water where they
commingle. Midsummer and midwinter are principal breeding seasons.
Larval development takes place in the surface waters. The young oyster exists at
first in a free-swimming condition, which may cease within 5 days of fertilisation of
the eeg, but is capable, it is believed, of being considerably prolonged ; during this
period the rudiments of a shell are acquired.
The next stage is that of " spat attached as a rule to Algae, either rooted or
floating, or to Zoophytes' but the animal, though now capable of 6xing itself, is
highly locomotive and can creep as much as an inch in a minute. This it does
generally in an upward direction, probably from an instinct of avoiding sand ; nor is
it, like the adult oyster, deterred from movement by light. The maximum diameter
of the oygter may increase during the " spat " stage from *4 of a millimetre to 1*5
millimetreg and upwards.
The rate of growth of the animal during the first and second years of its life is
shown to be rapid. In the third year growth becomes much slower, and in the fourth
year still more slow ; but the thickness and weight of the shell continue to increase
greatly even after the external measurements have become almost stationary. The
oyster may be considered mature in its fourth year, when its diameter measured at
r jht angles to the hinge line is about 3^ inches ; it is at its best however in its
mth; and it seldom, apparently, survives its sixth year.
The food of the oyster consists of microscopic organisms, both animal and vege
table; but, while silt, etc., is rejected after being formed into a small pellet, minute
grains of sand and other non-nutritious particles are sometimes swallowed. The natural
position of the oyster is with the right or less convex valve underneath and with the
posterior edge of the shell elevated at an angle of about 20 degrees ; when undis-
turbed it holds its shell slightly open with the lips about one'third of an inch apart,
f* placed with the under side uppermost the oyster turns itself over by a violent
jerk from a retractile sucker or " foot" which it is able to protrude from its shell to
ae ma oh as 2^ inches. By means of this "foot " the oyster is also able to travel,
wgh slowly, from one place to another ; while the " footis being advanced^ the
ves 0 f the shell are held widely open, and when it is retracted they are closed with a
BD ap, a manoeuvre which aids considerably in the forward movement. An oyster has
^ known to progress 27 inches in this manner in 12 hours. The first care of the
TOr when it has attained a suitable position is to attach itself by a byssus or
JRinous thread, generally of more than one strand, to some convenient object; the