ECOLOQICAL STUDIES AT LOUQH INE
269
puber than is Thais from the Rapids. In each of a series of experiments
a single Portunus puber was placed in a cage with twenty Thais from
Carrigathorna and twenty from the Rapids of comparable sizes. The
cages were placed off Glannafeen Beach a little below the lowest tide.
Two days later the Thais from the Rapids remained without serious
damage, apart from a few below 20 mm, whereas of those from Carrigathorna many up to a height of 25 mm were smashed.
(b) Carcinus maenas and Thais lapillus. A series of similar tests were
carried out with Carcinus maenus of various sizes. In each test one crab
was placed in a cage in the shallow sublittoral with twenty Thais
lapillus from the Rapids and twenty from Carrigathorna of various
sizes; in a few tests twenty Ocenebra erinacea from the Rapids were
added as well as the Thais. The cages were inspected daily for 5 days
or more, and the prey was removed when smashed or seriously damaged.
The results are summarized in Fig. 65. Many more Thais from Carrigathorna were destroyed than Thais from the Rapids. Small Thais were
more vulnerable than large ones; the larger the crab the larger the Thais
broken by it. A number of large Thais placed with crabs of intermediate
size had their bodies extracted from the intact shell. Presumably the
shells were too strong for the crabs to break open. The tests reached a
substantial “end point’’ in three days, after which there were few additional casualties.
5. Survival of Thais transferred to a sheltered locality
Thais of both types were transferred to sheltered localities in Barloge
Creek, where Thais of the Rapids type occurs naturally and where we
supposed that Thais would be liable to attack by predators. Particulars
of sites are given by Kitching et al. (1966). We chose two sites south of
the Rapids in order that tidal conditions should be the same as in the
open sea; at each site barnacles, but not mussels, were present as a
source of food. The sites were cleared of all existing Thais before the
start of the experiment, and all transferred Thais were marked with
Indian ink.
At one site (Donovan Point) where the shore consisted of continuous
rock, only four out of one hundred Thais of the Carrigathorna type as
compared with twenty out of one hundred of the Rapids type (taken
from Barloge Bay) remained after six weeks. At the other site (which
consisted of a ridge of rocks surrounded by gravel) fifty T h i s transferred from Carrigathorna had all disappeared by one month after the
start of the experiment, whereas nineteen out of fifty of the Rapids type
(taken from Vee cleft in Barloge Creek) were recovmed.
Surviving Thais from Carrigathorna were mostly in crevices, whereas
those from the Barloge area remained in the open. Many broken shells
269
puber than is Thais from the Rapids. In each of a series of experiments
a single Portunus puber was placed in a cage with twenty Thais from
Carrigathorna and twenty from the Rapids of comparable sizes. The
cages were placed off Glannafeen Beach a little below the lowest tide.
Two days later the Thais from the Rapids remained without serious
damage, apart from a few below 20 mm, whereas of those from Carrigathorna many up to a height of 25 mm were smashed.
(b) Carcinus maenas and Thais lapillus. A series of similar tests were
carried out with Carcinus maenus of various sizes. In each test one crab
was placed in a cage in the shallow sublittoral with twenty Thais
lapillus from the Rapids and twenty from Carrigathorna of various
sizes; in a few tests twenty Ocenebra erinacea from the Rapids were
added as well as the Thais. The cages were inspected daily for 5 days
or more, and the prey was removed when smashed or seriously damaged.
The results are summarized in Fig. 65. Many more Thais from Carrigathorna were destroyed than Thais from the Rapids. Small Thais were
more vulnerable than large ones; the larger the crab the larger the Thais
broken by it. A number of large Thais placed with crabs of intermediate
size had their bodies extracted from the intact shell. Presumably the
shells were too strong for the crabs to break open. The tests reached a
substantial “end point’’ in three days, after which there were few additional casualties.
5. Survival of Thais transferred to a sheltered locality
Thais of both types were transferred to sheltered localities in Barloge
Creek, where Thais of the Rapids type occurs naturally and where we
supposed that Thais would be liable to attack by predators. Particulars
of sites are given by Kitching et al. (1966). We chose two sites south of
the Rapids in order that tidal conditions should be the same as in the
open sea; at each site barnacles, but not mussels, were present as a
source of food. The sites were cleared of all existing Thais before the
start of the experiment, and all transferred Thais were marked with
Indian ink.
At one site (Donovan Point) where the shore consisted of continuous
rock, only four out of one hundred Thais of the Carrigathorna type as
compared with twenty out of one hundred of the Rapids type (taken
from Barloge Bay) remained after six weeks. At the other site (which
consisted of a ridge of rocks surrounded by gravel) fifty T h i s transferred from Carrigathorna had all disappeared by one month after the
start of the experiment, whereas nineteen out of fifty of the Rapids type
(taken from Vee cleft in Barloge Creek) were recovmed.
Surviving Thais from Carrigathorna were mostly in crevices, whereas
those from the Barloge area remained in the open. Many broken shells