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Growth, bioenergetics and life-span of Octopus cyanea and Octopus maya
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|Title:||Growth, bioenergetics and life-span of Octopus cyanea and Octopus maya|
|Authors:||Van Heukelem, William F.|
|LC Subject Headings:||Octopuses.|
|Issue Date:||Aug 1976|
|Publisher:||University of Hawaii at Manoa|
|Citation:||Van Heukelem, William F. Growth, bioenergetics and life-span of Octopus cyanea and Octopus maya. Honolulu (HI): University of Hawaii at Manoa, 1976.|
|Abstract:||The objectives of the work undertaken were to: (1)|
rear Octopus cyanea and Octopus maya through all stages of
the life cycle in the laboratory; (2) measure growth rates;
(3) determine energy budgets; (4) examine the effects of
temperature, size and age on food intake, growth, metabolism
and conversion efficiency; and (5) determine life-spans
of the two species.
Attempts to rear O. cyanea through the planktonic stage
were unsuccessful and data were obtained on feral animals in
the laboratory. O. maya was reared through four generations
from eggs collected at Campeche, Mexico.
Animals were fed ad libitum on living crabs. Weights
were recorded at I5-day intervals and food intake was quantified.
Dry matter, ash and caloric content of crab and O.
cyanea samples were determined.
Animals grew exponentially for the first third of their
benthic life, doubling their weight every 11-13 days at 22
- 27 degrees C. The exponential growth phase was followed by a period
of logarithmic growth which terminated at full sexual
maturity. Average maximum sizes attained by the two species
were comparable (3.2 kg for O. maya and 3.6 kg for O.
cyanea). O. cyanea settles from the plankton at an estimated
weight of 0.3 g and attains maximum size about 10.5
months later. O. maya hatched as benthic juveniles weighing 0.1 g and grew to maximum size in about 8.5 months. Maximum
size attained by both species varied from several hundred
grams to several kilograms depending on food availability.
Assimilation efficiency of O. cyanea was very high
(95%) and independent of animal size and food ration size.
Gross growth efficiency of both species averaged about
40% on a wet weight basis and was independent of size (old
animals excluded) and temperature. The relationship between
food intake and growth was linear in both species and showed
no sign of decrease at high ration level.
Material budgets indicated that on a wet weight basis,
40% of ingested food was used in growth, 55% in maintenance
and 5% was not absorbed. Energy budgets on a caloric basis
indicated that 60% of ingested energy was used in growth,
36% in total metabolism and 4% voided as feces.
Rates of food intake, growth and metabolism were about
twice as high at 30 as at 20 degrees C.
Females of both species died after brooding their eggs
and males died at about the same age. O. cyanea had a lifespan
of 12-15 months from settlement and O. maya lived an
average of 10 months from hatching in the laboratory.
Low light intensity and elevated temperature in the
laboratory were thought to produce early spawning and hence
short life-spans in laboratory animals. A theory is presented to explain large variations in
size at spawning and lack of seasonality. Growth, differentiation,
maturation and spawning are viewed as programmed
events in the life cycle. Light, temperature and food determine
the rate at which the program runs and hence size
and age at spawning. Senescence and death are viewed as
events occurring after the program is completed.
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|Appears in Collections:||Ph.D. - Zoology|