The Effect of Age on Growth-Resumption in Fish (Lebistes) Checked by Food Restriction

Effect of Delayed and Resumed Growth on the Longevity of a Fish (Lebistes reticulatus, Peters) in Captivity

“…It would equally be possible, at the other extreme, to maintain that none of our guppy experiments demon strate senescence in fish at all -since unsterilized live food was used throughout, and since, as we have previously shown (Comfort, 1961), a fair proportion of deaths to which a cause was assignable proved to be infective, we may only have measured the incubation period and mean duration of a group of fish diseases, while longer life in underfed fish is due to smaller inocula. The same, however, would apply to mammalian ageing under all ordinary conditions of measurement -the deaths of rats are equally often infective, at least so far as immediate cause is concerned.…”

“…The fish in one compartment of each such tank, numbering 7 to 12 individuals, received one measure by volume (average 670 mg dry weight) of live Tubifex worm per week in a single feeding, and those in the other compartment the same amount once a fortnight. The tanks were kept under continuous light in a hot room at 23° C (range 22.5°-24.5°): management and measurement were carried out as described in previous papers (Comfort, 1961;Comfort and Doljanski, 1959). At 600 days of age the retarded fish were put upon weekly instead of fortnightly feeding.…”

“…At 600 days of age the retarded fish were put upon weekly instead of fortnightly feeding. Life tables for retarded and unretarded fish were compiled by 100-day intervals with allowance for losses, again as already described for previous experiments (Comfort, 1961).…”

“…Studies of female guppies (Lebistes) under laboratory conditions have shown that their ageing is actuarially not very different from that of small mammals such as the rat: actual or potential growth may last to very high ages, but the force of mortality nevertheless increases steadily with time (Comfort, 1960(Comfort, , 1961. It remained to be shown what effect a period of delay in the growth curve would have upon subsequent longevity and mortality, and whether the actuarial response of these fish to underfeeding would follow the classical pattern for small rodents, in which dietary checking of development postpones the age-wise increase in mortality and lengthens life.…”

Aging and Kyphosis

“…In aging humans, annulus degeneration may also underlie kyphosis (7). Age-related kyphosis or spinal curvature has also been reported in several small tropical fish species (8,9), whose life spans approximate the mouse, including aging zebrafish (10). In contrast to humans, osteoporosis does not appear to be involved in fish kyphosis, at least in these species.…”