302
.
THE BIOLOGY OF FISHES
.
serious inammation and»thus weakening of the "sh, pre—=Ï
disposingîit to the attacksof— the'ever—present Saprolegnia;
One of the most deadly of these fungoid growths is Branehio— '
myces, which somehow gets into the capillaries of the gill— .
_
laments and its hyphæ spread there
such an extent that
,
the sh (Carp) is soon suocated. This occurs mostly
during Very hot days in summer and is more common ;in
some waters than others.
In fact, it is a peculiarity of all
.
these diseases that some rivers, for example, the Tweed, are
.
'
worse than others.
A de‘ciency of oxygen or air in sloWly
_
’
moving or stagnan't water, when greatly heated in the
‘
summer, also hasa similar effect on the gills;
,
,
_
; -Ü
'
'
Of the parasites that infest shes there is almost no end;
,
various Copepods without and manyworms within. There
'
are
over- fty species; of =Trematods alone;— -The latter
probably liVe in the; seXual condition in .gulls. The larva
'
(Diplostomum) devèlo‘ps—
the e'gg‘, in the
.
sh, mainly
_
freshwat‘erf0‘rmS; but also sorhemärrine,"and makesits‘Wayin the blood to
eye—ball, Where it Settlesaéitrst—
lens and causes cataract, the eye becoming
,
Although quite blindéd by the parasite, the ,»shesse‘emable
to' nd their’food by“ means-of their other senses_-—.= …Ithe
'Elbe thisdisease has been well known for—’a hundred years_ ,
'
and is exceedingly common,
,
affected the stock of sh
extentandthebhnded
sh are quite g00dto
"
A" more
parasite _. isoneoftheBand—worms_—-_2
(DiphyllobothriumorBothr10cephalus),whlchbegins1ts 1ifè4
'éyè1éîiii—àSmâ11‘freshWater-Côpèpô'Cl (cyapusg…àpmmus).
;
_îThiS £is
second host,P1ke
but also
Trout,Wh1tesh etc
pehètrates
-
'
from ' ‘ the : _gut,
'
fin—"to other
pri "the muscles, and when
again the
man, the full—sized
and—"may beCome a serious
It
is “said to be ”the comÔneSt parasite of human beings
“
'
Turkestan and—Japan; but it alSo o*c“:curs in Eur0pe,gSwitzer—'
’
_
‘
land, NOrth’ Russia, and thefBalti‘cpr0Vinces of Germany
_
P(Plehn, ; 1924).
some other: worm