﻿36 
  PEOPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  

  

  PARASITISM. 
  

  

  There 
  are 
  questions 
  associated 
  with 
  the 
  parasitism 
  of 
  fresh-water 
  

   mussels 
  wliich 
  have 
  previously 
  had 
  little 
  discussion. 
  Obviously 
  the 
  

   basis 
  for 
  a 
  consideration 
  of 
  these 
  must 
  be 
  upon 
  observation 
  of 
  natural 
  

   infections. 
  I 
  wish 
  to 
  discuss 
  these 
  under 
  the 
  following 
  heads: 
  

   Restricted 
  infection, 
  susceptibihty 
  and 
  immunity, 
  frequency 
  of 
  

   i]^.fection, 
  extent 
  of 
  individual 
  infection, 
  conditions 
  of 
  infection 
  in 
  

   nature, 
  etc. 
  

  

  Restricted 
  infection. 
  — 
  The 
  existence 
  of 
  specific 
  or 
  narrowly 
  restricted 
  

   parasitism 
  in 
  the 
  case 
  of 
  some 
  mussels 
  I 
  beheve 
  I 
  have 
  demonstrated 
  

   in 
  the 
  case 
  of 
  Q. 
  pustulosa 
  upoji 
  the 
  channel 
  cat, 
  Ictalurus 
  punctatus 
  

   (Howard, 
  1912). 
  A 
  similar 
  case 
  is 
  that 
  of 
  the 
  niggerhead 
  upon 
  

   Pomolohus 
  cJirysocMoris 
  (Surber, 
  1913). 
  These 
  are 
  not 
  surprising, 
  

   since 
  it 
  is 
  common, 
  especially 
  among 
  animals, 
  for 
  a 
  certain 
  species 
  

   of 
  parasite 
  to 
  be 
  restricted 
  to 
  a 
  given 
  species 
  or 
  genus 
  of 
  hosts, 
  as 
  

   Goniodes 
  stylifer, 
  the 
  louse 
  infesting 
  the 
  turkey, 
  and 
  Trichodectes 
  

   scalans 
  upon 
  the 
  ox. 
  If 
  by 
  accident 
  they 
  come 
  in 
  contact 
  with 
  some 
  

   other 
  animal 
  they 
  do 
  not 
  remain. 
  Why? 
  The 
  supposition 
  is 
  that 
  

   the 
  reaction 
  of 
  the 
  blood 
  or 
  something 
  about 
  the 
  foreign 
  hosts 
  is 
  

   unfavorable 
  to 
  them; 
  in 
  anthropomorphic 
  language, 
  "they 
  do 
  not 
  

   like 
  it." 
  

  

  To 
  what 
  extent 
  tliis 
  principle 
  of 
  limited 
  parasitism 
  extends 
  among 
  

   mussels 
  is 
  still 
  to 
  be 
  determined. 
  It 
  seems 
  obvious, 
  however, 
  that 
  

   a 
  solution 
  of 
  this 
  question 
  is 
  logically 
  to 
  be 
  sought 
  from 
  a 
  study 
  of 
  

   natural 
  infections. 
  

  

  The 
  method 
  of 
  determining 
  the 
  host 
  by 
  artificial 
  infection 
  has 
  

   proved 
  practicable 
  in 
  the 
  experiments 
  reported 
  by 
  Lefevre 
  and 
  

   Curtis 
  (1912), 
  but 
  in 
  these 
  cases 
  the 
  mussels 
  were 
  parasitic 
  upon 
  

   common 
  and 
  easily 
  obtamable 
  fish. 
  The 
  chief 
  commercial 
  species 
  

   employed 
  was 
  the 
  mucket, 
  Lamfsilis 
  ligamentina, 
  and 
  the 
  fish 
  suc- 
  

   cessfully 
  infected 
  were 
  the 
  sunfish, 
  Apomotis 
  cyanellus, 
  and 
  the 
  black 
  

   bass, 
  Micropterus 
  salmoides. 
  In 
  the 
  experiments 
  at 
  the 
  Fairport 
  

   biological 
  laboratory 
  black 
  bass, 
  sunfish, 
  and 
  crappies 
  were 
  infected 
  

   successfully; 
  the 
  pike, 
  Esox 
  lucius, 
  and 
  the 
  perch, 
  Perca 
  flavescens, 
  

   were 
  reported 
  doubtful. 
  From 
  these 
  results 
  it 
  would 
  seem 
  that 
  

   infection 
  with 
  the 
  mucket 
  is 
  limited 
  chiefly 
  to 
  the 
  Centrarchidse, 
  a 
  

   single 
  family 
  of 
  fishes. 
  The 
  hooked 
  glocliidia 
  of 
  Anodonta 
  corpu- 
  

   lenta 
  seem 
  less 
  restricted. 
  I 
  have 
  seen 
  these 
  upon 
  fish 
  of 
  the 
  follow- 
  

   ing 
  families: 
  Clupeidse, 
  Centrarchidse, 
  and 
  Scia3nidae. 
  A 
  similar 
  

   state 
  of 
  things 
  is 
  seen 
  in 
  the 
  bookless 
  external 
  infecting 
  glochidia 
  of 
  

   Q. 
  heros 
  successfully 
  maintaining 
  itself 
  on 
  the 
  Sciasnidge, 
  Siluridse, 
  

   and 
  Centrarchidse 
  (the 
  latter 
  two 
  observed 
  in 
  artificial 
  infection). 
  

  

  Susceptibility 
  arid 
  immunit)j. 
  — 
  The 
  commonness 
  of 
  infections 
  on 
  

   some 
  species 
  of 
  fish 
  in 
  nature 
  might 
  be 
  called 
  a 
  sign 
  of 
  susceptibiUty 
  

  

  