HABITAT SELEOTION BY AQUATIU MVERTEBRATES
323
been two attempts to analyse which constituents of the primary film
cause it to stimulate or inhibit settlement. Knight-Jones (1951) and
Meadows and Williams (1963), working on Spirorbis borealis larvae,
coated clean surfaces with micro-organisms by soaking them in the
appropriate culture.. The larvae preferred to settle on films of the green
algae Chlamydomonas and Prasinocladus, the diatom Navicula, and
the blue-green alga Synechococcus, but avoided a film of the green
alga Dunaliella. Meadows and Williams also showed that membrane
filtered sea water did not render surfaces attractive, while if the precipitate from the membrane-filtration was resuspended in the filtered sea
water, surfaces soaked in it became attractive again, a strong indication
that naturally occurring micro-organisms produce an attractive film.
An unusual example of the importance of micro-organisms for the
settlement of marine larvae is the influence of fungi on the settlement of
larval shipworms (genus Teredo). Shipworm larvae are responsive both
to surface roughness and to chemicals present in wood (Harington,
1921 ; Isham and Tierney, 1953), but they are also markedly influenced
by the state and type of fungal decay undergone by the wood. Kampf
et al. (1959) offered the larvae of Teredopedicellata Quatrefages a choice
of woods either treated artificially or decomposed by fungi. Few larvae
settled on wood with a layer of agar over it or on wood previously treated
with sodium hydroxide or sulphuric acid, all of which treatments were
said to simulate the softness associated with fungal decay. However
wood decomposed by the basidiomycete fungus Lentinus lepideus F.R.
was fairly attractive, while wood previously soaked in sea water for four
months and hence heavily infested with naturally occurring fungi was
extremely attractive. These observations might lead to a method for
the prevention of woodworm attack under natural conditions ; field
trials with wood treated before immersion with fungistatic or fungicidal
agents might be worth while to determine whether larvae are deterred
from settling. It would also be interesting to know whether other
animals that burrow into wood, such as the crustaceans Limnoria
lignorum Rathke and Chelura terebrans Phillipi, prefer to do so if the
wood is decomposed by fungi. One species, Limnoria tripunctata
Menzies, has a lower mortality when fed live mycelium of the fungus
Peritrichophora integra then when fed sterile wood (Schafer and Lane,
1967) ; however, the animals were not offered a choice. Schafer and
Lane's conclusions are a little difficult to follow. They do not give
enough details of their quantitative results, they imply that the
temperature rdgime of their experiments fluctuated and they do not
appear to have aerated the tubes in which the animals were maintained
(p. 294, loc. cit.).
323
been two attempts to analyse which constituents of the primary film
cause it to stimulate or inhibit settlement. Knight-Jones (1951) and
Meadows and Williams (1963), working on Spirorbis borealis larvae,
coated clean surfaces with micro-organisms by soaking them in the
appropriate culture.. The larvae preferred to settle on films of the green
algae Chlamydomonas and Prasinocladus, the diatom Navicula, and
the blue-green alga Synechococcus, but avoided a film of the green
alga Dunaliella. Meadows and Williams also showed that membrane
filtered sea water did not render surfaces attractive, while if the precipitate from the membrane-filtration was resuspended in the filtered sea
water, surfaces soaked in it became attractive again, a strong indication
that naturally occurring micro-organisms produce an attractive film.
An unusual example of the importance of micro-organisms for the
settlement of marine larvae is the influence of fungi on the settlement of
larval shipworms (genus Teredo). Shipworm larvae are responsive both
to surface roughness and to chemicals present in wood (Harington,
1921 ; Isham and Tierney, 1953), but they are also markedly influenced
by the state and type of fungal decay undergone by the wood. Kampf
et al. (1959) offered the larvae of Teredopedicellata Quatrefages a choice
of woods either treated artificially or decomposed by fungi. Few larvae
settled on wood with a layer of agar over it or on wood previously treated
with sodium hydroxide or sulphuric acid, all of which treatments were
said to simulate the softness associated with fungal decay. However
wood decomposed by the basidiomycete fungus Lentinus lepideus F.R.
was fairly attractive, while wood previously soaked in sea water for four
months and hence heavily infested with naturally occurring fungi was
extremely attractive. These observations might lead to a method for
the prevention of woodworm attack under natural conditions ; field
trials with wood treated before immersion with fungistatic or fungicidal
agents might be worth while to determine whether larvae are deterred
from settling. It would also be interesting to know whether other
animals that burrow into wood, such as the crustaceans Limnoria
lignorum Rathke and Chelura terebrans Phillipi, prefer to do so if the
wood is decomposed by fungi. One species, Limnoria tripunctata
Menzies, has a lower mortality when fed live mycelium of the fungus
Peritrichophora integra then when fed sterile wood (Schafer and Lane,
1967) ; however, the animals were not offered a choice. Schafer and
Lane's conclusions are a little difficult to follow. They do not give
enough details of their quantitative results, they imply that the
temperature rdgime of their experiments fluctuated and they do not
appear to have aerated the tubes in which the animals were maintained
(p. 294, loc. cit.).