SOME ASPECTS O F THE BIOLOGY OF T H E CHAETOCNATHS
365
1959a,b, 1965b), Murakami (1959), Dallot (1966, 1967), Horridge
(1966), Reeve (1964, 1966), Singarajah (1966), Horridge and Boultoii
(1967).
It has not been possible so far t o obtain in the laboratory the
complete cycle of development in the pelagic species, but anyway the
resn1t.s of these researches have supplied important information on the
breeding cycle and reproduction (Stevens, 1905, 1910 ; Vasiljev, 1925 ;
John, 1933 ; Jagersten, 1940 ; GhirardelIi, 1950a, 1952, 1953d, 1954a,
1956a; Dallot, 1966, 1967; Murakami, 1959; Reeve, 1964, 1966); regeneration (Kulmatycki, 1918 ; Ghirardelli, 195610, 1958a, 1959a,b, 196513) ;
feeding (Parry, 1944 ; Reeve, 1966 ; Murakami, 1959 ; Horridge, 1966 ;
Horridge and Boulton, 1967) ; corona ciliata and sensibility (Reisinger,
1934 ; Ghirardelli, 1958b, 1959a ; Horridge and Boulton, 1967) ; influence
of environmental factors on morphology (Murakami, 1959) and on
behaviour (Reeve, 1966 ; Sanzo, 1937, on eggs of Pterosagitta draco),
and finally on chemical factors and centrifugation on the development
of the eggs (Ghirardelli, 1955). Only few authors have reared for some
weeks some species of chaetognaths (Ghirardelli, after 1953, Spadella ;
Murakami, Sagitta crassa; Dallot, S. setosa, and Reeve, S. hispida). The
reason for the few laboratory studies involving rearing of the chaetognaths, especially the planktonic ones, lies in the fact that these animals
do not tolerate well the conditions of transport and those in the
laboratory. Chaetognaths for which there has been moderate success in
experiments are S. hispida and S. setosa which are planktonic members
of the phylum habitually frequenting inshore waters. Spadella cephaloptera is a benthic species also living in coastal waters on the seaweeds or
marine phanerogams or even in rock pools. This chaetognath is quite
resistant to laboratory conditions, undoubtedly because of its natural
habitat. Spadella cephaloptera up to this moment is the only one
species reared in the laboratory from hatching to sexual maturity
(G hirardelli, 1959~).
VII. ACKNOWLEDGEMENTS
The original observations recorded in the present article have been
made principally a t the Zoological Stations of Naples and Villefranchesur-Mer, at the Biological Institute of Dubrovnik and the Zoological
Institute of the University of Trieste, with the support of Consiglio
Nazionale delle Ricerche, Rome.
I remember with gratitude the late Prof. Reinhard Dohrn, former
Director of the Zoological Station of Naples.
I record my sincere thanks to G. Montalenti, Director of the Centro
di Biologia of the C.N.R. at the Zoological Station of Naples, P. Bongis,
365
1959a,b, 1965b), Murakami (1959), Dallot (1966, 1967), Horridge
(1966), Reeve (1964, 1966), Singarajah (1966), Horridge and Boultoii
(1967).
It has not been possible so far t o obtain in the laboratory the
complete cycle of development in the pelagic species, but anyway the
resn1t.s of these researches have supplied important information on the
breeding cycle and reproduction (Stevens, 1905, 1910 ; Vasiljev, 1925 ;
John, 1933 ; Jagersten, 1940 ; GhirardelIi, 1950a, 1952, 1953d, 1954a,
1956a; Dallot, 1966, 1967; Murakami, 1959; Reeve, 1964, 1966); regeneration (Kulmatycki, 1918 ; Ghirardelli, 195610, 1958a, 1959a,b, 196513) ;
feeding (Parry, 1944 ; Reeve, 1966 ; Murakami, 1959 ; Horridge, 1966 ;
Horridge and Boulton, 1967) ; corona ciliata and sensibility (Reisinger,
1934 ; Ghirardelli, 1958b, 1959a ; Horridge and Boulton, 1967) ; influence
of environmental factors on morphology (Murakami, 1959) and on
behaviour (Reeve, 1966 ; Sanzo, 1937, on eggs of Pterosagitta draco),
and finally on chemical factors and centrifugation on the development
of the eggs (Ghirardelli, 1955). Only few authors have reared for some
weeks some species of chaetognaths (Ghirardelli, after 1953, Spadella ;
Murakami, Sagitta crassa; Dallot, S. setosa, and Reeve, S. hispida). The
reason for the few laboratory studies involving rearing of the chaetognaths, especially the planktonic ones, lies in the fact that these animals
do not tolerate well the conditions of transport and those in the
laboratory. Chaetognaths for which there has been moderate success in
experiments are S. hispida and S. setosa which are planktonic members
of the phylum habitually frequenting inshore waters. Spadella cephaloptera is a benthic species also living in coastal waters on the seaweeds or
marine phanerogams or even in rock pools. This chaetognath is quite
resistant to laboratory conditions, undoubtedly because of its natural
habitat. Spadella cephaloptera up to this moment is the only one
species reared in the laboratory from hatching to sexual maturity
(G hirardelli, 1959~).
VII. ACKNOWLEDGEMENTS
The original observations recorded in the present article have been
made principally a t the Zoological Stations of Naples and Villefranchesur-Mer, at the Biological Institute of Dubrovnik and the Zoological
Institute of the University of Trieste, with the support of Consiglio
Nazionale delle Ricerche, Rome.
I remember with gratitude the late Prof. Reinhard Dohrn, former
Director of the Zoological Station of Naples.
I record my sincere thanks to G. Montalenti, Director of the Centro
di Biologia of the C.N.R. at the Zoological Station of Naples, P. Bongis,