Colonial coordination in anthozoans: Pennatulacea†

Abstract

Morphological and physiological evidence from five species of pennatulid octocorals indicates that a through-conducting colonial nerve net controls colony-wide responses including polyp withdrawal, bioluminescence and rachidial contraction. This nerve net is synaptic, and located in the ectoderm and mesoglea of the colonial tissue. Nerve net impulses recorded extracellularly, show initial increases in conduction velocity during repetitive stimulation which promote faci'ation of effectors. The response-amplitude of these effectors is frequency dependent. Bridge experiments suggest that interneural facilitation may contribute to the conduction velocity changes. Photometric measurements with concurrent electrophysiological recordings reveal that bioluminescence is under the control of the colonial nerve net. Luminescent responses show a frequency-dependent facilitation similar to that of other effectors. These physiological data, together with morphological data on the location and shape of autozooid photocytes suggest that the photocytes may be modified circular or radial muscle cells. A second through-conducting colonial system was detected in three pennatulid species, the function of this system, however, was not evident.

Neuronal and nonneuronal taurine-like immunoreactivity in the sea pansy, Renilla koellikeri (Cnidaria, Anthozoa)

“…Protective retraction of autozooid polyps into the colonial mass, although relatively slow, is the fastest motor response of the sea pansy. Anderson and Case (1975) have shown that the "colonial nerve net", corresponding to the mesogleal nerve net of this study [described also by Satterlie et al (1976Satterlie et al ( , 1980], coordinates polyp retraction by connecting with the zooid nerve net at the top of the column of the autozooid. Taurine induces a folding of the tentacles over the mouth and a bending of the autozooid column toward the center of the colony (M. Anctil and S. Angelo Alves, unpublished work), the first two of the three steps of the retraction sequence (Parker 1920).…”

“…3c, d) as described by Satterlie et al (1976Satterlie et al ( , 1980 and Pani et al (1995). However, their identification is tentative because of the interfering presence of immunostained spicule cells nearby (see below).…”

Tyrosine hydroxylase and dopamine-β-hydroxylase immunoreactivities in the cnidarian Renilla koellikeri

“…The mesogleal nerve-net of the sea pansy and other sea pens comprises bipolar and multipolar neurons associated with a meshwork of amoebocytes and their pseudopods (Buisson and Franc 1969;Titschack 1970;Satterlie et al 1980). In whole-mounts, the amoebocyte meshwork was immunoreactive to TH, DBH and PNMT antisera (Fig.…”

Antho‐RFamide‐containing neurons in the primitive nervous system of the anthozoan Renilla koellikeri

“…This widespread net may function as a through-conducting nerve-net, i.e., coordinating colonial movements associated with defense (polyp retraction, colonial mass contraction), feeding, and spawning (Buisson, 1970(Buisson, , 1974Satterlie et al, 1976Satterlie et al, , 1980. Antho-RFamide might share its activities in this colonial through-conducting nerve-net with other transmitters, such as norepinephrine (Pani et al, 1995;Anctil et al, 2002).…”

“…The mesogleal layer expands considerably into the colonial mass compared with polyps (Fig. 2), and includes calcareous spicules in addition to neurons and amoebocytes (Satterlie et al, 1980). Consequently, the colonial, mesogleal nerve-net is tridimensional instead of the bidimensional net in polyp mesoglea.…”