>
>Dear Tunicatists,
      The atria/otic vesicle discussion continued between Thomas Stach and
myself.
       I asked his permission to send our last two  previous e-mails to the
Tunicate list, and he kindly gave it,  saying that he never would commit
the crime of ignoring fossil evidence. In the hope of not boring everybody
too much I therefore forward these e-mails to the world's tunicatists.
Thomas' observations about hearing and sight(!) in tunicates are anyway of
general interest.
       By the way, if any tunicatist, passing through London, wishes to see
our dead animals and the remarkable microtomographic reconstructions of the
stem-group tunicate Jaekelocarpus being prepared by Patricio
Dominguez,   they would be very welcome. The invitation is not confined to
Thomas Stach.
        The e-mails are given here in reverse order of date.
                                 Best wishes,
                                Dick Jefferies


>Richard Jefferies <[log in to unmask]> schrieb am 08.02.02:
> > Dear Thomas,
> >    I agree that fossil evidence has its difficulties in that we cannot do
> > physiological experiments, such as banging on the table. In that sense we
> > cannot demonstrate that Lagynocystis could hear.
> >    On the other hand you,  being confined to  extant animals,  have no
> > beast still alive which possesses left, right and median atria together
> > with left and right acoustic ganglia. You have no more right to disregard
> > the fossil evidence than I have to disregard the physiology.
> >     As for being unfamiliar with Lagynocystis and its close kin,  we could
> > easily put that right if, next time you are in Europe, you accept my
> > standing invitation and come and see the material.
> >     I would appreciate your permission to send this letter, together with
> > your e-mail which provoked it, to the Tunicate List.
> >     I was interested in your deduction that ascidians are sensitive to
> > light. How do they do it?
> >                                Ich bin, wie immer,  Dein alter aber
> > ritterlicher Feind,
> >                                                      Herzliche Gruesse,
> >                                                             Dick
>...............................................................................................................................................................................
>
> >
 From Thomas Stach, 5 February 2002

> >Dear Dick,
> > >
> > >the chivalrous has to go back to you. Unfortunately you have chosen a
> > >weapon to joust, which I am not too familiar with. Moreover, the
> > >Lagynocystis sword is very dull along it's edge and, what is even more
> > >regrettable, can itself at least not be sharpened when it comes to
> hearing
> > >physiology. I have performed a little experiment in the lab where I keep
> > >Microcosmus exasperatus and Styela plicata at the moment. When I approch
> > >the aquaria to feed the animals, they retract their siphons in horror.
> > >That tells me that these animals can probably see and that they can not
> > >learn a great deal. Amphiprion in an aquarium closeby get very excited
> > >when anyone comes near, as they associate people approaching their little
> > >home with food. Anyway, if I loudly clap my hands about half a meter away
> > >from the ascidian aquaria, the animals do not show any reaction
> > >whatsoever. On the other hand, when I knock on the laboratory table 3-4
> > >meters away, they instantly retract their siphons. Now unfortunately, I
> > >have no cephalochordates at the present and failed to look for hearing in
> > >these curious animals last time. But unlike with Lagynocystis, we could...
> > >
> > >I hope you are doing fine.
> > >
> > >Greetings,
> > >
> > >Thomas
>..........................................................................................................................................................................

 From Dick Jefferies, 31 January 2002

> > >Dear Tunicatists and Thomas Stach,
> > > > I agree that the presence of a cupula is the main reason for
> > > > suggesting homology between neuromasts and the cupular organs of
> > > > tunicates. An additional reason is that tunicates, as Sveva's
> observation
> > > > eloquently shows, can hear.
> > >It is chivalrous (ritterlich!) of Thomas to cite the absence of
> > >cupulate hair cells in amphioxus, as against their presence in tunicates
> > >and vertebrates, as evidence for my heresy that the chordates are related
> > >as: (acraniates (tunicates + craniates)). With deep regret, however, I
> > >cannot accept his argument.
> > >The reason is that among mitrates the stem-group acraniate
> > >Lagynocystis had left and right atria, with left and right gill slits,
> left
> > >and right acoustic ganglia and presumably cupular organs in the left and
> > >right atria. This indicates that, like other mitrates and extant
> > >ascidians, it would probably have been able to hear if a door slammed at
> > >the other end of the corridor. Extant amphioxus, however, has lost the
> left
> > >and right atria and the acoustic ganglia (and the cupular organs if they
> > >existed) but keeps the median ventral atrium which Lagynocystis, alone
> > >among mitrates, possessed.
> > >Does anybody know if amphioxus can hear?
> > >Best wishes,
> > >Dick Jefferies