Both descriptive and functional approaches are possible.
Descriptive approaches will allow you to look at mRNA or protein expression within
the tissue. It is possible to perform whole mount in situ hybridization,
in toto fluorescence microscopy,
paraffin embedding and sections,
light sheet fluorescent microscopy,
Alizarin red and alcian blue clear staining,
and micro CT.
Here you can see the references where you can find a detailed description of
these techniques. Some functional approaches are also possible.
These approaches are bead implantations, brdU or edU injection, DiI injection or
DiI cell labelling, in ovo drug treatment, and embryo culture.
More particularly, bead implantations and in ovo drug treatment will allow you to
explore the role of a gene or a pathway in a biological process.
BrdU injection can give you the possibility to analyse cycling cells, and DiI injection
to follow the trajectory of a cell within the embryo.
Here again, you will find references for detailed descriptions of these techniques.
It is however not possible to do transgensis or gene editing with cartilagenous fish.
Why? Because we don't have access to the one-cell-stage embryo.
The catshark egg, for example, is like the chicken egg: the fertilisation is internal
and the first divisions are occuring within the oviduct,
and in addition, the embryo is inside the eggshell, so we don't have access to the
embryo and we cannot microinject directly in it. It is however possible to inject
a drug within the eggshell, so the embryo will be in contact with the drug
and if the drug is inhibiting or activating a signalling pathway, you can see or study
the implication of this signalling pathway in a biological process
as Yasmine said previously.
In contrast, fertilisation is external in amphioxus or sea urchins
or ascidians, and you can directly microinject the one-cell stage with
for example, mRNA, morphelinos, or molecular tools to make gene editing.
It is important to have in mind that the mode of development of each organism
is different, and this means that
some experiments will be possible with an
with one organism and some other experiments will not be possible.
In any case, each organism has its specificity and its own interest.