Cryptic species discussion

[Alexander Martynov]

  North Atlantic and arctic nudibranch "Coryphella" salmonacea
(Couthouy, 1839) was recorded in 70s from Sea of Japan and no
distinguishable characters was mentioned. Externally and internally
Atalantic and Pacific exemplars really practically same, and only
one well different feature I found - atlantic and arctic specimens
have penis in form of the fold, pacific - in form of whole cone.
These characters is constant in molluscs from so far from each
other regions - Barents and Kara Seas, Japan, Okhotsk Seas
and Alaskan waters. To pacific specimens I can applied before this
unclear name "Coryphella" japonica Volodchenko, 1941, because
to lucky type material saved. In arctic this species reached
Laptev Sea, in Pacific - coast of Alaska. That I can say about
this situation? This species are obviously allopatric and
differents in penial morphology appeared probably during isolation.
This species may named "formally" as cryptic because so similar
to each other, and "biologically" as sibling because its obviously
sister species from cladistic's point of view. But I prefer thoughts
that its some more example of dividing species with amphiboreal
and enormous areals and called this situation as puzzling
similar species.
  To sympatric example, another flabellinid nudibranch,
Coryphella browni Picton, 1980 very slightly distinguished
from Coryphella verrucosa (M.Sars, 1829)by external shape and color,
but have very different penis. Both species are inhabit in
British waters. To word, Nudibranchia its a treasure of penial
diversity - form, armature, accessory structure etc.
  We can secondary applied to term cryptic or sibling species
new content, like in message of Detlev Cordes,
>"Cryptic species" does not say anything about their phylogenetic
>relationships - they are difficult to recognize, and need to be
>investigated with more complicated methods - behavioural comparison,
>molecular approach -  so this is our problem, that we first use our eyes to
>separate species. Instead "sibling species" are defined by means of their
>phylogenetic "sister relationships" (in german: "sibling species" =
>"Zwillingsarten") and in my opinion they are TWO taxa only.,
but many cases and many differents combination characters of
the similar species are provided to us more and more complicate
terminology, i.e. "conchologically sibling species".
So, necessary of terms cryptic/sibling species as alternative to
"normal" species is dubious.
Cryptic/sibling species problem is also have dense connect
to eternal species problem. Above mentioned examples shows
species, where at least few characters constant for distinguished,
but especially in freshwater malacology from century to
century rush the waves of splitting/lumping and
characters flow from specimen to specimen.


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Alexander Martynov (doris at AM3963.spb.edu)
Zoological Institute
St.Petersburg
Thu, 21 Oct 99 23:57 +0300 MSK