RE: NANFA--Fundulus dispar

Bruce Stallsmith (fundulus_at_hotmail.com)
Mon, 05 Jun 2000 21:30:37 EDT

Jan, you raise an interesting point about the relationship(s) between
freshwater and marine species in the genus _Fundulus_. As a group they're
all secondary freshwater fishes, in that their far distant ancestors were
marine. But I don't remember reading any theories about whether existing
freshwater forms (dispar, stellifer, diaphanus...) are derived from recent
ancestral marine forms (heteroclitus, majalis, luciae...), or vice versa.
The semilunar periodicity of marine species could easily be a fairly recent
adaptation to the lunar influences on tidal cycles; they breed in salt
marshes or mangrove swamps where the viability of eggs is of course strongly
influenced by tidal variations. I guess you could make an argument that such
a lunar peridocity in freshwater species would be best interpreted as a
vestigial character left over from marine ancestors. Of course I've never
heard of any such periodicity... but it's fun to speculate!

--Bruce Stallsmith
Huntsville, AL

>From: "Hoover, Jan J WES" <HOOVERJ_at_wes.army.mil>
>Reply-To: nanfa_at_aquaria.net
>To: "'nanfa_at_aquaria.net'" <nanfa at aquaria.net>
>Subject: RE: NANFA--Fundulus dispar
>Date: Mon, 5 Jun 2000 15:54:42 -0500
>
>
>Fundulus eggs seem destined for prolonged prehatching periods. Dessicated
>eggs of freshwater species take longer to hatch because dessication slows
>down embryo development. Eggs of estuarine killies often take 10-14 days
>to
>hatch. Spawning is tied in with a semi-lunar cycle: eggs are laid and
>hatch
>on new and full moon spring tides. To my knowledge, semilunar periodicity
>is not been documented in freshwater killies. Is it possible that
>prolonged
>hatching times of freshwater species are holdovers from marine ancestors?

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