Posted: Nov 18 2006, 07:16 PM

Turbonilla toyatani vs. T. riisei & T. interrupta, Mosquito Lagoon micros

Turbonilla riisei Mörch, 1875 (Turbonilla pilsbryi Bush, 1899 is a junior synonym)
Turbonilla interrupta (Totten, 1835)
Turbonilla toyatani Henderson and Bartsch, 1914

In 2006 I sent vials of micros collected in Mosquito Lagoon, Brevard Co., FL to several LTS members.  Their obligation was to identify the shells.  One of the shells was a Turbonilla.  Four of the members made suggestions.  Tom and Matt suggested that the Turbonilla was Turbonilla cf. riisei and Dan’s and Wayne’s feeling was that it may be Turbonilla interrupta.  I believed it was Turbonilla toyatani, but did a review considering all three.

 

First step I always take is to determine if we have any confirmed finds of a species from the area or areas near by. For the Florida eastern coast I rely upon the following:

1. Harry Lee’s checklists for Peanut Island and Northeast Florida Marine Mollusks.

2. Molluscan Biodiversity In The Indian River Lagoon, Florida, Paula M. Mikkelsen, Paul S. Mikkelsen and David J. Karlen, Bulletin of Marine Science, 57(1): 94-127, 1995. (Mosquito Lagoon is the northern end of the Indian River Lagoon.)

3. Nearshore Marine Ecology at Hutchinson Island, Florida: 1971-1974, XI. Mollusks, William G. Lyons, Florida Marine Research Institute, No. 47, November 1989.

4. My personal checklists (with contributions from others) covering Miami to St. Augustine.

 

(Note: I do not have any T. riisei or T. interrupta – so no images. The below images are all of the shells from Mosquito Lagoon.)

Let's first consider T. interrupta.

None of the above four references

report T. interrupta. Among the

characters that Abbott describes for

T. interrupta are, “wax-yellow,” “broad,

low axial ribs” with “the intercostals

spaces being not as wide” as the ribs.

The Mosquito Lagoon Turbonilla does

not meet these characters. The axial

ribs in particular are not very broad

and are definitely narrower than

the intercostal spaces are wide.

Next, we'll consider T. riisei, which is reported only by Lyons (all his collecting was done offshore) and on Lee’s checklist for NE Florida (found among beach drift and scallop tailings); none from Lagoonal waters. Abbott does not treat T. riisei or T. pilsbryi, but Lyons and Redfern do. And, best of all, T. pilsbryi is treated in Turbonilla (Gastropoda: Pyramidellidae) species described by Katherine Jeannette Bush: Scanning Electron Microscope Studies of the Type Material in the Academy of Natural Sciences of Philadelphia, Ricardo S. Absalao and Alexandre D. Pimenta, Proceedings of the Academy of Natural Sciences of Philadelphia, 149: 77-91, 29 January 1999. The first character that argues against the Mosquito Lagoon being T. riisei is that T. riisei is in the subgenus Strioturbonilla (having numerous fine, densely packed spiral striae on the teleoconch, usually limited to the intercoastal spaces). Redfern describes T. riisei as “The ribs are separated by crowded spiral threads.” The Mosquito Lagoon species is clearly in the subgenus Pyrgiscus (having strong spiral lines or sharply incised grooves). It is also apparent when compared to the images of T. riisei in Lyons, Redfern and Bush that it’s teleoconch whorls are distinctly more convex (“well-rounded’ Lyons) and consisting of far fewer whorls causing Lyons to state “Shell stout.” Bush’s original description describes T. riisei as having six swollen whorls.  CLICK for photo of     

 T. riisei.

Lastly, there's T. toyatani, which is reported in both of Lee’s lists, in Lyons and in my lists from Ft. Pierce north to Mosquito Lagoon. Lyons describes T. toyatani as “white, moderately large, with well-rounded, somewhat expanded whorls. Axial ribs nearly straight, continuing weakly on base. Intercostals with 6 or 7 strong incisions on spire, 9 or 10 on penultimate whorl.” Lyons compared his shells directly with the holotype to make his ID. Except for the “white,” this description fits the Mosquito Lagoon Turbonillas. The color bands fade quickly on this species, especially if not immediately stored in alcohol. Lyons collected only two specimens, both dead. I sent a vial of about 80 of the Mosquito Lagoon Turbonillas to Harry Lee for examination. His comments were that “These shells are remarkably uniform. Certainly these are what Lyons called T. toyatani. T. riisei is not related.”

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5/5/13  Harry Lee: