Laevipilina theresae, a new monoplacophoran species from Antarctica 
(Mollusca) 
Michael Schrödl 
Schrödl, M. (2006): Laevipilina theresae, a new monoplacophoran species from 
Antarctica (Mollusca). - Spixiana 29/3: 225-227 
The monoplacophoran mollusc Laevipilina theresae, spec. nov. is described from 
a living specimen collected off Kapp Norwegia, Eastern Weddell Sea, at approx. 
800 m depth. This is the third monoplacophoran species known from Antarctica. 
Laevipilina theresae, spec. nov. is unique in having its apex clearly surpassing the 
anterior shell margin and showing two concentric bulges around the base of the 
apex. The new species additionally differs from the sympatric L. antarctica Waren 
& Hain, 1992 due to its less depressed shell. Brown markings along the mantle and 
foot edges and in the mouth region indicate the presence of symbiotic bacteria as 
already known from L. antarctica. 
Dr. Michael Schrödl, Zoologische Staatssammlung München, Münchhausenstr. 
21, 81247 München, Germany; e-mail: schroedl@zi.biologie.uni-muenchen.de 
Introduction 
With a fossil record back to the Cambrian, Extant 
monoplacophorans are still amongst the most enig- 
matic and wanted molluscs. The 25 species known 
worldwide occur from approx. 200 m down to 
abyssal depths (see Waren & Hain 1992, Goud & 
Gittenberger 1993, Urgorri et al. 2005). Most records 
refer to empty shells or severely damaged specimens, 
only very few researchers were lucky enough to 
obtain and observe a living animal. In Antarctica, 
two species were previously known. Micropilina 
arntzi Waren & Hain, 1992 is a tiny species (approx. 
1 mm) only known from the Lazarev Sea (Waren & 
Hain 1992). Laevipilina antarctica Waren & Hain, 1992 
shows a much wider distribution on the Antarctic 
shelf and upper Continental slope from the Lazarev 
Sea to the Eastern Weddell Sea (Waren & Hain 1992); 
a specimen recently found below 3000 m depth 
shows this species to be surprisingly eurybathic 
(Schrödl et al. 2006). During the EASIZ III expedition 
on RV "Polarstern", a completely intact, living 
Laevipilina specimen was sorted out from a bathyal 
sand sample. This specimen significantly differs from 
any other congener and is described as a new species 
herein. 
Methods 
During the ANT XVII-3 (EASIZ III) expedition on 
RV "Polarstern", any available sea bottom Substrates 
such as boulders, stones, sand, and mud samples 
were carefully revised for monoplacophorans by the 
author. The single specimen (ZSM Moll 20050898) 
obtained was collected north off Kapp Norvegia, 
Antarctica, at Station PS67/138-1 (71°08.90'S 013° 
12.80'W, 71°08.80'S 013°13.20'W), by an epibenthic 
sledge (EBS) at 765-840 m depth on sandy bottom, 
11 April 2000. The entire EBS sand sample was 
sorted in a cooling Container at °C. The specimen 
was photographed and observed alive, then briefly 
relaxed in isotonic MgCl 2 Solution, and fixed in glu- 
taraldehyde. Finally, the specimen was embedded 
in Spurr's resin and serially sectioned, except for the 
penostracum which is preserved in ethanol 78 %. 
225 
Fig. 1. Laevipilina theresae, spec. nov., living holotype. A. Dorsal view. Note the apex (at the top) surpassing the 
shell margin, and the diagnostic two concentric swellings separating the apex from the rest of the shell. B. Ventral 
view. Note the nearly circular sucker-like foot, the 5 pairs of gills serially arranged along the circumpedal mantle 
cavity, the elongate velar lobes (at the top), and the postoral tentacles in between velum and foot, having just a 
few short and inconspicuous projections. 
Laevipilina theresae, spec. nov. 
Fig. 1 
Monoplacophora sp. Sirenko & Schrödl, 2001: 86. 
Laevipilina sp. Schrödl, Linse & Schwabe, in review. 
Holotype: Zoologische Staatssammlung München (pe- 
riostracum: ZSM Moll. 20050898; plus series of histo- 
logical and ultrastructural sections), collected by Michael 
Schrödl, 11 April 2000, from a sand sample obtained 
north of Kapp Norvegia, Antarctica, at 765-840 m depth. 
Description 
The living animal (Fig. 1) had a transparent shell 
and a whitish to slightly pinkish translucent body. 
Two pairs of dorsal pouches with brown dots were 
shining through the shell as were 8 pairs of shell 
muscles (Fig. 1 A). In ventral view (Fig. 1 B), the "head 
area", the foot edge and sides and the mantle edge 
was brownish, the anterior mantle edge was darker 
red-brown. Brown coloration referred to more or 
less densely arranged, minute brown dots. 
The mouth area is very similar to that of L. ant- 
arctica as described by Waren & Hain (1992): velar 
lobes are elongated and nearly reach the anterior 
foot margin. The inconspicuous anterior lip is sepa- 
rated from the velum by a narrow groove. The 
posterior lip is a transverse swelling in its anterior 
part; swollen ridges project posterolaterally bearing 
just a few (up to 5) short and blunt postoral tentacles 
on each side. The foot is circular to slightly oval and 
sucker-like. There are 5 pairs of similar-sized gills 
with 3 digits arranged ventrolaterally along the 
circumpedal mantle cavity (Fig. 1B). The anus opens 
ventroterminally as a simple hole. 
The shell is limpet-like depressed and fragile. 
Dimensions are: 2.5 mm length, 2.1 mm width, and 
1 mm height. The apex is dorsally rounded, anteri- 
orly directed, and surpasses the anterior shell mar- 
gin. The base of the apex bears two concentric, 
whitish bulges. The shell slope is slightly convex, 
with a depression at the base of the apex. The aper- 
ture is nearly oval, only slightly narrower anteri- 
orly. The shell edge is sharp. The shell surface is 
smooth except for showing fine concentric growth 
marks. The periostracum is net-like sculptured, with 
fine radial ridges crossed by concentric growth 
marks; dimensions and proportions of Spaces vary 
considerably. 
Etymology. Laevipilina theresae, spec. nov. is named af- 
ter my daughter Theresa who had to let go her dad to 
sea for three months. 
226 
Remarks 
Acknowledgements 
Previously, four Laevipilina species were considered 
to be valid (Urgorri et al. 2005); all are characterized 
by their small sizes (2-3 mm) and their (nearly) 
smooth and fragile, moderately elevated Shells. The 
soft parts of the specimen examined herein closely 
resemble previous descriptions of Laevipilina antarc- 
tica by Waren & Hain (1992) and Schaefer & Hasz- 
prunar (1996), especially with regard to the poorly 
developed postoral tentacles and the presence of 5 
pairs of gills. Its shell, however, with a height/length 
relation of 0.4 is less depressed than that of the 
holotype of L. antarctica (0.24) and those of other 
recently collected and measured specimens of L. ant- 
arctica (0.29-0.32; see Schrödl et al. 2006). The apex 
of L. antarctica is rather stout ('"globular") and does 
not project the anterior shell border (Waren & Hain 
1992, Schrödl et al. 2006), while being more pointed 
and clearly surpassing anteriorly in L. theresae, spec. 
nov. The only congener with similar shell propor- 
tions (see comparison by Urgorri et al. 2005) and a 
(slightly) projecting apex is L. rolani Waren & Bou- 
chet, 1990, from off north western Spain; however, 
this species clearly differs in having 15-20 digitiform 
postoral tentacles (see Waren & Bouchet 1990). 
A second, somewhat damaged specimen assigned 
to L. rolani by Urgorri & Troncoso (1994), however, 
has an apex that does not surpass the anterior shell 
margin and no postoral tentacles could be detected. 
Laevipilina theresae differs from any known congeners 
due to the presence of two unique concentric swell- 
ings at the base of the apex. 
Interestingly, L. theresae shows the same brown 
dots in the head region and along the foot and man- 
tle edges (but not on the gills) as documented for 
Irving L. antarctica (see Waren & Hain 1992: fig. 19) 
and still present (but faded) in a preserved abyssal 
specimen (Schrödl et al. 2006). In L. antarctica, such 
brown dots appear to correspond with symbiotic 
bacteria associated to the microvillar border and 
aggregated into special epidermal bacteriocytes 
described by Haszprunar et al. (1995). Thus, the 
presence of bacteria can be presumed for L. theresae 
as well, and will be substantiated by ultrastructural 
study in the future. Revealing the exact function of 
such symbiotic bacteria and confirming their poten- 
tial occurrence in further Laevipilina species with 
dark spots along the mantle margin, e.g. L. rolani 
and L. cachuchensis Urgorri, Garcia-Alvarez & Luque, 
2005, might significantly contribute to understand 
the ecology of still "living fossil" monoplacopho- 
rans. 
My gratitude goes to Wolf Arntz (AWI) for letting me 
participate at the EASIZ III "autumn" expedition to 
Antarctica. Anne-Nina Loerz (NIWA) did a great job 
driving the EBS under heavy storm condition. Thanks 
to Jens Bohn (ZSM) and Ole Ziemer for help and mental 
support during sorting innumerable sand samples. 
Gerhard Haszprunar (ZSM) is especially thanked for 
directing my attention to these fascinating animals and 
for reading the typescript. 
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