THE TERES COMPLEX

by E. L. Heiman * )

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This article was published in the September 2001 (Issue #4) issue of the journal "TRITON" by the Israel Malacological Society.. I present it below with small changes. Ed.

Copyright by the Israel Malacological Society
All Rights Reserved

 

Introduction:

Blasicrura teres (Gmelin, 1791) is a rather variable species widely distributed in the Indo-Pacific region from the Red Sea, East Africa and South Africa to Panama. Scientists consider that it belongs to the "teres complex," which includes: Blasicrura teres (Gmelin, 1791), Blasicrura subteres (Weinkauff, 1881), Blasicrura latior (Melvill, 1888), Blasicrura rashleighana (Melvill, 1888), Blasicrura burgessi (Kay, 1981) and Blasicrura alisonae (Burgess, 1983). All members of this complex except B. rashleighana are superficially similar to B. teres and sometimes confused with it. Their taxonomic status is discussed below.

Several of the B. teres shell characters could be used for analyzing the variability of the teres complex.

The shell shape can be cylindrical to sub-cylindrical (Fig. 1) or elliptical (Fig.2). The former is recognized when a shell is clearly elongated and its sides are more or less straight.

A shell with a pronounced labial callus (callus deposited on the outer lip) is illustrated in Fig. 3. When a callus is deposited on the margin related to the base (columellar callus) it is better recognized when viewed from the posterior end as shown in Fig. 4. In B. rashleighana both labial and columellar callus can be observed as is shown in #5 and easily checked by palpation.

The number and size of the dark marginal dots (Fig. 6) as well as the dark dots on the base are sometimes used as a differentiating character. Below, dots up to 1 mm are considered small and dots, which are >1 mm are considered large.

The teres complex. Table 1 summarizes the opinion of various malacologists about the different taxa of the teres complex.

B. subteres is endemic to Polynesia. Shells of subteres are considerably smaller and narrower than the shells of other taxa of the complex, possess more numerous labial and especially columellar teeth and their shape is cylindrical.

The Schilders' formula for subteres (21.47.26.28) is substantially different from that of other taxa of the complex. Still shells of subteres are so outwardly similar to small shells of teres that Schilder & Schilder, 1971 considered subteres a subspecies of teres. Several other authors treated subteres as a valid species. Anyhow, the Polynesian subteres populations are easily separable from other taxa of the complex.

Both subspecies of B. rashleighana, B. r. rashleighana (Melvill, 1888) and B. r. eunota (Taylor, 1916) can be easily distinguished as having a depressed shell with labral and columellar callus (Fig. 5), dark small dots on both sides of the base and a reduced number of teeth. The formula for these subspecies reads: 16.62.19.19 for r. rashleighana and 24.66.19.17 for r. eunota.

The opinion of malacologists about B. latior, B. burgessi and B. alisonae is far from being in harmony.

The rather complicated taxonomic history of latior is worth tracing:
Melvill, 1888 described latior as a variety of C. tabescens (Dillwyn, 1817) in the following way: "(a) latior (var. nov.). Cf. Reeve, Conch. Icon., pl.xivf.66a. A pyriform shell broader and more stunted than the type, with brighter coloration, and very distinct dorsolateral spots. A handsome and rare form, almost sub-specific." Melvill, referred to a picture of a broad shell from a work by Reeve, 1846 (f. 66a) as an illustration to his description of latior. This picture can be seen in Fig.7. In the picture one can see a broad teres shell with small marginal dots.

Reeve added the following comment to this picture: "I have figured a curious broad growth of this species from Mr. Cuming's collection, because it is one of extremely rare occurrences." We can assume that the above mentioned specimen was not from the Hawaiian Islands since H. Cuming did not visit this area on his journeys.

Burgess, 1977 published pictures of shells from Melvill's collection, which he assumed are type specimens of latior and rashleighana, and concluded that "Cypraea latior is properly a synonym of C. teres." (Burgess, 1969).
But in Burgess, 1970 latior is mentioned as a valid species!

Dillwyn, 1817, in his description of Cypraea tabescens, referred to illustrations 296 and 297 appearing in an old work by Martini, 1769. One of them (Fig. 297) can be seen in Fig.8. In this picture one can see a shell of elliptical shape with small marginal dots. Later Cypraea tabescens came to be considered a synonym of B. teres by all authors.

According to Schilder (1965a) Melvill's holotype of latior is lost. Burgess apparently was unfamiliar with this work by F. A. Schilder. He compared in both, the British Museum, in London and the National Museum of Wales, in Cardiff, "type" of C. latior and stated that "C. latior should be deleted from the list of valid species." Later, after C. burgessi was described, Burgess confessed his mistake with Melvill's types (Burgess, 1985:149) and considered latior a synonym of burgessi.

Lorenz & Hubert (1993, 2000) perhaps did not pay attention to the above mentioned mistake of Burgess and the difference in shell characters of latior and burgessi (columellar callus) and considered these two species identical. Hence latior, in their opinion, has priority and they consider burgessi a synonym of latior. Synonym, according to ICZN, is "each of two or more names of the same rank used to denote the same taxonomic taxon". B .latior and B. burgessi are apparently not the same taxonomic taxon.

Bradner & Kay, 1996 treated latior as a valid species though they used the term "species" loosely to include cowries that some authors call species, subspecies, or in some cases even forms".

We can conclude now: latior was described as a variety of teres. An important shell character - the columellar callus - is not mentioned in its original description and is clearly not seen in the picture from Reeve's work. It is apparently a variety with a wide shell, which can be found in teres populations, and as such latior should remain a synonym of teres at least until Reeve's collection in the British Museum is studied. This study can answer a question whether a shell, which was used as an original for the above mentioned illustration (f. 66a) in Reeve's work, can be identified and used as a neotype of Cypraea latior.Melvill, 1888.

B. burgessi was described as a species endemic to Hawaiian Islands. The following shell features differentiate burgessi from teres (Kay, 1981):

These two shell characters are important for separating burgessi from teres. Without them differentiating between burgessi, teres and alisonae could be possible only on the basis of animal characteristics.

Strangely enough I did not see in literature of the last 30 years any picture of burgessi distinctly showing its columellar callus (similar to Fig. 4). All illustrations show base, dorsal or side views of the shell. I obtained several shells of burgessi from dealers and collectors. All of them have a prominent labial callus with a step typical for teres and did not have a prominent columellar callus even remotely similar to Fig. 4. Their base and the columellar margin are callused more than usual but the same degree of base callousness is not rare in shells from many populations of teres- see for example fig.8 Plate 9 in Salvat & Rives, 1990. Perhaps burgessi is so rare that dealers and collectors do not have enough experience to diagnose it correctly.

Mr. R. Dayle (http://www.cowrys.org) illustrated several views (including the posterior one) of an unusual cowry within the teres complex at his web site. He collected this specimen in Hawaii and forwarded it to C. M. Burgess for examination. Dr. Burgess studied the living animal and the shell and concluded that it is Cypraea burgessi. On the mentioned posterior view one can see a very prominent labial callus typical for B. teres. The columellar callus is not visible.

Cypraea alisonae Burgess, 1983 was described on the basis of color pictures of living animals. Shell characters mentioned in the description of this species can not be used, in my opinion, as delimiting qualities in comparing alisonae with teres. B. alisonae was described as an additional species in the teres complex. Burgess, 1983 mentioned a rather wide range of distribution of this species: Hawaii, American Samoa, W. Australia and even hinted at Philippines, Okinawa and East Africa. Indeed, Drivas & Jay, 1987 figured (Plate 11, Fig.3) a shell from the teres complex as B. alisonae. If all that is correct there are two species: B. teres and B. alisonae having practically identical shells and area of habitat. Collectors and cowry students can not differentiate between them until cowry biology of these species is better understood.

 


Conclusion:

Three of five taxa within the teres complex: B. teres, B. subteres, and B. rashleighana are well separable conchologically.
B alisonae is not separable from B. teres conchologically.
B. burgessi remains a mystery until more authentic conchological material will be available.
Meanwhile I feel that B. burgessi is not separable conchologically from B. teres and B. alisonae.
B. latior is a variety of B. teres, which can be characterized by a wide shell of elliptical shape, and dark and often large dots on the shell margins. Intermediate forms of each of the mentioned characters of this variety can be traced in several teres populations in the world.
B. subteres is endemic to Polynesia and B. burgessi and B. rashleighana are endemic to Hawaii and perhaps near-by Pacific islands.
It seems that the only species of the teres complex, which should be used for comparison when one studies teres populations in the Indian Ocean and the Western Pacific region is B. teres.

 

Discussion:

Shells are one of many elements of cowry biology.
Scientists considered during last 250 years that knowing shell characteristics is enough for delimiting species and subspecies.
When species having very similar, almost indistinguishable shell (sibling species) were discovered this situation turned out to be more complicated and confused.
Is it possible that sibling species have completely similar shells or we still do not know how to distinguish them?
Are shells of B. teres, B. burgessi and B. alisonae identical?
Are B. teres and B. alisonae inhabit the same area from Hawaii Is. to East Africa?
These questions can be answered at least partly

 

Table 1
Taxa belonging to the "teres complex" according to different authors

author
species
teres
subteres
latior
rashlei-
ghana
burgessi
alisonae
             

the formula
27.54.24.23
21.47.26.28
     
Schilder & Schilder, 1938
valid
valid
var. of teres
valid
   

Allan, 1956
valid
valid
syn. of teres
valid
   

Burgess, 1962
valid
valid
syn. of rashleighana
valid
   

Schilder, 1965b
valid
subsp. of teres
ssp. of rashleighana
valid
   
Cate, 1966 valid valid valid
valid
valid
syn. of teres
valid
   

Burgess, 1969
valid
valid
syn. of teres
valid
   

Burgess , 1970
valid
valid
valid sp.
valid
   
Schilder & Schilder, 1971
valid
subsp.
of teres
ssp. of rashleighana
valid
   

Burgess, 1977
valid
valid sp.
syn. of teres
valid
   
Kay, 1981
valid
valid
syn. of burgessi
valid
valid
 
Burgess, 1985
valid
valid
syn. of burgessi
valid
valid
valid
Cossignani &Passamonti, 1991
valid
valid
valid
valid
valid
syn. of teres
Raybaudi, 1992
valid
valid
ssp.. of teres
valid
subsp. of teres
subsp. of teres
Emerson &Chaney, 1995
valid
   
valid
 
valid
Bradner & Kay, 1996
valid
valid
valid
valid
valid
valid
Lorenz & Hubert, 2000
valid
valid
valid
valid
syn. of latior
syn. of teres

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Fig.1 A subcylindrical shell Fig.
2 An elliptical shell Fig.

3 Labial callus
     
Fig. 4 Columellar callus

Back
2nd Reference

Fig. 5 C. rashleighana Fig
Fig. 6 Marginal dots


Fig. 7 C. latior.
Fig. 8 C. tabescens

 

References:

Allan, J. 1956. Cowry shells of world seas. 170 pp. Georgian House, Melbourne.
Brander, H. & Kay, E. A. 1996 An Atlas of cowrie radulae (Mollusca: Gastropoda: Cypraeoidea: Cypraeidae). The Festivus, 27 Supplement, 179 pp.
Burgess, C. M. 1983. Another new Cypraea in the teres complex (Gastropoda: Cypraeaidae). Venus 42 (2):183 - 191.
Burgess, C. M. 1969. Discussion of Cypraea rashleighana Melvill, C. teres Gmelin C. latior Melvill, and C. subteres Weinkauff. HSN 9:4-5.
Burgess, C. M. 1970. The living cowries. A. S. Barnes and Company, Inc. Cranbury, New Jersey.
Burgess, C. M. 1977. The "new" cowries. HSN, 12:1-8.
Burgess, C. M. 1985. Cowries of the World. 289 pp. Cape Town: Gordon Verhoef, Seacomber Publications Cate, C. N. 1966. Has Cypraea latior Melvill, 1888 been correctly identified? HSN1:6-7.
Cossignani, V. & Passamonti, M. Cypraeidae. Systematic catalogue synonyms and values. 136 pp. Mostra Mondiale mlacologia, Cupra Maritima, Ancona, Italy.
Dance, S. P. 1986. A history of shell collecting. 265 pp. Brill & Backhuys, Leiden.
Dillwyn, L. W. 1817. A descriptive catalogue of recent shells, arranged according to the Linnean method; with particular attention to the synonymy. London. P. 463.
Drivas, J. & Jay, M. 1987. Coquillages de la Reunion et de l'ile Maurice. Delaxhaux & Niestle S.A., editeurs, Neuchatel (Suisse)-Paris.
Emerson, W. K & Chaney, H. W. 1995 A zoogeographic review of the Cypraeidae (Mollusca:Gastropoda) occuring in the Eastern Pacific Ocean. The Veliger 38(1):8-21.
Kay, E. A. 1981. A new species of Cypraea from the Hawaiian Islands. Venus 40 (3):111 -122.
Lorenz, Jr.F. & Hubert, A. 1993. A Guide to worldwide Cowries. 571 pp. Verlag Christa Hemmen Wiesbaden, Germany.
Lorenz, Jr.F. & Hubert, A. 2000. A Guide to worldwide Cowries. 584 pp. ConchBooks, Hackenheim, Germany.
Martini, F.H.W. 1769.Neues Syst. Conch.Cabinet. Kapitel. VII, pp. 302-408. Nurnberg.
Melvill, J. C. 1888. A survey of the genus Cypraea (Linne), its nomenclature, geographical distribution, and distinctive affinities: with description of two new species, and several varieties. Memoirs and Proceedings of the Manchester Literary and philosophical Society (4.),1: 184-252.
Reeve, L. 1846 Monograph of the genus Cypraea. London.
Salva, B. & Rives, C. 1990. Coquillages de Tahiti. 190 pp. Delaxhaux & Niestle S.A., Neuchatel (Suisse)-Paris.
Schilder, F. A. 1965a. The type localities of living Cypraeidae. Malakologische Abhandlungen Staatliches Museum fur Tierkunde in DresdenSchilder 2(14):193-233.
Schilder, F. A. 1965b. The geographical distribution of cowries. The Veliger, 7(3):171- 183.
Schilder, F.A. & Schilder, M. 1938. Prodrome of a Monograph on Living Cypraeidae. Proc.of the Malocological Society of London, 23: 119-231.
Schilder, M. & Schilder, F. A. 1971. A catalogue of living and fossil cowries Institut Royal des sciences naturelles de Belgique, 246 pp.
Schilder, M. 1967. Length, breadth, and dentition in living cowries. The Veliger 9(4):369-376

 


*) E. L. Heiman P.O.Box 664 Rehovot 76100 Israel E-mail: heimel@netvision.net.il

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