The study of Nicaraguan land snails is fragmentary. Since the year 1992 some 160 specimens of a small Opeaslike gastropod have been collected in Nicaragua that correspond to Baker's description of genus Pseudopeas (Dysopeas) with spirals extended to all whorls. The first site was at El Castillo on the San Juan River in Southern Nicaragua, among volcanic building blocks, dislodged from the castle ramparts (López, 1992). A second location was at the Isletas, a group of islands in Cocibolca (Nicaragua) Lake near the town of Granada and a third on the Campus of the URACCAN university by the town of Bluefields on the Caribbean coast (Table 1).

Collecting was done in humid surroundings, close to bodies of water among gravel and sandy soil, under stones or wood debris (López 1992; López & Pérez 1996, 1998; López, & Urcuyo, 2009). Surrounding soil was gathered in bags for later observation under a stereoscope (NIKON, SMZ-10A) to detect minute specimens and accompanying fauna. Live specimens were placed in 70% alcohol and soiled specimens cleansed in ultrasonic bath (MEDELCO, INC. MODEL MD5-115).

Lots recorded in ACCESS tables are numbered by two digits separated by a colon, the first digit for the year and the second for the order of sequence in that year. Thus, 92:02 is the second lot found in 1992. Each entry also contains the number and dimensions of specimens, location coordinates and date, as well as other details.

UCA Mollusk Collection (UCACM) contains 10 lots of Dysopeas sp. for a total of 160 specimens (Table 1).

Two voucher spms sent to LACM.

Previous mention: Pseudopeas sp. Two specimens, Isleta de Ken, Isletas de Granada (Pérez 1999).

Accompanying fauna at type locality: Lamellaxis micra, L. gracilis, Leptinaria lamellata, L. guatemalensis, Cecilioides consobrinus, Bulimulus corneus, Succinea hyalina, S. recisa, Miradiscops opal, Thysanophora crinita.

According to Pilsbry (1906) the presence of the characteristic spiral protoconch sculpture sufficiently determines his genus Pseudopeas.Baker's additional condition (1927) that the protoconch spiral sculpture extends over the remaining whorls also sufficiently determines his subgenus (P.) Dysopeas. The difference between the two is not a different protoconch sculpture, but only that in Dysopeas the characteristic spirals extend beyond the initial whorl onto the body whorls. And the reason why this protoconch spiral sculpture is necessary and sufficient for determination of the complex Pseudopeas/ Dysopeas is simply that no other known genus has it. Pilsbry himself (1906) mentions that although on some specimens of Paropeas, like P. achatinaceum, there are two or three very weak protoconch spirals, they are actually only folds between whorls and not sculpture as in Pseudopeas (Naggs, 1994).

It has been objected that to date no previous mention has been made of the complex Pseudopeas/Dysopeas in Mesoamerica. This would seem to be a good reason in favor of a recent genus extension, as here reported. However the extension might not be so recent if one fails to observe the characteristic nepionic sculpture. A revision of private and public collections may well reveal specimens of Pseudopeas mislabeled Opeas, Subulina, Spiraxis, or Lamellaxis.

The nepionic sculpture of the Pseudopeas viviparumMiller protoconch is described by its author (1879) as of one whorl "minutely decussate", and by Pilsbry (1906) as one and a half whorls with very delicate, close, striate spirals. Pilsbry adds (1906) that Pseudopeas has a protoconch of some two whorls "spirally striate" and figures P. saxatile (Morelet, 1885) from West Africa (Figure 2A) with typical apical sculpture of Pseudopeas, spiral and granulate. Although Pilsbry does not mention the granulation, it is clearly shown in his figure.

Baker (1927) figures Dysopeas translucidum protoconch (Figure 2B) and describes it as globose, of 2 to 2.5 convex whorls separated by a deep suture with a sculpture of very weak growth lines some 35 in number near the beginning of the second whorl.

Altogether, the descriptions and illustrations by Miller (1879), Putzeys (1899), Pilsbry (1906; Figure 1A, 2A) & Baker (1927; Figure 1B, 2B) accurately match the protoconch and shell sculpture and profile of the Nicaraguan specimens in the genus Pseudopeas.

Pseudopeas shares some sculpture traits and protoconch development with Spiraxidae like MicromenaBaker 1939, Rectaxis Baker 1926 and even with Lamellaxis gracilis, which might cause confusion. In Pilbry's opinion the spirally striated protoconch firmly determines the genus Pseudopeas, without need of further criteria such as dissection or radula study, described as 13-1-13 by Baker (1927). Additional reasons like dimensions, body sculpture pattern, profile and crystalline structure further distinguish the complex Pseudopeas/Dysopeas from these look-alikes, such as Spiraxis funibus (Figure 3B) and S. alvaradoi, both described from Guatemala by Goodrich & van der Schalie (1937), which are common and widely length, whereas Pseudopeas grow to 8 mm. Another difference is that Spiraxidae protoconch spirals are dissected by the diagonal ribs into individual chevron-shaped segments, very characteristic of these species (Figure 3B). In Pseudopeas the spirals are continuous, though slightly raised at intersections with ribs (Figure 3A), thin and weak in Spiraxidae, but thick, sturdy, porcelain-like in Pseudopeas and other Subulinidae. Crystal structure seen in small punctures or corroded areas of Dysopeas specimens reveals it is formed by three successive layers spread in Nicaragua. Other similar Spiraxidae in the subgenus Rectaxis Baker and Micromena (Baker, 1939) are also present in various localities.

One general difference between these small Spiraxidae and Pseudopeas is size, with Micromena barely reaching 3 mm and other Spiraxidae attaining 5 to 6 mm maximum of orthorhombic interlaced crystals (Figure 4) which determine the tough aragonite material of the shell (Callil & Mansur 2005), in contrast with the weaker structure of Spiraxidae and Subulinidae. But as mentioned, the most important and definitive discriminating trait is the characteristic nepionic sculpture, (Figure 2A, 2B), which is totally absent in Spiraxidae (Figure 3B), Lamellaxis, Opeas and all other recognized genera. Independently of protoconch sculpture presence or absence, its profile also discriminates the genus. In Pseudopeas, it is dome-like, whereas in Spiraxis it is bulbous.

Acknowledgements

We thank Mark and Lara G. McKaye for field assistance, and Wayne Arendt, Jorge Huete, Marvin Torrez and several anonymous reviewers. UCA authorities generously contributed to expenses in transportation and maintenance over the years.

References

Baker, B. (1927). The mollusca collected by the University of Michigan in Venezuela. Oc. Pap. Mus. Zool. 182:10 -12.

Baker, B. (1939). Micromena Baker. Nautilus 53: 11-14.

Callil, C. & Mansur, M. (2005). Ultrastructural analysis of the shells of Anodontites trapesialis (Lamarck) and Anodontites elongatus (Swaison) (Mollusca, Bivalvia, Etherioidea) from the Mato Grosso Pantanal Region, BrazilRev. Bras. Zool. 22: 3.

Goodrich, C. & van der Schalie, H. (1937)Mollusca of Petén and North Alta Vera Paz, Guatemala. University of Michigan, Museum of Zoology. Misc. Pub. 34: 23-24.

López, A. (1992). Shelling in Nicaragua's El Castillo. Hawaiian Shell News, 40:1,4.

López, A. & Pérez, M. (1996). Nuevos registros de gastrópodos advenedizos para la malacofauna continental de Nicaragua. Rev. Biol. Trop. 44: 302-303.

López, A. & Pérez, M. (1998). Nuevos registros de caracoles terrestres en Nicaragua. Rev. Biol. Trop . 46: 167-168.

López, A. & Urcuyo, J. (2009). Moluscos de Nicaragua IIGastrópodos. Araucaria, Managua, Nicaragua.

Miller, K. (1879). Opeas Viviparum. Mal.Blatt25:197.

Morelet, A. (1885). Coquilles terrestres et fluviatiles de l'Afrique équinoxiale. Journal de Conchyliologie 33: 20-33.

Naggs, F. (1994). The reproductive anatomy of Paropeas achatinaceum and a new concept of ParopeasJournal Moll. Stud60:175-191.

Pérez, M. (1999). Estudio Taxonómico y Biogeográfico Preliminar de la Malacofauna Continental. Continental (Mollusca: Gastrópoda) del Pacífico de Nicaragua, p. 260.

Pilsbry, H.A. (1906). Manual of Conchology, (2)18; (70):65-160, Taf. 11-20.

Putzeys. (1899). Diagnoses de quelques coquilles et d'un sousgenre nouveau provenant de l'Etat indépendant du Congo. Ann. Soc. Malac. Belg., Bull. 34: LV - LX.