Meramecia (Submeramecia) diamphida Cook

Fernández, Hugo R., 2002, Interstitial water mites of Argentina: Omartacarus Cook (Omartacaridae) and Meramecia Cook (Limnesiidae) (Acari: Hydrachnidia), Zootaxa 73, pp. 1-6 : 4-5

Meramecia (Submeramecia) diamphida Cook

Meramecia (Submeramecia) diamphida Cook, 1980 . 65.­ Ferradas & Mattoni, 1999. 114. ­ Fernández, 2001. 22.

Female: Entire dorsal shield 535 in length; anterior plate of the dorsal shield 143 in length, 208 in width; posterior plate of dorsal shield 381 in length, 241 in width.

Specimens examined: Argentina, San Luis. Departamento Pringles. Rosario River, 900 masl, 4 Km of the La Toma town. 1 female ( A29029 IML), in leg. M. Peralta.

Remarks: At the present the subgenus Submeramecia includes only M. diamphida , known from Argentina. Recently Fernández (2001) indicated the notable separation among localities of M. diamphida in Argentina (Tucuman, Cordoba, Misiones). This species seems equivalent in distribution to M. (Meramecia) ocularis Cook from United States ( Smith and Cook, 1994). This species is widespread throughout the Appalachians from Alabama to New Brunswick. This aspect of water mite distribution is accepted as common in subterranean forms (Di Sabatino et al. 2000). However this generalized assumption of wide distributions among meiofaunal taxa has been recently questioned (Rundle et al. 2000).

Meramecia (Parameramecia) saltensis Fernández : ad nov. comb.

Meramecia saltensis Fernández, 2001 . Physis, 58 (134­135): 22.

Recently a new species of Meramecia was described based on one female specimen collected in Salta province, Argentina ( Fernández, 2001). After the study of the original description ( Smith and Cook, 1994) of the subgenus Parameramecia from Arizona ( U.S.A.) and comparison of M. saltensis with M. (P.) multipora Smith and Cook, I conclude that the Argentine species fits well within the subgenus description.

The inclusion of the new species from Salta requires a revision of the diagnosis of the subgenus Parameramecia . Acetabula number should be expanded as follows: 4­8 in the anterior group, 4­7 in the middle group, and 5­11 in the posterior group.

A good character for differentiating members of the subgenera Meramecia and Parameramecia is the size of the peg like seta on P­II, which is much more robust in Parameramecia species.

In contrast, the ventral P­IV setae seem to be variable in length among Parameramecia species. Likewise, in Meramecia saltensis the thick ventral setae on tibiae of legs I are located distally, while in M. multipora they are located near the middle of the segment. Thus, the location of these setae is not a good character for differentiating between subgenera as proposed Smith and Cook (1994). Finally, the legs of M. saltensis have setiferous blade­like spines as do members of the Meramecia subgenus. The spines of this type are absent in other Parameramecia species, being autopomorphic for M. multipora .

Remarks: The geographic distribution of Parameramecia is disjunct ( United States and Argentina). However, this distribution may be a result of the absence of collections in the Neotropics ( Cook, 1980).