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The acocil C. montezumae is a freshwater crayfish endemic to the Central Plateau of Mexico, but, in recent years, the natural population of this species has diminished considerably. In this work was investigated growth performance and feeding of this crayfish reared at high densities. A random block experimental design with two repetitions and three treatments (77, 154 and 231 crayfish/m2) was carried out. Organisms were fed every third day with 15% of their total biomass of shrimp commercial food with 25% of crude protein, and individual food consumption (IFC) was calculated. Significant differences (ANOVA, P < 0.05) were detected in final weight, absolute increase, relative rate of increase, instantaneous rate of increase, yield and survival rate between the densities, with those reared at a density of 77 organisms/m2 reaching the largest sizes. There were no-significant differences (P > 0.05) among treatments in terms of initial weight, specific growth rate and feed conversion l rate. [ABSTRACT FROM AUTHOR]

Nine species, including two new species of decapod crustaceans, are described from the Paleocene Rancho Nuevo Formation, collected from two localities of the Parras Basin, southeast Coahuila state, Mexico. The astacid Enoploclytia gardnerae (Rathbun, 1935) is represented by a pair of large chelae and one cephalothorax. An incomplete nephropid carapace is identified as Enoploclytia sp. Partial specimens of a callianassid and a pagurid are described. One partial carapace representing Linuparus wilcoxensis Rathbun, 1935 is described. A new raninid, Macroacaena venturai new species extends the genus into Mexico. Paraverrucoides alahamensis (Rathbun, 1935) is the most abundant species, followed by Tehuacana tehuacana Stenzel, 1944 and Viapinnixa perrilliatae new species. Taxonomic affinities of this assemblage confirm influence of the Mississippi Embayment, particularly from Paleocene stratigraphic units of Texas and Alabama. [ABSTRACT FROM AUTHOR]