Guido Pereira

Taxonomic Importance of the Frontal Appendage in the Genus Dendrocephalus (Anostraca: Thamnocephalidae)

ABSTRACT A morphological analysis of the frontal appendage of the genus Dendrocephalus (Anostraca: Thamnocephalidae) shows that the basic morphological pattern (number and arrangement of the branches) is constant, and diagnostic for the genus. The morphology of branches 2D/ 2A/2V should be used as the main characteristic in the diagnosis of the species. A reformulated diagnosis of this genus is included.

NEW SPECIES, CLADISTIC RELATIONSHIPS, AND BIOGEOGRAPHY OF THE GENUS FREDIUS (DECAPODA: BRACHYURA: PSEUDOTHELPHUSIDAE) FROM SOUTH AMERICA

ABSTRACT The taxonomy of the genus Fredius Pretzmann, 1967, is reviewed, and new taxa are described: Fredius adpressus, F. adpressus piaroensis, F. platyacanthus, and F. estevisi siapensis. The 8 species of this genus inhabit 4 major basins of different geological age in northern South America. The Orinoco basin is the oldest, followed by the Essequibo-Cuyuni basin. The lower Amazon basin, formed from Tertiary to Holocene by alluvionic deposition, is younger than these two. The Atlantic area, formed mainly by marine regressions, is the youngest. The phylogenetic relationships within Fredius, studied by means of a cladistic analysis, were compared with the relationships of these areas using Brooks parsimony analysis. The phylogenetic data fully agree with the area cladogram. The position of the ancestors within the area cladogram shows that most of them were present in a hypothetical major basin comprising the present Orinoco, Essequibo, and Cuyuni rivers, and that much of the evolution of the group occurred there. There is some ambiguity about the possible origin of 2 widespread species. The most parsimonious explanation for one of them is that it originated in the Atlantic drainage and then dispersed into the lower Amazon basin.

Assessment of the decapod crustacean diversity in the Guayana Shield region aiming at conservation decisions

The current state of knowledge of freshwater decapod crustacean diversity of the Guayana Shield Region is briefly assessed, based upon information gathered from the scientific literature as well as unpublished data from academic theses, technical reports, and carcinological collections. The decapod fauna of the region is presently known to include 64 species and subspecies within six families and 17 genera. Diversity by countries, basins, and rivers is listed, comments on endemic, rare or threatened species are made, and information about relevant taxonomic literature is presented. Seven priority areas for conservation actions concerning crustacean decapods are suggested and related to the 25 priority areas defined by the Fishes and Freshwater Working Group at the Guayana Shield Conservation Priority Setting Workshop, held at Paramaribo (Suriname) in April 2002.

Two New Species of Dendrocephalus (Anostraca: Thamnocephalidae) From Venezuela

ABSTRACT The new species Dendrocephalus venezolanus and Dendrocephalus affinis (Anostraca: Thamnocephalidae), collected in Venezuela, are described. The descriptions are based principally on the morphology of the frontal appendage typical of the genus. A differential diagnosis and photographs taken using the scanning electron microscope are included.

Phylogenetic Relationships in Some Species of the Genus Macrobrachium Based on Nucleotide Sequences of the Mitochondrial Gene Cytochrome Oxidase I

A phylogeny for four species of the freshwater prawn genus Macrobrachium (M. carcinus, M. olfersii,M. acanthurus and M. rosenbergu) based on the partial nucleotide sequence of the mitochondrial cytochrome c oxidase subunit I gene is presented. The results are consistent with previous studies based on morphological data.

The First Two Larval Stages of Two Freshwater Shrimps Genus Macrobrachium (Decapoda, Palaemonidae) Reared in the Laboratory, with a Discussion on the Significance of Abbreviated Development for the Radiation of the Genus

The description of the first two larval stages of Macrobrachium cortezi Rodriguez, 1982 and M. rodriguezi, Pereira, 1986, are presented for the first time. The origin and significance of abbreviated development in Macrobrachium is discussed.