Update Date: February 10, 2009

Animal Diversity and Evolution
Hybrid Male Sterility between the Fresh- and Brackish-water Types of Ninespine Stickleback Pungitius pungitius (Pisces, Gasterosteidae)
Authors: Hiroshi Takahashi, Terumi Nagai and Akira Goto
Zoological Science 22 (1): 35-40
Reason for recommendation: Through hybridization experiments between brackish-water and freshwater ecotypes of the Japanese bar-redfin stickleback, this study revealed that exclusively male hybrids are invariably sterile, and that this sex-dependent hybrid breakdown is caused by abnormalities in spermatogenesis. Sticklebacks are globally renowned as a research model for studying cases of parallel speciation driven by rapidly divergent ecotypes. This study is highly novel in discovering sex-dependent hybrid breakdown in sticklebacks for the first time and confirming its mechanism, and it represents a research report of profound significance by introducing new perspectives into the study of the processes through which rapid parallel evolution is achieved.

Cell Biology
Impaired Flagellar Regeneration Due to Uncoordinated Expression of Two Divergent Actin Genes in Chlamydomonas
Author: Takako Kato-Minoura
Zoological Science 22 (5):571-577
Reason for recommendation: Chlamydomonas has two actin-related proteins, but the function of NAP was previously unclear. This high-value paper demonstrates the importance of NAP in flagellar regeneration by revealing that TF5 cells, in which a 5’UTR-NAP+CrA chimeric gene was introduced into the ida5 mutant, exhibit abnormalities during flagellar regeneration, and that the expression level of CrA increases during the early stage of flagellar regeneration.

Developmental Biology
Expression Patterns of a twist-Related Gene in Embryos of the Spider Achaearanea tepidariorum Reveal Divergent Aspects of Mesoderm Development in the Fly and Spider
Authors: Kazunori Yamazaki, Yasuko Akiyama-Oda and Hiroki Oda
Zoological Science Vol. 22 (2): 177-185
Reason for recommendation: This paper isolates the mesoderm-related genes Twist and snail from the spider species Achaearanea tepidariorum, observes their expression during development, and compares and discusses them with the expression patterns and functions known in Drosophila. Despite being homologous genes, there are major differences in the cell lineages, patterns, and temporal changes of their expression in spiders compared to those in Drosophila. This demonstrates the bold reuse of genes in evolution, the evolution of gene regulation as a background to this, and consequently, the diversification of early developmental patterns as its output. Supported by appropriate schemes showing spider development and comparisons with insects, as well as reliable data, this paper provides important insights in the field of EvoDevo.

Endocrinology
Title: Involvement of Drinking and Intestinal Sodium Absorption in Hyponatremic Effect of Atrial Natriuretic Peptide in Seawater Eels
Authors: Takehiro Tsukada, J. Clifford Rankin and Yoshio Takei
Zoological Science 22 (1):77-85
Reason for recommendation: Atrial natriuretic peptide (ANP) is a hormone that reduces sodium in the body and promotes seawater adaptation. In this paper, using the euryhaline teleost eel, the authors demonstrated that ANP promotes seawater adaptation by suppressing drinking behavior and inhibiting sodium absorption from the intestine, thereby lowering serum sodium concentrations. Particularly noteworthy, in a manner rare in recent studies, is the quantitative analysis of sodium dynamics in conscious animals achieved through skillful surgery.