隠れた多様性の発見：形態学的検討とミトコンドリア遺伝子解析で明らかにした新種のブラジル新熱帯地域産淡水エビ（Decapoda: Caridea: Palaemonidae）

Uncovering a hidden diversity: a new species of freshwater shrimp Macrobrachium (Decapoda: Caridea: Palaemonidae) from Neotropical region (Brazil) revealed by morphological review and mitochondrial genes analyses.

• Natalia Rossi
• Célio Magalhães
• Elis R Mesquita
• Fernando L Mantelatto

抄録

ブラジルのサンフランシスコ川流域に生息する淡水パラエモンエビが新種であることが判明した。しかし，m. veredensis sp. nov.は滑らかな甲羅を持ち，第二前脚部の棘突起が少ないのに対し，m. brasilienseは甲羅の前面に小さな棘突起があり，第二前脚部の掌には棘突起，棘突起，セタエがある。このような微妙な違いを持つ類似の形態にもかかわらず、DNA解析で明らかな遺伝的な違いが証明された。分子解析は、16S rDNAについては528塩基対（bp）の43の配列と、COI mtDNAについては581bpの新規配列を16個用いて行った。その結果、M. veredensis sp. nov.とM. brasilienseとの間のヌクレオチド分岐（16Sで7.0-8.5%、COIで11.8-12.5%）、系統的なトポロジーとハプロタイプネットワークの構成、サンフランシスコ川流域の固有種であることから、新分類群の認識を支持するものとなった。

A freshwater palaemonid shrimp from the São Francisco river basin in Brazil has been found to be a new species and is herein nominated as Macrobrachium veredensis sp. nov. It is morphologically similar to M. brasiliense (Heller, 1862), which is found in many rivers of South America. However, M. veredensis sp. nov. has a smooth carapace and few spinules on the second pereopods, while M. brasiliense has the anterolateral surface of the carapace with small spinules and the palm of the second pereopods with spines, spinules and setae. Despite their similar morphology with these subtle differences, the remarkable genetic different evidenced in DNA analysis. Molecular analyses were based on 43 sequences with 528 base pairs (bp) for 16S rDNA, and 16 new sequences with 581bp, without pseudogenes, for COI mtDNA. The nucleotide divergence between M. veredensis sp. nov. and M. brasiliense (7.0-8.5% for 16S and 11.8-12.5% for COI.), the phylogenetic topology and the haplotype network configuration and it is endemism to a region of the São Francisco river basin support the recognition of a new taxon.