Pneumothorax as a predatory goal for the sabertooth cat (<i>Smilodon fatalis</i>)

Smilodon fatalis was a large extinct felid distinguished by their two impressive maxillary canines and surprisingly low canine fracture rates. Previous theories regarding their attack strategy have suggested delivering damage by a bite with their maxillary canines. It has also been previously suggested that the canines could have been used to deliver a non-biting stab with an open jaw. It has been generally hypothesized that the attack was delivered to the neck of their large herbivore prey. Smilodon fatalis could have used their canines in a non-biting stab delivered with a closed jaw for the sole purpose of creating a pneumothorax. Creation of a pneumothorax would maximize immediate attack lethality, and minimize exposure of its canines to fracture.

基于线粒体16SrRNA基因序列的长江下游重要水体脆弱象鼻溞群体遗传结构分析

为了解长江下游地区10个水体脆弱象鼻溞群体的遗传结构,研究测定了脆弱象鼻溞(Bosmina fatalis)线粒体16SrRNA基因序列,结果显示,100个样本中共有8个变异位点,定义了9个单倍型,单倍型多样性(Hd=0.284)和核苷酸多样性(Nd=0.000 76)均较低。AMOVA分子变异分析结果表明,脆弱象鼻溞遗传分化主要来自群体内,占93.33%,群体间的变异低,占6.67%。Fst值统计检验表明,各水体之间遗传分化不显著。系统发育树和中介网络图说明脆弱象鼻溞单倍型间关系较近,未形成明显谱系地理格局。中性检验和错配分布结果说明脆弱象鼻溞出现过群体扩张现象。