生物学概要

作者: 加林 B. 拉斯本(Galen B. Rathbun)

鸟类与哺乳动物学部门,加利福尼亚州科学院


Phylogeny
中文

发展史

在哺乳动物里,很少会有像象鼩(qú)这样,在系谱归属的问题上拥有如此丰富的被误解的历史。
一直以来,人们认为象鼩与鼩鼱、刺猬和鼹鼠有密切关系并将其归属于食虫类,直至十九世纪中晚期,大部分的象鼩物种才被西方的科学家首次发现并加以描述。
从那以后,人们逐渐意识到它们与其他现存的任何一种哺乳动物并没有特别密切的关系,导致生物学家又错误地将它们与有蹄类、灵长类和兔形目联系在一起。
随着近代分子技术在研究进化关系过程中的使用,除了传统的形态学方法,已经证实象鼩代表着一个古老的单源非洲物种。 目前大多数的生物学家将象鼩归属到一个新的种群中,即非洲兽总目(Afrotheria),包括一些其他独特的非洲种群和分支。 非洲兽总目包括:非洲象、海牛、蹄兔、土豚(非洲食蚁兽)、象鼩、黄金鼹鼠和马达加斯加刺猬。
(Hedges 2001; Springer et al. 2004; Seiffert 2007).

Few mammals have had a more colorful history of misunderstood ancestry than the elephant-shrews, or sengis. Most species were first described by Western scientists in the mid to late 19th century, when they were considered closely related to true shrews, hedgehogs, and moles in the order Insectivora. Since then, there has been an increasing realization that they are not closely related to any other group of living mammals, resulting in biologists mistakenly associating them with ungulates, primates, and rabbits. The recent use of molecular techniques to study evolutionary relationships, in addition to the more traditional morphological methods, has confirmed that elephant-shrews represent an ancient monophyletic African radiation. Most biologists currently include the elephant-shrews in a new supercohort, the Afrotheria, which encompasses several other distinctive African groups or clades. These include elephants, sea cows, and hyraxes (the Paenungulata); the aardvark and elephant-shrews, and the golden-moles and tenrecs (Hedges 2001; Springer et al. 2004; Seiffert 2007).

原文链接(original link)

金臀象鼩

英文名:Golden-rumped sengi

学名:Rhynchocyon chrysopygus

Taxonomy
中文

分类学

现存象鼩有20个种类,虽然可能会增加一些新的种类描述(Rathbun 2009; Andanje et al. 2010),但它们的分类几乎是明确的(Corbet and Hanks 1968; Rovero, Rathbun, et al., 2008; Smit et al. 2008; Dumbacher et al. 2014)
所有现存的象鼩种类都在同一个科下,每个科下有两个亚科。
巨型象鼩有4个属;
软毛象鼩有4个属;
岩象鼩属(Petrodromus)是单形的;
巨泡象鼩属(Macroscelides)有3个种类;
象鼩属(Elephantulus)包含10个种类;
北非象鼩E. rozeti (Dumbacher et al., 2016)在中新世(大约2300万年前)时期更多样化,当时还有另外的4个科存在(Holroyd 2010)。 北非象鼩最新发现的化石标本也证实了这个观点。(Grossman and Holroyd 2009; Tabuce et al., 2012)
一些已经灭绝的象鼩被发现拥有与现存蹄兔非常相似的齿列,因此最初被描述为蹄兔。(Patterson 1965, Butler 1995)
现在"sengis(桑吉)"这个常用名字被许多生物学家使用来替代"elephant-shrew(象鼩)",试图把食虫目象鼩科(Macroscelidea)从劳亚食虫目中真正的鼩鼱(鼩鼱科Family Soricidae)分离出来。。

象鼩是非洲特有的物种,它们分布在除了非洲西部和广阔的沙哈拉之外的整个非洲大陆。非洲南部和东部是多样化的中心。大多种类集中在非洲南部和东部。(Corbet and Hanks 1968; Rathbun 2009)
短耳象鼩(Macroscelides)只在非洲西南部被发现,种类数目最多的象鼩分布在非洲南部,其次是非洲东部。
东非象鼩(Rhynchocyon)仅存在于非洲东部和中部。
岩象鼩(Petrodromus)分布得最为广泛。
北非象鼩(Petrosaltatorrozeti)仅在非洲大陆的西北边缘被发现,沙哈拉沙漠将它们和其他种类的象鼩隔开了。

The 20 living species of sengis are well-defined, and their taxonomy is considered nearly definitive (Corbet and Hanks 1968; Rovero, Rathbun, et al., 2008; Smit et al. 2008; Dumbacher et al. 2014), although a few additional new species might be described (Rathbun 2009; Andanje et al. 2010). All living species are in a single family with two subfamilies. The giant elephant-shrews include the genus Rhynchocyon with four species, and the soft-furred elephant-shrews include four genera. Petrodromus is monospecific, Macroscelides has three species, and Elephantulus contains 10 species. The genus Petrosaltator has been created for E. rozeti (Dumbacher et al., 2016) Elephant-shrews were much more diverse during the Miocene period (about 23 million years ago), when an additional four families existed (Holroyd 2010). New fossil forms are also being described (Grossman and Holroyd 2009; Tabuce et al., 2012). Some extinct forms had herbivorous-style teeth that were so similar to the dentition found in living hyraxes that they were first described as hyraxes (Patterson 1965, Butler 1995). The common name "sengi" is being used in place of elephant-shrew by many biologists to try and disassociate the Macroscelidea from the true shrews (family Soricidae) in the order Eulipotyphla (Insectivora).

Sengis are restricted to Africa, and are distributed throughout the continent with the exception of western Africa and the vast Sahara region (Corbet and Hanks 1968; Rathbun 2009). Southern and eastern Africa are centers of diversity. Macroscelides is only found in southwestern Africa, and the greatest number of Elephantulus species occur in southern Africa, followed by eastern Africa. Rhynchocyon only occurs in central and eastern Africa. Petrodromus is among the most widespread. Petrosaltatorrozeti is found only along the northwestern edge of the continent, separated from all other sengis by the Sahara.

原文链接(original link)

赤象鼩

英文名:Face-washing rufous sengi

学名:Elephantulus rufescens

Morphology
中文

形态特征

东非象鼩(Rhynchocyon)是象鼩中是体型最大和色彩最斑斓的。(详见相册)。
成年象鼩个体重为350-700克,头部/身体到尾部的长度最长分别可达31厘米和25厘米。
软毛类的象鼩有着类似的身体比例,但体重的区间为25克(短耳象鼩)到200克(岩象鼩)不等。
象鼩属(Elephantulus)通常为50-60克。
体型最小的是褐足象鼩。(Corbet and Hanks 1968)
大部分的象鼩都是小窝生产并且天性早熟,除了东非象鼩(Rhynchocyon)的幼仔需要哺育一段时间。(Rathbun 1979, Neal 1995)
它们细长的骨架非常适合游走活动。(Evans 1942)
《象鼩尾巴》这篇文章里对象鼩提供了一些更详尽的特征描述。
相对较长的消化道包括盲肠。(Spinks and Perrin, 1995)
生殖道的几个特征是不同的,包括发情周期、多排卵 (Horst 1946, Tripp 1971)
腹部睾丸及阴茎结构。(Woodall 1995)

Rhynchocyon includes the largest and most colorful sengis (see Photographic Gallery). Adults weigh 350-700 g, with head/body and tail lengths up to 310 mm and 250 mm, respectively. The soft-furred species have similar body proportions, but range from about 25 g for Macroscelides to about 200 g for Petrodromus. Species of Elephantulus are 50-60 g. The smaller species are shades of brown and gray (Corbet and Hanks 1968). Most sengi species are born precocial in small litters, although Rhynchocyon young are more altricial (Rathbun 1979, Neal 1995). The long limb bones are adapted for cursorial locomotion (Evans 1942). Some features of sengi tails provide insights into their biology. The relatively long digestive tract includes a caecum (Spinks and Perrin, 1995). Several features of the reproductive tract are distinctive, including the estrus cycle, polyovulation (Horst 1946, Tripp 1971), abdominal testes, and the structure of the penis (Woodall 1995).

原文链接(original link)
Physiology
中文

生理学

象鼩有着和大部分哺乳动物类似的代谢率。然而其中的一些物种能够改变它们的生理机能以适应极端环境 (Perrin 1995a)。 例如有些物种在遭遇低温时会出现生理机能放缓(Lovegrove et al. 2001)。 它们的消化生理机能与其他小型食虫类哺乳动物非常相似(Woodall and Currie 1989),尽管它们可能有着食草类的祖先。

Sengi metabolic rates are typical of most mammals of similar size. However, several species are able to alter their physiology to meet environmental extremes (Perrin 1995a). For example, some species exhibit torpor when they encounter low temperatures (Lovegrove et al. 2001). Their digestive physiology is similar to that of other insectivorous small mammals (Woodall and Currie 1989), despite their likely herbivorous ancestry.

原文链接(original link)

赤象鼩绘画

学名:Elephantulus rufescens

Ecology
中文

生态学

东非象鼩和岩象鼩的分布,主要局限在低地和山地森林和茂密的林地,而象鼩属和巨象鼩在更干燥的低地也会被发现,例如热带草原、灌木丛林地、岩石岩层和沙漠地区(Rathbun 2009)。
几乎在所有情况下,象鼩跟其他小型哺乳动物相比,它们的分布密度低(FitzGibbon 1995, Perrin 1995b)。
在低纬度地区,象鼩的繁殖是持续的,但在高纬度地区,它们的繁殖率是季节性的(Neal 1995)。
所有的象鼩都会捕食无脊椎动物,不过大部分的软毛类的物种还会以小野果,种子和绿色植物作为补充食物(Rathbun 1979, Kerley 1995)。
蛇、猛禽和食肉动物被认为是象鼩的天敌。象鼩是多种的寄生虫的宿主(Fourie et al. 1995)。

Rhynchoycon and Petrodromus are largely confined to lowland and montane forests and dense woodlands, while Elephantulus and Macroscelides are found in more arid lowlands, such as savannahs, scrublands, rocky outcrops, and deserts (Rathbun 2009). In nearly all cases, sengis are found in low densities compared to many other small mammals (FitzGibbon 1995, Perrin 1995b). At low latitudes reproduction is continuous, but at higher latitudes it is seasonal (Neal 1995). All sengis prey on invertebrates, although most soft-furred species supplement this diet with small fruits, seeds, and green plant matter (Rathbun 1979, Kerley 1995). Snakes, raptors, and carnivores are known predators of sengis. A wide variety of parasites are hosted by macroscelids (Fourie et al. 1995).

原文链接(original link)
Behavior
中文

行为

对四种典型象鼩的实地研究已经完成(Sauer 1973, Rathbun 1979, FitzGibbon 1995; Schubert et al. 2009; Oxenham and Perrin 2009)。
最近的实地研究表明,象鼩实行一夫一妻制,对于入侵者,它们采取针对性别的共同守护领地(雄性对战雄性,雌性对战雌性),不过这种观点并不一定适用于所有的种类(Rathbun and Dumbacher, 2014)。
大部分的软毛类动物都经常在黄昏或清晨活动,少部分活动在白天和夜晚进行,但巨象鼩非常特殊,它们只在白天活动。
象鼩有着非常发达的视觉、听觉和嗅觉。大多数的象鼩会用它们的肛周,胸骨和尾下的汗腺去标记它们的领地。
象鼩通常不会发声,但大部分的象鼩在焦虑时会频繁的跺脚或者用尾巴击打地面。
大多数软毛类动物会在其他动物巢穴基础之上打洞,或者自己打洞,东非象鼩会用落叶在森林的地面上筑巢。
部分种类的象鼩会用落叶维护复杂的路径系统,甚至有好几种象鼩会有专用的庇护习惯,例如一些巨大岩石的缝隙或者在灌木丛底部有相对暴露的斑点。

Field studies of representatives of four genera have been completed (Sauer 1973, Rathbun 1979, FitzGibbon 1995; Schubert et al. 2009; Oxenham and Perrin 2009). Monogamous pairs defend congruent territories sex-specifically (males vs. males and females vs. females), although this view may not be true for all species, given recent field studies (Rathbun and Dumbacher, 2014). The giant sengis are strictly diurnal, while the soft-furred species are often crepuscular, with some activity during both day and night. Sengis have well-developed senses of sight, hearing, and smell. Most scent mark their territories with perianal, sternal, subcaudal, or foot glands. Although vocalizations are not common, many species frequently foot drum or tail slap the substrate in stressful situations. Rhynchocyon builds leaf nests on the forest floor, while most soft-furred species use burrows of other species, or construct their own. Some species maintain complicated trail systems through leaf-litter, and several have specialized sheltering habits, such as rock crevices in boulder fields, or relatively exposed spots on runs at the base of bushes.

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Husbandry
中文

驯养

在过去的20多年里,随着对象鼩习性的了解越来越多,已经成功的针对几种软毛象鼩的实现了驯养和繁殖。此项成功为圈养动物的研究提供了更多的可持续性研究(Perrin 1995b; Olbricht 2008)。
尽管Rhynchocyon比较难以圈养,但是最近已经可以在圈养的条件下进行繁殖。
只有Petrodromus在圈养的条件下不会繁殖(Tripp 1971, Nicoll and Rathbun 1990),尽管它们相对来比较容易维护。

In the past 20 years, with increasing knowledge of their natural history, several soft-furred sengis have been successfully kept and bred in captivity. These successes have resulted in increased research on captive animals (Perrin 1995b; Olbricht 2008). Although Rhynchocyon is difficult to maintain, it has recently been bred in captivity. Only Petrodromus has not reproduced in captivity (Tripp 1971, Nicoll and Rathbun 1990), even though it is relatively easy to maintain.

原文链接(original link)

四指象鼩

英文名:Four-toed sengi

学名:Petrodromus tetradactylus

Conservation
中文

物种保护

在2016 IUCN给出的红色濒危物种名单上,20种的象鼩被认为是“关注度低”,其他3种Elephantulus被列为“资料缺乏”和 2种巨型象鼩处在受威胁的状态。
金臀象鼩(Rhynchocyon chrysopygus)处在“濒危”状态。
灰脸象鼩(R. udzungwensis)为“渐危”状态。
虽然checkered sengi (R. cirnei) 和 black and rufous sengi (R. petersi)象鼩已经被列入“无危动物”,但这仅仅是因为归类的协议不够灵活的结果。
所有象鼩的现状都处在受威胁的状态因为它们所依赖的深林正在受到林木砍伐和农业发展。
在某些地区象鼩作为食物被猎杀也是一个问题。

On the 2016 IUCN Red List of mammals, most of the 19 sengis are considered "Least Concern", but three species of Elephantulus are listed as "Data Deficient" and two species of giant sengis are at risk. The golden-rumped sengi (Rhynchocyon chrysopygus) is "endangered" and the gray-faced sengi (R. udzungwensis) is "vulnerable". Although the checkered sengi (R. cirnei) and black and rufous sengi (R. petersi) have been down-listed to "least concern", which is the result of inflexibility in the listing protocols. The status of all Rhynchocyon are of concern because they occur in restricted or fragmented forest habitats (Nicoll and Rathbun 1990) that are being heavily impacted by logging practices and clearing for agricultural and urban development (Rathbun and Kyalo 2000). Subsistence hunting for food may also be a problem in some areas.

原文链接(original link)
Summary
中文

总结

对象鼩这个物种生物特性更详尽的描述最近已经出版了(Rathbun 2009),化石的形式可以在 (Holroyd 2010)中找到。
更多关于象鼩的更详尽的描述,可以在《Handbook of the Mammals of the World - Volume 8》这本书中找到。

A more detailed summary of the biology of extant sengis has been recently published (Rathbun 2009), and a review of fossil forms can be found in (Holroyd 2010). A more comprehensive review of sengi natural history can be found in Heritage, S. 2018. Macroscelidea. Pp. 206-234 in Wilson, D.E. and R. A. Mittermeier (eds.). Handbook of the Mammals of the World, Volume 8, Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona, Spain.

原文链接(original link)
Literature Cited

文献引用

下方列出了一些关于象鼩的更为重要的文献引用,包括一些课题的评论。 更多的引用请查询相关文献

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