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New Mexico whiptail lizard

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New Mexico whiptail lizard
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Scientific Classification
Binomial Name

Cnemidophorus neomexicanus[1]

Tiny whiptail.jpg
Size of a Whiptail

New Mexico whiptail lizard is a species of lizard known by the scientific name Cnemidophorus neomexicanus. They are perhaps best known as an all female species that relies strictly on auto-reproduction (parthenogenesis, which is the development of an egg without fertilization). They get their name from their long, whiplike tails.[2]

It is found in the Southern United States (Arizona and New Mexico) and parts of northern Mexico (Chihuahua)[3]. They were made the official state reptile of New Mexico in 2003.[2] Prior to 1998, the whiptail lizard had not been known to occur in Arizona. Discovery of this unique and small population occurred near the Puerco Ruins at Petrified Forest National Park [4].

Body Design

Tail is longer than body

This is a fairly small reptile (approximately <82 mm or 3.25" from snout to vent), slim trunk, brownish to black coloration. The lizard has a long, narrow, blue to gray-green, tipped tail; a slender, pointed snout. The body is marked with seven yellow or cream colored stripes; and numerous light spots. The Arizona whiptail only has a wavy, mid-dorsal stripe. The body is covered with small granular scales. Arizona Whiptail Lizard expert, T.C. Brennan (2015) reported, "The scales on the tail are larger, keeled, and rectangular" The scales on the belly are large, smooth, and rectangular. The scales on top of the head are large, smooth, and plate-like." [4].

Life Cycle

Adult Whiptail

The New Mexico Whiptail lizard cannot sexually reproduce because they are all females.[5] [3] [4] [2]. However, these lizards, simulate reproduction by way of pseudocopulation (which is when they act out sexual intercourse). The whiptails of the genus Aspidocelis [6] [7] are lizards, created by a hybridization of the western whiptail (A. Inornatus) [4] [2] and the little striped whiptail (A. tigris). Generally, crossbred species (like the mule) are typically sterile. However, the New Mexico Whiptail reproduces by a complex series of events (that appear like cloning) where it's eggs require no fertilization, and its offspring are nearly a genetic duplicate of the mother.[5] [6] [7] An interesting fact that is a part of the process: two females will act out having sex as if one was a male. This is believed to increase the fertility of these lizards as it assists in producing more eggs than in females who don’t go through this act. The lizard who acts in the traditional female role assumes an inferior position while the other female lizard who assumes a superior position (hence the term pseudocopulation). Remarkably, the Whiptail lizards who assume the "female role" end up producing larger eggs than the lizard acting out the male role.[5] This hybrid species, reproduces by laying eggs that have never encountered any sperm [6] [7] . No external fertilization occurs [3] [4] as a result of two closely related species mated to create asexual hybrids. [6] [7] . This phenomenon shouldn’t work . Previously reptile researchers believed that the unfertilized eggs and hatchlings were clones of their mothers [3] [4] [2]. However, this has now been disproved. The internal self- fertilization that does occur, does NOT produce perfect offspring clones. Recent research by doctoral student Aracely Lutes at Baumann Lab demonstrated that the New Mexico Whiptail lizard produces two times the number of chromosomes as other types of Whiptail lizards which mate normally. Lutes discovered that, this occurs as a result of a " process of recombination of these chromosomes, somewhat similar to what happens in normal male/female pairings, which then produces genetically diverse offspring."[5]

Generally, sperm and egg cells are created through a process called meiosis, (where a cell’s chromosomes are copied before the cell divides twice). This produces four daughter cells, meaning that the egg cells only contain half the amount of chromosomes of other cells. The joining of egg and sperm, that contain half the genes, this helps balance out the chromosomes, to create the next generation [6][7]. But the Whiptails are unique because they begin the process with two times as many chromosomes. Lutes, proved that these all-female whiptails have a slightly different type of meiosis. They double their chromosomes two times initially in the process, this results in the making of eight copies for each chromosome. In the normal two cycles of cell division, those copies are separated two each among the four daughter cells [6] [7]. She measured the amount of DNA in the egg cells of two closely related whiptails, just prior to the first cycle of meiosis. She discovered in this stage, the chromosomes of the asexual checkered whiptail (A. tesselatus) make up two times as much as the sexual Texan spotted whiptail (A. gularis), despite the fact that both types have similarly sized genes. Microscopically, Lutes counted two times the usual number of chromosomes in the egg cells of the checkered whiptails [6] [7].

Surprisingly enough, possessing eight sets of chromosomes instead of four is an easier process; as they do not require a lot for this to occur. This is the result of two processes. First, a cell can double its DNA but fail to divide into two, or two cells can fuse together [6] [7].

Ecology

Little White Whiptail (Aspidoscelis gypsi)

In Arizona, the New Mexico Whiptail lizard population lives on a shrubby and sandy floodplain (within the Plains Grassland community). They are also found in and around the Puerco Ruins at Petrified Forest National Park, elevation approximately 5,500'or 1,675 m) [4] .

The New Mexico Whiptail Lizard's diet mainly consists of insects such as termites, beetles, moths, grasshoppers, ants, and a variety of larvae and similar insects. It also consumes organic material found by digging in the soil under bushes and around the bases of rocks, and other surface debris. [3] [4]

Protection from Predators

The alertness, agility and speed of this lizard, help it outsmart predators such as roadrunners, thrashers, snakes ,and Gila monsters. These tiny sneaky lizards can sprint up to 15 miles per hour(as fast as a roadrunner). Whiptail lizards are known for escaping capture by sacrificing their tails. Their tail is designed, when grasped, to break off along a fracture plane in the vertebrae. The dismembered tail wriggles violently, which startles and distracts the predator while the lizard dashes to safety.[2]

Video

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 wikimedia.org. cnemidiphorus Wikispecies. Web. last-update october 21, 2013.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 New Mexico Whiptail Lizard State Symbols USA. Web. Accessed February 4, 2015. Unknown Author.
  3. 3.0 3.1 3.2 3.3 3.4 New Mexico whiptail “Wikipedia”. Web. Accessed January 27, 2015. Unknown Author.
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Brennan, Thomas. New Mexico Whiptail The Reptiles and Amphibians of Arizona. Web. January 27, 2015.
  5. 5.0 5.1 5.2 5.3 Hiskey, D. New Mexico Whiptail Lizards are All Females Today I Found Out. Web. Accessed February 4, 2015.
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Young, Edward.Extra chromosomes allow all-female lizards to reproduce without males Discover Magazine. Web. Accessed January 27, 2015.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 . Lutes, Aracely; Neaves William; Baumann Diana; Wiegraebe Winfried; Baumann Peter. Sister chromosome pairing maintains heterozygosity in parthenogenetic lizards “Nature”. Web. Accessed January 27, 2015.