A hemipenis (plural hemipenes) is one of a pair of intromittent organs of male squamates (snakes, lizards and worm lizards).[1][2][3] Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. They come in a variety of shapes, depending on species, with ornamentation, such as spines or hooks. The female homologue is the hemiclitoris.
Hemipenes can be examined on a living snake or lizard by gently squeezing on the tail and massaging towards the vent, which is the cloacal opening on the underside of the tail. This will cause the hemipenis to evert out of the body. However, this method can also make it difficult to identify the sex of a dead specimen if it is damaged or dry.
lizard lock sex position
The lock-and-key mechanism or hypothesis is the idea that genital morphology has evolved to maintain reproductive isolation between species, by ensuring that mating can only occur between a male and female of the same species. The idea was first postulated in 1844 by French entomologist, Leon Dufour, who observed the diversity of genital morphology among Dipteran flies.[10] It is thought that the physiological differences between species prevents hybridization. The genital lock-and-key mechanism can operate in two ways: by the direct prevention of copulation and insemination due to physical incompatibilities, or by a sensory lock-and-key that induce behavioral responses that disrupt mating attempts.[11][12] This mechanism is found across the animal kingdom, from Lepidoptera to Squamata.
In snakes and lizards, morphological differences in the reproductive organs are believed to exist to help the male copulate with the female. Spikes and hooks are thought to assist the male in fixing the hemipenis in place during mating, and are made specifically compatible to the female of the species. For example, species with branched hemipenes have females with branched cloacas, and species with many spikes have females with thicker cloacal walls, compared to those of species with males having little or no spines. This huge variety among the reproductive organs of squamata is of interest to taxonomists, as it may be able to shed light on evolutionary relationships among reptiles.[9]
Often times, female snakes and lizards also have the ability to control whether they get pregnant immediately after mating or not, to account for the fact that the ideal time for mating may not translate to the most optimal time for ovulation and gestation. Consequently, females can store sperm internally[14] for as long as five years, or possibly longer.[15] This phenomenon is known as cryptic female choice, as the physiological mechanisms making this possible are hidden within the body, and the female has the ability to influence when egg fertilization occurs.
Most research in the area of squamata reproductive organs has focused on the male hemipenis, but recent studies have investigated the homologous paired structures in females, dubbed "hemiclitores". Researchers first investigated females of Phymaturus and Liolaemus lizards and discovered a structure that was previously undescribed. The hemiclitoris was observed to be smaller than a hemipenis,[17] and the organs were consistently observed in the lizards in the study. While the specific functions are yet to be identified, this study brings attention to a squamata apomorphy that will likely continue to be investigated in detail. A 2022 study showed that snakes also have hemiclitores of widely differing structure.[18]
Security procedures such as desk services, security patrols, evening lock up, and restricted-access plans are regularly reviewed and open to changes and improvements. Students are expected to observe lock-up procedures and cooperate with programs designed to maintain the security of residents. Propping of entrance doors is prohibited. The Colorado State University Police Department (491-6425 or 911) is on duty 24 hours per day, seven days a week.
Sleeping/Alarm Clock Where will your alarm(s) be placed? What about the snooze button? What happens if someone is sleeping through the alarm? How much sleep do you need nightly? How will your class schedules affect your sleeping habits? What time do you go to bed? What time do you need to get up? How will you work through differences in sleeping patterns? Will you use a fan or keep windows open?
Personal Belongings Will you share or borrow any personal items? Which items cannot be used by anyone other than the owner? Set clear expectations for the use of these items: Is permission is required to use them? Is maintenance is required? If you purchase items together, how will you split the bill, and who will own them at the end of the year? If you do share some belongings, make sure they are accessible to all roommates and are not hidden or locked away.
Abstract:The extant reptiles are one of the most diverse clades among terrestrial vertebrates and one of a few groups with instances of parthenogenesis. Due to the hybrid origin of parthenogenetic species, reference genomes of the parental species as well as of the parthenogenetic progeny are indispensable to explore the genetic foundations of parthenogenetic reproduction. Here, we report on the first genome assembly of rock lizard Darevskia valentini, a paternal species for several parthenogenetic lineages. The novel genome was used in the reconstruction of the comprehensive phylogeny of Squamata inferred independently from 7369 trees of single-copy orthologs and a supermatrix of 378 conserved proteins. We also investigated Hox clusters, the loci that are often regarded as playing an important role in the speciation of animal groups with drastically diverse morphology. We demonstrated that Hox clusters of D. valentini are invaded with transposons and contain the HoxC1 gene that has been considered to be lost in the amniote ancestor. This study provides confirmation for previous works and releases new genomic data that will contribute to future discoveries on the mechanisms of parthenogenesis as well as support comparative studies among reptiles.Keywords: genome sequencing; de novo genome assembly; rock lizard; parthenogenesis; Lacertidae; Hox genes; microRNA
Study design and supervision: J.R.M., D.G.M., and N.J.G. Writing: J.R.M., D.G.M., L.U., S.Pa., V.L.G., and N.J.G. Long-read sequencing: C.G.B., J.R.M., E.S.B., V.L.G., and D.G.M. Transcriptome analysis: E.S.B., V.L.G., and D.G.M. Protein analysis: L.U., J.R.M., D.G.M., and N.J.G. Data handling, deposition, and analysis: S.Pa., D.G.M., C.G.B., D.P.D., E.S.B., V.L.G., P.M.H., S.Pr., A.N.E., J.R.M., and N.J.G.
And on and on it went. Trucks arrived, trucks left, and all the while the lizards plied their trade, moving between the rigs and the restaurant like it was a routine that played out the same way night after night after night.
Locks may not be tampered with in any way that interferes with the use of keys or prevents locking/unlocking of doors. Locks may not be added to any doors in the unit, nor may they be changed or replaced except by authorized housing personnel. No door may be propped open; a possible $50 charge will be assessed for a propped door. The use of a dead bolt in the lock position in order to keep the door propped open is prohibited. Allowing individuals access into a housing facility through an unauthorized or locked entrance is prohibited. (See the Police and Regulations Section for more information).
Nails, tacks, or any adhesive products that will do damage to surfaces is not permitted. Painting, wallpapering, and paneling of a unit by residents is strictly prohibited. Posters, pictures, and other decorative objects may be attached to interior surfaces of a unit with the understanding that the resident of the unit will be held financially responsible for any resulting damages. Shelves or other items are not to be attached to walls or ceilings. Carpet may not be affixed to the floor surface. Cinder blocks are not permitted to lift or adjust beds, desks, chairs, tables, couches, or other furniture. Residents will be charged for the repair of any damages from the violation of these policies.
Windows are to remain closed at all times when air conditioning is on and functioning properly. Students are encouraged to keep windows closed to ensure efficient / safe operation of student housing facilities. Housing staff may elect to permanently seal windows if deemed necessary to maintain the efficient / safe operation of the facility. Windows are not to be used as entrance or exit to units. Signs, pictures, banners, empty bottles, and similar objects may not be displayed in windows so that they block or impede access, exit, or view to the unit in time of emergency. This is to ensure the health and safety of students and rescue personnel. Students are not permitted to remove their window screens.
Residents will be permitted three courtesy lockouts without charge. Upon the fourth lockout, and every subsequent lockout, a $65 fee will be issued to the resident and a lock change may be conducted for security precautions. Residents should keep their room key and Panther ID Card with them at all times. For specific procedures for lockout, contact your Front Desk.
The cost of replacing a lost key, re-keying the lock core and issuing additional replacement keys for your roommate(s) is nonrefundable. The required amount is billable through Housing/ Residence Life and Dining Services and payable at the Cashier window located in the Ellington Building. Report your lost key immediately to the Office of Housing/Residence Life and Dining Service; failure to do so jeopardizes your security and the security of others. APSU ID cards to access your building are replaceable through University Facilities for a charge. University Facilities is in Room 207 of the Morgan University Center.
Each residence hall is supervised directly by a trained residence hall director (RHD). The RHD coordinates the administrative and community activities of a specific residence hall. RHD offices are located in each residence hall. Although the RHD is there to assist you whenever you need it, the staff member with whom you will have the most direct contact is the resident assistant (RA). This person, also trained for his/her position, lives on your floor or on a nearby floor, is available to assist you with residence hall or apartment living and serves as an informational resource to Austin Peay. The RA is there to ensure community living standards are maintained and to work with all residents to plan informative and enjoyable activities. 2ff7e9595c
コメント