In-pair copulation

Copulatory samples were collected either within established partnerships (> 1 month) (designated as In-Pair Copulations or IPCs) or outside of an established partnership (= Extra-Pair Copulations or EPCs). In this study, the following situations qualified... 

SPERM COMPETITION AND SPERM NUMBERS DURING IN-PAIR COPULATION... 

One of the first successes in the study of human sperm competition was the demonstration that the number of sperm in a man s ejaculate during In-Pair Copulation (IPC) with an established partner was a function of the risk of that partner already containing sperm from another man (Baker and Beilis 1989b). Later, it was shown that individual males made this adjustment from one IPC to the next (Baker and Beilis 1993a, 1995). 

Figure 4. The number of sperm inseminated during In-Pair Copulation (IPC) increases with the risk that the female contains sperm from another man. Risk of sperm competition is measured as the percent of time the couple have spent together since their last IPC (or the last 10 days, whichever is the shorter). Lower percent times together are associated with higher risks of sperm competition. Residual sperm numbers calculated from the parameters listed in Table 1 modified by exclusion of percent time together. All of the parameters listed are therefore statistically controlled (including hours since last ejaculation). Pseudo-replication of data is avoided by including only the first IPC inseminate per couple. Number of couples per data point as shown, F, 47 =5.7, P=0.022.

Extra-pair copulations (N=15) In pair copulations (N=49) t-value P (one-tailed)... 

Walsh, C.J., Wilhelm, S.I., Cameron-Macmillan, M.L. and Storey, A.E. (2006) Extra-pair copulations in common murres I a mate attraction strategy Behaviour 143, 1241-1262. 

During this relationship, the man will routinely inseminate his partner at more or less frequent intervals, depending on many factors. During this routine in-pair sexual activity, the risk of sperm competition will vary from one copulation to another, again depending on many factors. 

Parahemophilia is an autosomal recessive bleeding disorder characterized by a reduced plasma concentration of the Factor V blood copulation protein. Deficiency arises from a 12 base-pair deletion in the Factor V gene that impairs the secretion of Factor V by hep-atocytes and results in an abnormal accumulation of immunoreactive Factor V antigen in the cytoplasm. In which region of the Factor V gene would this mutation most likely be located ... 

Ouye and Butt 32) have recently shown that a stable sex attractant for males can be extracted from copulating pairs of pink boUworm moths [Pectinophora gossypiella (Saunders)], with ether or methylene chloride, and Allen and coworkers ) have reported the extraction of a potent sex attractant from the abdomens of female tobacco homworm moths [Protoparce sexta (Johannson) ] with these same solvents. The chemical nature of these attractants as well as that of the southern armyworm moth [Prodenta eridania (Cramer) ] is at present under investigation in U. S. Department of Agriculture laboratories. 

Figure 2. Panel A depicts the percent of pairs that copulated in each of the three treatment groups. Panel B depicts the means and standard errors for the primary intromission latency in the three treatment groups. There were no differences among groups in either the occurrence of copulation or the primary intromission latency.

At the time of the test, bedding was clean or had just been removed from other chambers where it had been soiled for several hours by at least two estrous females, or soiled for about 30 minutes by a pair of copulating rats. No noncontact erections were displayed in any of the tests. 

The test enclosure (77 by 74 by 30 cm) had two chambers separated from each other by a solid metal partition. The front chamber (45 by 74 cm) was connected to the rear chamber (32 by 74 cm) by a small opening (5 by 5 cm) to allow passage of the female vole. Males were tethered in the front chamber such that a female could interact with either male without physical interference from the opposing male. The rear chamber was a neutral chamber. Food and water were provided ad libitum to each male and in the rear chamber. A long photoperiod of 14L 10D and ambient temperature of 24 2°C was maintained throughout the experiment. Each trio of voles was monitored for 84 h. As the videotapes are reviewed, the duration of all physical contacts between a female and each stimulus male and occurrences of copulation are scored for hours 40 to 75, a time period when females are expected to have achieved estrous and to have pair-bonded. To date, we have scored data for seven females. 

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