1. Testes size and sperm production (Rory, Emily, Hilary) 2. Strategic allocation of sperm/Sperm quality and male fertility (Nadia, Moira, Mimi, Morghen) 3. Evolution of sperm size and speed (skip variation in sperm morphology) (Lauren F., Madisen, Simone) 4. Seminal fluid proteins: the neglected weaponry/The evolution of sfps (Stephanie, Cindy, Kristin) 5. Strategic adjustments in seminal fluid composition (Lauren N, Siri, Emma, Dana) 6. Future directions (Caitlin, Sarah, May, Nora)

1. Testes Size and Sperm Production Consequently, increases in the level of sperm competition are expected to select for increased investment in testicular tissue. There is now taxonomically widespread evidence that sperm production increases with the level of sperm competition, both across and within species. The accumulating evidence that relative testes size increases with the level of sperm competition has led to the widespread acceptance of the role of sperm competition in shaping testes size.

My testes get bigger when there’s more sperm competition!

2. Strategic Allocation of Sperm/Sperm quality and male fertility Within a species, therefore, males are expected to adjust how they allocate sperm during a given mating, depending on the reproductive returns expected for their investment, which will depend on female quality and male perceptions of sperm competition levels For externally fertilizing species, there is little evidence that sperm morphology impacts fertilization success under either noncompetitive or competitive fertilization conditions. Faster swimming sperm appear to be competitively superior under noncompetitive and competitive fertilizations in a number of species and in both internal and external fertilizing species, despite the fundamental differences in the fertilization environments. Trade-offs between sperm number and size influence competitive fertilization success.

I’m bigger and faster, so I have a greater chance of fertilizing the egg. There are more of us! We have a greater chance of fertilizing the egg! *The type of sperm a male produces depends on the level of competition and quality of the female.

Strategic allocation & Sperm quality and male fertility I’m giving her the best of my sperm! content/uploads/2009/02/ruby-the-chihuahua.jpg

 Sperm competition has alternatively been argued to influence sperm size in one of two ways. Under conditions where males gain a reproductive advantage by inseminating large numbers of sperm, and assuming that sperm number trade-offs against sperm size, increases in the levels of sperm competition are thought to favor the production of smaller sperm  First, comparative studies in mammals, fishes, and birds have found that species experiencing greater levels of sperm competition have faster swimming and more motile sperm than species where sperm competition is relaxed or absent  …evolutionary changes in mating behavior (and thus the level of sperm competition) occurred before evolutionary changes in sperm size and speed 3. EVOLUTION OF SPERM SIZE AND SPEED

HIGH SPERM COMPETITION FINISH

4. Seminal Fluid Proteins “Seminal fluid proteins (sfps) play a role in the nourishment, protection, capacitation, and motility of sperm within the female reproductive tract and should therefore be expected to contribute to a male’s fertilization success” “Here, protein secretions from the male accessory glands contribute to the seminal fluid and have been found to play major roles in the movement of sperm through and storage in the female reproductive tract, the competitive fertilization success of a male’s sperm, the future receptivity of females to remating, and female investment in ovi-position” “Seminal fluid productivity and function are expected to evolve in response to sperm competition.

Sperm interacting with sfp and egg Figure 2. Mechanisms of sperm–egg interaction. tACE1 and ADAM3 are dispensable factors for the binding of sperm to the zona pellucida, whereas tACE3 and IZUMO1 play important roles in the fusion of gametes to sperm. ADAM: a disintegrin and metalloprotease; ZP: zona pellucida; tACE1: testis angiotensin-converting enzyme 1; tACE3: testis angiotensin-converting enzyme 3.

5. Adjustments in Seminal Fluid Composition Seminal fluid proteins play an important role in nourishment, protection, capacitation, and motility of sperm in the reproductive tract. Adjustments in composition are made based on sperm competition and female mate quality. Seminal fluid composition is tailored to each individual mating event. This is important because the production of seminal fluid is more costly than the production of sperm themselves.

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6. Future Directions ● “We argue that it is time to begin to consider the ejaculate as an integrated functional unit and to assess the fitness of whole ejaculates in a multivariate analytical framework.” ● “Sperm competition thus appears to favor the evolution of fertilization competency. Future studies, both within and between species, that focus on the fertilization process itself will be of great interest.” ● “We believe that modern genomic approaches such as these will not only enhance our understanding of the evolutionary consequences of sperm competition for ejaculate form and function but will also provide us with the knowledge of what makes a male fertile, knowledge that can be brought to bare on real-world problems of male fertility and infertility.”

Sperm length Chemistry Male fertility Sperm Wars Gene competency Sperm speed