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Cryptic Female Choice
Cryptic female choice is a form of mate choice which occurs both in pre- and post-copulatory circumstances in which females of certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not. It occurs in internally fertilizing species and involves differential use of sperm by females when sperm are available in the reproductive tract. The present understanding of cryptic female choice is largely thanks to the extensive research and analysis done by William G. Eberhard. The term ‘cryptic’ according to Eberhard is meant to describe an internal and thereby hidden choice some female organisms are able to make following insemination with regards to sperm selection. In male species with intromittent organs, during copulation (zoology), copulation, a male inserts his reproductive organ into that of a female so as to inseminate her with his genetic material ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mate Choice
Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior.Bateson, Paul Patrick Gordon. "Mate Choice." Mate Choice, Cambridge University Press, 1985 In other words, before an animal engages with a potential mate, they first evaluate various aspects of that mate which are indicative of quality—such as the resources or phenotypes they have—and evaluate whether or not those particular Phenotypic trait, trait(s) are somehow beneficial to them. The evaluation will then incur a response of some sort. These mechanisms are a part of evolutionary change because they operate in a way that causes the qualities that are desired in a mate to be more frequently passed on to each generation over time. For example, if female peacocks desire mates who have a colourful plumage, then this trait will increase in frequency over time as male peacocks with a colourful ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyspermy
In biology, polyspermy describes the Fertilisation, fertilization of an Ovum, egg by more than one Spermatozoon, sperm. Ploidy, Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy, on the other hand, contains three or more copies of each chromosome—one from the egg and one each from multiple sperm. Usually, the result is an unviable zygote. This may occur because sperm are too efficient at reaching and fertilizing eggs due to the selective pressures of sperm competition. Such a situation is often deleterious to the female: in other words, the male–male competition among sperm spills over to create sexual conflict. Pathological polyspermy and the blocks In the classical case (at least from the historical human perspective), monospermic fertilization is the norm. For monospermic organisms, polyspermy is a detrimental process where eggs are incorrectly fertilized. It causes the formation of multiple microtubule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harpobittacus
''Harpobittacus'' is a genus of hangingfly of the family Bittacidae found in Australia. Habitat and Development Species of ''Harpobittacus'' are found in moist environments as larvae and adults. The adults are active from October to February and lay their eggs in the summer. They undergo metamorphosis, beginning with the female laying her cube–shaped eggs in the soil. The larva pupate underground, remaining moist to prevent desiccation and once they hatch, they feed on soil, mosses, dead insects, and leaf litter. Adults normally display black bodies with orange markings and have claws at the ends of their long legs. They catch prey by hanging from vegetation with their forelegs and capturing small insects that get close with their hind-legs. They feed by holding the insect in their mouth, sucking out the soft tissues and juices and dropping the empty chitinous shells. Mating ''Harpobittacus'' species exhibit some less common mating strategies, including pheromone secre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Idiosepius Paradoxus
''Idiosepius paradoxus'', also known as the northern pygmy squid, is a species of pygmy squid native to the western Pacific Ocean. This species can be found inhabiting shallow, inshore waters around central China, South Korea, and Japan.Reid, A. 2005. Family Idiosepiidae. ''In:'' P. Jereb & C.F.E. Roper, eds. ''Cephalopods of the world. An annotated and illustrated catalogue of species known to date. Volume 1. Chambered nautiluses and sepioids (Nautilidae, Sepiidae, Sepiolidae, Sepiadariidae, Idiosepiidae and Spirulidae)''. FAO Species Catalogue for Fishery Purposes. No. 4, Vol. 1. Rome, FAO. pp. 208–210. Appearance This species is part of the smallest known squid genus, growing only to in mantle length. Females tend to be larger than males, and the presence of nidamental glands for secretion of egg jelly differentiates them from males. Males can be identified by the presence of a singular white testis found posteriorly in the body. Both sexes have a unique organ found on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruce Effect
The Bruce effect, or pregnancy block, is the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect was first noted in 1959 by Hilda M. Bruce, and has primarily been studied in laboratory mice (''Mus musculus''). In mice, pregnancy can only be terminated prior to embryo implantation, but other species will interrupt even a late-term pregnancy. The Bruce effect is also observed in deer-mice, meadow voles, collared lemmings, and it has also been proposed, but not confirmed, in other non-rodent species such as lions and geladas. Discovery In an experiment published in 1959, zoologist Hilda Bruce of the National Institute for Medical Research in London housed pregnant mice with male mice that were not the father of the carried embryo. As a result, the rate of miscarriages increased, followed by mating with the new male. No increased rate of miscarriages occurred when pregnant mice were paired with c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theropithecus Gelada
The gelada (''Theropithecus gelada'', , ), sometimes called the bleeding-heart monkey or the gelada baboon, is a species of Old World monkey found only in the Ethiopian Highlands, living at elevations of above sea level. It is the only living member of the genus ''Theropithecus'', a name derived from the Ancient Greek, Greek root words for "beast-ape" (θηρο-πίθηκος : thēro-píthēkos). Like its close relatives in genus ''Papio'', the baboons, it is largely terrestrial animal, terrestrial, spending much of its time foraging in grasslands, with grasses comprising up to 90% of its diet. It has buff to dark brown hair with a dark face and pale eyelids. Adult males have longer hair on their backs and a conspicuous bright red patch of skin shaped like an hourglass on their chests. Females also have a bare patch of skin but it is less pronounced, except during Estrous cycle, estrus, when it brightens and exhibits a "necklace" of fluid-filled blisters. Males average and fema ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pisaura Mirabilis
The nursery web spider ''Pisaura mirabilis'' is a spider species of the family Pisauridae. Description Striking characteristics of ''Pisaura mirabilis'' are its long legs (the fourth pair being the longest) and its slender abdomen ( opisthosoma). The male is between 10 and 13 mm, while the female is 12 to 15 mm. After final ecdysis, the male spiders weigh on average 54 mg and females 68 mg. The prosoma ( cephalothorax) is variable in color, ranging from light to reddish brown and from gray to black. A lighter stripe is visible down the middle of the prosoma. The opisthosoma (abdomen) is long and narrow and tapered towards the rear end. The female spiders has a dark patch ( epigyne) on the underside of her abdomen that includes the copulatory organs. Male genital openings can be found at the same location, but remain inconspicuous. Patterning and coloration varies due to polymorphism. These patterns, which can be caused by hair and pigments, change wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatophore
A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores may additionally contain nourishment for the female, in which case it is called a nuptial gift, as in the instance of bush crickets. In the case of the toxic moth '' Utetheisa ornatrix'', the spermatophore includes sperm, nutrients, and pyrrolizidine alkaloids which prevent predation because it is poisonous to most organisms. However, in some species such as the Edith's checkerspot butterfly, the "gift" provides little nutrient value. The weight of the spermatophore transferred at mating has little effect on female reproductive output. Arthropods Spermatophores are the norm in arachnid Arachnids are arthro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelymorpha Alternans
''Chelymorpha alternans'', the neotropical tortoise beetle, is a species of leaf beetle in the family Chrysomelidae and the Cassidinae subfamily. Its name is derived from its body shape and patterning. The first half of its name, '' Chelymorpha'', means 'turtle/tortoise form' while the second part, ''alternans,'' means 'alternating'. ''C. alternans'' is best known for demonstrating color polymorphism on its pronotum and elytra; these polymorphisms can vary from individual to individual. There are five different phenotypes which often leads to misidentification with a close beetle relative, '' Chelymorpha cribraria''. Description Female adult neotropical tortoise beetles are usually around 11–12 mm in length and 4–5 mm in width. Males tend to be smaller and more circular than females, usually around 5–8 mm in length and 3–5 mm in width. In terms of larvae, 1st instar larvae are approximately 2 mm in length, growing an average of 1 mm until the 3rd instar. Finally, 4t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassidinae
The Cassidinae (tortoise and leaf-mining beetles) are a subfamily of the leaf beetles, or Chrysomelidae. The antennae arise close to each other and some members have the pronotal and elytral edges extended to the side and covering the legs so as to give them the common name of tortoise beetles. Some members, such as in the tribe Hispini, are notable for the spiny outgrowths to the pronotum and elytra. Description The "cassidoids" have a rounded outline with the edges of the pronotum and elytra expanded, spreading out to cover the legs and head. They are often colourful and metallic, with ornate sculpturing; a few species have the ability to change colour due to water movements within the translucent cuticle. All members of the subfamily have the mouthparts reduced into a cavity in the head capsule, the legs have four segmented tarsi. The hispoids have larvae that are ecological diverse as leaf miners or cryptic exophagous feeders, while the cassidoids feed freely externally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
