Practical 5 Flashcards
Do Salmon (species from lab 5) have internal or external fertilisation?
External Fertilisation
Are Salmon semelparous or iteroparous?
These salmon were semelparous (although Atlantic salmon are iteroparous)
What are the advantages to being semelparous?
Larger clutch size, shorter generation times, higher chance of at least one individual surviving till adulthood. Put all their resources into mating.
What are the advantages to being iteroparous?
Less individuals born but they are stronger, parental care of offspring and eggs
In female dusky flathead (Platycephalus sp.) the gonads occupy the majority of the body cavity. What does this imply about the size and number of eggs?
Large number of small eggs
Why would you expect dusky flathead to have a distinct breeding season?
lots of eggs implies that a species is more likely to have a distinct breeding season
Is sperm storage likely dusky flathead?
There is no sperm storage in females for this species as they are external fertilisers.
Do male dusky flathead have an intromittent organ?
Males do not have intromittent organs as they do not need to perform internal fertilization.
What are some unusual aspects of seahorse reproduction?
Male gives birth (females deposits eggs in males pouch)
What is the level of reproductive investment in Seahorses?
Males have a high level of investment as they must carry the eggs around in a pouch and feed the eggs with both oxygen and nutrients via a system of capillaries.
What are the advantages of males looking after the eggs in seahorses?
Males are able to protect the developing offspring as the eggs are deposited in the pouch. All the young are then deposited in a single event meaning that there is a greater chance of survival immediately prior to release.
How does the male guppy achieve internal fertilisation?
The male guppy’s anal fin develops into a gonopodium (sexual organ) to transfer sperm into the female’s cloaca
How do the life histories of the guppy and the dusky flathead differ?
Dusky flathead has external fertilisation and larger clutch sizes proportional to the fish, while guppy has larger investment and smaller clutch sizes (going for larger survival rate
However guppy is more r-selected, as they mature faster and don’t live very long, while the flathead is k-selected due to growing large and other attributes, despite having many offspring. Therefore, guppy’s are also ovoviviparous.
How do sharks achieve internal fertilisation?
The male sharks have two claspers to anchor themselves to the female, and then transfer sperm pockets into the female through the clasper into the cloaca Claspers are an evolutionary hallmark for sharks, one of the first to develop internal fertilisation.
What is oviparity?
albumen and a horny outer shell are secreted by the nudimental gland in the oviduct to form an egg case. Vitellogenesis (the process of provisioning eggs) occurs, before they are ovulated with energy-rich supplies.
What is ovo-viviparity?
the eggs develop in the oviduct, with development fuelled predominantly from the egg yolk before hatching and birth occurs. Nutrients may be added during development via histotroph secretions from the uterus
What is viviparity?
the embryo develops with the direct provision of nutrients by a maternal-fetal vascular connection, via a placenta
Discuss the egg size (& yolk content), morphology, and number of offspring in oviparous species
relatively large egg size, a lot of yolk content, large morphology in development. More effective development if the egg is left alone however susceptible to prey
Discuss the egg size (& yolk content), morphology, and number of offspring in ovo-viviparous species
egg size much smaller, much more egg content, small morphology, only released from parent once developed enough to survive on its own. Much safer as eggs are still with parents however, less offspring are produced.
Discuss the egg size (& yolk content), morphology, and number of offspring in viviparous species
Egg size medium to large, little yolk content and egg becomes placenta (edible) as a form of nutrients for the egg. Number of offspring is very little however there is a lot of development offspring before release into the environment. The parent is normally very vulnerable to prey during pregnancy. True placental viviparous have little to no yolk - nutrients provided by placenta
How can one identify that a shark is a viviparous species?
Umbilical cord means placenta = viviparous
Why does a sand tiger shark produce so many eggs when only 1-2 offspring are produced?
They produce a lot of eggs in order to feed the young that are growing inside the mother, the eggs are infertile eggs, due to the embryos eating the unfertilised eggs the mother does not need to give resources to her embryos and can keep living for herself.
Anura: Internal or External Fertilisation? Intromittent Organ? Reproductive mode? Parental care?
External Fertilisation, no intromittent organ, Ovo or viviparous, no Parental care.
Caudata: Internal or External Fertilisation? Intromittent Organ? Reproductive mode? Parental care?
Both Internal and external fertilisation, no intromittent organ, Mostly oviparous but very little are viviparous, most have no parental care but some tropical species do.
