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Minne Life Cycles and Adaptations of Marine organisms > Life Cycles Animals Lecture 3 > Flashcards

Life Cycles Animals Lecture 3 Flashcards

1
Q

Focusing on the number of reproductive events, 2 main categories can be distinguished.

A
  • Semelparous species
  • Iteroparous species
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2
Q

Semelparous species

A

Species that reproduce only once during their life and then die

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3
Q

Iteroparous species

A
  • Species that reproduce more than once.
  • The number of reproductive events can vary:

A) Species may reproduce during one reproductive season (one year)

B) Species may reproduce during several reproductive season (several years)

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4
Q

Semelparous species include…

A
  • Molluscs: octopus, squid, some clams, etc.
  • Some annelids: nereids
  • Fish: salmons, eels, lampreys, …
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5
Q

What is another example of a semelparous species?

A

the European eel

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6
Q

Do larvae and juveniles of the European eel look a like?

A
  • No, larvae and juveniles are very
    different from a morphological point
    of view.
  • They were classified as different species.
  • Leptocephalus larva is typical of Elopomorpha fish
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7
Q

How was the complex life cycle of the European eel discovered?

A

The complex life cycle of the European eels was discovered thanks to the catch of leptocephali larvae with
different sizes.

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8
Q

What does the metamorphosis of the European eel larvae look like?

A
  • Leptocephali are transparent, with a maximum length of 85 mm.
    Their stage lasts between 3 to 4 years.
  • The juvenile, called glass eels, are between 65 and 80 mm of length, and migrate to freshwater streams between October and February.
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9
Q

What happens to the eels after the attainment of sexual maturity?

A

After the attainment of sexual maturity,
between 6 and 12 years, adults perform a
long migration towards the Sargasso Sea
where they will spawn and then die.

Before migrations, they undergo several
morphological and physiological
modifications.

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10
Q

What is a difficult taxon when it comes to defining iteroparity and semelparity?

A

Cephalopods

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11
Q

Main elements to take in consideration when defining iteroparity

A
  • There is a resting phase in gonads
  • The interval between successive batch laying.
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12
Q

1 category of spawning once (formerly semelparity) in cephalopods

A
  • Simultaneous terminal spawning: eggs are released in a short time interval, only once, before death.
  • This is a type of spawning where ovulation is synchronous, and there is no oocyte maturation during the spawning period.
  • The egg spawning pattern is monocyclic, and the egg-laying occurs in a very short period at the end of the
    animal’s life.
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13
Q

4 categories of spawning more than once (formerly iteroparity) in cephalopods

A
  • Polycyclic spawning
  • Multiple spawning
  • Intermittent terminal spawning
  • Continuous spawning
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14
Q

Polycyclic spawning (as category of spawning more than once)

A
  • Reproductive strategy where the spawning pattern shows several cycles and the gonads regenerate after each breeding period, making new reproductive cycles possible.
  • There appears to be a single spawning season each year with the animal surviving, feeding and growing between spawning
    events.
  • Eggs mature in several distinct clutches and egg-laying occurs in separate batches during each spawning period.
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15
Q

Multiple spawning (as category of spawning more than once)

A

Reproductive pattern, group-synchronous ovulation occurs in the ovary.

The spawning pattern is monocyclic, and egg-laying occurs in separate batches, somatic growth continuing between separate spawning events.

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16
Q

Intermittent terminal spawning (as category of spawning more than once)

A

Group-synchronous ovulation occurs in the ovary.

Spawning is monocyclic and egg-laying occurs in separate batches during the
spawning period, which is usually relatively long

This type of strategy differs from `multiple spawning’ in that somatic growth does not take place between spawning events.

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17
Q

Continuous spawning (as category of spawning more than once)

A

Ovulation is characterized by continuous asynchronous production of ova in the ovary after spawning has commenced.

In this monocyclic spawning pattern, adults spawn continuously during their relatively extended life-spans and somatic growth
takes place during spawning events.

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18
Q

This diagram is important to understand for the exam.

A

Diagram illustrating 5 cephalopod reproductive strategies

19
Q

How can the number of reproductive events be determined?

A
  • By analysing the ovaries.
  • In particular, the size frequency distribution of the oocytes and the different stages of maturity of female gamtes present in the ovary may provide a first indication.
20
Q

What is expected in semelparous species when determining amount of reproductive events?

A

The presence of only one stage of maturity of female gametes is expected: females will release the entire amount of eggs and no other oogonia or oocytes will mature.

21
Q

What is expected in iteroparous species when determining amount of reproductive events?

A

More than one stage of female gametes is expected to occur in the ovary.

The number of stages may differ according to the interval between spawning events.

So there may be 1 spawning in a week, 1 in 3 weeks, 1 in 2 months, etc.

22
Q

What does the size frequency distribution of oocytes indicate?

A
  • it reflects oocytes maturation and therefore vitellogenesis
  • provides indication on the number of
    reproductive events
23
Q

What does this size frequency distribution show?

A

Synchronous ovary

One reproductive event: there are no small oocytes – previtellogenic oocytes – for next reproductive events

24
Q

What does this size frequency distribution show?

A

Group synchronous

At least 2 reproductive events separated in time (e.g., in different seasons):

there are two modes, one of large-sized
oocytes to be released in the reproductive season, and one of very small oocytes, for the following season.

25
Q

What does this size frequency distribution show?

A

Asynchronous

Several events in a reproductive season: there are oocytes of different sizes

26
Q

For how many years/seasons does a species reproduce?

A

There is wide variability among species
* One season per year during the entire life (from sexual maturity)
* Every two or more years

The knowledge of the interval between seasons allows to estimate the actual number of reproducing individuals per year.

If a species reproduce every two-years, the number of reproducing individuals is half the number of potential reproducers

27
Q

How is the time interval between reproductive season in sea turtles called?

A
  • Remigration interval
  • Remigration intervals to nesting
    beaches can vary within and
    among populations and may be
    linked to foraging success.
28
Q

In which species does it occur that females reproduce once every 2 years?

A
  • Some cetacean species
  • Some shark species
29
Q

In several species, individuals may skip a reproductive season because of….

A
  • Low food availability
  • Poor female conditions
  • Environmental factors
30
Q

At what age do individuals of the common cuttlefish reproduce?

A

Their first or second year.

The two cohorts reproduce in different periods of the reproductive season.

Different cohorts may co-occur and their reproductive period may overlap only partially.

31
Q

What does this table about the common cuttlefish show?

A

Individuals born in spring will reproduce in summer of their 1st years.

Individuals born in summer will reproduce in spring of their 2nd year.

32
Q

What does the presence of different generations of reproducers depend on?

A

The presence of different generations of reproducers depends on the longevity after sexual maturity.

33
Q

What are the consequences of the number of generations contributing to reproduction?

A

The consequences include the potential for compensation in bad years if several generations occur, acting as reservoirs for reproduction and genetic variability.

34
Q

What is the “storage effect” in relation to overlapping generations?

A

The “storage effect” theory suggests that overlapping generations result in the accumulation of adult biomass over many year-classes, acting as a ‘seed bank’ that improves the chance for future population growth.

35
Q

How do species fluctuations in abundances differ between species with one generation of reproducers and those with several generations?

A

Fluctuations are more frequent in species with one generation of reproducers, usually annual species. Fishery, especially targeting large-sized individuals, can further amplify these fluctuations by reducing age classes.

36
Q

Can different cohorts of reproducers spawn at different sites and/or time?

A

Yes.

Different conditions may favour certain
sites or times, therefore eggs/larval survival of certain cohorts.

37
Q

Global capture and aquaculture of the European eel (graphs)

A
38
Q

Are semelparous species more or less vulnerable to exploitation in comparison to iteroparous species?

A

Semelparous species are often more vulnerable to exploitation since they are usually caught before reproduction.

In the case of the European eels, for instance, they are often caught during the migrations.

Semelparous species often need specific management

39
Q

What are the components of reproductive investment?

A

Reproductive investment may include investment in gametes (e.g., gonads, eggs), parental care, and other behaviors linked to reproduction, such as long reproductive migrations and environmental changes.

40
Q

Why is semelparity expected to be advantageous from an evolutionary perspective?

A

Semelparity is expected to be advantageous if the mortality of adults is high, leaving few chances to breed again.

In such cases, investing all resources in reproduction, even at the expense of survival, may be beneficial.

41
Q

How does the reproductive period vary among species?

A

The reproductive period of a species may vary in duration throughout the year

42
Q

What are the reproductive patterns of species inhabiting tropical areas?

A
  • Species inhabiting tropical areas may reproduce all year round,
  • Lacking a specific pattern or presenting cyclic reproductive patterns linked to factors such as lunar phases or rainy periods
43
Q

What are the reproductive patterns of species inhabiting temperate or cold areas?

A

Species inhabiting temperate or cold areas often exhibit seasonal reproduction.

They may reproduce in different seasons, commonly during spring or autumn, and may also display cyclic reproductive patterns.

44
Q

Optimal reproduction moment can be dependent on various factors…

A
  • Reproducers
  • Egg deposition
  • Egg development
  • Larval hatching
  • Larval survival (predator abundance, prey abundance, etc.)
  • Larval dispersal
  • Recruitment

Minne Life Cycles and Adaptations of Marine organisms (14 decks)

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