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Minne Life Cycles and Adaptations of Marine organisms > Life cycles Animals Lecture 2 > Flashcards

Life cycles Animals Lecture 2 Flashcards

1
Q

Name several aspects of reproduction that characterize the life cycle and life history traits of a species

A
  • Sexual maturity
  • Number of reproductive events in the life period
  • Sexual patterns
  • Fecundity & fertility
  • Sexual selection and mating system
  • Parental care
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2
Q

Sexual maturity

A

An individual attains sexual maturity when it is capable of reproducing. This marks the transition from the juvenile to the adult stage.

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3
Q

Age at sexual maturity

A

The age at which an organism reaches sexual maturity. It varies among species, even within the same taxonomic group.

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4
Q

Size at sexual maturity

A

The size an organism reaches when it becomes sexually mature. It varies among species and is often positively correlated with asymptotic size (L∞).

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5
Q

Reproductive load

A

Ppt:
The ratio of size at sexual maturity (Lm) to asymptotic size (L∞).
Lm/ L∞ : 0.4 – 0.7

Reproductive load is usually higher in small-sized species

Google definition:
The ratio between the average length at first maturity and the maximum length reached in a population.

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6
Q

Engraulis encrasicolus

A
  • European anchovy
  • Reproductive load: 0.63
  • Asymptotic size (L∞) = 17 cm
  • Relatively high reproductive load
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7
Q

Rhincodon typus

A
  • Whale shark
  • Reproductive load: 0.48
  • Asymptotic size (L∞): 20 meters
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8
Q

Chaenocephalus aceratus

A
  • Blackfin icefish
  • Reproductive load: 0.70
  • Asymptotic size (L∞) = 67 cm
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9
Q

Size/age at sexual maturity can refer to..

A
  • Minimum: size/age of the smallest/youngest sexually mature individual
  • L/A50: size/age at which 50% of the individuals is sexually mature
  • Size/age at maturity is usually represented by a curve.
  • In viviparous species, it may be useful to know also the
    minimum size/age at first parturition (giving birth to offspring)
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10
Q

How can sexual maturity be evaluated?

A

Sexual maturity can be evaluated through different methods depending on factors like type of reproduction and species characteristics.

Methods include:
- analysis of gonads
- presence of embryos (in viviparous species)
- presence of color or structures appearing only in mature individuals
- observation of individuals performing parental care (caring for eggs)

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11
Q

Analysis of gonads

A
  • Gonads of sexually mature individuals present mature gametes, but usually only a
    defined period in species presenting seasonal reproduction (i.e., during the reproductive season or just
    before it).
  • If reproduction is seasonal, a resting period of gonads usually occurs and it is not so easy to distinguish mature and immature individuals.
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12
Q

How can analysis of gonads be conducted?

A
  • Microscopic
  • Macroscopic
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13
Q

Macroscopic gonad analysis

A
  • The macroscopic analysis usually includes the recording of features that can be seen by naked eyes.
  • Macroscopic analysis is a rapid method.
  • It allows establishing if an individual is able to reproduce during that specific reproductive season or if it just stopped reproducing (at the end of the reproductive season).
  • This method usually can not provide information on past reproductive events (several months before the
    analysis).
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14
Q

Microscopic gonad analysis

A
  • The microscopic analysis allows attributing the stage of maturity after histological analysis of the gonads.
  • This method requires longer time than macroscopic one.
  • It often provides more precise information on the stage of maturity of gametes.
  • It can provide also information on past reproductive events, but this depends on the species.
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15
Q

What factors are considered in developing scales of maturity for gonads?

A
  • Scales of maturity for gonads are based on factors like the general aspect, shape, relative dimension, position, and color of the gonads.
  • Different scales have been developed for various taxonomic groups, requiring knowledge of reproductive apparatus morphology for evaluation.
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16
Q

Difference between gonad maturity and sexual maturity

A
  • An individual can have a maturing gonads and be sexually immature or mature
  • Every individual with a mature gonad is sexually mature.
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17
Q

Macroscopic maturity scale for bony fish

A
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18
Q

Main characteristics in relation to gonad analysis

A
  • size of the gonads in relation to body cavity
  • appearance (colour, etc.)
  • size of oocytes.

Appearance and relative size of other reproductive structures may help in evaluating maturity stage.

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19
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 1 - immature = virgin

Gonad description:
- Small pinkish and translucent ovary shorter than 1/3 of the body cavity.

  • Eggs not visible to naked eye.
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20
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 2A virgin developing

Gonad description:
- Small pinkish/reddish ovary shorter than ½ of body cavity.

  • Eggs not visible to naked eye
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21
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 2C - maturing

Gonad description:
- Ovary pinkish/yellow in colour with granu- lar appearance, about 2/3 length of the body cavity.

  • Eggs are visible to naked eye trough
    the ovaric tunica, which is not yet translucent.
  • Under light pressure eggs are not expelled.
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21
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 3 - Mature/ spawner

Gonad description:
- Ovary orange/pink in colour, with conspicuous superficial blood vessels
From 2/3 to full length of the body cavity.

  • Large transparent, ripe eggs are clearly visible and could be expelled under light pressure.
  • In more advanced conditions, eggs escape freely.
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22
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 2B - recovering

Gonad description:
- Pinkish-reddish/reddish-orange and translucent ovary about ½ length of body cavity.

  • Blood ked eye.
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23
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 4A - spent

Gonad description:
- Reddish ovary shrunken to about ½ length of the body cavity.

  • Flaccid ovaric walls; ovary
    may contain remnants of disintegrating opaque and/or translucent eggs.
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24
Q

Define macroscopic maturity scale of M. Barbatus in this picture

A

Stage: 4B - resting

Gonad description:
- Pinkish/reddish and translucent ovary. About 1/3 length of body cavity.

  • Eggs not visible to naked eye.
25
Q
A

Maturity scale for oviparous (egg-laying) elasmobranchs

26
Q

Maturity scale for oviparous elasmobranchs (males)

A
27
Q

Maturity scale for oviparous elasmobranchs (females)

A
28
Q

Maturity scale for viviparous (give birth directly) elasmobranchs

(The stage of pregnancy is included)

A
29
Q

What does the reproductive apparatus in female cephalopods consist of?

A
  • Ovary (O)
  • Genital ducts (FD)
  • Nidamental glands and accessory nidamental glands (AC.N.G.)
30
Q

What does the reproductive apparatus in male cephalopods consist of?

A
  • Testis
  • Spermatophoric complex:
    deferent duct, genital sac,
    Needham’s pocket, genital
    opening
31
Q

Maturing stages in female cuttlefish

A
32
Q

Maturing stages in male cuttlefish

A
33
Q

Maturity scale of Crustacean decapoda (crabs, lobsters, etc.)

A
34
Q

Description of the microscopic maturity scale of M. barbatus females (H&E, haematoxylin and eosin)

A

For high resolution picture:

https://iris.unica.it/retrieve/e2f56ed8-f9eb-3eaf-e053-3a05fe0a5d97/Follesa%20et%20al%202019%20b.pdf

35
Q

Which female gamtes do you see in this picture?

A

Oogonia
Pre-vitellogenic oocytes
Vitellogenic oocytes

36
Q

Which male gametes do you see in this picture?

A

Spermatogonia
Spermatocytes
Spermatids
Sper

37
Q

Maturing of oviducal glands

A
  • in the oviducal glands the ducts
    develop,
  • secretion starts to be produced
  • even sperm may be found.

(Gravid = pregnant)

38
Q
A

Maturity of gonads can be determined on a monthly basis

(What does the graph show??)

39
Q

When are individuals sexually mature based on the gonads?

A

Individuals with mature, close to maturity or spent gonads are sexually
mature

40
Q

How do the claspers of elasmobranchs males provide information on sexual maturity?

A
  • They become longer than pelvic fins
    (in most species)
  • They also become calcified as males mature.

As a consequence, even in a gonadal resting period claspers provide an
accurate information on
the attainment (het behalen van) of sexual
maturity.

41
Q

Is gestation (period between conception and birth) length in cetaceans short or long?

A

Long

41
Q

In what type of species can it be useful to distinguish between size/age at maturity and size/age at first parturition?

A

In viviparous species

42
Q

Reproductive cycle of toothed-whales

A

Reproductive cycle of toothed-whales:

  • minimum 3 years
  • In many species; 1 year gestation and 2 years lactation period
  • Mating, calving and weaning are distinct events in cycle with each occuring over several months
  • Calving timed to match peak ecosystem producivity
42
Q

Reproductive cycle of baleen whales

A

Reproductive cycle of baleen whales:

  • minimum of 2 years
  • events tightly correlated with annual migratory cycle
  • Most mating and calving: on wintering grounds
  • Calves are weaned (krijgen borstvoeding) when arriving on feeding ground during their first summer
  • Females complete 1 migratory cycle while pregnant and first half of next cycle with a nursing calf
43
Q

What do eggs indicate in species caring eggs?

A
  • egg presence signals the attainment of sexual maturity.
  • The absence of eggs does not indicate sexual immaturity.
44
Q

Relation of coloration and sexual maturity

A
  • In some species, coloration irreversibly changes with maturity.
  • In other species, nuptial colorations are present only during the reproductive period. (rapid short-term colour changes)
45
Q
A

Color phases exhibited by Nassau grouper while on the spawning aggregation.

The colorations shown are:
A: Barred
B: Bicolor
C: Dark
D: White belly

Red dots on side of fish are laser points used to determine length of fish (250mm apart)

46
Q

Intra-specific variability in size/age at maturity can be found…

A
  • Between the two sexes
  • Within sex, depending on the adopted reproductive strategy
  • Among geographic areas
  • As response to variation in abundances/density
  • As response to fishery
47
Q

Differences in size/age at sexual
maturity between sexes occurs in
several species.

A
  • In several elasmobranchs, females
    mature later and at larger sizes than
    males.
  • In these species, there is also
    a sexual dimorphism in size with
    females attaining larger sizes then
    males.
  • In some other, oviparous, species size
    at maturity of males and females is
    similar.
  • A possible role of viviparity and the
    advantage of being larger for
    fecundity is believed to be at the
    basis of these differences.
48
Q

When can Intrasexual difference in size/age at sexual maturity occur?

A
  • in some species with alternative reproductive strategies.
  • In some species, males may adopt
    different strategies and according to
    that they can mature earlier (at
    smaller sizes) or later (at larger sizes).
  • In some salmons, males migrate to
    the sea or do not migrate, according
    to the adopted strategy
49
Q

What are the 3 male morphs described in the isopod Paracerceis sculpta?

A
  • α males: dominant
  • β males: mimicking females
  • γ males: smallest in size
50
Q

The 3 male morphs differ in age at maturity

A
  • α males: 84 days
  • β males: 62 days
  • γ males: 58 days

Concluding that genetics determine the strategy of the males

51
Q
A

Intraspecific geographic variability in size/age at sexual maturity has been found in several species

52
Q
A
  • A latitudinal gradient in size at sexual maturity and maximum size has
    been found in several species.
  • Geographic variability can
    also be related to peculiar characteristics of
    areas.
53
Q
A
  • In several populations of different
    commercial species, a decrease in the
    size/age at sexual maturity has been
    found.
  • This decrease has been put in relation
    with fishery exploitation.
54
Q

How does large size/age at maturity affect the vulnerability of exploited species?

A

Large size/age at maturity makes exploited species more vulnerable because individuals are more likely to be caught before reaching sexual maturity and, consequently, before reproducing.

55
Q
A

There are several examples showing that larger species, maturing later and at larger sizes, show stronger decline in abundance as effect of fishery respect to smaller, earlier maturing ones.

56
Q

Generation length

A
  • The average age of parents of the current cohort (i.e., newborn individuals in the
    population).
  • Generation length therefore reflects the turnover rate of breeding individuals in a population.
  • Generation length is greater than the age at first breeding and less than the age of the oldest breeding individual, except in taxa that breed only once.
57
Q

What important information can generation length tell us?

A

Generation length provides information useful to predict the recovery capacity of a population/species and the
expected time for the recovery.

58
Q
A

Generation length of 58 species of cetaceans estimated on the basis of life history traits, age structure of a
population, survival at each age, etc. (life tables)

59
Q

Generation length shows wide variability

A

Minne Life Cycles and Adaptations of Marine organisms (23 decks)

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