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Animal Diversity > Development & Aquatic Insects > Flashcards

Development & Aquatic Insects Flashcards

1
Q

What is Ametaboly?

A

These insects hatch from the egg in a form resembling adult but lacking genitalia (primitive developmental pattern) e.g.

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2
Q

What is Hemimetaboly?

A

Incomplete metamorphosis
- Juvenile stages are called nymphs
- In all but the youngest instars, wings (or wing buds) are visible externally

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3
Q

What is Holometaboly?

A

Complete metamorphosis during pupal stage
- Juvenile stages prior to pupation are called larvae
- Wings and other structures are present internally in juvenile stages as groups of undifferentiated cells

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4
Q

What are some features of the egg stage in insect development?

A
  • Eggs can be laid singly, in clusters, or in oothecae
  • A lot of insects spend winter/dry season as eggs (diapause)
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5
Q

What are immature holometabolous insects called?

A

Larvae or pupae

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6
Q

What are immature hemimetabolous insects called?

A

Nymphs

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7
Q

Why might holometaboly be beneficial?

A
  • Reduces competition between adults and juveniles for the same food source
  • Allows for developmental plasticity (e.g. adults and nymphs may occupy different ecological niches)
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8
Q

What are three different types of larvae?

A
  • Oligopod larvae: 3 pairs of thoracic legs
  • Polypod larvae: 3 pairs of thoracic legs + abdominal prolegs
  • Apod larvae: no legs
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9
Q

When does metamorphosis between instars occur and what controls metamorphosis

A
  • Onset of metamorphosis between instars generally occurs due to the insect reaching a certain size
  • Metamorphosis is under the control of hormones (e.g. juvenile hormone)
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10
Q

What are the two main processes in pupa (holometabolous insects)?

A
  • Pupation is the moult into the pupal stage
  • Eclosion is the process of emerging from the pupae
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11
Q

What are the main features of the adult (imago) stage?

A
  • Adult stage is defined by sexual maturity after the final moult, can be triggered by environmental changes. Reproduction is the major goal of the imago
  • Newly emerged adults have a soft cuticle, they swallow air to increase haemolymph pressure and expand
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12
Q

What is voltinism?

A

The number of generations per year

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13
Q

What are the three different types of voltinism?

A
  • Univoltine (one generation per year)
  • Bivoltine (two generations per year)
  • Mutlivoltine (many generations per year)
  • Semivoltine (less than one generation per year) e.g. cicadas take 13 or 17 years to mature
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14
Q

What are some of the environmental (abiotic and biotic) factors that effect development (growth rate)?

A
  • Temperature, moisture
  • Type and amount of food
  • Presence of environmental signals
  • Mutagens/toxins can lead to fluctuating symmetry/developmental abnormalities
  • Other organisms including competitors and predators (e.g. influence on food availability)
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15
Q

What is diapause? And what are some environmental cues that could cause diapause?

A

The delay in development in response to adverse environmental
- Physiological shanges before diapause: storage of lipids, proteins and carbs, accumulation of anti-freeze polyhydric alcohols (winter diapause)
- During diapause, the metabolism is lowered and development stops
Environmental cues (e.g. photoperiod, temperature, food quality) alter levels of juvenile hormone and diapause hormone, triggering diapause.

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16
Q

What are the different types of water based on their oxygen supply, and how does this affect aquatic insects?

A
  • In lentic (standing) water, oxygen diffuses through water slowly. Insects may have to live in low oxygen conditions for long periods
  • In lotic (flowing) water, oxygen diffuses with currents and turbulences and is less limiting.
17
Q

How do the aquatic insects exchange system differ from terrestrial insects, and what limitations does this pose?

A
  • Exchange systems depend upon oxygen diffusion. In the majority of terrestrial insects, trachea open to atmosphere via spiracles
  • For some small aquatic animals, oxygen can easily permeate the body wall
  • Larger insects require augmentation of gaseous exchange:
    1. Oxygen uptake with a closed tracheal system
    2. Oxygen uptake with an open spiracular system
    3. Behavioural ventilation
18
Q

Why might a closed tracheal system in aquatic insects be advantageous?

A

Aquatic insects have a closed tracheal system, where air is trapped in a network of tubes (tracheae) and brought directly to the cells, because it allows them to efficiently extract oxygen from the water and maintain a higher oxygen concentration gradient. This is important because oxygen is less abundant in water than in air.

The closed tracheal system prevents the loss of oxygen to the surrounding water, ensuring that oxygen reaches the tissues where it is needed for respiration. Additionally, this system helps prevent the entry of water into the tracheae, which could disrupt gas exchange and buoyancy control in aquatic insects.

19
Q

What type of aquatic insect has an open tracheal system, and how does it manage to keep ventilating?

A

Diving beetles

20
Q

What structure is present in aquatic insects with closed tracheal systems, and what does it help to increase?

A

The role of gills is to increase the gaseous exchange surface area

21
Q

What is behavioural ventilation?

A

Insects moving their gills to increase gaseous exchange

22
Q

Why might aquatic insects choose certain environments?

A
  • Due to the flow > if the flow is higher this maximises the insects oxygen uptake
23
Q

What characterises lotic systems (streams, rivers)? And what might the velocity of flowing water have an effect on?

A

Lotic systems:
- Unidirectional, fluctuating flow
- Unstable channel and bed morphology
The velocity of flowing water is a major influence on:
- Substrate type and size
- Transport of fine particles (food or other)
- Maintenance of high oxygen

24
Q

What are the two sources of food for stream invertebrates?

A
  • Autochthonous (from within the stream e.g. algae)
  • Allochthonous (from surrounding vegetation e.g. leaves from tree)
25
Q

What groups can stream insects be divided into based on their feeding mode? And what benefits do their presence in streams provide?

A

Shredders - eat leaves
Collectors - filter material from the water column
Grazers - scrape algae from rocks
Scavengers - eat animal remains
Predators - eat other organisms
- They contribute to water purification by breaking down organic matter that can be metabolised by bacteria
- Aquatic macroinvertebrate community reflects the health of the stream

26
Q

What factors impact stream water quality here in Aotearoa?

A
  • Agriculture: pesticides, nitrogen runoff
  • Urban/domestic: detergent, waste oil, sewage
  • Industrial: resource consents may allow industries to discharge into rivers for decades
27
Q

What is the concept of river continuum?

A
  • Rivers can be strongly influenced by the surrounding vegetation
  • As stream size increases, the influence of the surrounding vegetation decreases: organic matter input, exposure to sun etc.
  • Therefore, the further upriver one goes, in theory there should be more shredders and grazer compared to downstream, where there are more predatory and collector insects, due to the increasing stream size.
28
Q

Why might the concept of river continuum not apply in Aotearoa?

A
  • NZ has few trees that lose their leaves in autumn, and only a few shredders
  • NZ streams are also comparatively steep, so organic matter doesn’t hang around for long periods
29
Q

What are the main features of lentic systems (standing water) and their invertebrate make-up?

A
  • Oxygen availability is more of a problem compared to streams
  • Water surface is used by more species (the neustic community)
  • Some members of the neustic communities live in lentic, estuarine or even oceanic environments
  • Immediatly below the water surface is home to organisms such as mosquito larvae
  • Benethis communities of lakes support large populations of midges.

Animal Diversity (9 decks)

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