Entomology: Reproduction

• Entomology units 2.1 - 2.5 learning outcomes and key concepts

Unit 2.1

• Parthenogenesis is a form of asexual reproduction.
• Facultative parthenogenesis is reproduction sexually or asexually.
• Obligatory parthenogenesis is reproduction only asexually.
• The advantage of giving up sexual reproduction may be to reproduce quickly.
• Progenesis is the early maturation of gonads in a larval stage.
• Neoteny is the retention of juvenile features in the adult stage.
• Hermaphroditism is when an organism has both male and female reproductive organs.
• An ovotestis is a gonad that contains both testicular and ovarian tissue.
• Polyembryony is when multiple embryos develop from a single fertilized egg.
• An obstacle to polyembryony is competition among the developing embryos.
• A reproductive endosymbiont is a microorganism that lives within a host organism and affects its reproduction.
• Vertical transmission of an endosymbiont is the transfer of the symbiont from parent to offspring.

Unit 2.2

• Ontogeny is the development of an organism from its earliest stage to maturity.
• Katatrepsis is the turning downward of the embryo during insect development.
• Short germ band development creates the posterior segments from a posterior growth zone
• Long germ band development forms all segments simultaneously.
• Eclosion is the emergence of an insect from the pupal cuticle or egg.
• The Lord Howe Stick insect was extirpated from Lord Howe Island due to introduced rats.
• Captive breeding programs saved the Lord Howe Stick insect from extinction.
• Nymphs are immature insects that resemble smaller versions of the adult.
• Larvae are immature insects that are distinctly different from the adult.
• Polypod larvae have both thoracic and abdominal legs.
• Oligopod larvae have thoracic legs but lack abdominal legs.
• Apod larvae lack both thoracic and abdominal legs.
• Some species have two distinct larval forms.
• Juvenile hormone and ecdysteroid cycles regulate the timing and frequency of molting.

Unit 2.3

• A cocoon is a silk casing spun by the larva of some insects to protect the pupa.
• A chrysalis is the pupal stage of a butterfly.
• The technical term for hatching and pupa emergence is eclosion.
• Univoltine species have one generation per year.
• Bivoltine species have two generations per year.
• Multivoltine species have multiple generations per year.
• Semivoltine species take more than one year to complete a generation.
• Diapause is a period of dormancy in response to adverse environmental conditions.
• A primary trigger for diapause in facultative diapause groups is photoperiod.
• Insects can be susceptible to temperature changes due to being poikilothermic.
• Insects survive cold periods using cold tolerance, freeze avoidance, supercooling, and diapause.
• Insects avoid overheating using behavioral adaptations, physiological adaptations, evaporative cooling, and heat shock proteins.
• Migration is the seasonal movement of animals from one region to another.
• Migration differs from dispersal in habitats due to being directional and involving return.
• Sexual dimorphism is when males and females of a species have different physical characteristics.
• Polymorphism is the occurrence of multiple forms or morphs within a population.
• Polyphenism is when environmental factors cause distinct phenotypes within the same species.
• Eusocial insect castes can be due to polyphenism, genetic polymorphism, or both.
• Poikilothermic organisms have a body temperature that varies with the environment.
• Physiological time is the amount of heat required for an insect to complete development.
• Photoperiodism is the physiological response of organisms to the length of day or night.
• Abiotic factors impact insect development and life cycles.
• Biotic factors impact insect development and life cycles.
• Species distribution modeling helps understand how climate change impacts species ranges.
• Plecopteran nymphs are found in clean, lotic (flowing water) environments.
• Bioindicators are species that are used to assess the health of an environment.
• Disjunct distribution is when a species has geographically separated populations.

Unit 2.4

• Solitary behavior lacks social interaction or cooperation.
• Sociality advantages include increased protection, resource sharing, and division of labor.
• Sociality changes may not be steps but rather a continuum.
• Aggregation is a group of individuals in the same place or area.
• Quasisociality is communal living with cooperative brood care.
• Subsociality is parental care of offspring.
• Semisociality is cooperative brood care and some division of labor.
• Parental care is a step towards social behavior.
• The three variants of parental care seen in insects are:
  • Providing food
  • Defense
  • Shelter
• Eusocial species require:
  • Reproductive division of labor
  • Cooperative brood care
  • Overlapping generations
• The four insect orders with eusocial species are:
  • Hymenoptera (ants, bees, wasps)
  • Isoptera (termites)
  • Hemiptera (aphids)
  • Thysanoptera (thrips)
• Hymenoptera are a "natural laboratory" to study eusociality origins and evolution.
• Termites and snapping shrimp are species outside of insects that have become eusocial.
• Castes include reproductives (queens and kings), workers, and soldiers.
• A female reproductive in eusocial species is called a queen.
• Multiple male reproductives in the same colony are called drones
• A single male reproductive is called a king.
• Soldiers have specialized morphology or behavior for defense.
• Not all eusocial species have soldiers.
• Repletes and phragmotics are additional castes found in ants.
• Repletes act as living storage vessels
• Phragmotics use their bodies to block entrances.
• The genetic system for determining sex in hymenoptera contributes to the origin of eusociality. Group selection has minor importance in the origin of eusociality.
• Three forces contribute to the origin of eusociality in hymenoptera
  • Haplodiploidy
  • High relatedness
  • Ecological factors
• Termite eusociality origin is harder to understand than hymenoptera eusociality.
• Termite eusociality may result from nutrient poor diet, patch distribution, and trophallaxis
• Roach studies improves understanding of eusociality in termites.
• Inquilines are species that live as parasites or commensals in the nests of social insects.
• Mimicry is when one species evolves to resemble another.

Unit 2.5

• Orthoptera is distinguished from others by having:
  • Saltatorial hind legs
  • Tegmina forewings
• The ovipositor deposits eggs.
• Orthoptera impacts human agriculture by consuming crops.
• Fungivores eat fungi.
• Insect mycophagy differs from insects that "farm" fungi.
• Some insects only eat fungi, including a few ants, two beetle families, and fungus gnats.
• Fungivores' diets are facilitated by modified mouthparts.
• Mycophagy may have led groups to herbivory.
• Ecological interactions:
  • Mutualism is a relationship where both species benefit.
  • Antagonism is a relationship where one species benefits and the other is harmed.
  • Commensalism is a relationship where one species benefits and the other is unaffected.
• Fungal/insect mutualisms have evolved multiple times.
• Fungal/insect mutualisms are a diverse selection.
• Benefits from insect/fungi mutualism, except for dispersal, include:
  • Nutrition
  • Defense
  • Habitat
• Leaf cutter ants, some termites, ambrosia beetles, and bark beetles have all ecological beeinfits
• Complex domestication of fungi occurs with beneficial benefits.
• Facultative mutualists benefit from the relationship but can survive without it.
• Obligate mutualists cannot survive without the relationship.
• Coevolution influences fungi behavior, morphology, and chemical traits.
• Cospeciation is when two species evolve in tandem.
• Leaf cutter mutualism is "three-fold".
• Entomopathogenic fungi "eat" an insect through its life cycle.
• Insects are subject to pathogens.
• Host specificity is the range of hosts that a parasite can infect.
• Pathogenic fungi enter an insect through the cuticle, spiracles, or gut.
• Cordyceps infects and kills a host.
• Mechanisms limit fungi pathogens impact in eusocial systems such as ants and bees.
• Grooming, allo-grooming, aggression, self-removal, and "fever" are mechanisms that limits fungi pathogens impact.
• Insect "fever" differs from mammalian fever, and uses behavioral thermoregulation.
• Cordyceps doesn't infect humans.
• Mantophasmatodea was identified relatively recently and are found in Africa.
• Grylloblattodea fills a niche in cold environments.
• Grylloblattodea are found in disjunct distribution.
• The most common transmission mechanism for entomopathogenic bacteria is horizontal transmission.
• Entomopathogenic bacteria are less understood than other types of pathogenic bacteria.
• Bacillus thuringiensis (Bt) kills insects by producing a toxin.
• Bt cotton and Bt corn are transgenic organisms.
• Lysinibacillus sphaericus targets mosquitoes.
• Biocontrol uses bacteria or fungi.
• Biocontrol may be better than pesticides.
• Pesticide qualities:
  • Host-specificity
  • Environmental persistence
  • Safety

Further Key Concepts

• Buchnera bacteria are involved in nutritional mutualism with aphids.
• Interactions are like mitochondria and chloroplasts.
• Vertical transmission is from parent to offspring.
• Reproductive manipulation advantages benefit endosymbionts.
• Wolbachia bacteria and insects have an ecological relationship
• Endosymbionts can be pushed to mutualism and antagonism.
• Four reproductive parasitism mechanisms exist in Wolbachia.
• Obligate symbionts have a specific pattern in genomes.
• Antimicrobial peptides (AMPs) are the is the insects immune system
• Insects and mammals have different immune systems.
• Symbionts avoid the host's immune system through evasion, suppression, and tolerance
• Wolbachia benefits insect hosts and varies across different insects with Wolbachia.
• Embioptera spins silk from glands in their forelegs.
• Silk creates shelters and to trap food.
• Sexual dimorphism is present in this group.
• Phasmatodea mimics sticks and leaves.
• Phasmatodea species studies are of interest to the origin and loss of flight in insects.
• Many Phasmatodea groups have asexual species.