Ento - Maintaining Homeostasis

Vocabulary terms

Malpighian Tubule

primary excretory and osmoregulatory organs in insects, functioning like kidneys to filter the hemolymph (insect blood) and produce pre-urine

Gastric Caecum

pouches connected to the midgut that serve to increase surface area for digestive enzyme secretion and nutrient absorption

Organs of the Foregut

Esophagus, Pharynx, Mouth, Crop, Gizzard, and Gastric caecum

Organs of the Hindgut

Anterior Intestine, Rectum, Malpighian Tubule, and anus

Crop

a temporary storage pouch for food, which is then passed to the proventriculus gizzard for further digestion and absorption

Gizzard

a muscular organ in the foregut that grinds food into smaller particles for digestion

Steps of the excretory system

1. The Malpighian tubules, bathed in hemolymph, begin the process by actively secreting ions into their lumen. This process pulls water and other solutes from the hemolymph to form a primary urine

2. The primary urine, containing nitrogenous waste products like uric acid, salts, and excess water, flows from the Malpighian tubules into the hindgut

3. As the fluid moves through the rectum, the rectal pads actively absorb most of the water and useful substances back into the hemolymph

4. The remaining waste, now a concentrated, semi-solid mass (often in the form of uric acid crystals), is expelled from the insect's body through the anus

Frass

technical term for insect waste

Pre-oral digestion

involves salivary enzymes that begin to break down solid food before it is fully ingested, liquefies prey or plant tissues into a digestible slurry that can then be swallowed and further processed in the midgut

Filter Chamber

a specialized structure within the digestive tract of sap-feeders that concentrates nutrients by diverting excess water from the midgut and Malpighian tubules to the rectum

Hematophagous

blood-feeding insects, primarily belonging to the orders Diptera (mosquitoes, flies, midges), Hemiptera (bed bugs, kissing bugs), Phthiraptera (lice), and Siphonaptera (fleas); use specialized mouthparts to pierce and suck blood from vertebrate hosts

Cuticular gas exchange

oxygen diffusing directly through the insect's external covering, the cuticle, and into the body; the cuticle must be sufficiently thin or contain pores that allow oxygen to pass through, Once oxygen diffuses through the cuticle, it moves directly into the insect's cells and tissues, Carbon dioxide, a waste product of cellular respiration, also diffuses out of the insect's body through the cuticle

Tracheal System

a network of internal, air-filled tubes and sacs that delivers oxygen directly to the body's cells; Air enters the system through external openings called spiracles, which lead to branching tracheae. These tracheae then further divide into even finer tracheoles that reach every cell

Ventilation

primarily use a tracheal system for ventilation, with air entering through paired openings called spiracles, moving through a network of branching tubes (tracheae) to the tissues via capillary-like tracheoles

Open respiratory system in aquatic insects

typically involves the spiracle-tracheal system where air enters through spiracles, travels down tracheal tubes, and diffuses into tissues

Aquatic insects adapt this system by periodically surfacing to replenish air bubbles, using siphons (like a snorkeler's tube) to access air, or employing physical gills like a plastron to extract dissolved oxygen from the water

Closed respiratory system in aquatic insects

a network of air-filled tubes (tracheae) that has no functional external openings (spiracles) for gas exchange. Instead of breathing atmospheric air, these insects must obtain all their oxygen from the surrounding water.

Hemolymph

the fluid equivalent of blood in insects, circulating within their open circulatory system to transport nutrients, hormones, waste products, and immune cells throughout the body

Components of Hemolymph

Plasma and Hemocytes

Components of plasma

water, ions, macromolecules(& subunits), nitrogenous wastes, and pigments

Hemocytes

the primary immune cells circulating in the hemolymph (insect blood) and are responsible for both cellular and humoral immunity, performing functions

Hemostasis

the process by which bleeding is stopped and wounds are sealed, achieved primarily through the rapid formation of a coagulated hemolymph clot

Phagocytosis

a core mechanism of their innate immunity, where specialized blood cells called hemocytes (primarily plasmatocytes and granulocytes) recognize and engulf small pathogens like bacteria and fungi, or self-dead cells

Encapsulation

a cellular immune response where hemocytes (blood cells) recognize and attach to foreign invaders like parasitoid eggs or pathogens, forming a protective capsule around them to isolate and neutralize the threat

Detoxification

a biological process to reduce the harmful effects of toxins, such as plant compounds and synthetic pesticides, from their environment. This complex system involves enzymatic reactions that alter toxic molecules to make them less harmful or easier to excrete, as well as symbiotic relationships with gut microbes that help degrade toxins

Hydrostatic organ

a body part that uses internal fluid pressure to create movement or to change its shape; Insects do not possess a single "hydrostatic organ" but rather use hydrostatic pressure in different ways, primarily in their larval stage and to aid certain movements in their adult stage. Unlike soft-bodied organisms that rely on a hydrostatic skeleton for all movement (such as worms), insects have a rigid exoskeleton, but they still utilize fluid-filled spaces to generate force. 

Reflex bleeding

a defensive behavior in insects where a noxious fluid, usually hemolymph, is deliberately exuded from pores or joints when the insect is threatened. This "blood" often contains bitter, acrid, or toxic chemicals, serving as a physical and chemical deterrent to predators.