Lecture 16 - Intro to Nematodes (Quiz 8)

pseudocoelomic

nematodes are ____, meaning that they have a body cavity but lack a peritoneal lining derives from the mesoderm

hemolymph

the pseudocoelom contains

digestive system

nematodes have a complete _____ _____ because they have a mouth and an anus

water

nematodes require a ___ film to survive

cuticle

a metabolically active, outermost covering that varies between species, sex, and life cycle stage

hydrostatic skeleton

the basal zone of the cuticle is imperative for the ____ ____, where it allows for stretching and compression that provides a means for locomotion

muscles

the cuticle provides resistance for ____ in the hydrostatic skeleton

alae

lateral/sublateral cuticular thickening

cervical

___ alae is at the anterior end

caudal

___ alae is at the tail end

hypodermis

the layer below the cuticle

functions of the hypodermis

- synthesizes cuticle

- metabolism

quadrants

cords divide body muscles into ____

longitudinal

nematodes only have ___ muscles as opposed to circular ones

hydrostatic skeleton

the pseudocoelom is a component of the ____ _____ that uses liquid to allow for locomotion

apply pressure

the hydrostatic skeleton requires ability to _____ ____ to the liquid (muscle contractions)

locomotion

(study this process separately) dorsal muscles contract and compress the cuticle on that side --> force transmitted through fluid to opposite side --> stretches cuticle on that side

sides

nematodes swim on their ___ (kinda funny)

anterior nerve ring

nerve cells encircling the esophagus (the "brain")

posterior nerve ring

the ____ ____ ____ is smaller than the anterior nerve ring and functions in defecation, copulation, and reverse movement

amphids

bilateral sense organs that replace the 5th and 6th cephallic papillae at a deep cuticular pit

host detection

amphids are about the only thing open in larvae infective stages as they allow for ___ ___ and development

cervical papillae (deirids)

paired somatic sensilla at the level of the nerve ring

phasmids

posterior sensilla that have similar structure to amphids but with fewer nerve endings and are less glandular --- may be involved in growth too

buccal cavity

the ___ ___ is between the mouth and esophagus and has taxonomic significance. it may form a rigid buccal capsule or have an armament

esophagus

the ___ is a cuticle-lined muscular pump that sucks food in and forces into the intestine against high pressure

FALSE

TRUE/FALSE: the intestine has muscular activity

filariform

(aka strongyliform) type of esophagus that lacks an esophageal bulb

strongyliform

(aka filariform) type of esophagus that lacks an esophageal bulb

rhabditiform

type of esophagus with at least one esophageal bulb

rectum

this part of the digestive system causes hydrostatic pressure around the anus, leading to defecation

parthenogenic

Strongyloides spp. are ___ (no need for males! yay!) in the homogonic cycle

self-fertilizing

C. elegans think they're special because they're ___-____ hermaphrodites

live birth

most nematodes lay eggs but Trichinella and filarids give ___ ___ to L1 and vermiform embryos, respectively

amoeboid

nematode sperm is ___ instead of flagellated

villopodia

pseudopodia of nematode sperm used for locomotion

tails

male ___ are used for copulation

bursate

__- nematodes have "hand-like"/"fan-like" structures used to wrap around the female and run up and down until they find the vulva and mate

non-bursate

___-___ nematodes have a smaller tail --- which is really a modified caudal papillae

spicules

paired, hard structures on the dorsal wall of the cloaca that can be used taxonomically

spicules

___ are inserted into the vulva during copulation and hold the vulva open (yeesh)

ovary

where the germinal zone and its oogonia product lie

oviduct

where the maturation zone is and oocytes are produced and spermatheca fertilization occurs

uterus

muscular structure where shell formation occurs in addition to molding the shape of the developing embryo and adding additional components

vulva

the last part of the female's reproductive system where there is an opening in the body wall

ovijector

there is a muscular ___ at the distal end of the female (may not be important)

pheromones

nematodes use ___ as sex attractants

coiled

females seek the ___ tail of the male and may wander to find it

caudal papillae

___ ___ of the male detect the vulva

spicules

probing for mating occurs with ___ (sensory endings)

eggshell

the ___ of a nematode has 3 layers and some are operculated. the degree of development within the egg varies by species

stimuli

those with infective egg stages need to be ingested and exposed to host-specific ____ to hatch

lethargus

temporary cessation of growth associated with a molt (plateau in growth) where cuticle synthesis and protein expression occur

apolysis

after formation of a new cuticle, ___ occurs where the old cuticle separates

ecdysis

the shedding of the old cuticle following apolysis

ensheathment

the partial molt, typically in the infective stage, where a new cuticle forms and separates but doesn't shed (yet)

exsheathment

where the old cuticle performs ecdysis in response to a signal

infective

the first stage larva L1 are often ___ and are in the egg

microfilaria

Larval offspring of the group of filarids with a vermiform embryo that lacks a complete digestive tract

vector

microfilaria are infective for the ___

development

infective stages halt growth and typically require host-specific cues to resume ____ (such as eggs hatching or L3 molting)

L3

the infective stage in all Rhabditia; may be in egg or free-living (motile) and are ensheathed with specific behaviors and cuticular modifications to find a host

oral

route of transmission that eggs always use and larvae sometimes use

percutaneous

route of transmission that is only used by L3 (it is vector-borne)

vertical transmission

route of infection that involves parent to offspring

prenatal (transplacental) or lactogenic (transmammary)

vertical transmission may be ___ (____) or ____ (___)

(answer to parentheses are interchangeable with the term before)

migrate

infective stages may or may not ___ to find predilection sites

somatic migration

(study this process separately - see Dr. Hawdon's slides don't use this one it's too detailed)

arrested development

an extended and variable period of time where development is halted

L3

as an infective stage, the ___ may prolong arrested development in the environment until it encounters a host, where it exsheathes and resumes development

hypobiosis

the ability of the invading population to prolong developmental arrest of L3 WITHIN hosts

BEFORE

in hypobiosis, the L3 larva enters the host and exsheaths (BEFORE/AFTER) it arrests development

TRUE

TRUE/FALSE: stage of arrest is species-dependent

infective stage

hypobiosis allows the survival of the ___ ___ such as in the case of seasonal variation and paratenesis

synchronize

hypobiosis may ___ life cycles by vertical transmission to offspring

naive

tissue-arrested larvae are transmitted to immunologically ___ offspring

Toxocara

___ larvae arrest in older dogs and transmit transplacentally to offspring

lactogenic

hookworm L3 arrests in muscle and activates around parturition, entering the mammary gland and spreading by ___ transfer