Fall semester lecture note outline
Updated: 16 November 2006
The text below simply represents a crude lecture outline of one of the topics covered in class. It
is not meant to substitute for attending lectures or ignoring the textbook. Additional material,
including line drawings, kodachromes, and more extensive information on life-cycles and basic
biology, will be supplied in the lectures.
TOPIC 52. Chordates as Parasites
Although the majority of parasites in the world are invertebrates, it
should be of no surprise that parasitism has arisen within the chordates
as well. Classic examples include the remora, which attach to sharks and
rays, the jawless fishes (lamprey and hagfish) which prey upon other
fish, vampire bats, and brood parasitism among birds. However, additional
parasitism within the chordates exist, some of which I have outlined
- Agnatha "jawless" (lamprey and hagfish)
- This class of chordates is similar to fish, but lack jaws, scales and
paired fins. They have a simple two-chambered heart and external gill
- Agnathans possess toothed outgrowths in the oral region
where they bore into the sides of fish and suck out the blood and/or
- Lampreys (Petromyzonidae)
- 8 genera and nearly 40 species of lamprey are known to exist. Most
are free-living predators but a few are parasitic, attacking fish and
weakening or killing them.
- Eggs hatch into ammocoetes larvae
- Mouth is round, with sucker-like mouth full of rows of teeth. The
tongue is rasp-like
- Single nostril on dorsal surface of head
- Complete braincase
- Rudimentary vertebrae
- Extant parasitic species include (several others may also be found to
- Eudontomyzon danfordi (Carpathian lamprey)
- Ichthyomyzon bdellium (Ohio lamprey)
- Ichthyomyzon castaneus (Chestnut lamprey)
- Ichthyomyzon unicuspis (Silver lamprey)
- Lampetra ayresii (River lamprey)
- Lampetra fluviatilis (European river lamprey)
- Lampetra morii (Korean lamprey)
- Lampetra reissneri (Far Eastern brook lamprey)
- Lampetra similis (Klamath river lamprey)
- Lampetra spadicea (Mexican lamprey)
- Lampetra tridentata (Pacific lamprey)
- Lethenteron camtschaticum (Arctic lamprey)
- Mordacia lapicida (Chilean lamprey)
- Mordacia mordax (Australian lamprey)
- Petromyzon marinus (Sea lamprey)
- Hagfish (Myxinidae)
- Currently, there are 66 known species of hagfish in 5 genera
Myxine, Nemamyxine, Paramyxine, Quadratus). A
variety of species are yet to be named.
- More primitive than the lamprey.
- Direct development without larval stage.
- 4 pair sensory tentacles around the mouth.
- 3 accessory hearts
- Partial braincase
- Long, slender fish which produce copious amounts of slime.
- Generally found in cold oceans, often living on or in a muddy bottom
and in large groups of individuals
- A large part of the diet consists of polychaetes
- Two pair of rasps on the tongue, used to tear off chunks of prey
- Scavenge dead and dying fish; also feed on invertebrates.
Occasionally target healthy fish. Rasp and
bite into a fish, boring into the tissues and body cavity to feed.
- Osteichthyes (teleost fish)
- Remoras are perciform fish within the family Echeneidae
- Measure 0.2-2 meters in length
- Atlantic, Indian, Pacific oceans
- Head flattened with adhesive disc with transverse, moveable lamina
- Feed on ectoparasites, small fish, and left overs from the host meals
- Considered by most authors to be commensals
- 8 species of remora are considered valid
- Echeneis naucrates (live sharksucker or slender suckerfish) is
very common in warm
marine waters and can be found up and down the western Atlantic coast
from Nova Scotia to Uruguay. It associates with a variety of vertebrates
including sharks, rays, whales, dolphins, large teleost fish, and turtles.
It may also attach to ships and swim with divers. This remora feeds on
remnants of host meals, on small fish, and host parasites. Juvenile
remoras sometimes act as cleaner fish for parrotfish.
- Echeneis neucratoides (whitefin sharksucker) is found in
subtropical regions of the Atlantic and Caribbean
- Phtheirichthys lineatus (slender suckerfish) occurs in tropical
and subtropical regions of the Atlantic and Caribbean. Commonly attaches
to barracuda, various other teleosts, and turtles. Clings to body and
inside gill chambers.
- Remora australis (whalesucker) is worldwide, predominately a
warm water species, and attaches only to whales and dolphins (Cetacea)
- Remora brachyptera (spearfish remora) is found in warm waters
of the Atlantic. It attaches within the gill chambers of swordfish and
several other species of fish
- Remora osteochir (marlin sucker) is a subtropical, cosmopolitan
species which prefers sailfish and marlin. It attaches to either the gill
chambers or body of the host.
- Remora remora (common remora) is a very cosmopolitan species
that prefers warmer waters. It commonly attaches to sharks, large
teleosts, turtles, and sometimes ships. Feeds on ectoparasitic copepods.
- Remorina albescens (white suckerfish) is cosmopolitan in warm
waters and prefers Manta rays, where it likes to attach inside the mouth
and gill chambers. Occasionally it can be found associated
with sharks and black marlin.
- Pearlfish (Ophidiiformes - Carapidae)
- Ophidiiformes represent the "Cusk eels" and some species
within the family Carapidae (pearlfish) live
symbiotically within benthic invertebrates. The relationship
of the fish to the host is quasi-parasitic; only in a few
cases is the parasitism overt. In most cases, the fish either
consumes food that could be used by the host or, in most cases, simply
takes up space
- Some representative species
- Carapus acus (pearl fish) is found in the Eastern
Atlantic, residing within holothurians
- Carapus bermudensis (pearlfish) is found in the
Western Pacific on reefs. This fish lives in the body cavity of sea
cucumbers by day and forages at night
- Carapus borabornsis (pinhead pearlfish) lives in
some species of sea cucumbers in the Indo-Pacific
- Carapus dubius (Pacific pearlfish) is found in the
Eastern Pacific in the body cavity of cockles, pearl shells, and pen
- Carapus homei (silver pearlfish) resides within
some sea cucumbers in the Indo-Pacific
- Carapus mourlani (star pearlfish) is found in sea
stars and holothurians in the Indo-Pacific
- Encheliophis gracilis (graceful pearlfish) lives in
some sea stars and sea cucumbers in the Indo-West Pacific
- Encheliophis sagamianus (pearlfish) off the coast
of Japan in deep water in holothurians
- Encheliophis vermicularis (worm pearlfish) in sea
cucumbers in the Indo-Pacific
- Encheliophis vermiops (pygmy pearlfish) has
been rarely found in the Indo-Pacific in burrowning holothurians
- Onuxodon fowleri (bivalve pearlfish) is found in
the Indo-Pacific and prefers clams and oysters
- Onuxodon margaritiferae (bivalve pearlfish) occurs
in marine waters off western Australia. It prefers to reside within sea
cucumbers and the mantle cavity of bivalves
- Onuxodon parvibrachium (oyster pearlfish) resides
within the giant oyster (Pycnodonta hyotis) in the Indo-Pacific
- Parasitic male fish (Lophiiformes)
- The order Lophiiformes (over 210 spp) contains a variety of families
of fish commonly
termed "anglerfish," "toadfish," "monkfish," "dreamers," and "sea-devils."
- Members from at least 4 families contain some deep sea species with
parasitic males. Because the species are often poorly known, other
species and families may eventually be found to have parasitic males.
- Males are small, and attach to a female with their teeth. The teeth
and jaw then gradually recede and the circulatory systems of the two fish
merge. They become irreversibly joined. Males then provide a constant
supply of sperm to the female. Probably an adaptation because of the
difficulty of finding a mate in some deep sea situations.
- Families containing one or more parasitic species (families may
contain both parasitic and non-parasitic species and the number of
species listed does not reflect the total number of parasitic species
within each family)
- Caulophrynidae (fantails - 5 spp total in 2 genera)
- Ceratiidae (seadevils - 4 spp total in 2 genera)
- Linophrynidae (leftvents - 26 spp total in 5 genera)
- Oneirodidae (dreamers - 58 spp total in 13 genera)
- Vampire fish, Candiru, or Canero (Vandellia cirrhosa)
- The family Trichomycteridae (order: Siluriformes) contains 42 genera
and 178 described species of freshwater fish commonly referred to as the
"pencil catfish" or "parasitic catfish." Representative species are
distributed throughout South America, Costa Rica, and Panama
- Most species are slender, sometimes transparent or nearly so, and only
reach a few centimeters in length
- Most species inhabit sandy to muddy bottoms; some are nocturnal
- Most species are harmless, feeding on protozoa, rotifers, and insect
larvae off the bottoms of rivers
- Some species are capable of burrowing through the body wall of
fish and have been found in the body cavity. Whether this is incidental
or common is not known.
- Some species are truly parasitic, however, entering the gill
chambers of larger fish, erecting a spine (or series of spines) to hold
them into place, and
feeding off blood from the gill filaments for a minute or two
- Rarely, in the Amazon, members of the genus Vandellia (and
perhaps a few closely related species in other genera) accidently
enter the urethra of humans urinating in the water. Even more rarely, the
anus and vagina have been reported to serve as suitable
orifices. Apparently, the adage states, the urine is mistaken for urea
given off in low quantity by fish gills (but at least one paper disputes
this hypothesis). The species
most commonly reported as intraurethral is Vandellia
- Surgical removal of the catfish is necessary. Reputed are a
couple of local plant remedies (the Xagua plant and Buitach apple), which
are inserted into the affected
area and are supposed to kill and dissolve the fish.
- See also 1973, Urology 1: 265-267
- All members of the family are banned from import into the U.S.
- Brood parasitism
- This is an association where one bird (the parasitic bird) lays
its eggs within the nest of another bird (the host or foster bird). The
foster bird then cares for the offspring of the invader. Most of this is
- About 1% of all birds (103 species) are known to
practice brood parasitism
- Some species of birds reject the eggs of a brood parasite, whereas
others will accept the egg.
- Some foster hosts raise the parasite along with their own young. In
other cases, such as in cuckoo parasitism, either the female cuckoo will
remove or damage a host egg when laying her own or the offspring will
evict all other eggs from the nest upon hatching.
- Some representatives
- Anatidae - A number of anatids display various types of brood
parasitism, both intra- and inter-specific. Because the young are
precocial (up and around soon after hatching), the impact of the
parasitism on the host tends to be low.
- the South American black-headed duck (Heteronetta
atricapilla) lays its eggs within the nests of other waterfowl,
especially red-fronted coots and rosy-billed pochards. The offspring are
capable of running around soon after hatching so they do not need to be
fed by the foster parent. Their parasitism is considered to be fairly benign.
- the female goldeneye duck (Bucephala clangula) can double
her reproductive output by combining brood parasitism with normal nesting.
She will lay her eggs within other goldeneye nests, and also nests of a
variety of other species of waterfowl.
- The redheaded duck (Aythya americana) will lay eggs not
only in their own nests, but also the nests of conspecifics and other
types of waterfowl.
- other known brood parasites include ruddy ducks, canvasbacks, black
teal, blue-winged teal, northern shovelers, whistling-ducks, mallards,
gadwalls, norther pintails, and others.
- Cuculidae - Of the 143 known species of cuckoo, 50 old world species
(Cuculinae, Centropinae, Coccyzinae) and 3 new world species
(Neomorphinae) are known to be parasitic.
- European cuckoo (Cuculus canorus) eggs are often very similar
to host eggs, both in size and markings. Many hosts are very good at
detecting foreign eggs within the nest.
- Female cuckoos know which species of host she will have the most
success parasitizing, apparently based on past experience with that host
as a brood parasite herself.
- Cuckoo eggs require 0.5-1.5 days shorter incubation than host eggs.
Once the hatchling is about 10 hours old, it pushes any solid object it
contacts out of the nest including unhatched eggs and host offspring
- Foster parents continue to feed the oversized offspring, which has
mouth markings very similar to host hatchlings.
- Estrildidae - All 19 species within the genus Vidua are brood
parasites. Other estrildids raise the offspring as their own.
- Indicatoridae - All 17 species of African honeyguides
(Indicator, Melichneutes, Melignomon,
Prodotiscus) are parasitic. Preferred hosts include barbets,
although some utilize nests of woodpeckers and bee-eaters. Upon hatching,
the offspring uses a sharp mandibular hook to punch holes in the host
eggs. This hook drops off as the bird grows older.
- Icteridae - Of the 6 known species of
cowbirds, 5 are known to be parasitic. Brown-headed cowbirds tend to use
neotropical migrant birds as hosts and parasitism has been so
successful that populations of some of these migrants are declining with
up to 70% of the nests of some hosts being parasitized.
- Molothrus aeneus (bronzed cowbird) - South, Central, and North
- Molothrus ater (brown-headed cowbird) - North America
- the female cowbird will lay an egg within a nest after the host has
already laid two or more eggs, but before incubation has begun. This
usually occurs just before sunrise.
- the female cowbird usually removes one or more of the host eggs by
piercing the egg with her bill and carrying it away to be eaten.
- if the cowbird egg is too dissimilar to the host eggs, some birds will
abandon their nest or remove the cowbird eggs.
- Molothrus badius (bay-winged cowbird) - South America
- Molothrus bonariensis (shiny cowbird) - South, Central, and
- Molothrus rufoaxillaris (screaming cowbird) - South America
- Scaphidura oryzivora (giant cowbird) - South, Central, and
- Ploceidae - Of the 117 known species, only Anomalospiza
imberbis (cuckoo-weaver or cuckoo-finch) South of the Sahara is known
to be parasitic where it lays its eggs in the nests of some
species of warblers, especially cisticolas and prinias.
- Some other avian species actually practice intraspecific brood
parasitism, where they place eggs within the nests of members of their
own species. These include snow geese and cliff swallows.
- Oxpeckers "tick birds" (Buphagidae)
- Considered quasi-parasitic, with both parasitic and mutualistic
- Two species of oxpeckers exist. Buphagus
erythrorhynchus (red-billed oxpecker) and Buphagus
oxpecker). The former species prefers thicker haired animals like
antelope and giraffe, whereas the latter likes
thinner haired animals like buffalo or rhinoceros. However, considerable
overlap in feeding preference occurs.
- Some host species, for instance elephants, are reputed not to tolerate
- They often occur in small flocks, eating ectoparasites such as ticks,
lice, flies, and fleas. However, they also readily consume secretions
(earwax, sweat, tears, saliva, mucus), dead skin, wound tissues,
- Birds cannot survive simply on insects. The ticks they eat are
engorged, and it is actually the blood within the ticks that is the
predominate source of energy for the birds. However, studies have
that the birds only spend about 5% of their time foraging for ticks and
that other sources of food may be more important
- Recent studies suggest
that oxpeckers do little to reduce the number of ticks per host animal.
However, even eliminating low numbers of engorged females may
greatly affect the number of larval ticks that eventually end up in the
- One study (2000, Behavioral Ecology 11: 154-166) noted that
oxpeckers will actually enlarge a
break in the skin caused either by ticks or a scratch, and that animals
without oxpeckers had fewer wounds and a faster wound healing time. Most
foraging by oxpeckers seems to be in obtaining blood and secretions from a
host, rather than in removing ticks
- Arctic skua or parasitic jaeger (Stercorarius parasiticus)
- These (Charadriiformes) birds are holoarctic (arctic and subarctic
Canada, Russia) and breed in grassy or mossy tundra near water
- They tend to be opportunistic feeders, predominately predatory, with a
diet that includes fish, insects, rodents, carrion, other birds, and bird
- These birds are noted for robbing food from other birds (ingested or
otherwise). They will sometimes pursue and hound other fish-eating birds
to a point causing the victim to regurgitate a recently ingested meal
which the Skua will then steal. Perhaps not parasitism
per sec, but along with its name its interesting enough to be
included on this page
- Sharp-beaked finch or Vampire bird (Geospiza nebulosa)
- 13 species of finches in the genus Geospiza occur within the
- Many species eat ectoparasitic arthropods found in the plummage of
- The sharp-beaked finch lives in the highlands of some of the central
and western islands. It commonly pecks open the eggs of boobies (or
sometimes rolls an egg around until it cracks open from a fall) to feed
on the contents
- On Wolf Island, populations of sharp-beaked finches have also
developed a habit of pecking at the skin of the legs of boobies until
blood is drawn. The birds then drink the blood and have been given the
name "Vampire finch."
- Galapagos mockingbirds (Nesomimus spp.)
- Three species, N. macdonaldi (Espanola mockingbird), N.
melanotis (San Cristobal mockingbird), and N.
parvulus (Galapagos mockingbird) all drink blood from living hosts
which may include land iguanas, marine iguanas, tortoises, lava lizards,
geckos, sea lions, seabirds, boobies, Waved
albatross chicks, and/or goats.
- In many (but not all) cases, wounds are already established by other
causes prior to the birds targeting the host.
- Mockingbirds on some islands drink blood, whereas birds on other
islands do not seem to drink blood.
- Birds have also attempted to drink blood from minor wounds of
researchers (1987, Auk 104: 517-521).
- Vampire bats
- Vampire bats are native to Central and South America and can often be
found in caves during the day either singly or in groups
- Small bats, 6-8 cm in length
- Three species exist (Desmodus rotundus, Diaemus
youngi, Diphylla ecaudata)
- Species tend to be timid, but eventually chisel out a piece of skin of
sleeping animals such as cattle,
goats, swine, horses, and even large birds. The bat then laps up the
blood over a 15-20 minute period of time
- A potent anticoagulant ("draculin") is found within the saliva. It is
a noncompetitive inhibitor of activated factor X
- Vampire bats need to ingest about 2 tablespoons of blood each day to
stay healthy. Failure to feed will result in rapid deterioration. These
bats will also regurgitate a blood meal and share with a roostmate
- Although many cases of vampire bats feeding on humans are probably
myth, there are numerous true documented cases. These cases even include
whole families being parasitized on a nightly basis
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