Geographic Range
Echinophthirius horridus
is found in northern holarctic regions (Durden and Musser, 1994), i.e., in temperate,
subarctic, and arctic coastal areas of the north Atlantic and Pacific Oceans, where
its seal hosts may also be found (Grzimek, 1990).
- Other Geographic Terms
- holarctic
Habitat
The immediate habitat of
E. horridus
may be described as the skin of its only known host, the true seal (
Phoca vitulina
). The more indirect habitat of this parasite is the habitat in which its seal hosts
live. True seals, also known as harbor seals, bask and sleep on both rocky coastal
ledges and sandy beaches which are uncovered at low tide. These seals stay near the
shore in order to feed in the shallow coastal waters.
- Aquatic Biomes
- coastal
Physical Description
Anoplurans, or sucking lice, resemble their chewing relatives in that they have small, wingless, flattened bodies. However, while chewing lice (order Mallophaga ) retain mandibles for biting into their hosts, these structures are completely absent in Anopluran lice. Instead, Anoplurans have mouthparts that are highly modified for sucking the blood of their hosts. These mouthparts include four elongate stylets that form a fascicle, which pierces through the host's skin, withdraws blood, and conveys salivary material into the wound (Roberts and Janovy, 2000).
Anoplurans of the genus
Echinophthirius
have large fore-, mid-, and hindlegs, each equipped with a blunt claw that is used
to grasp tightly to the skin and fur of their Pinniped hosts as they move about on
land or in water (Kim et al., 1986). The head and thorax of these lice are thickly
covered in hairs called setae and no eyes are present externally (Miller, 1971). Their
abdomen is leathery with six pairs of small respiratory spiracles (Price and Graham,
1997).
- Other Physical Features
- ectothermic
- bilateral symmetry
Development
Like all Anopluran lice, the developmental stages of
E. horridus
include an egg, three nymphal instars, and an adult stage (Roberts and Janovy, 2000).
The hatching of an egg is followed by a slow metamorphosis, during which the nymph
becomes slightly more similar to an adult with each of the three moltings of its exoskeleton.
This mode of development is termed hemimetabolous.
- Development - Life Cycle
- metamorphosis
Reproduction
No information is available on the mating system of these lice.
Echinophthirius horridus
reproduces only when its seal hosts are on land (Thompson, 1998). Eggs are fertilized
when sperm from a male's pseudopenis is deposited into a female's genital opening;
the female then glues the fertilized eggs to the fur of her seal host (Kim et al.,
1986).
- Key Reproductive Features
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- oviparous
Female lice provide nutrients for their eggs until they are laid; then they abandon
them.
- Parental Investment
-
pre-fertilization
- provisioning
-
protecting
- female
Lifespan/Longevity
The lifespan of E. horridus is not known.
Behavior
In the family Echinophthiriidae , to which E. horridus belongs, some of the body setae have become highly modified into flattened, overlapping scales (Grzimek, 1975). In some species, these setae help to trap an air bubble, or plastron, around the body of the louse through which the louse respirates (Marshall, 1981). However, E. horridus is not capable of this form of respiration. In the water, E. horridus stretches out its legs and cannot move (Messner, 1998).
The tendency for seals to form groups at traditional "haul-out" sites facilitates
the transmission of
E. horridus
(Thompson, 1998). Studies of just how these lice spread have suggested contradictory
methods. One study indicated that
E. horridus
was transmitted vertically from mother to pup while nursing, while another study
suggested horizontal transmission (Thompson, 1998). It is evident in either case,
however, that physical contact between seals while on land is necessary for the dispersal
of
E. horridus
.
Communication and Perception
Anopluran lice have short antennae bearing chemoreceptors and tactile hairs. They are also thought to have the ability to detect chemicals in the host's bloodstream that let them know when they have hit a blood vessel.
No information is available on how these lice communicate with one another.
Food Habits
Echinophthirius horridus
feeds exclusively on the blood of true seals (
Phoca vitulina
) during all stages of development (Geraci et al., 1981).
Echinophthirius horridus
uses the blunt claws on the ends of its legs to grasp tightly onto the seal while
feeding. The louse uses its sucking fascicle to pierce through the skin of the seal
directly into a blood vessel from which it withdraws blood. This mode of feeding by
the direct insertion of mouthparts into a blood vessel is termed solenophagy (Greek
for pipe + eating). A two-chambered pump located within the louse's head acts as a
suction, while salivary anticoagulants keep the blood flowing smoothly (Roberts and
Janovy, 2000).
- Primary Diet
- carnivore
- Animal Foods
- blood
Ecosystem Roles
Echinophthirius horridus
is an obligate ectoparasite of
true seals
. There are two important ways in which
E. horridus
affects its seal hosts. First, high burdens of these ectoparasites may compromise
the seal's diving ability and thus its ability to successfully capture prey (Thompson,
1998). This can become even more serious if a nursing mother seal cannot catch enough
food to ensure a healthy milk supply for her pup. In addition,
E. horridus
has been found to be an intermediate host of the seal heartworm,
Dipetalonema spirocauda
, which can be fatal (Geraci, 1981; Lunneryd, 1992). It is not known if either of
these effects of
E. horridus
on its host are serious enough to cause a significant decrease in seal populations,
but the threat is present.
- Ecosystem Impact
- parasite
Economic Importance for Humans: Negative
This parasite has no known impact on humans.
Additional Links
Contributors
Allison Poor (editor), University of Michigan-Ann Arbor.
Julie Ritter (author), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor.
- holarctic
-
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- polar
-
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- metamorphosis
-
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- parasite
-
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
- motile
-
having the capacity to move from one place to another.
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- parasite
-
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
- carnivore
-
an animal that mainly eats meat
- sanguivore
-
an animal that mainly eats blood
References
Durden, L., G. Musser. 1994. The sucking lice of the world: A taxonomic checklist with records of mammalian hosts and geographical distributions. Bulletin of the American Museum of Natural History , 218: 90.
Geraci, J., D. St. Aubin, B. Hicks. 1981. The seal louse, Echinophthirius horridus : An intermediate host of the seal heartworm, Dipetalonema spirocauda (Nematoda). Canadian Journal of Zoology , 59 (7): 1457-1459.
Grzimek, B. 1975. Animal Life Encyclopedia, Volume 2: Insects . New York: VanNostrand Reinhold Company.
Grzimek, B. 1990. Encyclopedia of Mammals, Volume 4 . New York: McGraw-Hill Publishing Company.
Kim, K., H. Pratt, C. Stojanovich. 1986. The Sucking Lice of North America; An Illustrated Manual for Identification . University Park, PA: The Pennsylvania State University Press.
Lunneryd, S. 1992. Dipetalonema spirocauda and Corynosoma strumosum infection in harbour seal from the Kettegat-Skagerrak and the Baltic. Sarsia , 76 (4): 267-271.
Marshall, A. 1981. The Ecology of Ectoparasitic Insects . New York: Academic Press.
Messner, B. July, 1998. Is the sucking louse of seal capable of plastron respiration? The respiration of the sucking louse of seal Echinophthirius horridus . Drosera , 98 (1): 11-18.
Miller, F. 1971. Scanning electron microscopy of Echinophthirius horridus , Antarctophthirus callorhini , and Proechinophthirius fluctus with emphasis on antennal structures. Journal of Parasitology , 57: 668-674.
Price, M., O. Graham. July, 1997. Chewing and sucking lice as parasites of mammals and birds. United States Department of Agriculture, Technical Bulletin , 1849: 113-119.
Roberts, L., J. Janovy. 2000. Foundations of Parasitology; Sixth Edition . Boston: McGraw-Hill Higher Education.
Thompson, P. 1998. Prevalence and intensity of the ectoparasite Echinophthirius horridus on harbor seals ( Phoca vitulina ): Effects of host age and inter-annual variability in host food availability. Parasitology , 117 (4): 393-403.