Clistosaccus paguri

Geographic Range

The geographic range of Clistosaccus paguri lies within the northern latitudes of the two major oceans. In the Atlantic, they have been found from the White Sea in Russia to the shores of Nova Scotia. This parasite has also been sighted in E. Greenland, Sptizbergen, Iceland, Newfoundland, and the Faroes Islands. Clistosaccus paguri also live along the coast of Alaska in the North Pacific, from the Bering Sea to Kodiak Island, as well as in the Sea of Japan and the Sea of Okhotsk. (Høeg and Rybakov, 1992)

Habitat

The vertical distribution of Clistosaccus paguri in the oceans ranges from rather shallow waters to less than 1000 m depths.

The host specificity of C. paguri is low and they can be found on a surprising number of species. They normally parasitize crabs of the Infraorders Anomura and Caridea. Some specific examples, more commonly known as hermit crabs, include Anapagurus laevis, Pagurus bernhardus, P. capillatus, P. dalli, P. pubescens, and P. splendescens. (Høeg and Rybakov, 1992; Høeg, 1982)

  • Range depth
    1000 (high) m
    3280.84 (high) ft

Physical Description

Parasitic barnacles of the Order Rhizocephala lack any segmentation, a gut, or appendages. Rootlike processes are used to absorb nutrients from their crab hosts. An external protruding mass containing female gonads is also evident on the host's ventral side during mature stages of the life cycle.

Clistosaccus paguri is distinguished from similar species because it lacks a cuticular shield, and is white during all stages of development. In addition to the absence of aesthetascs, or chemosensory sensillae, larvae hatch without any morphological or size variations associated with sex. This ambiguity suggests sex may be determined by environmental cues. Early developmental stages prior to complete maturation into an adult are also characterized by a marked absence of a mantle aperture.

Clistosaccus paguri lack appendages and anchor themselves to their host with a stalk that continually grows with age. This stalk measures at least 2 mm in width and always exceeds 1/5th the length of the parasite's emerging externa, which may reach 2.5 mm to 10.5 mm at maturity. Lying at the end of the stalk, the roots extend in a dendritic fashion throughout host tissue. They typically do not reach beyond the abdomen and are distinctly semi-transparent. The externa that resides outside of the host's body is a structurally simple reproductive organ that basically consists of a muscular mantle that encloses a brood chamber and a visceral sac with a large ovary. At maturation an orifice appears to communicate with the external environment. (Høeg and Lützen, 1995; Høeg, 1982)

Development

Hatching as fully developed cyprids, the larvae of Clistosaccus paguri skip the naupliar stage of crustacean life cycles. As a result, each stage does not molt and will accomplish the tasks of host infection and male implantation of sperm cells all by itself. From a brood of sexually indistinct larvae, a "female" cyprid settles on the abdomen of a host crab, penetrates the integument with its atennule, and injects the cells that will develop into the internal parasite. After approximately 3 months, an externa becomes visible and begins to emerge. The protrusion may occur at any point during the host's molting cycle for the non-calcified abdominal cuticle is simply dissolved. Upon emergence, Clistosaccus paguri will subsist through a period of nearly 4 months without a mantle aperture. For other rhizocephalan barnacles, this opening typically serves as an entrance where male cyprids metamorphose into the sperm-producing trichogon larval stage, enter the mantle cavity, and migrate into a receptacle. Although they initially lack this aperture, Clistosaccus paguri externae do display the presence of a receptacle for receiving spermatogonia.

Similar to the earlier bypassing of the kentrogon stage during host invasion, "male" cyprids of C. paguri do not develop into trichogon larvae, but deliver their germ cells by means of the same antennule penetration method utilized by their female counterparts. Finding virgin externa is quite a challenge considering they must not only locate an appropriate host first, but also "blindly" perform all of their responsibilities without the aid of sensory aesthetascs. How this is accomplished is still unknown. Aside from newly emerged externae, a cyprid may also implant cells into a late stage, still internal primordium by penetrating both host and parasite integuments. Without any stimulation from male cyprids, an externa will remain in stasis and fail to further develop. Potential spermatogonia may also originate from a cyprid's embryonic cells. Once injected into mantle tissue, the cells migrate into a lumen within the center of the receptacle, where spermatogenesis begins. The cells differentiate, forming mature sperm, and fertilize the eggs produced by an adult female externa. The stage following male implantation and prior to oogenesis of the first batch of eggs lasts about 75 days. The last stage in the reproduction of Clistosaccus paguri exhibits signs of oviposition and formation of the mantle aperture. The duration of this stage leading to release of the first brood of cyprids has been estimated to be about 2.4 months. This species generally releases only one or two broods.

It is important to note that Clistosaccus paguri pass through the stages of their life cycle without discernable signs of molting. (Høeg, 1982; Høeg, 1990)

Reproduction

From a brood of sexually indistinct larvae, a "female" cyprid settles on the abdomen of a host crab, penetrates the integument with its atennule, and injects the cells that will develop into the internal parasite. After approximately 3 months, an externa (gonadal mass that is external) becomes visible and begins to emerge. The protrusion may occur at any point during the host's molting cycle for the non-calcified abdominal cuticle is simply dissolved. Upon emergence, Clistosaccus paguri will subsist through a period of nearly 4 months without a mantle aperture. For other rhizocephalan barnacles, this opening typically serves as an entrance where male cyprids metamorphose into the sperm-producing trichogon larval stage, enter the mantle cavity, and migrate into a receptacle. Although they initially lack this aperture, Clistosaccus paguri externae do display the presence of a receptacle for receiving spermatogonia.

Similar to the earlier bypassing of the kentrogon stage during host invasion, "male" cyprids of C. paguri do not develop into trichogon larvae, but deliver their germ cells by means of the same antennule penetration method utilized by their female counterparts. Finding virgin externa is quite a challenge considering they must not only locate an appropriate host first, but also "blindly" perform all of their responsibilities without the aid of sensory aesthetascs. A cyprid may also implant cells into a late stage, still internal primordium by penetrating both host and parasite integuments. Without any stimulation from male cyprids, an externa will remain in stasis and fail to further develop. Potential spermatogonia may also originate from a cyprid's embryonic cells. Once injected into mantle tissue, the cells migrate into a lumen within the center of the receptacle, where spermatogenesis begins. The cells differentiate, forming mature sperm, and fertilize the eggs produced by an adult female externa. The stage following male implantation and prior to oogenesis of the first batch of eggs lasts about 75 days. The last stage in the reproduction of Clistosaccus paguri exhibits signs of oviposition and formation of the mantle aperture. The duration of this stage leading to release of the first brood of cyprids has been estimated to be about 2.4 months. This species generally releases only one or two broods. (Høeg, 1982; Høeg, 1990; Roberts and Janovy, Jr., 2000)

Behavior

Høeg & Lützen (1995) describe the phenomenon of re-infection in hosts of Clistosaccus paguri as a contagious distribution. If the presence of one parasite improves the chances for another to settle on the same host, then an excess of multiple infections will be a straightforward consequence of re-infection. This characterization differs from a Poisson distribution, which operates on chance alone, in that the incidence of multiple infections displays a clearly asymmetrical numerical distribution along with a great variance in the size of observed externae. This statistical picture excludes the likelihood of polyembryony but better corresponds with multiple infections taking place over a period of time. One explanation offers the scenario in which cyprids, although possessing motility, remain within the vicinity of the host's shell and give rise to re-infection. Another possibility already mentioned states simply that a host's ability to remain healthy decreases as a result of each parasite it harbors.

Clistosaccus paguri castrate their host like most other rhizocephalans, although parasitic sterilization may be a better term for the gonads of either sex do not degenerate completely. Any effect on the host's regular molting cycle following emergence of a parasite is undetermined. (Høeg and Lützen, 1995; Høeg, 1982)

Communication and Perception

Crustaceans have various sensory resceptors, mainly setae over the body. Photoreceptors are also generally present. (Brusca and Brusca, 2003)

Food Habits

Unlike other rhizocephalans, host penetration is not preceded with the formation of a kentrogon larval phase or an injection stylet. Instead, the antennule of cyprids actively moves back and forth all the while dissolving the cuticle of the host. This pumping mechanism contrasts with the "straight-through" push utilized by other species' more rugged stylets. A functional female cyprid of Clistosaccus paguri infects the host just below the integument on the dorsal left side of the abdomen no deeper than approximately 50 µm and attaches at the site where the externa will eventually emerge. Evidence suggests that the cyprid's embryonic cells are injected into the host's hemocoel since these cells lack any specialized morphology or function in the free-swimming larva. The inoculated material forms a conspicuous mass above and lateral to the central nervous system, where tumor growth begins. Prior to the sprouting of a ramifying system of roots at late-stage internae, the developing parasite can receive nutrients via the absorptive function of its general epithelium. The roots arise only following nucleus differentiation and development. (Høeg, 1990)

  • Animal Foods
  • body fluids

Ecosystem Roles

The host specificity of C. paguri is low and they can be found on a surprising number of species. They normally parasitize crabs of the Infraorders Anomura and Caridea. Some specific examples, more commonly known as hermit crabs, include Anapagurus laevis, Pagurus bernhardus, P. capillatus, P. dalli, P. pubescens, and P. splendescens.

Species Used as Host

Other Comments

Clistosaccus paguri is sympatric with the rhizocephalan Peltogaster paguri throughout most of the former's geographic range. Although they share the same environments and are at times confused with each other, the two species are easily distinguished based on physical characteristics.

Due to their distinctive life stages, or lack thereof, Clistosaccus paguri are more accurately classified in the Suborder Akentrogonida.

Contributors

Renee Sherman Mulcrone (editor).

James Tseng (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

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

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Høeg, J. 1985. Male Cypris Settlement In Clistosaccus Paguri Lilljeborg (Crustacea: Cirripedia: Rhizocephala). Journal of Experimental Marine Biology and Ecology, 89: 221-235.

Høeg, J. 1982. The Anatomy And Development Of The Rhizocephalan Barnacle Clistosaccus Paguri Lilljeborg And Relation To Its Host Pagurus Bernhardus (L.). Journal of Experimental Marine Biology and Ecology, 58: 87-125.

Høeg, J. 1995. The Biology And Life Cycle Of The Rhizocephala (Cirripedia). Journal of the Marine Biological Association of the United Kingdom, 75: 517-550.

Høeg, J. 1990. “Akentrogonid” Host Invasion And An Entirely New Type Of Life Cycle In The Rhizocephalan Parasite Clistosaccus Paguri (Thecostraca: Cirripedia). Journal of Crustacean Biology, 10: 37-52.

Høeg, J., J. Lützen. 1995. Life Cycle And Reproduction In The Cirripedia Rhizocephala. Oceanography and Marine Biology: an Annual Review, 33: 427-485.

Høeg, J., A. Rybakov. 1996. Development And Taxonomy Of The Mycetomorphidae And The Significance Of Their Reproductive System In Rhizocephalan Evolution (Crustacea: Cirripedia: Rhizocephala). Zoologischer Anzeiger, 234: 253-269.

Høeg, J., A. Rybakov. 1992. Revision Of The Rhizocephala Akentrogonida (Cirripedia), With A List Of All The Species And A Key To The Identification Of Families. Journal of Crustacean Biology, 12: 600-609.

Raibaut, A., J. Trilles. 1993. The Sexuality Of Parasitic Crustaceans. Advances in Parasitology, 32: 367-444.

Roberts, L., J. Janovy, Jr.. 2000. Gerald D. Schmidt & Larry S. Roberts' Foundations Of Parasitology, Sixth Edition. United States of America: McGraw-Hill.