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.
Crustaceans have various sensory resceptors, mainly setae over the body. Photoreceptors are also generally present.
Communication Channels: visual ; tactile ; chemical
Perception Channels: tactile ; chemical
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.
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:
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.
Animal Foods: body fluids
Primary Diet: carnivore (Eats body fluids)
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.
Biogeographic Regions: atlantic ocean (Native ); pacific ocean (Native )
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.
Range depth: 1000 (high) m.
Habitat Regions: saltwater or marine
Aquatic Biomes: coastal
Other Habitat Features: intertidal or littoral
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.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
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.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal )
