Rhizocephalan Parasite Research Articles

Effects of the Briarosaccus callosus Infestation on the Commercial Golden King Crab Lithodes aequispina

Commercial crab populations off the Kamchatka coasts are infested to a considerable degree by the rhizocephalan parasite Briarosaccus callosus: of 769 Lithodes aequispina males examined, 43 (5.7%) were parasitized. Infestations result in the feminization of the crabs, a significant decrease in the cheliped length, and a significant decrease in the carapace length and width. We suggest that commercial selection of healthy males, and the returning of unsuitable crabs, including infested ones, back into the sea, results in an increase of the proportion of infested crabs in the population, their elimination from reproduction, and, eventually, the gradual degradation of a whole population. To minimize as far as possible the negative effects of commercial crab harvesting, all infested crab specimens caught must be destroyed, either aboard or elsewhere, instead of throwing them back into the sea.

Observations on the agonistic behavior of the swimming crab Charybdis longicollis Leene infected by the rhizocephalan barnacle Heterosaccus dollfusi Boschma

The effects of the invasive rhizocephalan parasite Heterosaccus dollfusi on the agonistic behavior of the invasive swimming crab Charybdis longicollis were quantitatively analyzed under standardized conditions. The behavior of uninfected male crabs contained more aggressive elements than that of uninfected females. In encounters between infected males, markedly fewer and less aggressive elements were displayed than in encounters between uninfected males, whereas in encounters between infected females, more aggressive elements were displayed than in encounters between uninfected females. It is suggested that the presence of the parasite reduces belligerence in male crabs, possibly to avoid injury and to enhance the life expectancy of host and parasite.

Adaptive Responses of the Larvae of Cirripede Barnacle Peltogasterella gracilis to Changes in Seawater Temperature and Salinity

The responses of the larvae of the cirripede barnacle Peltogasterella gracilis (Crustacea: Cirripedia: Rhizocephala) that parasitizes the hermit crab Pagurus pectinatus to different combinations of seawater temperature (25, 22, 20, 16, and 12°C) and salinity (from 34 to 8‰) were studied in a laboratory. The nauplii of P. gracilis completed the entire cycle of development at 22 to 12°C in a narrow range of salinity (from 34 to 28‰), which agrees well with the environmental conditions of the crab hosts' habitat. At favorable temperatures (22–20°C) and salinity (34–28‰), the nauplii reached the cypris stage in 88 ± 2 h, while at 12°C and 34–30‰, the naupliar development took 156 ± 5 h. The cypris larvae appeared more resistant compared with the nauplii, in terms of changes in both the temperature and salinity of seawater. They actively swam at all experimental temperatures and in the salinity range of 34–18‰. At temperatures (22–16°C) and salinities (34–24‰) favorable for the cyprids, their longevity in plankton equaled 6–10 days. Thus, the nauplii of P. gracilis is the more vulnerable stage of development in the life cycle of this parasitic barnacle. The tolerance against changes in environmental factors is due to the adaptive capabilities of parasitic larvae and the environmental conditions in the habitats of its host, a typical marine crustacean. The insignificant parasitization rate of the hermit crab by its rhizocephalan parasite may be explained by the death of the nauplii of P. gracilis, which occurs when they enter to the surface water layer.

Bivalve molluscs, Mytilus trossulus and Hiatella arctica, as facultative epibionts of the crab, Hemigrapsus sanguineus, infested by the rhizocephalan, Sacculina polygenea

At the period of sexual reproduction of the rhizocephalan parasite, Sacculina polygenea, the sacculinized crab, Hemigrapsus sanguineus, can serve as a temporary carrier for juvenile bivalve molluscs, Mytilus trossulus and Hiatella arctica as facultative epibionts. Such epizoans are never found on the crabs without the rhizocephalan externae or scars produced by the externae. The correlation between sacculinization and the bivalve epibionts is presumably due to maternal ‘brooding care’ with altering grooming behaviour of the crabs infested by S. polygenea.

Morphological modifications caused by Sacculina polygenea in Hemigrapsus sanguineus (De Haan) (Brachyura: Grapsidae)

The morphological modifications caused by Sacculina polygenea in the grapsid crab Hemigrapsus sanguineus were examined. Parasitized males carrying externa were divided into seven stages of feminization by the degree of reduction of the first and second pleopods and the appearance of biramous pleopods on the third to fifth abdominal segments. All males examined retained first pleopods and most of them were Stage I or II. The development of femaletype biramous pleopods rarely occurs. Only 10.1% crabs were in advanced stages of feminization. Enlargement of the abdomen and reduction of chela height in parasitized males were pro nounced in small males and less so in larger males. Modification caused by the rhizocephalan parasite likely proceeds from when the host is young and small.

Loxothylacus ihlei Boschma, (Rhizocephala) and its effects on the mud crab, Scylla serrata (Forskål), in northern Australia

Abstract. Loxothylacus ihlei, a rhizocephalan parasite of the mud crab, Scylla serrata (Forskål), is reported for the first time in Australian waters. The parasite is described and found to be variable in a number of characters. Most infected S. serrata, collected from commercial catches in the Northern Territory, Australia, were significantly smaller than uninfected crabs, and their abdominal flaps were relatively larger than those of mature females. Annual prevalence of infection was low (2.1%), with the monthly variation ranging from negligible early in the year to around 7% in November.

イソガニに寄生するフクロムシの寄生状態

イソガニに寄生するフクロムシの寄生状態

Population Dynamics and Life History Characteristics of the Blue Crabs Callinectes similis and C. sapidus in Bay Environments of the Northern Gulf of Mexico

Abstract. The population dynamics and life history characteristics of Callinectes similis and C. sapidus in the Mobile Bay‐Mississippi Sound estuarine system of the northern Gulf of Mexico were studied. We report that C. similis is numerically dominant in open‐bays, while C. sapidus is more abundant in shallow salt marshes. Juvenile C. similis recruit into both open‐bays and salt marshes, but juvenile C. sapidus primarily recruit into shallow salt marshes. Sex ratios of C. similis and C. sapidus were generally skewed towards higher proportions of males than females. Callinectes similis appears to have a life cycle similar to that of C. sapidus. Egg‐carrying C. similis migrate to higher salinity waters and presumably release larvae to nearshore shelf waters; following development, the larvae re‐invade estuaries as megalopae. Juvenile C. similis grow more slowly than C. sapidus. This may be attributable to reduced feeding rates. Marked differences in fecundity and reproductive effort were found between these species. Callinectes similis and C. sapidus, respectively, produced 2.4–5.5 times 105 and 2.1–3.2 times 106 eggs and invested 24–49 and 171–372 kJ per brood. Rhizocephalan barnacle infestation by Loxothylacus texanus was encountered in C. sapidus, while sympatric C. similis were free of this rhizocephalan parasite.

First Canadian record of Paralomis bouvieri Hansen, 1908 (Decapoda: Anomura: Lithodidae), infected by the rhizocephalan Briarosaccus callosus (Cirripedia: Peltogastridae) and carrying a hyperparasitic cryptoniscinid isopod (Epicaridea)

The stone crab Paralomis bouvieri is reported for the first time from Canadian Atlantic waters. Combined records now indicate a continuous boreal circum-Atlantic distribution. This is also the first documentation of the rhizocephalan parasite Briarosaccus callosus infecting P. bouvieri. Growth rings on the cuticular shield of B. callosus showed an age of about 4 years. A secondary hyperparasitic infection by a cryptoniscinid isopod was also noted. The crabs were found in much shallower waters than previously recorded. Host, parasite, and hyperparasite specimens have been deposited at the Atlantic Reference Centre, Huntsman Marine Science Centre, St. Andrews, New Brunswick, Canada.

ANATOMY OF ARCTUROSACCUS KUSSAKINI, NEW GENUS, NEW SPECIES (RHIZOCEPHALA: AKENTROGONIDA), FROM THE ULTRAABYSSAL ISOPOD ANTARCTURUS ZENKEWITCHI KUSSAKIN (ARCTURIDAE)

ABSTRACT Arcturosaccuskussakini, new genus, new species, is a rhizocephalan parasite of the ultraabyssal isopod crustacean Antarcturus zenkewitchi Kussakin, collected off the east coast of Iturup Island, Kuril Islands, Russia. The morphology of the Rhizocephala Akentrogonida is reviewed and compared to this new species. Arcturosaccus has multiple layers of cuticle in the mesenteric canal, and a few spermatogenic islets floating free in the mantle cavity. By these characters, the new species seems most closely related to the genera Duplorbis and Cryptogaster, but differs from them by (1) the presence of the paired ovary, (2) the position of the mesentery, and (3) the mantle aperture, and by the shape of the externa. Naupliar instars are absent in the life cycle of Arcturosaccus kussakini and the larvae hatch as cyprids.

Effect of Salinity on Osmoregulation and Survival of a Rhizocephalan Parasite, Loxothylacus panopaei, and Its Crab Host, Rhithropanopeus harrisii

The rhizocephalanLoxothylacus panopaei parasitizes the estuarine crabRhithropanopeus harrisii. Parasitized crabs are abundant during summers when salinities increase to around 15‰ in the crab–s habitat and scarce when salinities are lower. The two hypotheses that were proposed to explain this pattern were (1) that the parasite interferes with crab osmoregulation causing the host to die in low salinity water and (2) that salinity tolerance of the parasite larvae controls the incidence of parasitism. The first hypothesis was shown to be incorrect because (1) osmoregulation of infected crabs was, not altered by the parasite and (2) crab mortality did not increase in low salinity water down to 1‰. Unparasitized and parasitized crabs and the parasite itself were hypersomotic at low salinities (below 27‰ for the crabs). The parasite became slightly hyperosmotic at high salinities while the crabs were slightly hypoosmotic. The second hypothesis appears correct, becauseL. panopaei larvae survived poorly in salinities below 10‰ but well in salinities from 10 to 15‰. ThusR. harrisii, have a reproductive refuge at salinities below 10‰, because parasite larvae cannot survive and infect the mud crab at these low salinities.

Boschmaella japonica, New Species, a Parasite on the Barnacles Chthamalus challengeri and Balanus amphitrite amphitrite from Japan (Crustacea: Cirripedia: Rhizocephala: Chthamalophilidae)

Abstract A new rhizocephalan parasite which infests the barnacles Chthamalus challengeri and Balanus amphitrite amphitrite is described. It is known only from the type locality, Aburatsubo, Kanagawa Prefecture, Japan. Its position in the family Chthamalophilidae is assured by the cyprids lacking a thorax, by the position of the mesenteric canal opposite to the stalk, and by its host being a balanomorph barnacle. Among the three previously described species of the Chthamalophilidae, the new species most closely resembles Boschmaella balani, but it differs in details of the internal root system and in the externa being found both on the host body and on the inner mantle. About two‐thirds of the infested hosts carry more than one externa.

Bocquetia rosea, New Genus, New Species, an Unusual Rhizocephalan Parasite of a Sponge-Inhabiting Barnacle, Membranobalanus orcutti (Pilsbry), from California

Bocquetia rosea, New Genus, New Species, an Unusual Rhizocephalan Parasite of a Sponge-Inhabiting Barnacle, Membranobalanus orcutti (Pilsbry), from California

Correlation between cypris age, settlement rate and anatomical development inLernaeodiscus porcellanae(Cirripedia: Rhizocephala)

The correlation between settlement rate, cypris age and anatomical maturation on the ultrastructural level was studied in female cyprids ofLernaeodiscus porcellanae, a rhizocephalan parasite of the porcelain crabPetrolisthes cabrilloi. There is no settlement on crabs until the cyprids are at least 2–3 days old, and maximum settlement activity is only reached 5 days after the moult from nauplius to cyprid (at 15 °C). Thereafter the settlement rate decreases again, possibly due to depletion of energy reserves in the non-feeding cyprids. Ultrastructural investigations show that the female cyprids cannot metamorphose into a kentrogon until 2–3 days after the moult from nauplius to cyprid, which explains the absence of settlement in young cyprids. Competence to metamorphose depends on changes in the cement glands, the epidermis and the antennules. The cypris moult cycle is arrested at an early stage and moult activity is only resumed after settlement. This ensures that the cyprids will not initiate metamorphosis while free-swimming.

Morphology of the Externa of Briarosaccus callosus Boschma (Rhizocephala) and the Relationship with Its Host Lithodes aequispina Benedict (Anomura)

During 3 surveys of fjords in northern British Columbia between October 1983 and July 1984, a total of 707 rhizocephalan parasites (Briarosaccus callosus) on 572 anomuran king crabs (Lithodes aequispina) were examined. Briarosaccus callosus is a large species with extemae varying from 9 to 165 mm in curve length. Lithodes aequispina is probably infected with B. callosus early in life. The extema of B. callosus begin producing clutches of eggs shortly after emergence from the crab host when still small in size (9 to 15 mm in curve length). Each clutch of eggs is deposited into the mantle cavity where the eggs develop into nauplii which are probably extruded by the muscular contractions of the mantle wall. The extema then moults the outer covering and the mantle cavity lining and the entire cycle is repeated. There appears to be no seasonality in B. callosus reproduction and at least 33 cycles may occur during the life of an average sized (curve length of 95 mm) parasite. The majority (96%) of the extemae were attached to the flexible cuticle of the ventral surface of the abdomen and were oriented perpendicular to the long axis of the crab with the opening of the mantle cavity directed towards the crab's left side. Exterae do not appear to prohibit the crab from moulting, thus both host and parasite grow together for what may be the duration of the crab's life. Multiple parasitism may affect the growth of the crab and the extemae but the size of male and female crabs with 1 extema were similar to that of uninfected female crabs. Boschma (1930) described Briarosaccus cal- losus, a rhizocephalan parasite, from a museum specimen of Lithodes agassizii collected at a depth of 494 or 864 m off Florida or North Carolina, U.S.A., in 1886. Briarosaccus callosus has since been recorded world-wide from 7 other ano-

Cryptogaster Cumacei N. Gen., N. Sp., Premier Rhizocéphale Parasite D'Un Cumacé

Cryptogaster cumacei n. sp., n. gen., is the first record of a rhizocephalan parasite on Cumacea. The adult and its cypris larva are described. The systematic affinities of this new species are discussed.

The Life History of Lernaeodiscus Porcellanae (Cirripedia: Rhizocephala) and Co-evolution With Its Porcellanid Host

ABSTRACT The elaborate life history of the rhizocephalan parasite Lernaeodiscus includes a number of counterdefensive measures specifically adapted to circumvent defense systems of the host crab Petrolisthes. Lernaeodiscus is dioecious. The externa produces large male and small female cyprids. The female cyprids invade the host by means of a kentrogon stage. The sole site of invasion is the gills. The female parasite later erupts on the ventral side of the abdomen as a virgin externa. This has to be hyperparasitized by a male cyprid in order to reach sexual maturity. The life cycle is completed in about 5 months. Autogrooming is the crab's primary defense against infestation and ordinarily only crabs slightly deficient in this regard become infested. Once inside, the parasite gains control of the host crab and induces it to accept the parasite as self—in effect, as its own reproductive system. This nullifies all remaining defenses the crab might have against the parasite. In addition, infested male crabs become behaviorally and morphologically female, so that they provide maternal care for the external reproductive body of the parasite, as do infested female crabs, rather than attempting to remove the parasite from their body. While the parasite has diverted all of the reproductive resources and capabilities of the crab to its own use, the crab otherwise carries out its life as a normal member of the intertidal community.

On the fine structure of the regressing ecdysial glands of carcinus maenas L. (Crustacea Decapoda) parasitized by Sacculina carcini Thompson.

The ecdysial glands (Y organs) of the crab Carcinus maenas regress in the presence of an external parasite, Sacculina carcini. This regression is more or less severe and may lead to complete autolysis. Three gradual stages in this involutionary process are described. In stage I, the gland cells are nearly normal. Nuclei and cytoplasmic organelles remain unchanged, but large vacuoles begin to appear. Stage II corresponds to more or less drastic nuclear pyknosis and cytoplasmic alterations. Myelin figures are large and numerous. Lysosomes and autophagic vacuoles with phosphatase activity are abundant. However, the general cellular architecture remains preserved. Stage III corresponds to irreversible cytolysis; nuclear envelopes and plasma membranes have disappeared. What remains is an accumulation of cellular debris becoming engulfed by circulating hemocytes. Not all of the gland cells of any given Y organ show the same degree of regression; degeneration is asynchronous. Structures seemingly corresponding to absorptive roots of the parasite are seen. Their lumen is coated with microvilli. The putative direct and indirect influences of the rhizocephalan parasite on its host are discussed. Our results on regressing Y organs of parasitized crabs are compared with those on regressing ecdysial glands of insects.

Population structure of four species of porcellanid crabs (Decapoda: Anomura) occurring on the coast of Karachi

The population structure of 4 species of porcellanid crabs, including 2 species of Petrolisthes (P. boscii and P. rufescens) and 2 of Pachycheles (P. tomentosus and P. natalensis) was investigated. Sex ratios deviated from the expected 1:1 distribution in some size classes of the 4 species, but conformed in general to this pattern on the entire population basis. Probability curves developed from sex ratios differ markedly in shape and slope and resemble Wenner's (1972) anomalous and intermediate types. Ovigerous females of Petrolisthes boscii occurred for 9 months, of P. rufescens for 11 months; those of Pachycheles tomentosus and P. natalensis occurred throughout the year. In every size class, a considerably higher number of female Pachycheles tomentosus and P. natalensis became ovigerous than in Petrolisthes boscii and P. rufescens. Size-frequency distributions of the 4 species were unimodal, indicating that recruitment to crab populations was gradual. Juveniles of Petrolisthes boscii and P. rufescens were most abundant towards the commencement of the southwest monsoon season, in June–July; juveniles of Pachycheles tomentosus and P. natalensis were most abundant during the premonsoon month of March. Thirteen percent of Pachycheles natalensis were infected by a bopyrid parasite; the bopyrid also infected 5.2% of Petrolisthes rufescens and 0.6% of P. boscii. The latter two species were also infected by a rhizocephalan parasite, the infection rates being inverse to those by the bopyrid, i.e., 0.3 and 6.4%, respectively.

A Rhizocephalan Parasite of the Crab Charybdis Hoplites (Wood-Mason)

[La presente note donne la description d'une nouvelle espece du genre Heterosaccus, H. dollfusi, parasite de Charybdis (Goniohellenus) hoplites (Wood-Mason) du Golfe de Suez. Les organes mâles different de ceux des autres especes du genre en aboutissant dans un sac commun, globuleux, na laissant pas apercevoir a l'etat adulte sa double origine., La presente note donne la description d'une nouvelle espece du genre Heterosaccus, H. dollfusi, parasite de Charybdis (Goniohellenus) hoplites (Wood-Mason) du Golfe de Suez. Les organes mâles different de ceux des autres especes du genre en aboutissant dans un sac commun, globuleux, na laissant pas apercevoir a l'etat adulte sa double origine.]