Loxothylacus Texanus Research Articles

Effects of the Parasite Loxothylacus texanus on the Agonistic Behavior of the Crab Callinectes rathbunae

Effects of the Parasite Loxothylacus texanus on the Agonistic Behavior of the Crab Callinectes rathbunae

CIRRIPEDIA (CRUSTACEA) DE LA ZONA INTERMAREAL E INFRALITORAL DE LA REGION DE SANTA MARTA, COLOMBIA

In orden to inventory the species of Cirripedia occuring from the Ciénaga Grande de Santa Marta to Nenguange Bay in the Tayrona National Park, specimens of this group of crustaceans were periodically collected in 1985 and 1986. To date eight species have been reported in the Colombian Caribbean, wich are distributed from Cartagena to Guajira. Among the 14 species reported in this work a Rhizocephala, Loxothylacus texanus lives as parasite of crabs of the genus Callinectes; a Lepadomorpha Oco/asmis muelleri, lives epibionthic on the gills of C. sapidus, and also 12 free living Balanomorpha, are included. The first two species and seven belonging to the Balanomorpha are new records for the Colombian Caribbean, -then rising the number ot reported species to 17.

Variations in prevalence of viral, bacterial, and rhizocephalan diseases and parasites of the blue crab (Callinectes sapidus)

Prevalence of blue crab diseases and parasites has not been consistently monitored in the Gulf of Mexico. To establish current prevalence levels and to more fully understand population dynamics, commercial landing trends, and effects of future natural and anthropogenic disasters on animal health, we measured the prevalence of white spot syndrome virus (WSSV), Loxothylacus texanus, shell disease, and Vibrio spp. in blue crabs collected from Louisiana in 2013 and the beginning of 2014. We used PCR to detect WSSV and L. texanus infections, visual gross diagnosis for L. texanus externae and shell disease, and standard microbiological culture techniques and biochemical testing for Vibrio spp. We found no crabs infected with WSSV or L. texanus. Absence of L. texanus parasitization was expected based on the sampled salinities and the sampling focus on large crabs. Shell disease was present at a level of 54.8% and was most prevalent in the winter and summer and least prevalent in the spring. Vibrio spp. were found in the hemolymph of 22.3% of the crabs and prevalence varied by site, season, and sex. Additionally, three of 39 crabs tested were infected with reo-like virus.

Shell Disease in Callinectes rathbunae Contreras, 1930, Parasitized by Loxothylacus texanus Boschma, 1933

Shell Disease in Callinectes rathbunae Contreras, 1930, Parasitized by Loxothylacus texanus Boschma, 1933

Anatomy of virgin and mature externae of Loxothylacus texanus, parasitic on the dark blue crab Callinectes rathbunae (Crustacea: Cirripedia: Rhizocephala: Sacculinidae)

Rhizocephalan parasites are dioecious organisms, in that one or several dwarf males are implanted into the external part of the female parasite soon after it emerges from the interior of the host animal. The structure of the female externa and its resident males is crucial for understanding both the reproductive biology and the taxonomy of these specialized parasites. We use scanning electron microscopy and histological methods to study the anatomy of juvenile and the mature externae of the rhizocephalan barnacle Loxothylacus texanus parasitizing the blue crab Callinectes rathbunae. We put emphasis on the implantation of males and the histology of the female reproductive organs. In the virgin externae, male cyprids attach around a cuticular hood covering the mantle aperture, which is partially blocked by a plug of cuticle so only trichogon larvae, not cyprids, can access the mantle cavity. This resembles the situation known from Sacculina carcini. The mature externa is characterized by a visceral mass that contains the ovary, paired colleteric glands, a single male receptacle, but paired receptacle ducts. The proximal attachment of the visceral mass is located at some distance from the basal stalk, as is characteristic for the genus Loxothylacus. The internal anatomy of the mature externa of L. texanus is in most features similar to that seen in other species of the Sacculinidae, which comprises the majority of rhizocephalan species. However, the single receptacle creates a situation where the two implanted males cannot be kept separate as in most other rhizocephalans, but pass through spermatogenesis in a common chamber. This may have unknown effects on the reproductive biology such as male-male competition.

Hepatopancreas alteration of the blue crab Callinectes sapidus by the rhizocephalan barnacle Loxothylacus texanus

A histological study of the hepatopancreas of the blue crab Callinectes sapidus parasitized by the rhizocephalan barnacle Loxothylacus texanus was conducted to explore if the degree of development of the parasite’s rootlet system was correlated to its maturation process as seen by external characters of its reproductive body or externa. Four types of crabs were examined: control, with virgin and mature externa, and scarred. A clear progression with an increase in number and size of the parasite’s rootlets in the hosts’ hepatopancreas can be seen. Although the hepatopancreatic tubules remain functional, the hepatopancreas appears as a loose structure, completely infiltrated with L. texanus rootlets, in advanced stages of the parasitism.

Investigations of Internal Interactions between the Parasitic Barnacle Loxothylacus texanus (Rhizocephala: Sacculinidae) and Its Host Callinectes sapidus (Brachyura: Portunidae) using PCR Techniques

We describe techniques that enable the preservation of tissues from the rhizocephalan barnacle, Loxothylacus texanus, inside the body cavities of blue crab hosts, Callinectes sapidus, in a manner that minimizes the degradative activities of hepatopancreatic enzymes. These procedures allow the extraction and amplification of both parasite and host 18S rDNA within the same sample and enable one to distinguish between parasitized and unparasitized crab tissue in as little as two weeks after infection, well before any external manifestations of the parasites. Two PCR-based approaches were taken to identify the presence of L. texanus. In the first approach, a set of primers specific for L. texanus was used to specifically amplify 18S sequence in a background of C. sapidus DNA or the DNA of other barnacle species. In the second approach, a set of general primers was used to amplify 18S sequence from C. sapidus and a variety of barnacle species. The products of this PCR were then digested with an enzyme that recognizes a restriction site present only in the L. texanus PCR product to yield a unique pattern of fragments. With these techniques, we could detect as few as five parasitic cypris larvae in water samples, as well as L. texanus in the tissue of a small crab collected from the field and in the four anterior periopods of a crab bearing the external stage of the parasite. In experiments with potential hosts of varying sizes and molt stages, we confirmed that the parasite was significantly more effective in infecting crabs less than 30 mm carapace width than larger individuals. These techniques will facilitate future investigations of ecological and physiological interactions between these important crustacean parasites and their hosts and will help to determine the economic impact of this parasite on blue crab fisheries.

Investigations of Internal Interactions between the Parasitic Barnacle Loxothylacus Texanus (Rhizocephala: Sacculinidae) and Its Host Callinectes Sapidus (Brachyura: Portunidae) Using PCR Techniques

We describe techniques that enable the preservation of tissues from the rhizocephalan barnacle, Loxothylacus texanus, inside the body cavities of blue crab hosts, Callinectes sapidus, in a manner that minimizes the degradative activities of hepatopancreatic enzymes. These procedures allow the extraction and amplification of both parasite and host 18S rDNA within the same sample and enable one to distinguish between parasitized and unparasitized crab tissue in as little as two weeks after infection, well before any external manifestations of the parasites. Two PCR-based approaches were taken to identify the presence of L. texanus. In the first approach, a set of primers specific for L. texanus was used to specifically amplify 18S sequence in a background of C. sapidus DNA or the DNA of other barnacle species. In the second approach, a set of general primers was used to amplify 18S sequence from C. sapidus and a variety of barnacle species. The products of this PCR were then digested with an enzyme that recognizes a restriction site present only in the L. texanus PCR product to yield a unique pattern of fragments. With these techniques, we could detect as few as five parasitic cypris larvae in water samples, as well as L. texanus in the tissue of a small crab collected from the field and in the four anterior periopods of a crab bearing the external stage of the parasite. In experiments with potential hosts of varying sizes and molt stages, we confirmed that the parasite was significantly more effective in infecting crabs less than 30 mm carapace width than larger individuals. These techniques will facilitate future investigations of ecological and physiological interactions between these important crustacean parasites and their hosts and will help to determine the economic impact of this parasite on blue crab fisheries.

Observations on the Behavior of the Dark Crab Callinectes rathbunae Contreras Parasitized with the Rhizocephalan Loxothylacus texanus Boschma

Observations on the Behavior of the Dark Crab Callinectes rathbunae Contreras Parasitized with the Rhizocephalan Loxothylacus texanus Boschma

What constrains the geographic and host range of the rhizocephalan Loxothylacus texanus in the wild?

In the Gulf of Mexico, the rhizocephalan barnacle Loxothylacus texanus parasitizes members of the genus Callinectes. In the past, research has primarily focused on the interaction between L. texanus and its blue crab host Callinectes sapidus. Only recently investigators have begun to examine the association that this parasite shares with other Gulf of Mexico hosts and little is known about interactions outside of the Gulf of Mexico. In the current study, settlement of L. texanus on a variety of potential hosts was examined. Settlement of L. texanus occurred not only on C. sapidus but also on the congener Callinectes similis, the grapsid Sesarma cinereum and the xanthid Rhithropanopeus harrisii collected from the Gulf of Mexico. L. texanus also settled on C. sapidus from Delaware Bay and Callinectes ornatus from Brazil. A carbohydrate-based cue appears to be the trigger for settlement in all cases. These results suggest that larval settlement may not play as important a role in determining host specificity as is often assumed. In fact, this type of nonspecific settlement may over evolutionary time lead to establishment of the parasite on new host species. Other factors such as physical barriers and immune response may aid in the control of such parasitic infections.

Effects of salinity on larval stages of the rhizocephalan barnacle Loxothylacus texanus: survival and metamorphosis in response to the host, Callinectes sapidus

It is known that the rhizocephalan barnacle Loxothylacus texanus infects the greater blue crab, Callinectes sapidus, in the Gulf of Mexico and adjacent waters, however, factors that affect the prevalence and distribution of this parasite, particularly the dispersive larval stages of this organism, are not well understood. In the current study, the effects of salinity on larval survival and the metamorphosis of L. texanus in response to postmolt host exoskeleton were examined. Acute and acclimated responses were similar. Larval survival was highest in the 20–35‰ range, with 100% mortality of nauplii at all salinities <20‰ and >50‰. L. texanus cyprids were able to metamorphose over a broad range of salinities (15–60‰). In several cases, metamorphosis was actually greatest at high salinities (40–50‰). These data predict that L. texanus larvae would be concentrated in portions of Gulf of Mexico waters with salinities >20‰ such as the mouths of estuaries and bays. Conversely, upper regions of estuaries may be inhospitable to the dispersive (naupliar) stage of the parasite and may serve as a refuge from infection for host crabs.

Characterization of settlement cues used by the rhizocephalan barnacle Loxothylacus texanus

Populations of the greater blue crab Callinectes sapidus throughout the Gulf of Mexico, as far north as South Carolina, USA, are infected by the rhizocephalan barnacle Loxothylacus texanus. Larvae are non-feeding and have approximately 3 d from the onset of metamorphosis from their naupliar stage to successfully encounter and recognize a host before their nutrient stores are depleted. The female cypris and kentrogon stages are the initial infective agents. Chemical cues, like those used by free-living barnacles to identify settlement sites, appear to be important in the identi- fication of potential hosts by this parasitic barnacle. The cypris larvae of L. texanus settle in response to carbohydrate or glycoprotein cues found in the epicuticle layer of C. sapidus exoskeletons. These cues are associated with the epicuticle layer only, not the biofilm associated with the carapace. In fact, the carapace biofilm and lipid-based compounds found in the outer layer of the epicuticle appear to afford crabs some protection against settlement by L. texanus.

Osmoregulatory disturbances induced by the parasitic barnacle Loxothylacus texanus (Rhizocephala) in the crab Callinectes rathbunae (Portunidae)

The osmoregulatory response of the blue crab Callinectes rathbunae parasitized with the rhizocephalan barnacle Loxothylacus texanus, and subjected to sudden salinity changes, was experimentally measured in the laboratory. Parasitized and control crabs were exposed to salinity changes every 3 h and their hemolymph osmolality measured. Two experiments, one with increasing salinity conditions (5‰, 12‰, 19‰, 25‰) and a second one with decreasing salinities (35‰, 25‰, 15‰, 5‰) were conducted. The results show that L. texanus significantly alters the hemolymph osmolality of C. rathbunae maintaining it at lower than normal levels. In the increasing salinity trial, the hypoosmotic hemolymph condition of parasitized crabs was present at all salinities tested, whereas in the decreasing salinity trial a significant effect was found only at salinities of 5‰ and 15‰. Since C. rathbunae is constantly subjected to abrupt salinity changes in the tropical estuaries where it occurs, moving into high salinity areas may be the only way to cope with the impact of L. texanus.

Oxygen consumption of the crab Callinectes rathbunae parasitized by the rhizocephalan barnacle Loxothylacus texanus as a function of salinity

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 235:189-194 (2002) - doi:10.3354/meps235189 Oxygen consumption of the crab Callinectes rathbunae parasitized by the rhizocephalan barnacle Loxothylacus texanus as a function of salinity Rafael Robles1,2, Fernando Alvarez1,*, Guillermina Alcaraz3 1Colección Nacional de Crustáceos, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 70-153, 04510 D. F., Mexico 2Department of Biology, University of Louisiana, Lafayette, PO Box 42451, Lafayette, Louisiana 70504-2451, USA 3Laboratorio de Ecofisiología, Departamento de Biología, Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-371, 04510 D. F., Mexico *Corresponding author. E-mail: falvarez@servidor.unam.mx ABSTRACT: Rhizocephalan parasitism is one of the most important biotic factors affecting commercially valuable crab species in families such as Portunidae and Lithodidae. In addition to the long term and permanent effects of this parasitism on the hosts (e.g. sterilization, cessation of growth), other functional problems may arise due to the considerable size of the parasite and to its particular position inside and outside of the host. In this study, experiments with the Mexican blue crab Callinectes rathbunae parasitized by the rhizocephalan barnacle Loxothylacus texanus were conducted in the laboratory to test whether the parasite affects the host¹s oxygen consumption rate under changing salinity conditions. A total of 83 crabs (49 parasitized and 34 controls), all initially acclimated to a salinity of 5, were used for metabolic rate measurements over sequential 24 h periods at salinities of 5, 15 and 25. During this 3 d period, oxygen consumption of individual crabs was measured 5 times per day. Parasitized crabs were classified, according to the degree of maturation of the parasite, as: (1) crabs with internal parasites, bearing a modified abdomen; (2) crabs with virgin, immature, recently emerged parasites; and (3) crabs with mature, fully developed parasites. Crabs with internal and virgin parasites did not show differences in oxygen consumption rates with respect to control crabs. Crabs with mature parasites consumed from 57 to 139% more than other crabs under all salinity conditions. Although there is a significant metabolic cost for the host associated to the presence of mature L. texanus, it is not clear what specific process is responsible for the observed results. Since the increased oxygen consumption was unrelated to salinity, it is concluded that the host¹s osmoregulatory capabilities are not affected; other possible explanations include the constant grooming and maintenance of the parasite. At the population level, our results suggest that hosts bearing mature parasites may move within the estuaries from low to high salinity areas in order to reduce the metabolic energy expenditure caused by the combination of the parasite and hypoosmotic conditions. KEY WORDS: Oxygen consumption · Callinectes rathbunae · Loxothylacus texanus Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 235. Online publication date: June 19, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Limb Autotomy as an Investigatory Tool: Host Molt-Stage Affects the Success Rate of Infective Larvae of a Rhizocephalan Barnacle

D. M. Skinner was the first biologist to systematically investigate the effect of multiple limb autotomy on ecdysis in decapod crustaceans. She proposed the existence of (1) limb autotomy factor anecdysis (LAFan) which initiates precocious molting, and (2) limb autotomy factor proecdysis (LAFpro) which postpones proecdysis. Mean time to ecdysis did not differ significantly among groups of small juvenile Callinectes sapidus with zero, two, four, and six limbs removed. Variance was significantly less for the group missing six limbs; i.e., autotomy of six limbs synchronized the molt-cycle. These patterns were consistent with the hypotheses that LAFan exerts an additive effect, i.e. , more anecdysial crabs enter proecdysis as more limbs are autotomized and that a delay of proecdysis occurs above a threshold (>4) of autotomized limbs. Multiple limb autotomy provides investigators with easy access to crabs in metecdysial molt-stages which is useful in studying interactions between rhizocephalan barnacles and their hosts. While 71% of metecdysial C. sapidus exposed to infective larvae of the sacculinid rhizocephalan, Loxothylacus texanus , developed the external stage of the parasite, no similarlysized anecdysial crab was parasitized, suggesting that these crabs are not susceptible to infection during anecdysis. Size of C. sapidus at infection was inversely proportional to the number of ecdyses between infection and emergence of the parasite, but not correlated to final host size. These data suggest that there is a minimum threshold for host size; smaller hosts undergo more ecdyses before attaining the threshold. Rhizocephalans are being considered as biological control agents and there is a need to understand how they find and infect hosts. Because limb autotomy is such a useful research tool, D. M. Skinner's contributions to our understanding of how limb autotomy influences the crustacean molt cycle will continue to pay significant dividends in crustacean biology.

Parasitization of Callinectes rathbunae and Callinectes sapidus by the Rhizocephalan Barnacle Loxothylacus texanus in Alvarado Lagoon, Veracruz, Mexico

Collinecles rathbunae and CalIinectessapEdus in Alvarado Lagoon, Mexico, were sampled monthly for one year to determine the extent of parasitization by the rhizocephalan cirripede Loxofhylucus lemnus. Prevalence levels. host sex ratio, carapace width-weight variation, and distribution of the number of parasites among hosts were analyzed. Loxotlrylocr~s fexanus was present almost exclusively in C. rathbrinoe with a mean prevalcnct of 7.58%. while Iess than 1% of all C. sapidus were parasitized. CalIintctes rofhbunae constitutes a new host record for this parasite. A study of infection revealed significant variation in prevalence and host size throughout the study period. The sex ratio of parasitized crabs differed from that of the total sample with mares being parasitized more often, and the comparison of carapace width-weight relationships revealed Lower weights OF parasitized crabs.

Records of Loxothylacus texanus (Cirripedia: Rhizocephala) Parasitizing the Blue Crab Callinectes sapidus in Tamiahua Lagoon, Mexico

ABSTRACT The rhizocephalan barnacle Loxothylacus texanus parasitizes the blue crab Callinectes sapidus in the Gulf of Mexico. In Tamiahua Lagoon, Mexico, although 4 species of Callinectes co-occur, only C. sapidus is parasitized. Parasite prevalence, number of parasite externae per host, host size, and host sex ratio were recorded during 5 sampling trips from November 1984 to October 1985. Overall parasite prevalence in Tamiahua Lagoon (13.3%) can be considered high, compared to values reported for other areas along the northern Gulf of Mexico, and contrary to what previous studies had suggested.

Distribution of Loxothylacus texanus (Cirripedia: Rhizocephala) Parasitizing Crabs of the Genus Callinectes in the Southwestern Gulf of Mexico

A preliminary study on the interaction between the parasitic barnacle Loxothylacus texanus and two of its host species, the blue crab Callinectes sapidus and the dark blue crab C. rathbunae, in the Gulf of Mexico is presented. Data were obtained from 923 crabs, 162 C. sapidus and 761 C. rathbunae, deposited in the Colección de Crustáceos, Instituto de Biologia, Universidad Nacional Autónoma de México (UNAM), that were collected in 14 coastal lagoons and sites along the Mexican coast of the Gulf of Mexico. The distribution of L. texanus parasitizing each one of the host species, mean host size variation, distribution of number of parasite externae per host, and morphological modifications of the abdomen of the hosts are analyzed.

RECORDS OF LOXOTHYLACUS TEXANUS (CIRRIPEDIA: RHIZOCEPHALA) PARASITIZING THE BLUE CRAB CALLINECTES SAPIDUS IN TAMIAHUA LAGOON, MEXICO

The rhizocephalan barnacle Loxothylacus texanus parasitizes the blue crab Callinectes sapidus in the Gulf of Mexico. In Tamiahua Lagoon, Mexico, although 4 species of Callinectes co-occur, only C. sapidus is parasitized. Parasite prevalence, number of parasite externae per host, host size, and host sex ratio were recorded during 5 sampling trips from November 1984 to October 1985. Overall parasite prevalence in Tamiahua Lagoon (13.3%) can be considered high, compared to values reported for other areas along the northern Gulf of Mexico, and contrary to what previous studies had suggested.

PHYLOGENETICSTUDY OF CIRRIPEDES AND SELECTED RELATIVES (THECOSTRACA) BASED ON 18S RDNA SEQUENCE ANALYSIS

ABSTRACT Sequence data from PCR-amplified 18S rDNA were used to infer phylogenetic relationships among the thecostracan crustacean taxa Ascothoracida (Ulophysema oeresundense), Acrothoracica (Berndtia purpurea, Trypetesa lampas), Rhizocephala (Loxothylacus texanus), and Thoracica (Calantica villosa, Lepas anatifera, Octolasmis lowei, Chthamalus fragilis, Chelonibia patula, Tetraclita stalactifera, Balanus eburneus). Sequence-divergence estimates ranged from 1.8% for 2 acrothoracican taxa to 24.3% for an ascothoracidan and a balanomorph thoracican. Parsimony, invariants, and neighbor-joining analyses all showed the Ascothoracida and Acrothoracica to be sister taxa and very early thecostracan lineages widely separated from the Rhizocephala, which in turn is the sister group to the Thoracica. A comparison of the secondary structure of the V3 variable domain in the 18S rRNA molecule for these taxa supports this result somewhat: the acrothoracican V3 structure is phenetically more similar to that of the ascothoracidan and branchiopods than to the other cirripedes. There is some disagreement between a morphology-based phylogeny and the current one based on molecular characters. It may result from molecular evidence suggesting an early origin and divergence of the Acrothoracica from the main cirripede lineage, as well as a substitution rate in the lineage leading to the Rhizocephala + Thoracica that is very much higher (10-12 times) than those in the other thecostracan lineages examined. Within the Thoracica, the sessile balanomorphs appear to be derived from a lineage related to scalpelloid lepadomorphs, but variation in the 18S molecule among balanomorphs is insufficient to permit inference of relationships within this group. We conclude that the Thecostraca, represented here by the subclasses Ascothoracida and Cirripedia (the latter including the Acrothoracica, Rhizocephala, and Thoracica), is a monophyletic taxon.