Cyprid Ultrastructure and Adult Morphology in Ptychascus Barnwelli, New Species, and P. Glaber (Cirripedia: Rhizocephala), Parasites on Semiterrestrial Crabs (original) (raw)
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Bulletin of Marine Science, 2009
Members of the Rhizocephala are parasitic barnacles in the Crustacea. The life cycle of the Rhizocephala is composed of planktonic larval stages and an endoparasitic adult stage. Most studies have used temperate species as models, and little is known about rhizocephalan ecology in subtropical and tropical waters. Because reproduction and larval development of the Rhizocephala can vary with the environment, tropical Rhizocephala may have different life history patterns than their temperate counterparts. we investigated the larval morphology of the tropical Polyascus plana Boschma, 1933 (parasitic on the crab, Grapsus albolineatus Lamarck, 1818 which inhabits exposed rocky shores) using light microscopy and scanning electron microscopy. Crabs with Polyascus externae were collected and maintained at 22-25 °C aerated seawater. Released nauplii were transferred into beakers containing 500 ml of aerated, filtered, and autoclaved seawater and the culture was maintained at 15, 20, and 25 °C. Larval development was completed in 66 hrs from hatching at 20 °C, similar to the subtropical sacculinids, loxothylascus panopaei Gissler, 1884 and loxothylacus texanus Boschma, 1933. The short larval development time of P. plana could be an adaptation to enhance successful settlement along exposed rocky shores. Naupliar morphology differed between the sexes. The hind body of female nauplii (stages I-Iv) is more slender than that of males. The first seta and head shield of males have pores, but they are lacking in females. Male cyprids can be distinguished from females by a large posterior aesthetasc on segment III. Larval sex ratio was variable and there may be a seasonal component, with a higher percentage of females in summer and of males in winter. This seasonal variation in the larval sex ratio suggests that summer is the recruitment season for new parasites, and winter is the period for implantation of males into virgin externae.
Acta Zoologica, 1989
. Cypris ultrastructure. metamorphosis and sex in seven families of parasitic barnacles (Crustacea: Cirripedia: Rhizocephala).-Acta zooi. Stockh. 70: 229-242. Cypris morphology in the Rhizocephala differs both between the sexes of individual species and between the species. The large aesthetasc on the third antennular segment is unique to male cyprids of the Lernaeodiscidae, Peltogasteridae and Sacculinidae (suborder Kentrogonida) and Mycelomorphii vancouvercnsis (suborder Akentrogonida). A fourth segmental aesthetasc. common to both sexes, is much longer in males than in females. A spinous process on the attachment disc is another male-specilic character, but is absent altogether in the Lernaeodiscidae. It is argued that these aesthetascs help locate the settlement targets. Except in Mycetomorpha vancourierensis. aesthetascs have been secondarily lost in cyprids ot the suborder Akentrogonida. and there are no other morphological means for separating the male and female settling stage. In cyprids o( Syton hippolytes (Sylonidae) and of Mycetomorpha vancomerensis and Thompsonia sp. (Akentrogonidae) the long and slender antennules are probably used in penetration without formation of a kentrogon. as already reported for Clistosuccus paguri (Clistosaccidae). Cyprids of Sylon hippolytes and Clistosaccm paguri are almost morphologically identical.
Journal of Fish Diseases, 1978
SoccuZwiagrani/'era was found in 12% of commercial sandcrabs, Portunus pelagicus, in Moreton Bay irrespective of sex. Although male and female crabs were randomly distributed about Moreton Bay, egg bearing females were most common at the seaward station. This and the distribution of epizoic barnacles on gills and carapace suggest the sexes school separately. The increased prevalence of barnacles on the carapace of infected crabs indicates Sacculina inhibits moulting. The distribution of interna infections in small crabs towards south and west and externa infections in large crabs in the easterly, seaward stations suggests Sacculina preferentially attacks young crabs as they move inshore and then induces crabs to behave like "berried' (i.e. egg bearing) females by moving seaward as they grow. Morphologically female crabs are little changed by Sacculina, but the males show considerable modification which is reflected most accurately in the shortening ofthe chelar propodus to proportions similar to normal females. Infected crabs are sterile and internally the hepatopancreas becomes green rather than tan. Parasitized crabs were seen to groom their externae as 'berried' females groom their egg masses.
Animal Biology, 2007
Hermit crabs of the species Pagurus criniticornis (Dana, 1852) parasitized by the poorly known colonial rhizocephalan Peltogasterella socialis (Müller, 1863), were collected in the infralittoral rocky/sandy area of Anchieta Island (São Paulo), Brazil. We report the presence and pattern of occurrence of this rhizocephalan in the P. criniticornis population. The hermit crabs were obtained monthly during 1999 by two people using SCUBA methods. A total of 992 hermit crabs were captured and examined for rhizocephalans. The studied population showed non-normal size distribution and only 2.11% of the sample specimens carried externae of P. socialis. The parasite occurrence was seasonal and varied with host size. Some signs of feminization were observed on P. criniticornis pleopods (elongation of the endopod and reduction of the exopod of pleopods for males and reduction in the size of endopods for females). This is the first report on this parasite/host relationship for this South American host species. This is the first record of P. socialis (Müller, 1863) subsequent to the species' description, and possible occurrence of the parasite on hermit crabs in the Bahamas is also reported.
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.
Journal of Crustacean Biology, 1999
A total of 16,692 specimens of Paralomis granulosa was collected in the Beagle Channel, Tierra del Fuego, Argentina. between July 1996 and July 1997. This lithodid was parasitized by a bopyrid isopod identified as Pseudione tuberculata. Infested crabs exhibited a conspicuous bulge on their carapaces, which accommodated the parasite housed in the branchial chamber. The prevalence of infestation by P. tuberculata decreased with crab size, from 45.6% at 1O-19.9-mm to 0% at 90-99.9mm carapace length. Bopyrids were found on 251 occasions in the left branchial chamber and only once in the right branchial chamber. Except for two immature female parasites found in the branchial chamber of a small crab, all parasites were mature females, each usually carrying a dwarf male attached to its abdomen. The length of the female isopodsand that of their hosts were positively correlated. These two observations suggest that the parasites infest P. granulosa early in the life of the host, and remain on, and grow up with the host throughout its life. The finding of crabs without bopyrids, but with distended branchial chambers, shows that some crabs survive the infestation. While breeding is inhibited in parasitized hosts, the prevalence of the parasite is already low (about 1.2%) at the size of host maturity. Therefore, we suggest that the reproductive potential of the crab population is not seriously affected by the sterilizing effect of the parasite. Finally, the cooccurrence of this bopyrid and a second parasite, the rhizocephalan Briarosaccus callosus, was recorded. but the prevalence of double infestations was low.
Israel Journal of Ecology & Evolution, 2008
Within parasitic barnacles of the family Sacculinidae, the genus Heterosaccus is the third largest, with 12 species infesting various brachyuran hosts throughout the world. As part of an effort to reconstruct rhizocephalan phylogeny we performed an analysis of four species of Heterosaccus and of selected sacculinid and non-sacculinid rhizocephalans. We used both molecular sequence data (16s rDNA and 18s rDNA) and morphological characters from an SEM analysis of the cypris larvae. Using Bayesian methods we obtained a highly supported tree in which the four species of Heterosaccus form a monophylum, whereas both the genus Sacculina and the family Sacculinidae are polyphyletic. The sistergroup to Heterosaccus is a clade consisting of the sacculinids Loxothylacus panopaei and the "classical" rhizocephalan Sacculina carcini. The molecular results found support in cypris morphology, where we identified two distinct synapomorphies for Heterosaccus, both present in male cyprids only: A large flap extending posteriorly from the third antennular segment, and the male-specific aesthetasc on the third segment being reduced to a rudiment or lacking completely. Female cyprids didn't show generic level apomorphies but resembled those of other sacculinid species. No morphological synapomorphies were identified between Heterosaccus, L. panopaei and S. carcini. While larval characters proved to be informative, we conclude that future studies on rhizocephalan taxonomy must rely primarily on molecular data, both to provide an overall phylogenetic framework and to assure an accurate identification of species for biogeographical and other biological purposes.
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2002
SEM and light microscopic studies on the larvae of the rhizocephalan barnacles Peltogasterella gracilis and P. sulcata reared in the laboratory revealed the presence of 5 naupliar instars, the newly found stage being instar 3. It resembles instar 2 but is larger and has a body slightly tapering towards the posterior end, a reduced subapical (preaxial) seta on the antennule, and both transverse grooves and a specific denticle ornamentation on the hind body of female larvae. In cultures, the larvae of both species develop into cyprids within 4-5 days after release. Peltogasterella nauplii have a size comparable to that seen in Sacculina and Peltogaster, but they are much smaller than the larvae of the cold-water Briarosaccus. The nauplii of Peltogasterella are lecitotrophic and have limb setation and other feeding structures highly reduced. Peltogasterella nauplii have a cuticular flotation collar encircling the body, but it is very small, delicate, and almost smooth. It therefore differs from the homologous, but much larger, and heavily ornamented flotation collars seen in nauplii of Peltogaster and Briarosaccus. A characteristic feature in Peltogasterella nauplii is the single subterminal seta at the distal end of each frontolateral horn, whereas nauplii of Briarosaccus and Peltogaster have two such setae. The antennulary basipod carries a short additional seta, which represents the only remaining rudiment of gnathobases. Nauplii of Briarosaccus and Peltogaster have a homologous, but significantly longer seta, whereas Sacculina nauplii lack this seta altogether. The nauplii of P. gracilis and P. sulcata are very similar in size and morphology, but those of P. sulcata differ by somewhat longer frontolateral horns and furcal spines. Another distinctive feature of P. gracilis nauplii is the ventral ornamentation of the hind body that shows different pattern at different stages of development and reflects an internal development of segments. This ornamentation is only weakly pronounced in P. sulcata nauplii. Comparison with larval development in Briarosaccus tenellus leads to the conclusion that the rhizocephalan ground pattern comprises six naupliar stages just as in other cirripedes (e.g., Thoracica). Comparison of lattice organ morphology indicates a sister group relationship between the families Peltogastridae and Lernaeodiscidae. Our study highlights the value of SEM revealed larval characters and of characters other than appendage setation as being important in rhizocephalan phylogeny.