Shell recruitment in the Mediterranean hermit crab Clibanarius erythropus

Gastropod shells are vital for the majority of hermit crab species, being essential for their survival, growth, protection, and reproduction. Given their importance, shells are acquired and transferred between crabs through several modalities. We conducted observations and experiments at the Asinara Island (Sardinia, Italy) to investigate the efficacy of the different behavioral tactics adopted by the hermit crab Clibanarius erythropus to acquire shells, such as: (1) locomotion and activity at different tidal phases; (2) attendance at shell-supplying sites (simulated predation sites with five different odors: live and dead gastropods, live and dead crabs, predator); and (3) interactions with conspecifics in aggregations on simulated gastropod predation sites. In each tidal phase, locomotion was slow (0.7 cm min^− 1) and, as a consequence, the probability of encountering empty shells and conspecifics was low. Simulated gastropod predation sites quickly attracted a larger number of hermit crabs than the other sites tested. Aggregations seemed to function as shell exchange markets, as previously suggested for other species: the first attendant took the experimental shell and a chain of shell exchanges among conspecifics followed. Our results show that, in C. erythropus, aggregation is the most efficient tactic for the acquisition of new shells, whereas in other species, such as Pagurus longicarpus, it is associated with exploitation ability due to the intense locomotion. The interspecific plasticity in hermit crabs' behavior is confirmed.     

Morphological and morphometric appraisal of the spermatophore of the southern hermit crab Isocheles sawayai (Anomura: Diogenidae), with comments on gonopores in both sexes

The spermatophore morphology of the hermit crab Isocheles sawayai from southwestern Atlantic (Brazil) is described. The spermatophores show similarities with those described for other members of the family Diogenidae, especially with the recently described Loxopagurus loxochelis. The spermatophore is composed of three major regions: a sperm filled head or ampulla, a columnar stalk and a foot or pedestal. The spermatophores show specific morphology in having a circular ampulla, and a constriction or neck between the ampulla (100 μm) and the thin (27 μm), long stalk (500 μm). The stalk penetrates less than half way into the spermatophore head. Most spermatophores show one of the small posterior projections on the underside of the ampulla as being bigger than the other, making it asymmetrical. The size of the spermatophore is related to hermit crab size with direct relationships found between spermatophore ampulla width, total length, and peduncle length with shield length of the hermit crab. The morphological characteristics of the spermatophore of I. sawayai are species-specific distinguishing it from other members of the family, and are useful to infer further phylogenetic relationships.     

Occurrence of an alternative pathway in the larval development of the crab Chasmagnathus granulata Dana, 1851 under laboratory conditions

Larvae of the crab Chasmagnathus granulata were collected in a salt marsh located in the Lagoa dos Patos, Brazil and reared from eclosion to metamorphosis under different dietary regimes. Larvae reared individually in beakers of 40 ml and fed Tetraselmis chuii (zoea III and zoea IV), showed a supplementary stage, here designated as zoea V, with morphological characteristics intermediary between zoea IV and megalopa. No zoeae V molted to megalopa stage. To confirm the occurrence of the supplementary stage, mass cultures of larvae of C. granulata were fed Artemia sp. at high densities, we again detected the fifth zoeal instar. However, when zoeae V were individually placed in beakers and fed Artemia nauplii, they succeeded in molting into megalopae. We observed the occurrence of two types of zoeae IV — a smaller type (from which originated the zoeae V) and a larger type (which directly developed into megalopae). We conclude that stressful nutritional/environmental conditions were responsible for the occurrence of this alternative path of development.     

Intraspecific competition of Glyptotendipes paripes (Diptera: Chironomidae) larvae under laboratory conditions

Glyptotendipes paripes larvae were reared in wells of tissue culture plates, in groups of 2, 4, 8, 16, and 32 (representing densities of about 1,300, 2,600, 5,200, 10,400, and 20,800 larvae per m², respectively). Larval groups were supplied with one of two concentrations (low or high) of food and larvae were individually observed to evaluate the effects of density on mortality, growth, development, behavior, and adult body size. Increased larval densities resulted in higher mortality, as well as slower larval growth and development. The distribution of developmental time became flatter at higher density, with a wider range of values, or even became bimodal. This was a consequence of the most rapidly developing individuals at higher densities emerging as adults sooner than the fastest developing individuals at lower densities, although overall mean developmental time was longer at higher densities. At higher densities, growth and development of smaller larvae were slowed, based on the relative difference in body length between competitors. When larger competitors emerged as adults or died, the growth of smaller larvae may have accelerated, resulting in increased variability of developmental times. The effect of larval density on adult body size was complex, with the largest body size found at the lowest density and a second peak of adult size at high-middle densities, with smaller adult body sizes found at low-middle, and high densities. Similarly, as with developmental time, the range of body size increased with increasing density. Examined food concentrations had no effect on larval mortality, but significantly affected developmental time, growth rate, and adult body size. At higher densities, larvae spent more time gathering food and were engaged in aggressive or antagonistic behaviors.     

Larval release behaviors of the striped hermit crab, Clibanarius vittatus (Bosc): Temporal pattern in hatching

Ovigerous hermit crabs, Clibanarius vittatus (Bosc), were examined in the laboratory to (1) determine if the time of larval release is a synchronous event, (2) determine the influence of a damaged gastropod shell during the egg hatching process, and (3) describe larval release behaviors. Ovigerous hermit crabs from natural light:dark (LD) and tidal cycles were moved to constant conditions 2-3 days prior to the predicted time of larval release. Larval release was synchronous, occurring near the time of expected sunset. Females with early-stage embryos placed under constant conditions displayed a free-running circadian rhythm, suggesting that the rhythm is under endogenous control. Hermit crabs with early-stage embryos that were placed under a shifted LD cycle (advanced 12 h relative to the ambient photoperiod) before being placed under constant conditions advanced their larval release rhythm by 12 h, indicating the rhythm can be entrained by the LD cycle. Hermit crabs with an intact shell released larvae in bursts at sunset over several consecutive nights (period = 24.2 h). In contrast, hermit crabs with damaged shells released larvae at different times over the course of a single day. Ovigerous females with intact shells exhibit several stereotypical hatching behaviors. The female stands on her walking legs and thrusts her abdomen, moving the shell in an oscillating motion. This movement may assist in breaking the outer membrane of the egg case. The female generates a water current inside the shell with her scaphognathite and mouthparts, which transports the newly hatched larvae out of the shell. Females in damaged shells did not display these behaviors; instead, larval release was a prolonged event with little movement of the female, and often the newly hatched larvae were not viable. These results indicate that an intact shell plays an important role in the hatching process for this hermit crab.     

Genetic divergence and larval dispersal in two spider crabs (Crustacea: Decapoda)

The spider crabs Inachus dorsettensis (Pennant) and Hyas coarctatus Leach are widespread in subtidal areas of muddy sand or gravel around western Europe. Both species have a life cycle with an obligatory planktonic larval phase of several weeks, which might be expected to cause widespread larval dispersal and consequent genetic homogeneity over considerable distances. However, earlier work on both taxa has indicated differences in growth pattern between populations separated by tens of kilometres. This study was undertaken to determine whether these differences were purely environmental or whether, despite the short distances involved, differences may have a genetic basis. A study of gene frequencies, as indicated by allozymes in samples of adults collected off the Isle of Man (northern Irish Sea), indicates significant genetic differentiation between populations over a geographical distance of only about 40 km in both Inachus dorsettensis ( = 0.086 ± 0.048) and Hyas coarctatus ( = 0.023 ± 0.017). Variability measures differed between species, showing I. dorsettensis to have a mean number of alleles per locus of 2.5–2.6 and a range of gene diversity of 0.216–0.241, while H. coarctatus showed lower values of mean number of alleles (1.9–2.0) and a range of gene diversity from 0.122 to 0.124. Given the high expected larval mobility of the two species the results are most surprising. Possible explanations are discussed in relation to population discontinuities and patterns of larval drift.     

Cladistics of Sunaristes,a genus of harpacticoid copepods associated with hermit crabs

Four species of Sunaristes (Canuellidae) are known to live in association with hermit crabs and exhibit a degree of host specificity. Although hermit crabs are common in many parts of the world, Sunaristes is notably absent from waters of the New World. The phylogeny of Sunaristes is here examined through a cladistic analysis. The reconstructed phologeny indicates that S. inaequalis and S. japonicus form a sister group, and its closest relative is S. tranteri. The sister taxon of this 3-species clade is S. paquri. It is assumed that Sunaristes evolved in the Paleocene on the north shore of the Tethys seaway. The constructed cladogram forms the basis for the analysis of vicariant events that led to the speciation and development of the present pattern of distribution of Sunaristes.     

Morphology of prezoea in the porcelain crab <Emphasis Type="Italic">Pachycheles stevensii</Emphasis> (Decapoda: Anomura: Porcellanidae) reared under laboratory conditions

Pachycheles stevensii Stimpson, 1858 is the only species of the family Porcellanidae (Decapoda, Anomura) living in the Russian waters of the Sea of Japan. The morphology of prezoeal larval stages of this crab obtained under laboratory conditions for the first time was studied and described in detail.Original Russian Text Copyright © 2005 by Biologiya Morya, Kornienko.     

Early development of the flathead,Percophis brasiliensis (Teleostei: Percophididae), from Southeastern Brazil

Morphological and osteological development of the flathead,Percophis brasiliensis, is described based on specimens collected from southeastern Brazilian waters. Identification of larvae was based on pigment pattern and meristic counts. Distinct melanophores were present on the bottom of the hindbrain, between the bases of the pelvic fins and on the bases of the pectoral fins. Within the family Percophididae onlyPercophis brasiliensis has 57 myomeres, which result in the larvae having an elongated body form. The larval pigment pattern and structure of the caudal complex suggest that the subfamilies Percophinae and Bembropinae are phylogenetically close, while the Hemerocoetinae belong to an advanced group within the family.     

Susceptibility of Cydia pomonella to Bacillus thuringiensis under laboratory and field conditions

The delta-endotoxin of 12 strains in 10 subspecies of Bacillus thuringiensis Berliner was highly active against Cydia pomonella (L.) when assayed under laboratory conditions on artificial diet. These results could not be confirmed in the field.The disappointing results obtained under field conditions are due to the behaviour of the target insect. C. pomonella larvae do not ingest food during penetration of the fruit. The larva bites pieces of the epidermis and deposits them without ingestion on top of the entry hole.

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Zusammenfassung Das delta-Endotoxin von B.t. war in Laborversuch auf Kunstmedium gegenüber den Larven des Apfelwicklers, C. pomonella, sehr aktiv. Die hohe Aktivität konnte aber unter Feldbedingungen nicht mehr bestätigt werden.Es wurde nachgewiesen, dass die unbefriedigenden Resultate von B. thuringiensis unter Feldbedingungen auf das Verhalten der Junglarven zurückzuführen sind: Die Larven nehmen während dem Eindringen in den Apfel keine Nahrung auf, sondern deponieren die herausgebissenen Epidermistücke über der Einbohrstelle.

     

A new fungal genus, Teracosphaeria, with a phialophora-like anamorph (Sordariomycetes, Ascomycota)

The new genus and species Teracosphaeria petroica is described for a perithecial ascomycete and its anamorph occurring on decayed wood collected in New Zealand. The fungus produces immersed, non-stromatic ceratosphaeria-like perithecia in nature, with hyaline, septate ascospores produced in unitunicate, non-amyloid asci. The anamorph produced in vitro is phialophora-like with lightly pigmented phialides terminating in flaring, deep collarettes that are often noticeably brown with conspicuous periclinal thickening. Phylogenetic analysis of LSU rDNA sequence data indicates that this fungus is distinct from morphologically similar fungi classified in the Chaetosphaeriales, the Trichosphaeriales or the Magnaporthaceae. It forms a monophyletic group with recently described, chaetosphaeria-like ascomycetes, such as the pyrenomycete genus Mirannulata, and shows affinity with the anamorphic species Dictyochaeta cylindrospora. The usefulness of describing anamorph genera for morphologically reduced anamorphs, when anamorph characteristics are actually part of the holomorph diagnosis, is discussed. An apparently contradictory example of the so-called Cordana and Pseudobotrytis anamorphs of Porosphaerella spp. is also discussed.     

Cesariella, a new genus of Laboulbeniales

Cesariella graeca gen. sp. nov. is described to accommodate a new species of the Laboulbeniales (Fungi, Ascomycota) parasitic on the endogean ground beetles Reicheadella aetolica and R. bischoffi (Coleoptera, Carabidae) from Greece. Cesariella is distinguished from the allied genus Laboulbenia by the presence of two cells borne on the inner side of cell III, and by the presence of a conspicuous remnant of the spore apex protruding laterally near the base of the appendage.     

Molecular phylogeny and biogeographic history of the European Maja spider crabs (Decapoda, Majidae)

We have assessed for the first time the phylogenetic relationships and biogeographic history of the crabs of the genus Maja that inhabit European coasts: M. brachydactyla, M. crispata, M. goltziana and M. squinado. Using mitochondrial markers, we have recovered a well-resolved phylogenetic tree that supports a single origin for the European species, most likely from an Indo-West Pacific ancestor during the Early Miocene. In this phylogeny, M. goltziana appears as the basal European species, with a sister lineage bifurcating into an Eastern Atlantic (M. brachydactyla) and a Mediterranean (M. crispata and M. squinado) clade. We propose the Tethyan Seaway as the initial colonization route, although an entrance through South Africa cannot be discounted. The Eastern Atlantic/Mediterranean split seems to predate the Messinian salinity crisis, which, in turn, could have promoted the recent divergence within the Mediterranean. In addition, Pleistocene glaciations could explain the current diversity in the Eastern Atlantic Ocean, where a unique mitochondrial lineage is found. According to this, the genetic profile of South African crabs appears to belong to M. brachydactyla, questioning the validity of the putative species M. capensis.     

Comparative morphology of larvae of coastal crabs (Crustacea: Decapoda: Varunidae)

The larval development of three crabs of the Varunidae family, (Hemigrapsus sanguineus, H. penicillatus, and H. longitarsis), widely spread in Russian waters of the Sea of Japan, were studied under laboratory conditions. At a temperature of 20–22°C and a salinity of 32‰ about 30% of larvae a complete developmental cycle, including five zoeal stages and megalopa, took from 22 to 30 days. All larval stages are illustrated and described in detail. Zoea I and zoea II of the studied crabs are not distinguishable. Zoea III–V of these species differ in the number of dorsomedial setae on the abdominal somite I and in the number of setae on the posterodorsal arch. The megalopae of three Hemigrapsus species possess a different number of segments, aesthetascs and setae on the antennular exopod. In spite of the great similarity of larvae of genera Hemigrapsus and Eriocheir, the latter possesses a number of distinctive features in all developmental stages, supporting the separation of these genera.     

Developmental patterns of larval growth in the edible spider crab, Maja brachydactyla (Decapoda: Majidae)

The large edible spider crab Maja brachydactyla Balss, 1922, an overexploited coastal fishery resource in Galicia (NW Spain), is considered as a potential aquaculture candidate. Patterns of its larval growth were studied under controlled laboratory conditions (constant 18 ± 1 °C; 36‰ salinity; photoperiod ca. 12:12 h; lipid-enriched Artemia metanauplii provided as food). From hatching through complete larval development and metamorphosis to the first juvenile crab instar, changes in carapace size, dry weight (DW), ash content, elemental composition (carbon, hydrogen, nitrogen; CHN), and proximate biochemical composition (total proteins, lipids, carbohydrates; Pr, L, Ch) were measured in successive stages (zoea I, II, megalopa, crab I). Body size may be described as a linear function of the number of molting cycles, whereas the amounts of DW, CHN, Pr, L, and Ch per individual increased exponentially (3 to 9 fold). The highest growth rates were observed in L, C and H, the lowest in DW, Pr and N. As a consequence of these patterns, the C:N mass ratio as well as the fractions of L, C and H (in % of DW) increased significantly, while those of Pr and N decreased from 26% to 16% of DW. Throughout development, however, Pr remained the principal biochemical component of total DW. Positive correlations between biochemical and CHN data allow for estimates of Pr from N and of L from C values per individual. The patterns of larval growth observed in M. brachydactyla are, in general, similar to those previously described for other brachyuran crabs with a planktotrophic mode of larval development.     

Morphology and development of Nigrosabulum globosum, a cleistothecial coprophile in the Bionectriaceae (Hypocreales)

Recent DNA sequence analyses indicated that Nigrosabulum globosum is a cleistothecial representative of the Bionectriaceae in the Hypocreales, but morphological characters supporting this relationship are unknown. Using light and electron microscopy we followed the development of the ascomata of this species, from the formation of gametangia through to the development of mature ascospores, and observed a series of characters that confirmed its hypocrealean affinities. These included the formation of a gel-filled centrum during early stages of ascoma development, the subsequent appearance of hyaline peridial tissue enclosed within a layer we interpret as representing a melanized uniloculate stroma, apically derived paraphyses, and an ascogenous system that gives rise to asci that were both cylindrical to clavate and globose. Ascospores, previously reported to be smooth, were ornamented with a honeycomb-like reticulum and were able to germinate within the ascoma. The carbonaceous outer (stromatic) walls of the mature, grit-like cleistothecia indicate possible resistance to UV radiation and desiccation. Furthermore, the complement of germinated ascospores would enable mature ascomata to function as propagules that could quickly initiate new growth when transferred to fresh substrate. Our reexamination of N. globosum also provides data that support the hypothesized close relationship with other bionectriaceous, cleistothecial coprophiles, i.e., species of Hapsidospora, and Bulbithecium in particular.     

Taxonomic notes on Pogonieae ( Orchidaceae ): Cleistesiopsis, a new genus segregated from Cleistes , and description of two new South American species, Cleistes batistana and C. elongata

Summary  A new genus, Cleistesiopsis, was segregated from Cleistes based on morphological and molecular characteristics, and two new species of Cleistes: C. batistana and C. elongata, both occurring in the Brazilian Central Plateau (Central-Western Brazil), are described and illustrated. Furthermore, a key to genera currently recognised within Pogonieae is presented.

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Resumo  Um novo gênero, Cleistesiopsis, é segregado de Cleistes com base em caracteres morfológicos e moleculares, e duas novas espécies de Cleistes: C. batistana e C. elongata, que ocorrem no Planalto Central, no Centro-Oeste do Brasil, s?o descritas e ilustradas. Além disso, uma chave para os gêneros que atualmente comp?em a tribo Pogonieae é apresentada.

     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.