Cypris Larvae Research Articles

Scanning electron microscopy of the fourth antennular segment ofBalanus amphitrite amphitrite

Despite extensive studies on settlement of the cypris larva ofBalanus amphitrite amphitriteDarwin (Crustacea: Cirripedia), the fine structure of the putative settlement receptors of this species has not been described. This study presents observations made with the scanning electron microscope of the fourth antennular segment and its associated setae.

The effect of bacterial films on the temporary adhesion and permanent fixation of cypris larvae,balanus amphitritedarwin

The relative tenacity of temporary adhesion of cypris larvae of the barnacle Balanus amphitrile Darwin was measured on three substrata (polystyrene, tissue‐culture polystyrene, and glass) with and without the presence of films of the marine bacterium Deleya marina (ATCC 25374). Cyprids that were day 0 (day of metamorphosis from the sixth stage nauplius) or day 2 (two days later) were used in the experiments. Concomitant with these measurements, fixation assays (22 h) were conducted on the same filmed and unfilmed substrata. Results indicate that although the three unfilmed substrata varied in their wettability, this had no apparent effect upon the tenacity of temporary adhesion. In addition, in contrast to reports for Balanus (= Semibalanus) balanoides (L.) there was no correlation between the tenacity of temporary adhesion and fixation to unfilmed substrata of these cyprids. The presence of bacterial films (cells and their extracellular polymers) resulted in (1) similar wettabilities for the three substrata, (2) varying effects on the tenacity of temporary adhesion for day 0 cyprids, and (3) similar effects on the tenacity of temporary adhesion for day 2 cyprids. No correlation was observed between the tenacity of temporary adhesion and fixation of cyprids to bacterial films on the three substrata. Bacterial film inhibition of fixation is hypothesized to be through cyprid chemoreceptors.

Comparative SEM Studies of Lattice Organs: Putative Sensory Structures on the Carapace of Larvae from Ascothoracida and Cirripedia (Crustacea Maxillopoda Thecostraca)

AbstractPutative sensory structures, called lattice organs, were studied with scanning electron microscopy from ascothoracid or cypris larvae representing a wide range of families of the Ascothoracida and Cirripedia. These organs, situated dorsally on the carapace were, with few exceptions, always found in two anterior and three posterior pairs. The lattice organ morphology displayed by the Ascothoracida, a seta–like structure with a terminal pore, is believed to be the most plesiomorphic condition. Within the Cirripedia lattice organ morphology varied from types resembling the Ascothoracida in the Acrothoracica and the lepadomorph Capitulum mitella, to an elongate pore field with a larger terminal pore in most Thoracica and Rhizocephala. Akentrogonid Rhizocephala seem to display the most apomorphic condition. While lattice organ morphology was generally constant at the family level, cases were seen where closely related species such as Chthamalus stellatusand Chthamalus montaguishowed minor, but clear cut differences.Lattice organs in 2 + 3 pairs are argued to represent a synapomorphy for the Ascothoracida and the Cirripedia. The results confirm that the cyprid morphology at the ultrastructural level will prove to be of high value in estimating phylogeny within the Cirripedia.

The interaction between Elminius modestus Darwin cyprids and biofilms of Deleya marina NCMB1877

The interaction between Elminius modestus Darwin cypris larvae and biofilms of Deleya marina NCMB1877 covering a range of surface types has been studied by the measurement of cypris temporary adhesion. A > 16 kDa water-soluble partial fraction of bacterial exudate significantly reduced temporary adhesion on all surfaces in a manner which was independent of the underlying surface wettability. In contrast, the underlying surface wettability influenced the effects produced by both 4-day and 1-month-old, whole biofilms. Cyprids adhered more strongly to 4-day-old films compared to control surfaces, but less strongly to 1-month-old films. We suggest that bacterium/substratum adhesion plays a significant role in the adhesion and settlement of cypris larvae. The production of stimulatory or inhibitory factors within the biofilm is dependent upon biofilm age. The interaction between underlying substratum properties and biofilm age together with the local bacterial community structure, will help to determining the degree to which a submerged surface will become fouled.

On the antennular secretion of the cyprid ofBalanus amphitrite amphitrite, and its role as a settlement pheromone

In exploring a substratum,Balanus amphitrite amphitriteDarwin (Crustacea: Cirripedia) cyprids deposit ‘footprints’ of antennular secretion. The results ofin vitrosettlement assays suggest that in addition to serving as a temporary adhesive, the secretion acts as a pheromone, in that its presence induces the settlement of conspecific cyprids. This result is in accord with a previous study onBalanus balanoides(L.)(=Semibalanus balanoides). In settlement assays, the pheromone is likely to contribute to an observed positive linear relationship between settlement and cyprid density. The density effect should thus be an important consideration in the design of barnacle settlement assays. In the field, cyprid searching behaviour may render a surface more attractive to settlement by cypris larvae.

The tenacity ofElminius modestusandBalanus perforatuscyprids to bacterial films grown under different shear regimes

The tenacity of cypris larvae of the barnacles (Crustacea: Cirripedia)Balanus perforatus(Bruguiere) andElminius modestusDarwin was measured on multispecies biofilms developed under contrasting shear regimes. For both species, relatively thin, dense biofilms associated with high shear (83 s-1) afforded increased tenacity over relatively thick, less dense films associated with low shear (15 s-1). Although both species showed reduced tenacity on low-shear films compared to high-shear films,E. modestuscyprids attached as strongly to low-shear films as they did to unfilmed surfaces.Balanus perforatuscyprids, however, attached less strongly to low-shear films than to unfilmed surfaces. The results show thatB. perforatusand E.modestusmay appreciate differences in bacterial communi-ties grown under different shear conditions and highlight the potential for biofilms as one of the many cues to barnacle settlement.

Remodeling of the Nauplius Eye into the Adult Ocelli during Metamorphosis of the Barnacle, Balanus amphitrite hawaiiensis: (Crustacea/cypris larva/photoreceptor/rhabdom/Ultrastructure).

The planktonic barnacle larva has a single median ocellus (nauplius eye), while the adult possesses two distinct sets of photoreceptors; a pair of lateral ocelli and a single median ocellus. The nauplius eye of the cypris larva of Balanus amphitrite hawaiiensis is composed of 14 visual cells grouped into three components (a pair of lateral components and a single ventral component) surrounding two centrally located pigment cells; each lateral component consists of 5 visual cells and the ventral component, 4 visual cells. In each component, the rhabdom is made up of apposing microvilli arising directly from the neighboring visual cell bodies. During metamorphosis into the adult form, the three components of the median ocellus become separated. Each lateral component migrates laterally on the mantle and is remodeled into the adult lateral ocellus, losing two visual cells but gaining new pigment and tapetum cells in the process. The ventral component remains in the mid portion and becomes the adult median ocellus without fundamental modification in composition. The visual cells in both ocelli undergo a marked increase in volume and form many finger-like dendrites. Rhabdomes are made up of interdigitating microvilli arising from the the dendrite tips.

Barnaclein vitroassays for biologically active substances: Toxicity and Settlement inhibition assays using mass culturedBalanus amphitrite amphitritedarwin

The development of non‐toxic or non‐polluting antifouling additives that can be formulated in practical coatings requires assays involving target organisms. Assays that test both for the effective and toxic concentrations of active compounds are useful. It is also desirable if the assay can provide information regarding the performance that can be expected if the compounds are incorporated into different matrices. Described here are the simple laboratory assays that have been developed using the barnacle, Balanus amphitrite, a common fouling organism found throughout temperate and tropical seas. One of the assays depends on synchronous year‐round mass culture, the procedure for which is described, of cypris larvae. The laboratory assays provide quantitative estimates of toxicity and settlement inhibition of barnacles. The methods described provide an excellent system for the use of barnacles to study the interaction of the test compounds and surfaces.

Effects of the nonsteroidal ecdysone mimic RH 5849 on larval crustaceans

AbstractThe effects of the nonsteroidal ecdysone mimic RH 5849 on larvae of a crab (Rhithropanopeus harrisii) and the cypris larva of a barnacle (Balanus amphitrite) have been investigated. Larvae were exposed to exogenous RH 5849 in the concentration range of 0.1–10.0 mg/L. The two lowest concentrations tested (0.1 and 1.0 mg/L) accelerated molting of crab zoeae. RH 5849 did not induce premature apolysis. A concentration of 10 mg/L RH 5849 was toxic to zoeae: these larvae underwent apolysis but not ecdysis and subsequently died. Attachment and metamorphosis of barnacle cyprids was enhanced by 10.0 mg/L RH 5849. Increased attachment may be a result of physiological aging of larvae by the ecdysone mimic. Increased metamorphosis is consistent with the stimulatory effect of 20‐hydroxyecdysone on this process. RH 5849 was first demonstrated as an ecdysone mimic in insects (Wing, Science, 241:467–469, '88). The present study provides preliminary evidence for a similar action in crustaceans. © 1992 Wiley‐Liss, Inc.

The link between cypris temporary adhesion and settlement ofBalanus balanoides(L.)

A link between cypris temporary adhesion and settlement has often been alluded to, but never tested. Data are presented here which confirm earlier assumptions of a correlation between increased levels of settlement and greater forces of temporary adhesion of the cypris larvae of Balanus balanoides (L.). Temporary adhesion reflects behaviour since cyprids with a propensity to swim exhibit mean forces of temporary adhesion significantly lower than cyprids with a propensity to explore surfaces (7.22 × 104 N.m−2 and 13.30 × 104 N.m−2 respectively). Furthermore, significantly more explorer cyprids in the assays settled than did swimmer cyprids (43% and 37% respectively). Swimming and exploring behaviours are discussed in the context of a behavioural cascade, ultimately leading to settlement, motivated by positive physiological and environmental feedback. The behavioural sequence may be abandoned at almost any time in the face of unsuitable stimuli but the experience is likely to alter future acceptance thresholds towards surfaces.

Inhibition of larval barnacle attachment to bacterial films: An investigation of physical properties

The effects of films of two strains of a marine bacterium, Deleya marina (ATCC 25374 and 27129) on the attachment response of cypris larvae of the balanomorph barnacle, Balanus amphitrite, were examined in the laboratory. Tests showed that the cell-surface hydrophobicities of the two bacteria in suspension were different. In contrast, films derived from these cells were both highly wettable (i.e., displayed high surface free energy). Assays (22 hours) compared permanent attachment of larval barnacles to films derived from exponential and stationary phase cells for both bacteria. These films either had no effect or inhibited attachment of both 0-day- and 4-day-old cypris larvae when compared with unfilmed controls. Our data indicate that inhibition of larval barnacle attachment by films of the two bacteria is the result of factors other than surface free energy. Production of chemical barnacle settlement inhibitors by the bacteria is hypothesized.

Morphology of Thompsonia Reinhardi, New Species (Cirripedia: Rhizocephala), Parasitic on the Northeast Pacific Hermit Crab Discorsopagurus Schmitti (Stevens)

ABSTRACT The distribution of the internal root system, the morphology of several external stages, and the cypris larva are described for the rhizocephalan Thompsonia reinhardi, new species. The morphology and various events during the life cycle are compared to other species of Thompsonia.

Patterns, Mechanisms, Consequences of Variability in Settlement and Recruitment of an Intertidal Barnacle

I examined the settlement or recruitment of the barnacle Chthamalus anisopoma at a variety of scales: temporally, over periods lasting 12 h to 1 mo, and spatially at sites separated by <1 cm to shores separated by 10 km. Both settlement and recruitment were variable at nearly all temporal and spatial scales that I examined. The majority of variability was attributable to differences in settlement or recruitment between sample periods. When only the spatial component was considered, variability decreased with scale. Large, consistent differences in settlement between geographic locations that are at approximately the same tidal height are probably the result of differential larval supply, whereas more subtle but still consistent differences in settlement between adjacent sites may, at least in part, be due to larval behavior. Differences in settlement between close sites were observed only when settlement was relatively high. This observation may be explained as follows. First, Chthamalus settle in pits or small depressions "suitable settlement sites (SSS's)" in the surface of a substrate. Second, within an SSS, space for settlement is restricted. Third, the density of SSS's differ between sites. When settlement is high, settlement differences between locations reflect differences in the number of SSS's, as all are used. However, when settlement is low, settlement will be similar between locations, since SSS's are not limiting. In a series of field experiments using both natural and artificial substrates I found that: (1) Cypris larvae of Chthamalus settled preferentially in the presence of a number of physical and biological factors. (2) Settlement was density dependent but growth and survivorship were not, which suggests exploitative but not interference intraspecific competition. (Although Chthamalus settle gregariously they space themselves out.) (3) Variability in the settlement of Chthamalus affected the ensuing adult population even at the highest settlement densities.

A new mechanism of host colonization: pedunculate barnacles of the genusOctolasmison the mangrove crabScylla serrata

Abstract Aquaculture of marine animals is increasing in importance as a means of producing a steady and reliable source of protein throughout tropical Asia. The mangrove crab, Scylla serrata, is commonly cultured in tidal ponds and sometimes held in cages suspended in the sea until marketable. As is the case with many edible crab species, its respiratory chambers are inhabited by stalked barnacles which occupy space on the gills normally available for exchange of oxygen and carbon dioxide. Previously biologists have assumed that the cyprids of epizoic stalked barnacles colonize potential hosts at all stages of the crab growth cycle in a manner analogous to the way in which acorn barnacle cyprids colonize inanimate substrata. However, the present discoveries demonstrate a new mechanism of colonization: the infective octolasmid cypris larvae collect on the host just prior to its molt and transfer from the old exoskeleton to the newly molted crab at the time of molt. Fortyone premolt crabs had an average of 196.5 cyprids while 20 intermolt crabs averaged only 2.7 cyprids per crab. Forty-one crabs were individually monitored through molt under controlled conditions and 87% of the cyprids on the crabs prior to molt were found to transfer from exuviae to the newly molted crabs.

Morphology of the Nervous System of Barnacles: the Median Ocellus ofBalanus Hameri (=Chirona Hameri)(Crustacea: Cirripedia)

The barnacle cypris larva possesses a pair of laterally placed compound eyes and a median nauplius eye which is tripartite in structure. Concomitant with the metamorphosis to the juvenile is the loss of compound eyes and the nauplius eye separates into its three constituent parts (Walley, 1969). The two dorsolateral components of the nauplius eye come to lie under the rostral shell plates, whereas the ventral component forms the median ocellus which underlies the mantle flaps of the scutal plates at the posterior margin of the adductor muscle (Figure 1).

Construction of the Pigment Shield of the Crustacean Compound Eye: A Review

This review attempts to bring together literature spanning one hundred years relating to the pigment shield of crustacean ommatidia. A consistent terminology of the pigment cells is suggested based on their positions in and around the ommatidia. Six different types are recognized: retinular, cone, distal, proximal, interommatidial, and basal pigments. The evolution of a pigment shield is described as three levels of complexity. An analysis of the available descriptions of crustacean pigment shields reveals many varying routes of evolution passing these levels. It is concluded that the crustacean pigment shield is a highly variable structure sensitive to functional demands and less bound to kinship. Compound eyes are present in most crustaceans but lacking in the subclasses Mystacocarida, Podocopa, Copepoda, and the orders Thermosbaenacea and Speleogriphacea. In the subclass Cirripedia only the cypris larva possesses compound eyes. Usually the compound eye has a pigment shield which fulfils important functions in screen

Inhibition of attachment of larval barnacles, Balanus amphitrite, by bacterial surface films

Films of bacteria on solid substrata can positively or negatively influence the attachment of marine invertebrate larvae. Effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite Darwin were examined in the laboratory. Bacteria, grown to mid-exponential phase and allowed to adsorb irreversibly to polystyrene petri dishes, attached in densities of 107 cells cm-2. Assays (22h) were used to compare the effects of adsorbed cells of 18 different bacterial species on larval barnacle attachment. Most of the adsorbed bacteria either inhibited or had no effect on larval attachment compared to clean surfaces. Experiments testing the effect of larval age on barnacle attachment were conducted with six species of bacteria and showed that older larvae attached in higher percentages to clean surfaces and that bacterial films generally inhibited larval attaschment. Both the species of bacteria and the in situ age of the adsorbed bacteria affected barnacle attachment response: older films of Deleya (Pseudomonas) marina were more inhibitory. Bacterial extracellular materials may be involved in the inhibitory process.

Influence of substratum heterogeneity and settled barnacle density on the settlement of cypris larvae

On the Atlantic coast of Canada, Semibalanus balanoides (L.) is widely distributed in the mid-intertidal zone, whereas in the Gulf of St. Lawrence, this species is mostly limited to crevices. We tested the hypothesis of regional differences in microhabitat selection by barnacle larvae at settlement in 1984 and 1985 at St. Andrews, New Brunswick, Canada. Since larvae settle in microhabitats already colonized by adults, the relative influence of settled barnacle density and of different scales of substratum heterogeneity on settlement were evaluated experimentally at Capucins, Quebec, (Gulf of St. Lawrence) and at St. Andrews, New Brunswick (Atlantic coast). On a large scale (>10 cm deep crevices) of heterogeneity, results show that, in the Gulf, cypris larvae settled nearly exclusively (93%) in natural crevices rather than on adjacent horizontal surfaces. On the Atlantic coast, settlement was more important outside than inside of crevices, when the substrata were either natural or artificial. This result is unique and contrasts sharply with all known reports on barnacle settlement in relation to surface contour. The influence of barnacle density on settlement was greater than that of large scale heterogeneity. On a small scale (<1.5 cm deep cracks), the presence of conspecifics had a stronger effect on settlement than heterogeneity in both regions. Field observations showed a relationship between larval settlement density and percentage of adult cover. Settlement increased up to 22 or 30% (Gulf and Atlantic coast) of adult cover and decreased afterwards. The results confirm the hypothesis of larval selection for cryptic habitats in the Gulf and the opposite behaviour (preferences for horizontal surfaces) on the Atlantic coast. This microhabitat selection is apparent at large scales of heterogeneity, whereas at small scales, the presence of conspecifics is the predominant factor.

Diet of alewives, Alosa pseudoharengus and blueback herring, A. aestivalis (Pisces: Clupeidae) in Minas Basin, Nova Scotia, a turbid, macrotidal estuary

Stomach contents of anadromous alewives, Alosa pseudoharengus and blueback herring, A. aestivalis, obtained from brush weir and drift net collections in Minas Basin, N.S., were examined. Diets showed much overlap in terms of resource use, but the dietary importance of major prey categories differed substantially between species. Alewives favoured larger, more benthic prey (e.g. amphipods, mysids and crangonids), while blueback herring appeared to concentrate their feeding on microzooplankters (e.g. calanoid copepods, cypris larvae and molluscan veligers). Interspecific differences in diet composition are largely attributed to the planktivorous feeding habits of small (81–155 mm fork length) blueback herring. Differences in prey suggest that alewives utilize a particulate feeding strategy while blueback herring are predominantly filter-feeders. Although competition for food in the Basin seems unlikely since high secondary production yields a superabundance of prey, differences in feeding behaviour between younger, smaller individuals of both species could be a means of avoiding competitive interactions in an environment where there are space/access limitations imposed by the tidal cycle.

Energy budget for the larval development ofElminius modestus (Crustacea: Cirripedia)

Biomass (CHN), respiration rate and food uptake were estimated for the larval development ofElminius modestus at three temperatures (12, 18, 24°C). Mean values of dry weight, elemental composition and energy equivalents increased exponentially with the development from nauplius II to VI. Dry weight, elemental composition and energy content exhibited the highest values at 18°C. Respiration rates increased with the larval stages expressed by a power function, but increased logarithmically with the dry weight of the larvae. The cypris larvae showed a reduced respiration rate compared with nauplius VI. The ingestion rate was measured at a concentration of 100 cells ofSkeletonema costatum μl−1. At 12 and 18°C ingestion rates increased exponentially and at 24°C by a logarithmic function. The fittings were used to estimate the energy budget ofE. modestus during larval development. The energy content of the larvae increased during the development from nauplius II to VI by a factor of 21 at 12°C, 25 at 24°C and 31 at 18°C. The estimated energy content of the freshly metamorphosed barnacle is 100 mJ (12°C), 130 mJ (24°C) and 150 mJ (18°C). The assimilation- (A/I) and gross growth efficiencies (K1) increased strongly during the development from nauplius II to VI (A/I: 6–14% in nauplius II to 50–90% in nauplius VI; K1: 4% in nauplius II to 75% in nauplius VI). The net growth efficiency (K2) showed a relatively constant level ranging between 57 and 83%.