Effects of gamma-aminobutyric acid on the settlement of larvae of the black chiton Katharina tunicata

Laboratory-cultured larvae of the black chiton Katharina tunicata (Wood), collected from central California in May and June of 1979 and 1980, settled preferentially on the encrusting coralline alga Lithothamnium sp. Metamorphosis, which involves the loss of the prototrochal ciliary band, occurred within a period of 2.5 h after larvae began crawling upon the alga. In response to gamma-aminobutyric acid (GABA) at a concentration of 10^-6 M, the lecithotrophic trochophore larvae ceased swimming and settled rapidly. Developmental metamorphosis did not follow settlement in the absence of encrusting coralline alga. However, when both GABA and Lithothamnium sp. were present, larval metamorphosis occurred within 2 h of settlement. Significantly different rates of settlement exist for sibling larvae of different ages; 12 d-old larvae responded more rapily and in greater numbers to treatment with GABA than 10 d-old larvae. Differences in settling rates are attributed to the onset of metamorphic competence.     

Studies on the fusion reaction in two species of Perophora (Ascidiacea)

Histological and electron microscopical studies were made on the fusion reaction between homogeneic stolons of the colonial ascidians Perophora japonica Oka and P. sagamiensis Tokioka. When two stolons make a tip-to-side contact, the epidermal cells of the lateral portion of one stolon become thick and form a protrusion. In the fusion reaction of P. japonica, epidermal cells of each stolon at the contact area extend cell processes immediately after contact. After an occurrence of degenerated epidermal cells, blood interchange between the two stolons is initiated by a partial elimination of the epidermal cells. Even after the establishment of blood interchange, the cuticlelike structure is often observed to remain at the contact area. In the fusion reaction of P. japonica, many amoebocytes are attached to the epidermal cells until the complete elimination of epidermal cells. In the fusion reaction of P. sagamiensis, many lymphocytes as well as amoebocytes are attached to the epidermal cells at the contact area.Contribution No. 461 of the Shimoda Marine Research Center     

Effects of self-fertilisation and other factors on the early development of the scallop Pecten maximus

Adult Pecten maximus (L.) were dredged off north-east Anglesey, Wales, UK, during 1981. A 2×5 factorial mating was carried out involving self- and cross-fertilisation and the use of stripped spermatozoa. Assessments of yield, normality, and larval size were made at the D larva stage and larval size and mortality were measured after a fortnight's growth of the veligers. Underlying genetic variation was evident at all stages, with egg and sperm generally having a significant interactive effect. Cultures sired with stripped spermatozoa had fewer larvae, with more abnormality, grew slower and suffered higher mortality than most other cultures. Larvae from selfed cultures grew significantly slower than all other larvae. Data from past larval cultures also show that selfed larvae have a reduced growth rate. it is suggested that stripped spermatozoa may interfere with egg and sperm interaction at fertilisation, thus reducing the viability of larvae. On the other hand, the poor growth rate of selfed larvae is probably due to overall reduced heterozygosity compared to outbred larvae.     

Effects of three years’ increase in density of the geometrid Epirrita autumnata on the change in metabolome of mountain birch trees (Betula pubescens ssp. czerepanovii)

The principal objective of the study was to characterize effects of increasing density of the autumnal moth, Epirrita autumnata (Lepidoptera, Geometridae), for 3 successive years on the change in metabolome of mountain birch trees (Betula pubescens ssp. czerepanovii). During the three study years (2000–2002), the larval density varied from low to very high (outbreak) density. Samples of leaves were collected from the same 12 trees at the same phenological stage of the trees each year. The leaves were collected from undamaged trees in the first year, from trees slightly damaged by larvae in the second year, and from trees heavily damaged by larvae in the third year. Metabolome analysis showed that the increase in density of E. autumnata larvae and degree of damage of birch trees caused multiple biochemical changes in the leaves, including increased concentrations of phenolic compounds (proanthocyanidins and hydrolysable tannins) and reduced concentrations of nutritive metabolites (monosaccharides, amino acids and some organic acids). These changes reduced the quality of leaves as food for larvae and, probably, were associated with induced chemical resistance of the birches to herbivorous insects. Additionally, the concentration of α-tocopherol was significantly higher in both slightly and heavily damaged trees. Mechanisms of changes in the metabolism of phenolic compounds and carbohydrates, and the role of α-tocopherol in their regulation are discussed.     

Ultrastructure of sperm and spermathecae in Micromaldane spp. (Polychaeta: Capitellida: Maldanidae)

Assessing the possibility that external fertilization has re-evolved requires the study of monophyletic groups that exhibit various reproductive methods. Maldanid polychaetes show a range of reproductive mechanisms, though previous studies of reproduction have hitherto been restricted to larger species with external fertilization. Micromaldane pamelae Rouse and M. nutricula Rouse are small, gonochoristic maldanids that brood directly developing larvae. Both species have sperm with elongate nuclei and an acrosome extending down each side of the anterior end of the nucleus. A true midpiece is absent; two mitochondria extend along the posterior region of the nucleus. Spermatids develop synchronously in large clusters connected by a cytophore. In M. pamelae sperm are released into the water as spermatozeugmata. These are comprised of clusters of sperm with their tails oriented to the centre and the sperm heads facing outwards. Females of M. pamelae and M. nutricula bear pairs of spermathecae ventrally (M. pamelae three pairs, between setigers 10 and 11, 11 and 12 and 12 and 13 and M. nutricula two pairs, between setigers 10 and 11 and setigers 11 and 12). The blind sacs are epidermal invaginations bound closely together. The entrance to each spermatheca may only be 1 to 2 m across with each spermatheca holding several hundred sperm. This represents the first detailed study of spermathecae in the Capitellida. The occurrence and structure of spermathecae and spermatozeugmata in other groups are discussed and compared with Micromaldane spp. Comparisons are made with non-polychaetes with the purpose of discussing functional aspects of reproductive mechanisms in marine metazoans in general. Elongate sperm nuclei are associated with sperm storage and/or large egg size. The lack of an elongate sperm midpiece may be an indicator of having to swim in water but does not contraindicate sperm storage. Spermatozeugmata may serve as an indication of sperm storage and brooding of larvae. Speculations on the phylogenetic significance of these reproductive features are limited by the fact that supposedly modified (i.e., derived) states may reflect functional/structura, constraints of small body size.     

Habitat selection in the tropical polychaeteSpirobranchus giganteus

Total body weight, tube length, abdomen weight and branchial crown weight of individualSpirobranchus giganteus (Pallas) living on four different coral species on the bank reef on the west coast of Barbados were investigated in 1986. Worms onDiploria strigosa were larger in all size parameters than those onMontastrea annularis, which were larger than those onMontastrea cavernosa, which were larger than those onPorites porites. The differences between worms onM. annularis andM. cavernosa were not significant. Variation in worm size on the different corals could result from variation in mortality and/or variation in growth. Whichever the case, larger worms may have higher lifetime reproductive success. Abdomen weight is an index of gamete production inS. giganteus, and increases with increasing body weight for worms on all corals. Moreover, larger worms do not have lower abdomen weight at a given body size than smaller worms. This may imply that faster growth does not reduce gamete production at body size. The coral species on which worms are largest are those most preferred by worm larvae in the laboratory and most heavily colonised by adult worms in the field. The results suggest adaptive habitat selection by planktonic larvae ofS. giganteus.     

Evidence for acclimation to hydrostatic pressure in Uca pugilator (Crustacea: Decapoda: Ocypodidae)

Groups of male Uca pugilator (Bosc) (Crustacea, Decapoda, Ocypodidae), acclimated to sublethal pressure (34 atm) subaqueously for 5 and 10 days, were observed subsequently at pressures up to 272 atm. Behavioral indicators of pressure resistance (“first response” and tetany) were employed to measure degrees of pressure acclimation in comparison with simultaneously and non-simultaneously conducted control experiments. No firm conclusions can be made on the basis of “first response” results, but the pressures required to induce tetany were significantly higher (P≤0.02, one-tailed comparison) in acclimated groups than in non-acclimated groups. These data and earlier studies by other investigators support the assertion that some shallow marine species are capable of at least limited short-term pressure acclimation.     

Latitudinal variation in the life history features of the black turban snail Tegula funebralis (Prosobranchia: Trochidae)

At higher latitudes along the west coast of the USA the herbivorous intertidal snail Tegula funebralis (Adams, 1854) lives longer, grows more slowly, but attains a larger size than further south. To the north, age distributions are less predictable and often far from stationary. The differences, which have some generality, can be explained either by a primary temperature effect joined with increased hazards to planktonic larvae in the north, or else may result from a combination of interactions between intensity of predation, population density and food supply. Growth rates of transplanted individuals suggest a genetic basis for the latitudinal differences.     

不同海拔高度短穗兔耳草克隆生长及克隆繁殖特征

研究了青藏铁路和青藏公路沿线 5个不同海拔高度样地中短穗兔耳草克隆生长和克隆繁殖的特征.结果表明,不同海拔高度短穗兔耳草匍匐茎数量、匍匐茎长度、基株干重、匍匐茎干重和无性系分株干重等均存在极显著差异(P<0. 01);匍匐茎数量与海拔高度之间存在明显的负线性相关性(P=0. 046 4);匍匐茎长度、基株干重、匍匐茎干重、单位长度上匍匐茎干重、无性系分株干重和匍匐茎分株总干重 /基株干重比值均与海拔高度之间存在极显著的二次多项式相关性(P<0. 01),但匍匐茎长度、匍匐茎分株总干重 /基株干重随海拔高度的变化趋势与基株干重、匍匐茎干重、单位长度上匍匐茎干重、无性系分株干重随海拔高度的变化趋势相反.在短穗兔耳草分布的海拔范围内,其克隆繁殖和克隆生长有一个“最佳”海拔高度,远离这一高度,其克隆繁殖和克隆生长会受到一定限制. 图 6表 2参 18     

Investigations of carotenoids in some fauna of the Adriatic Sea. II. Anemonia sulcata and Actinia equina (Coelenterata: Anthozoa)

Investigations have been carried out on the carotenoids in Anemonia sulcata (Pennant) and Actinia equina (L.) (Coelenterata: Anthozoa) from the Adriatic Sea. The presence of the carotenoids was determined by means of columnar and thin-layer chromatography. The following carotenoids were found: Anemonia sulcata: β-carotene, lutein-like (epoxy and free) and astaxanthin; Actinia equina: α-carotene, β-carotene, actinioerythrin, lutein-like (?) and astaxanthin (ester and free).     

Effects of temperature and delayed feeding on growth and survival of larvae of three species of subtropical marine fishes

In larvae of the bay anchovy Anchoa mitchilli (Valenciennes), the sea bream Archosargus rhomboidalis (Linnaeus), and the lined sole Achirus lineatus (Linnaeus), growth, survival, and starvation times were investigated at temperatures of 22° to 32°C. The rate at which hours after hatching until starvation decreased in relation to temperature for unfed larvae did not differ significantly among the 3 species, ranging from-5.4 to-6.3 h per degree increase in temperature. The total number of hours until starvation did differ for all 3 species: lined soles survived longest, bay anchovies were intermediate, and sea bream survived the least time. At 28°C, unfed sea bream could survive 90.1 h, bay anchovy 102.3 h, and lined sole 119.8 h. The eyes pigmented at nearly the same time after hatching for sea bream and bay anchovy, but took about 20 h longer at all temperatures for lined sole. Quadratic equations best described the relationship between hours after hatching when the eyes became pigmented and temperature. Eye-pigmentation times became nearly constant for all 3 species at temperatures above 28°C. At 28°C, eyes pigmented about 27 h after hatching for bay anchovy and sea bream but not until 47 h for lined sole. Hours after eye pigmentation when unfed larvae starved was a measure of the effective time that larvae had to commence feeding. Bay anchovies and lined soles were nearly alike in this respect, but sea bream starved at tewer hours after eye pigmentation. Slopes of regressions representing decrease in times to staration for increasing temperatures ranged from-3.7 to-4.4 h per degree increase in temperature, and were not significantly different among the 3 species. At 28°C, unfed lined soles starved at 70 a after eye pigmentation, bay anchovies starved at 72.5 h, and sea bream at only 62 h. Yolk absorption was most rapid for all species during the first 20 h after hatching, and was faster at higher temperatures. Amounts of yolk remaining at the time eyes became pigmented were less at higher temperatures for bay anchovy and lined sole, but were greater for sea bream, suggesting that sea bream used yolk more efficiently at higher temperatures. Either no yolk or small traces (>0.20%) remained at 24 h after eye pigmentation in all 3 species. Feeding was delayed for periods of 8, 16, 24, 32, 40 and 48 h after eye pigmentation for all species at a series of experimental temperatures from 24° to 32°C. Growth and survival were affected when food was withheld for more than 24 h at 28°C, but survival did not decrease markedly until food was withheld at least 8 h longer. At lower temperatures food could be withheld longer and at higher temperatures for less time. Feeding can be initiated by most larvae for several hours after all visible yolk reserves have been exhausted. All species tested can survive for 24 to 40 h after eye pigmentation at 24° to 28°C without food and still have relatively good growth and survival when food is offered. If the “critical period” is considered relative to time of hatching, lined soles need not find food for 3 to 3.5 days after hatching, but bay anchovy and sea bream must feed within 2.5 days of hatching.     

Reproduction and development of Sabella media,a sabellid polychaete with extratubular brooding

Known reproductive patterns in the polychaete family Sabellidae include: (1) broadcasting of gametes, (2) depositing of benthic egg masses, (3) brooding outside the lip of the tube, and (4) brooding within the tube. There is little information for sabellids in the third category; there-fore we have studied the reproductive biology of Sabella (=Demonax) media (Bush), one of the few species known to brood its early developmental stages outside the tube. A total of 32 adults of S. media with egg cocoons were collected from the surfaces of compound ascidians (Aplidium sp. and Didemnum sp.) and from holdfasts of a brown alga (Hedophyllum sessile) at Eagle Cove, San Juan Island, Washington, USA, from June 1981 through June 1982, between tidal levels of 0.0 and 0.6 m. The donutshaped cocoons, each containing over 1 000 eggs, are deposited just outside the tube aperture from April through September. Larval development takes place within the cocoon through the 3-setiger stage, at which time the larvae emerge (about 8 d after egg deposition). The newly hatched larvae are demersal and swim near the bottom of the culture dish for 1 d before settlement. Metamorphosis takes nearly a week, and initial formation of the tube is also gradual. The reproductive patterns within the family Sabellidae are discussed, and the adaptive significance of extratubular brooding considered.     

Poecilogony in Polydora hoplura (Polychaeta: Spionidae) from commercially important molluscs in South Africa

Females of the polychaete Polydora hoplura (Claparède 1869) that produced planktotrophic and adelphophagic larvae were compared genetically to determine whether the different reproductive morphs represented sibling species or poecilogony. Worms were collected from Saldanha Bay, South Africa (33°0′37.71S, 17°56′59.74E), and cultured in a laboratory setting from November 2012 to April 2013. The results based on mitochondrial and nuclear DNA (Cyt b and ATPSα, respectively) showed shared haplotypes between reproductive morphs for both markers. Additionally, variation in mtDNA sequences was significantly higher within morphs than between morphs (95.8 and 4.2 %, respectively). A comparison of developmental modes found that broods of planktotrophic larvae were larger than broods of adelphophagic larvae, while the latter had larger eggs and larvae at hatching. Developmental time from oviposition to settlement for planktotrophic and adelphophagic larvae was 40.2 and 16.6 days, respectively. Polydora hoplura represents the fifth confirmed case of poecilogony in the Spionidae.     

Biochemical changes during larval development of the xanthid crab Rhithro panopeus harrisii. II. Nucleic acids

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) contents were measured daily during the zoeal development of the crab Rhithropanopeus harrisii (Gould). DNA concentration (per unit protein) decreased as larvae increased in size. Total DNA content per larva showed an abrupt increase at the second molt and increased steadily during the third and fourth zoeal stages. Ratios of fresh weight to DNA were highest during the first two zoeal stages, dropped sharply at the second molt, then increased during the third and fourth zoeal stages. RNA:DNA ratios showed cyclical activity apparently related to the molt cycle. Assuming that fresh weight: DNA ratio reflects cell size and that DNA content reflects cell number, growth during the first two stages is due primarily to increase in cell size and during the last two stages to a combination of increase in cell size and number. Assuming further that RNA:DNA ratios reflect protein-synthesis activity, such activity in these larvae follows a rhythm related to the molt cycle.     

Tiger shark (Galeocerdo cuvier) movement patterns and habitat use determined by satellite tagging in eastern Australian waters

Partial migration is considered ubiquitous among vertebrates, but little is known about the movements of oceanodromous apex predators such as sharks, particularly at their range extents. PAT-Mk10 and SPOT5 electronic tags were used to investigate tiger shark (Galeocerdo cuvier) spatial dynamics, site fidelity and habitat use off eastern Australia between April 2007 and May 2013. Of the 18 tags deployed, 15 recorded information on depth and/or temperature, and horizontal movements. Tracking times ranged between four and 408 days, with two recovered pop-up archival tags allowing 63 days of high-resolution archived data to be analysed. Overall mean proportions of time-at-depth revealed that G. cuvier spent the majority of time-at-depths of <20 m, but undertook dives as deep as 920 m. Tagged sharks occupied ambient water temperatures from 29.5 °C at the surface to 5.9 °C at depth. Deep dives (>500 m) occurred mostly around dawn and dusk, but no definitive daily dive patterns were observed. Horizontal movements were characterised by combinations of resident and transient behaviour that coincided with seasonal changes in water temperature. While the majority of movement activity was focused around continental slope waters, large-scale migration was evident with one individual moving from offshore Sydney, Australia, to New Caledonia (c. 1,800 km) in 48 days. Periods of tiger shark residency outside of Australia’s fisheries management zones highlight the potential vulnerability of the species to unregulated fisheries and the importance of cross-jurisdictional arrangements for species’ management and conservation.     

Role of the nutritive value of sediment in regulating population dynamics of the deposit-feeding polychaete Streblospio shrubsolii

The importance of changes in nutritive value of the sediment in regulating the dynamics of the small deposit-feeding polychaete Streblospio shrubsolii (Buchanam, 1890) was examined. First, fluctuations in the population dynamics of S. shrubsolii and in the nutritive content of the sediment were studied on a seasonal scale. Subsequently, a manipulative field experiment was used to test the hypothesis that, in summer, availability of food regulates aspects of the population dynamics of S. shrubsolii. In summer 1997, sharp increases in protein concentrations and in the number of individuals of S. shrubsolii were found compared to all the other seasons. Densities of S. shrubsolii also showed an increase in the subsequent season. Newly recruited juveniles (19-31 setigers) were abundant in summer and autumn 1997, whereas the number of juveniles (32-42 setigers) increased in autumn 1997. Large numbers of adults were found in summer 1997. Significant negative correlations occurred in summer 1997 between the concentrations of proteins and the total number of individuals, the number of newly recruited juveniles and the density of adults. No differences in densities of juveniles, adults or total number of individuals were found among plots before starting the experiment. After 20 days of experimental enrichment, proteins showed a tendency to increase. After 40 days of enrichment, the total number of individuals was significantly greater in the enriched plots. Large numbers of newly recruited larvae and postlarval adults were found in the enriched plots. The experiment corroborated the model that the growth of population was limited by the availability of food in summer. Thus, in this season, patches of food could have a fundamental role in determining the population dynamics of small deposit-feeders under natural conditions and over short time scales.     

Dimethyl disulfide and dimethyl trisulfide: so similar yet so different in evoking biological responses in saprophilous flies

Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) are used by saprophilous insects to locate breeding sites (decaying organic matter), and by brood-site deceptive flowers to attract such insects. However, little is known about the relative importance of these two compounds in eliciting electrophysiological and behavioral responses in the insects. Here, we compared the relative attractiveness of DMDS and DMTS to saprophilous flies in field choice experiments and tested whether potential differences in field responses can be explained by differences in electrophysiological antennal responses to these compounds. Field experiments revealed that the attractiveness of a mixture of these compounds is due to DMTS alone. This result was confirmed by electroantennographic recordings in which flies of four tested species of Calliphoridae (Lucilia sericata, L. caesar, Calliphora vicina, Protocalliphora azurea) and one Muscidae (Musca domestica) respond clearly to DMTS, but not to DMDS. In house flies, however, DMTS elicited electrophysiological responses only, not reflected in behavioral assays. Despite the fact that DMTS and DMDS exhibit similar chemical structures, both the electroantennographic and field responses from saprophilous flies to these two compounds strongly differed. Our study suggests that oligosulfide-responsive saprophilous flies rely on DMTS and not DMDS for finding appropriate breeding sites and that DMTS and not DMDS could act as a key mediator for pollinator attraction in brood-site deceptive plants.     

Physiological development of brooded larvae from two pocilloporid corals in Taiwan

In southern Taiwan, brooded larvae of Pocillopora damicornis and Seriatopora caliendrum are released year-round in synchrony with new moons, and each larval release occurs over multiple days. Using P. damicornis and S. caliendrum as a model system, we describe within-brood variation in larval phenotypes and test for release-day effects that influence larval performance in the pelagic phase. Research was conducted in 2010 using larvae from corals collected in June and July from Nanwan Bay (21°56.179??N, 120°44.85??E). In June, larval phenotypes of both species were characterized immediately following release, and their competency to settle assessed. In July, larvae of P. damicornis were collected on 3?days over the peak release period and incubated for 7?C11?days at 28.0?°C and 320???mol?quanta?m^?2?s^?1; their phenotypes and settlement competency were measured every 2?days. P. damicornis larvae released close to peak release were 1.6 times larger in size, contained twice the number of Symbiodinium larva^?1, and were 44?% more likely to settle in the first 24?h than larvae released early in the brood. In addition, peak-release larvae respired at a lower rate than larvae released late in the brood. Similarly, S. caliendrum larvae released close to peak release were 1.4 times larger in size and were 33?% more likely to settle in the first 5?h than larvae released early in the brood. In July, P. damicornis larvae differed between early (2?days prior to peak), peak, and late (2?days after peak) release. Protein content of early-release larvae was lower than peak- and late-release larvae, and this difference persisted throughout the development. Further, release day affected the way larval respiration varied throughout development. By showing that brooded coral larvae differ between release days and display maternal effects influencing performance in the swimming phase, our results suggest that pocilloporid corals utilize bet-hedging to increase reproductive success.     

Diet selection of the Chilean stone crab Homalaspis plana

Diet selection of the Chilean stone crab Homolaspis plana (Milne-Edwards, 1834) was studied using the optimal foraging theory to explain its feeding strategy. The hypothesis that H. plana prefers prey species of the highest prey (“energy”) value was experimentally tested on adult crabs during 1980–1981. Food value was defined as the ratio between caloric content and consumption time, according to energy maximization as the criterion to optimize diet selection. Diet composition of adult crabs from the littoral of Valparaíso (Chile) and ingestion under laboratory conditions were studied to determine type, size and quantity of food to be offered in experiments on prey-type preference. Porcellanid crabs, barnacles and bivalves were the most frequently occurring items in stomachs from in situ conditions. In the aquaria, daily ingestion rates were quite variable among crabs and among days. H. plana showed no size preference for molluscs (Tegula atra, Semimytilus algosus) but preferred larger sizes of porcellanids. The order of preference for prey type was S. algosus>T. atra> porcellanids. However, no differences between their energy values were found and, therefore, the optimal foraging hypothesis was rejected. By extension, the energy maximization criterion alone may not explain the diet selection of H. plana under experimental conditions.