Cytogenetics of the darkling beetles Zophobas aff. confusus and Nyctobates gigas (Coleoptera, Tenebrionidae)

Males of Zophobas aff. confusus and Nyctobates gigas (Tenebrionidae) collected in the State of Pernambuco, Brazil, were studied through conventional staining, C-banding, silver nitrate impregnation (AgNO(3)), and the base specific fluorochromes CMA(3) and DAPI. Z. aff. confusus was found to have 2n = 20 (9+Xyp) while N. gigas exhibited 2n = 18 (8+neoXY). Large pericentromeric blocks of constitutive heterochromatin (CH) were detected throughout the autosomal complement of the two species, except in one autosomal pair of N. gigas in which no heterochromatic block was observed. The sex chromosomes of both species were almost totally heterochromatic. Double staining with CMA(3)/DA (distamycin) and DAPI/DA marked CH in Z. aff. confusus. However, DAPI staining was more intense. N. gigas was found to possess blocks of CH-positive CMA(3) and homogeneous DAPI. AgNO(3) staining also revealed differences between the two species. In Z. confusus an NOR was observed in the sexual bivalent Xyp and N. gigas was found to have an autosomal NOR.     

5-HYDROXYTRYPTAMINE, HISTAMINE AND N-ACETYLHISTAMINE IN THE NERVOUS SYSTEM OF DOSIDICUS GIGAS

Abstract— The optic ganglia, cerebral ganglia and mantle nerve of the squid Dosidicus gigas were examined for possible amines. Histamine was detected in all three tissues. The optic ganglia were also found to contain 5-HT and N -acetylhistamine, an infrequently found derivative of histamine.     

Acoustical and neural aspects of hearing in the Australian gleaning bats,Macroderma gigas andNyctophilus gouldi

1. The maximum acoustic gain of the external ear in Macroderma gigas was found to be 25-30 dB between 5-8 kHz and in Nyctophilus gouldi it reached 15-23 dB between 7-22 kHz. Pinna gain reached a peak of 16 dB near 4.5-6 kHz in M. gigas and 12-17 dB between 7-12 kHz in N. gouldi, with average gain of 6-10 dB up to 100 kHz. Pinna gain curves resemble that of a finite conical horn, including resonance. 2. The directional properties of the external ear in both species result from sound diffraction at the pinna face, as it approximates a circular aperture. The frequency dependent movement of the acoustic axis in azimuth and elevation is attributed to the asymmetrical structure of the pinnae. 3. Evoked potentials and neuronal responses were studied in the inferior colliculus. In M. gigas, the neural audiogram has sensitivity peaks at 10-20 kHz and 35-43 kHz, with extremely low thresholds (-18 dB SPL) in the low frequency region. In N. gouldi, the neural audiogram has sensitivity peaks at 8-14 kHz (lowest threshold 5 dB SPL) and 22-45 kHz. Removal of the contralateral pinna causes a frequency dependent loss in neural threshold sensitivity of up to 10-15 dB in both species. 4. The high frequency peak in the audiogram coincides with the sonar energy band in both species, whereas the low frequency region is used for social communication. Highly sensitive low frequency hearing is discussed in relation to hunting in bats by passive listening.     

Phenoloxidase activity in larval and juvenile homogenates and adult plasma and haemocytes of bivalve molluscs

Phenoloxidase (PO) activity was studied in larval and juvenile homogenates and in the plasma and haemocytes of adult Crassostrea gigas, Argopecten ventricosus, Nodipecten subnodosus, and Atrina maura. Samples were tested for the presence of PO activity by incubation with the substrate L-3, 4-dihydroxyphenylalanine using trypsin, alpha-chymotrypsin, laminarin, lipopolysaccharides (LPS), and sodium dodecyl sulphate (SDS) to elicit activation of prophenoloxidase (proPO) system. PO activity was not detected in larval homogenate. In juvenile homogenate, PO activity was found only in C. gigas and N. subnodosus. PO activity was present in adult samples and was enhanced by elicitors in the plasma of all species tested, but in haemocyte lysate supernatant (HLS) of only N. subnodosus. Activation of proPO by laminarin was suppressed by a protease inhibitor cocktail (P-2714) in plasma and HLS of all species tested.     

Revision of the Antarctic genus Notaeolidia (Gastropoda, Nudibranchia), with a description of a new species

New material from the Atlantic sector of the Antarctic Ocean allows a revision of the Antarctic genus Notaeolidia Eliot, 1905. One new species (Notaeolidia schmekelae sp.n.) is described. N. depressa Eliot, 1905 and N. gigas Eliot, 1905, which arc poorly known, arc redescribed. N. rufopicta Thiele, 1912, N. robsoni Odhner, 1934, N. subgigas Odhner, 1944, N. alutacea Minichev, 1972 and N. flava Minichev, 1972 are synonymized with N. depressa. N. purpurea Eliot, 1905 is synonymized with N. gigas. The monogeneric family Notaeolidiidae Odhner, 1926. is characterized by the following autapomorphy: "nephroproct in front of the genital apertures". Too little is known to elaborate the phylogenetic position of the family Notaeolidiidae within the cladobranch Nudibranchia.     

Reproductive activity of Strombus gigas (Mesogasteropoda: Strombidae) in differente habitats of Alacranes reef, Yucatán

The spawning relationships with temperature/photoperiod of Strombus gigas were investigated considering three habitats in Alacranes Reef, Yucatan, between February 1999 and March 2000. The sites were 22 degrees 34'N, 89 degrees 42'W (site 1); 22 degrees 29'N, 89"45'W (site 2) and 22 degrees 22'N, 89 degrees 39'W (site 3). At each site, transects (100 m x 10 m) were done. Different kinds of reproductive behavior of S. gigas was observed: such as copulating and egg-laying. Individuals alone and egg masses were registered as well. The S. gigas shell length and lip thickness were measured. High density of adults was found at site 2 with 87 conchs in one transect of 1000 m2. The mean density per m2 was 0.004 for site 1; 0.035 for site 2; and 0.003 for site 3. The mean shell length was 220 mm and the lip thickness mean was 16 mm (N = 783) for all sites. In February 1999 egg-laying female was found on sand. There was a high reproductive activity at site 2 with 8 egg-laying and 18 egg masses. Minimum reproductive activity was found at site 3 with 2 egg masses. The bottom-water temperature was related positively with copulating pairs (r = 0.723, f = 11.05, p < 0.01) and egg masses (r = 0.736, f = 11.82, p < 0.1). Correlation between photoperiod with copulating pairs (r = 0.857, f = 27.78, p < 0.01) and egg masses (r = 0.782, f = 15.77, p < 0.01) were found as well.     

Evidence for the Periplasmic Location of Hydrogenase in Desulfovibrio gigas

Hydrogenase has been found to be located in the periplasmic space of Desulfovibrio gigas, and it is proposed that hydrogenase plays an important and specific role in interspecies hydrogen transfer.     

The Hadal Amphipod Hirondellea gigas Possessing a Unique Cellulase for Digesting Wooden Debris Buried in the Deepest Seafloor

The Challenger Deep in the Mariana Trench is the deepest point in the ocean (10,994 m). Certain deep-sea animals can withstand the extreme pressure at this great depth. The amphipod Hirondellea gigas is a resident of the Challenger Deep. Amphipods are common inhabitants at great depths and serve as scavengers. However, there is relatively little information available regarding the physiology of H. gigas or this organism's ecological interactions in the hadopelagic zone. To understand the feeding behavior of this scavenger in the deepest oligotrophic hadal zone, we analyzed the digestive enzymes in whole-body extracts. We describe the detection of amylase, cellulase, mannanase, xylanase, and α-glycosidase activities that are capable of digesting plant-derived polysaccharides. Our identification of glucose, maltose, and cellobiose in the H. gigas extracts indicated that these enzymes function under great pressure in situ. In fact, the glucose content of H. gigas averaged 0.4% (w/dry-w). The purified H. gigas cellulase (HGcel) converted cellulose to glucose and cellobiose at an exceptional molar ratio of 2∶1 and efficiently produced glucose from dried wood, a natural cellulosic biomass, at 35°C. The enzyme activity increased under a high hydrostatic pressure of 100 MPa at 2°C, conditions equivalent to those found in the Challenger Deep. An analysis of the amino acid sequence of HGcel supported its classification as a family 31 glycosyl hydrolase. However, none of the enzymes of this family had previously been shown to possess cellulase activity. These results strongly suggested that H. gigas adapted to its extreme oligotrophic hadal oceanic environment by evolving digestive enzymes capable of digesting sunken wooden debris.     

X-ray crystal structures of Moorella thermoacetica FprA. Novel diiron site structure and mechanistic insights into a scavenging nitric oxide reductase

Several members of a widespread class of bacterial and archaeal metalloflavoproteins, called FprA, likely function as scavenging nitric oxide reductases (S-NORs). However, the only published X-ray crystal structure of an FprA is for a protein characterized as a rubredoxin:dioxygen oxidoreductase (ROO) from Desulfovibrio gigas. Therefore, the crystal structure of Moorella thermoacetica FprA, which has been established to function as an S-NOR, was solved in three different states: as isolated, reduced, and reduced, NO-reacted. As is the case for D. gigas ROO, the M. thermoacetica FprA contains a solvent-bridged non-heme, non-sulfur diiron site with five-coordinate iron centers bridged by an aspartate, and terminal glutamate, aspartate, and histidine ligands. However, the M. thermoacetica FprA diiron site showed four His ligands, two to each iron, in all three states, whereas the D. gigas ROO diiron site was reported to contain only three His ligands, even though the fourth His residue is conserved. The Fe1-Fe2 distance within the diiron site of M. thermoacetica FprA remained at 3.2-3.4 A with little or no movement of the protein ligands in the three different states and with conservation of the two proximal open coordination sites. Molecular modeling indicated that each open coordination site can accommodate an end-on NO. This relatively rigid and symmetrical diiron site structure is consistent with formation of a diferrous dinitrosyl as the committed catalytic intermediate leading to formation of N(2)O. These results provide new insight into the structural features that fine-tune biological non-heme diiron sites for dioxygen activation vs nitric oxide reduction.     

The amino acid sequence of coagulogen isolated from southeast Asian horseshoe crab, Tachypleus gigas

The amino acid sequence of coagulogen isolated from Southeast Asian horseshoe crab (Tachypleus gigas) has been determined. The NH2-terminal sequence of the first 51 residues was obtained by automated Edman degradation. The intact protein was then treated with a Tachypleus clotting enzyme, to form a gel and to remove an internal peptide C (28 residues) located near the NH2-terminal portion. The gel protein, which consisted of A chain (18 residues) and B chain (129 residues), was S-alkylated and the resulting two chains were separated by acetone precipitation. Among these segments, A chain and peptide C were assigned to the NH2-terminal portion of whole coagulogen, as judged from their amino acid compositions. On the other hand, the covalent structure of B chain was determined by sequencing the peptides obtained from its tryptic digest. The alignments of the tryptic peptides were deduced from the sequence homology in comparison with the previously established B chain sequence of Japanese horseshoe crab (T. tridentatus) coagulogen. T. gigas coagulogen had a total of 175 amino acids and a calculated molecular weight of 19,770. When the sequence was compared with those of Japanese and American horseshoe crab (Limulus polyphemus) coagulogens, extensive structural homology was found: T. tridentatus/T. gigas, 87% and L. polyphemus/T. gigas, 67%. This comparison suggests that Japanese and Southeast Asian horseshoe crabs have a crab, based on amino acid sequence data.     

NMR solution structures of two mutants of desulforedoxin

The differences in geometry at the metal centres in the two known [Fe-4S] proteins rubredoxin (Rd) and desulforedoxin (Dx) are postulated to be a result of the different spacing of the C-terminal cysteine pair in the two proteins. In order to address this question, two mutants of Desulfovibrio gigas Dx with modified cysteinyl spacing were prepared and their solution structures have been determined by NMR. Mutant 1 of Dx (DxM1) has a single glycine inserted between the adjacent cysteines (C28 and C29) found in the wild type Dx sequence. Mutant 3 (DxM3) has two amino acid residues, -P-V-, inserted between C28 and C29 in order to mimic the primary sequence found in Rd from Desulfovibrio gigas. The solution structure of DxM1 exists, like wild type Dx, as a dimer in solution although the single glycine inserted between the adjacent cysteines disrupts the stability of the dimer resulting in exchange between a dimer state and a small population of another, probably monomeric, state. For DxM3 the two amino acid residues inserted between the adjacent cysteines results in a monomeric protein that has a global fold near the metal centre very similar to that found in Rd.     

钙化作用对养殖长牡蛎及其附着生物呼吸熵的影响

呼吸熵(RQ)是动物生理及能量代谢的常用指标之一.在计算呼吸熵时,释放CO₂的量通常被直接应用.在具有钙化作用的海洋生物中,钙化会影响试验水体溶解无机碳(DIC)含量,如果被忽略可能会产生方法上的误差.本文通过呼吸瓶法对养殖长牡蛎及其3种附着生物(紫贻贝、玻璃海鞘和柄海鞘)呼吸熵与氧氮比(O/N)的测定,探讨水产动物呼吸熵测定中钙化作用的影响.结果表明: 长牡蛎与紫贻贝的钙化率分别为(56.37±14.85)和(17.95±7.21) μmol·g^-1·h^-1,并因此减少水体DIC(3.72±0.80)和(1.48±0.14) mg·L^-1,分别占到呼吸增加DIC的(60.9±7.6)%和(39.9±5.7)%.4种试验生物的呼吸熵分别为：长牡蛎1.38±0.19、紫贻贝1.18±0.11、玻璃海鞘1.11±0.05、柄海鞘1.32±0.19.除玻璃海鞘外,均与O/N的结果相符.而其中具有钙化作用的长牡蛎和紫贻贝校正前的呼吸熵仅为0.56±0.19和0.70±0.04,不符合O/N的测定值.表明生物钙化对水体中的DIC有明显地吸收固定作用,在呼吸熵的测定中应被准确计算在内.     

Pacific oyster hemocytes undergo apoptosis following cell-adhesion mediated by integrin-like molecules

Previously, we demonstrated that in the Pacific oyster (Crassostrea gigas, a bivalve mollusc) apoptosis could be induced in hemocytes by treatment with Arg-Gly-Asp (RGD) peptides which are known to function as an integrin ligand. However, it is unclear where the RGD peptides are binding to the C. gigas hemocytes, or what mechanism or molecules are involved, e.g., integrin-ligand interactions. Therefore, this study was undertaken to investigate the binding interactions in C. gigas hemocytes. Initially, to confirm the presence of RGD-recognizing integrin-like molecule(s) on the hemocytes, we assessed the enhancement of spreading ability, and found that spreading ability was enhanced by immobilized human fibronectin, a fibronectin fragment containing the RGD motif, and C. gigas plasma in the presence of divalent cations. Interestingly, viability of the spreading hemocytes dramatically decreased 24 h later and DNA fragmentation with oligonucleosomal laddering of 180-200 bp in length was detected in the dead hemocytes by electrophoresis and TUNEL assay. These results indicated that hemocyte adhesion mediated by integrin-like molecules triggered apoptosis and suggested that integrin-activation contributes to the induction of apoptosis. This is the first report showing the possibility of an integrin functioning in the induction of apoptosis in invertebrate hemocytes.     

Cloning and sequencing of the nifH gene of Desulfovibrio gigas

The Desulfovibrio gigas nifH gene has been cloned and sequenced. It consists of an open-reading frame of 822 base pairs encoding a 274 amino acid polypeptide. A potential ntrA-dependent promotor sequence is present. The gene lacks an upstream activator sequence homologous to those often found in nif genes subject to activation by nifA.     

Observations on Neobursaridium gigas Balech, 1941 (Ciliata Heterotrichida)

SYNOPSIS. A large heterotrich ciliate (Family: Bursariidae) found in a papyrus swamp in Uganda was used for oxygen tension experiments by Beadle & Nilsson, 1959, under the name of Bursaria sp. This organism has now been identified as Neobursaridium gigas Balech. The morphology of the organism was studied in living and stained specimens, especially with the silver impregnation technique, and the present findings are compared to those of Balech.     

A tolloid homologue from the Pacific oyster Crassostrea gigas

The genes governing mesoderm specification have been extensively studied in vertebrates, arthropods and nematodes. The latter two phyla belong to the Ecdysozoan clade but little is understood of the role that these genes might play in the development of the other major protostomal clade, the Lophotrochozoa. As part of a wider project to analyze the functions associated with transforming growth factor beta superfamily members in Lophotrochozoa, we have cloned a gene encoding a tolloid homologue from the bivalve mollusc Crassostrea gigas. Tolloid is a key developmental protein that regulates the activity of bone morphogenetic proteins (BMPs). We have determined the intron-exon structure of the gene encoding C. gigas tolloid and have compared it with those of homologous genes from both protostomes and deuterostomes. In order to analyze the functionality of oyster tolloid the zebrafish embryo has been employed as a reporter organism and we show that over-expression of this protein results in the ventralization of zebrafish embryos at 24h post fertilization. The expression of the C. gigas tolloid gene during embryonic and larval development as well as in adult tissues is also explored.     

Cloning, sequencing and expression of the tetraheme cytochrome c(3) from Desulfovibrio gigas

The gene encoding the tetraheme cytochrome c(3) from Desulfovibrio gigas was cloned and sequenced from a 2.7-kb EcoRI-PstI insert of D. gigas DNA. The derived amino acid sequence showed that the D. gigas cytochrome c(3) is synthesized as a precursor protein with an N-terminal signal peptide sequence of 25 residues and allowed the correction of the previous reported amino acid sequence (Matias et al. Protein Science 5 (1996) 1342-1354). Expression in D. vulgaris (Hildenborough) was possible by conjugal transfer of a recombinant broad-host-range vector pSUP104 containing a SmaI fragment of the D. gigas cytochrome c(3) gene. Biochemical, immunological and spectroscopic analysis of the purified protein showed that the recombinant cytochrome is identical to that isolated from D. gigas.     

Bathysauropsis gigas, a deep-sea aulopiform fish with a peculiar iris process and a pure-cone retina

The eyes of the benthic deep-sea fish Bathysauropsis gigas were examined macroscopically and histologically. A peculiar iris process was found in each eye of the fish. Photoreceptors in the retina were exclusively cones. These cones were all morphologically twin cones, and rods were not observed. The function of these specific characters remains unknown. The retinal structure of Chlorophthalmus albatrossis was described briefly for comparison. The entirely pure-twin-cone retina of Bathysauropsis gigas suggest a close relationship with the Chlorophthalmus.