Halophila ovalis in the Tropical Atlantic Ocean

A species of seagrass in the genus Halophila was found growing in a shallow lagoon on the west shore of Antigua in the Caribbean West Indies. Genetic analysis showed the plants were Halophila ovalis. In addition, the samples had no genetic deviation (using nrDNA sequences) from Halophila johnsonii, considered to be an endemic and endangered species in Florida, USA. Morphological analysis demonstrated the Antiguan Halophila to be well within the range of plant characteristics previously described in the literature for H. ovalis, except for leaf width and number of seeds per fruit, and again, not different from H. johnsonii and very closely related to H. ovalis from the Indo-Pacific. Ours is the first report of H. ovalis in the Tropical Atlantic bioregion.     

Sulfated flavonoids and leaf morphology of the Halophila ovalis—H. minor complex (hydrocharitaceae) in the Pacific Islands and Australia

Sulfated flavonoids showed a systematic pattern among Halophila populations of the Pacific and Australia. Large-leaved plants, typical of H. ovalis (R.Br.) Hook. f., in the Palau Islands (Belau) and in Australia contained sulfated flavonoids, but small-leaved plants that have received various treatments under H. ovalis, including ssp. bullosa (Setchell) den Hartog and ssp. hawaiiana (Doty & Stone) den Hartog, and under H. minor (Zoll.) den Hartog or H. ovata Gaud. in American Samoa, Western Samoa, Tonga, Fiji, Wallis I., New Caledonia, Yap, Guam, Hawaii and Australia lacked sulfated flavonoids. Plants collected in their natural habitats as well as those grown in experimental cultures showed the characteristic patterns of these secondary compounds. Although the large-leaved plants have the potential for producing the largest leaves in the complex, they are not separable from small-leaved plants in leaf dimensions or in number of pairs of cross veins under all environmental conditions. The production of sulfated flavonoids and the potential for greater leaf length are the characteristics that can be used to separate typical H. ovalis and ssp. australis (Doty & Stone) den Hartog from other members of the complex.     

Improving accuracy and efficiency in seagrass detection using state-of-the-art AI techniques

Seagrasses provide a wide range of ecosystem services in coastal marine environments. Despite their ecological and economic importance, these species are declining because of human impact. This decline has driven the need for monitoring and mapping to estimate the overall health and dynamics of seagrasses in coastal environments, often based on underwater images. However, seagrass detection from underwater digital images is not a trivial task; it requires taxonomic expertise and is time-consuming and expensive. Recently automatic approaches based on deep learning have revolutionised object detection performance in many computer vision applications, and there has been interest in applying this to automated seagrass detection from imagery. Deep learning–based techniques reduce the need for hardcore feature extraction by domain experts which is required in machine learning-based techniques. This study presents a YOLOv5-based one-stage detector and an EfficientDetD7–based two-stage detector for detecting seagrass, in this case, Halophila ovalis, one of the most widely distributed seagrass species. The EfficientDet-D7–based seagrass detector achieves the highest mAP of 0.484 on the ECUHO-2 dataset and mAP of 0.354 on the ECUHO-1 dataset, which are about 7% and 5% better than the state-of-the-art Halophila ovalis detection performance on those datasets, respectively. The proposed YOLOv5-based detector achieves an average inference time of 0.077 s and 0.043 s respectively which are much lower than the state-of-the-art approach on the same datasets.     

Seagrasses in the Zeit Bay area and at Ras Ghârib (Egyptian Red Sea coast)

The distribution and ecology of seagrasses along parts of the Egyptian Red Sea coasts have been investigated. Five of the 10 species ever reported from the Red Sea have been found in this area, i.e. Halodule uninervis (Forssk.) Aschers., Thalassodendron ciliatum (Forssk.) den Hartog, Halophila stipulacea (Forssk.) Aschers., Halophila ovalis (R. Br.) Hook. f. and Halophila ovata Gaud. H. ovata is recorded here for the first time for the west coast of the Red Sea. The finding of Halophila decipiens Ostenfeld represents a new record to the Red Sea; this species has been found at a depth of 30 m, near Ras Ghârib in the Gulf of Suez.     

Morphological diversity under controlled conditions for the Halophila ovalis-H. minor complex and the Halodule uninervis complex from Shark Bay,Western Australia

The wide range of leaf types that occurs within the populations of Halophila and Halodule in Shark Bay, Western Australia, was studied for plants under laboratory conditions. In the Halophila ovalis-H. minor complex, two types of plants appeared in the cultures, a large-leaved variant that is similar to typical H. ovalis (R.Br.) Hook. f. and a small-leaved variant that is more similar to H. minor (Zoll.) den Hartog. In Shark Bay, the two variants were not clearly separated because both produced leaves that varied in size, degree of waviness of leaf margins and intensity of anthocyanin pigmentation. In the Halodule uninervis (Forsk.) Aschers. complex, two types of plants, wide- and narrow-leaved variants, appeared in the cultures. In Shark Bay, the narrow-leaved plants differed in leaf width in muddy and silty microsites, but were always narrower than the wide-leaved variants. Only the narrow-leaved Halodule plants produced anthocyanin pigmentation both under field and laboratory conditions. The studies under controlled conditions indicate that the highly diverse leaves in Shark Bay result primarily from environmental influences on two types of Halophila and two types of Halodule.     

Fatty Acid and Sterol Composition of Mucor genevensis in Relation to Dimorphism and Anaerobic Growth

Fatty acid and sterol content and composition were determined for the dimorphic mold, Mucor genevensis, grown under a variety of experimental conditions. Fatty acids account for 6 to 9% of the dry weight of aerobically grown mycelium, and 70 to 80% of these are unsaturated. The organism contains γ-linolenic acid which is characteristic for Phycomycetes, and in sporangiospores this compound represents 40% of the total fatty acids. Of the sterols found in mycelium, 80% is ergosterol, and stigmasterol was positively identified as one of the minor components. In anaerobically grown yeastlike cells, sterol content is less than 10% of the level found in aerobically grown cells, and fatty acids amount to less than 2% of the dry weight. These fatty acids are predominantly short chain and less than 10% are unsaturated. Yeastlike cells obtained under aerobic conditions by growth in the presence of phenethyl alcohol have fatty acid and sterol compositions characteristic of aerobically grown mycelium. It is concluded that the dimorphology of the organism is not directly related to lipid composition.     

Seagrass Proliferation Precedes Mortality during Hypo-Salinity Events: A Stress-Induced Morphometric Response

Halophytes, such as seagrasses, predominantly form habitats in coastal and estuarine areas. These habitats can be seasonally exposed to hypo-salinity events during watershed runoff exposing them to dramatic salinity shifts and osmotic shock. The manifestation of this osmotic shock on seagrass morphology and phenology was tested in three Indo-Pacific seagrass species, Halophila ovalis, Halodule uninervis and Zostera muelleri, to hypo-salinity ranging from 3 to 36 PSU at 3 PSU increments for 10 weeks. All three species had broad salinity tolerance but demonstrated a moderate hypo-salinity stress response – analogous to a stress induced morphometric response (SIMR). Shoot proliferation occurred at salinities <30 PSU, with the largest increases, up to 400% increase in shoot density, occurring at the sub-lethal salinities <15 PSU, with the specific salinity associated with peak shoot density being variable among species. Resources were not diverted away from leaf growth or shoot development to support the new shoot production. However, at sub-lethal salinities where shoots proliferated, flowering was severely reduced for H. ovalis, the only species to flower during this experiment, demonstrating a diversion of resources away from sexual reproduction to support the investment in new shoots. This SIMR response preceded mortality, which occurred at 3 PSU for H. ovalis and 6 PSU for H. uninervis, while complete mortality was not reached for Z. muelleri. This is the first study to identify a SIMR in seagrasses, being detectable due to the fine resolution of salinity treatments tested. The detection of SIMR demonstrates the need for caution in interpreting in-situ changes in shoot density as shoot proliferation could be interpreted as a healthy or positive plant response to environmental conditions, when in fact it could signal pre-mortality stress.     

Variations in leaf soluble amino acids and ammonium content in subtropical seagrasses related to salinity stress

A survey of leaf soluble amino acids was conducted for four subtropical seagrasses grown at several salinities. Proline functioned as an organic osmoticum in Halodule wrightii Aschers., Thallasia testudinum Banks ex Koenig, and Ruppia maritima L., while alanine functioned in an osmoregulatory capacity in Halophila engelmanni Aschers. When light-and salinity-induced variations in leaf NH₄ and amide-N levels were compared in Halodule, Thalassia, and Halophila, ability to regulate leaf NH₄ levels was correlated with osmoregulatory capacity and maintenance of selected amino acid contents.     

Sterols and fatty acids of the red tide flagellates Heterosigma akashiwo and Chattonella antiqua (Raphidophyceae)

The fatty acids and sterols of the raphidophyte flagellates, Heterosigma akashiwo (Australian and Plymouth strains) and Chattonella antiqua (Japanese strain) are reported. The major sterol of both species is 24-ethylcholesterol, which is more commonly associated with higher plants and has rarely been reported in unicellular algae. C. antiqua also contained 24-dihydrozymosterol [cholest-8(9)-en-3β-ol], which is also uncommon in marine algae. The major fatty acids in both raphidophytes are 16:0, 18:4ω3, 20:5ω3, 16:1ω7 and 14:0. Polyunsaturated fatty acids accounted for 46–50% of the total fatty acids in both species. The fatty acid 18:5ω3 was detected in H. akashiwo, but not in C. antiqua. This acid is found in some dinoflagellates and Prymnesiophycean algae, but this is the first report of its presence in the Raphidophyceae. The lipid distributions obtained for H. akashiwo and C. antiqua provide unique signature profiles for use in taxonomic, food-web and organic geochemical studies. The fatty acid and sterol distributions of these two raphidophytes justify their assignment to a separate class within the ‘brown algal’ line.     

rDNA analysis of the Red Sea seagrass,Halophila, reveals vicariant evolutionary diversification

The effects of opening the Suez Canal as a connection between the Red Sea and the Mediterranean Sea were reported for a number of marine species. However, the evolutionary origin of the seagrasses in the Red Sea and the linking population genetics of seagrasses between the Arabian Sea, the Gulf of Aden, the Red Sea and the Mediterranean Sea have not yet been investigated in detail. The invasion of Halophila stipulacea Asch. from the Red Sea into the Mediterranean Sea after the opening of the Suez Canal was already recorded. We hypothesize that Halophila ovalis populations in the Red Sea developed through long-term historical processes such as vicariant evolutionary diversification. Seagrass samples were collected along the Egyptian coastline of the Red Sea and analysed by the molecular marker ITS. The sequences were compared with published ITS sequences from seagrasses collected in the whole area of interest. In this study, we reveal the linking population genetics, phylogeography and phylogenetics of two dominant seagrass species, Halophila stipulacea and Halophila ovalis, among species collected in the Red Sea and worldwide. The results indicate that the Red Sea Halophila ovalis populations do not group to Halophila ovalis worldwide, and Halophila major, Halophila ovalis collected worldwide and Halophila ovalis collected at the Red Sea are sister clades. Hence, vicariant evolutionary diversification for Halophila ovalis may occur in the Red Sea.     

Glycolipid composition of Hevea brasiliensis latex

Glycolipids of fresh latex from three clones of Hevea brasiliensis were characterized and quantified by HPLC/ESI-MS. Their fatty acyl and sterol components were further confirmed by GC/MS after saponification. The four detected glycolipid classes were steryl glucosides (SG), esterified steryl glucosides (ESG), monogalactosyl diacylglycerols (MGDG) and digalactosyl diacylglycerols (DGDG). Sterols in SG, ESG and total latex unsaponifiable were stigmasterol, β-sitosterol and Δ⁵-avenasterol. The latter was found instead of fucosterol formerly described. Galactolipids were mainly DGDG and had a fatty acid composition different from that of plant leaves as they contained less than 5% C18:3. Glycolipids, which represented 27–37% of total lipids, displayed important clonal variations in the proportions of the different fatty acids. ESG, MGDG and DGDG from clone PB235 differed notably by their higher content in furan fatty acid, which accounted for more than 40% of total fatty acids. Clonal variation was also observed in the relative proportions of glycolipid classes except MGDG (8%), with 43–51% DGDG, 30–34% SG and 7–19% ESG. When compared with other plant cell content, the unusual glycolipid composition of H. brasiliensis latex may be linked to the peculiar nature of this specialized cytoplasm expelled from laticiferous system, especially in terms of functional and structural properties.     

Fatty acids and sterols of selected hyphochytriomycetes and chytridiomycetes

The fatty acids and sterols of eight Chytridiomycetes and two Hyphochytriomycetes, and fatty acids of the OomycetePythium gracile, were analyzed by gas-liquid chromatography. In addition to the fatty acids anticipated for fungi, the two Hyphochytriomycetes (Hyphochytrium catenoides andRhizidiomyces apophysatus) and four of the Chytridiomycetes (Catenaria anguillulae, Blastocladiella emersonii, Monoblepharella sp., andAllomyces macrogynus) contained arachidonic acid as a major fatty acid of the polar lipid fraction, and this fatty acid was detected as a minor component ofRhizophlyctis rosea andSpizellomyces punctatum. Eicosapentaenoic acid constituted 4.6% of the polar lipid fatty acids inMonoblepharella sp., and trace amounts were detected in several other species. Both the gamma (ω-6) and alpha (ω-3) isomers of linolenic acid were detected in all of the species analyzed. Cholesterol was the predominant (≥73%) sterol ofB. emersonii, R. rosea, A. macrogynus, andChytridium confervae, and a minor (<12%) component ofC. anguillulae, andH. catenoides. The major sterols of the other species included lanosterol (C. anguillulae, 45%), stigmasta-5,22-dien-3β-ol (H. catenoides, 51%), 24-ethyl-cholesterol (S. punctatum, 38%;H. catenoides, 17%;Monoblepharella sp., 70%; andR. apophysatus, 84%), 24-methyl-cholesterol (H. catenoides, 23%;R. apophysatus, 14%;S. punctatum, 53%), and 24-methylene cholesterol (Rhizophydium sphaerotheca, 51%). Neither ergosterol nor fucosterol was detected in any of the species studied.     

New record for Halophila decipiens Ostenfeld in Kenya based on morphological and molecular evidence

The seagrass Halophila decipiens Ostenfeld was recorded for the first time in Kenya in 2003. It was growing in subtidal mixed meadows with H. ovalis in protected bays at a depth of 3 m. DNA sequence analysis and morphological characteristics confirmed the identification. It is possible that this species is more widely distributed in the east African region. There was very little sequence differentiation between the Kenyan H. decipiens and the other samples in the Indo-West Pacific, and between this region and the Atlantic Ocean, further validating from an evolutionary perspective recent dispersal of this species.     

Fatty acids,sterols and hydrocarbons in the leaves from eleven species of mangrove

The fatty acid, sterol and hydrocarbon compositions of the fresh leaves from eleven species of mangroves, cultivated in a shadehouse, are reported. The fatty acid and sterol analyses, whilst generally typical of higher plants, showed several chemotaxonomically significant differences between the species. The epicuticular wax hydrocarbons and fatty acids were low in abundance compared to previous reports of mangrove leaf lipids, which may reflect the importance of environmental influences on this group of compounds. Cluster analysis of selected subsets of the data showed clear chemotaxonomic divisions amongst the mangroves. The results grouped the mangroves into genera, except for the Rhizophora and Ceriops tagal which were not separated, and grouped the family Rhizophoraceae distinct from all other species except Xylocarpus granatum. Avicennia marina var. resinifera was able to be distinguished from Avicennia marina by cluster analysis, supporting its assignment as a distinct variety. The results show that the lipids of mangroves are chemotaxonomically significant.     

Lipid composition of a plasma membrane enriched fraction of maize roots

The lipid composition of a plasma membrane enriched fraction isolated from corn (Zea mays) roots was examined. On a wt basis, the lipid: protein ratio was 1.11. Phospholipids comprised 60% of total lipids with the major phospholipids being phosphatidylcholine (62%) and phosphatidylethanolamine (21%). Free sterol was the major neutral lipid. The sterol:phospholipid molar ratio was 0.31. The fatty acid composition of the membrane was predominantly linoleic (60%) and palmitic (30%).     

Lipid and Fatty Acid composition of chloroplast envelope membranes from species with differing net photosynthesis

Lipid and fatty acid compositions were determined for chloroplast envelope membranes isolated from spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L.) leaves. The lipid composition was similar in sunflower, spinach, and undifferentiated maize chloroplast envelope membranes and different in maize mesophyll chloroplast envelope membranes. The predominant lipid constituents in all envelope membranes were monogalactosyldiglyceride (27 to 46%), digalactosyldiglyceride (18 to 33%), and phosphatidylcholine (7 to 30%). The fatty acid composition was also similar in sunflower and spinach chloroplast envelope membranes in comparison to those from maize. The major acyl fatty acids of the chloroplast envelope membrane were palmitic (C_16:0, 41 and 36%) and linolenic (C_18:3, 29 and 40%) acids for spinach and sunflower; palmitic (77%) and stearic (C_18:0, 12%) acids for young maize; and palmitic (61%), stearic (14%), and linolenic (13%) acids for mature maize. The differences in lipid and acyl fatty acid compositions among these plants which vary in their rates of net photosynthesis were largely quantitative rather than qualitative.     

Triacylglyceride composition and fatty acyl saturation profile of a psychrophilic and psychrotolerant fungal species grown at different temperatures

Pseudogymnoascus destructans is a psychrophilic fungus that infects cutaneous tissues in cave dwelling bats, and it is the causal agent for white nose syndrome (WNS) in North American (NA) bat populations. Geomyces pannorum is a related psychrotolerant keratinolytic species that is rarely a pathogen of mammals. In this study, we grew P. destructans and G. pannorum in static liquid cultures at favourable and suboptimal temperatures to: 1) determine if triacylglyceride profiles are species-specific, and 2) determine if there are differences in fatty acyl (FA) saturation levels with respect to temperature. Total lipids isolated from both fungal spp. were separated by thin-layer chromatography and determined to be primarily sterols (∼15 %), free fatty acids (FFAs) (∼45 %), and triacylglycerides (TAGs) (∼50 %), with minor amounts of mono-/diacylglycerides and sterol esters. TAG compositions were profiled by matrix-assisted laser desorption–ionization time-of-flight mass spectrometry (MALDI–TOF). Total fatty acid methyl esters (FAMEs) and acyl lipid unsaturation levels were determined by gas chromatography–mass spectrometry (GC–MS). Pseudogymnoascus destructans produced higher proportions of unsaturated 18C fatty acids and TAGs than G. pannorum. Pseudogymnoascus destructans and G. pannorum produced up to a two-fold increase in 18:3 fatty acids at 5 °C than at higher temperatures. TAG proportion for P. destructans at upper and lower temperature growth limits was greater than 50 % of total dried mycelia mass. These results indicate fungal spp. alter acyl lipid unsaturation as a strategy to adapt to cold temperatures. Differences between their glycerolipid profiles also provide evidence for a different metabolic strategy to support psychrophilic growth, which may influence P. destructans' pathogenicity to bats.     

New insights into DNA barcoding of seagrasses

Taxonomists find some plant genera challenging because of the few morphological differences or unclear characters among closely related species, which leads to the misidentification of taxa. DNA barcoding is an approach to identify species by using short orthologous DNA sequences, known as ‘DNA barcodes’. Concatenated rbcL and matK sequences are considered DNA barcodes for seagrasses. However, these markers are not applicable to all members of seagrasses at the species level, especially within the genus Halophila. Our previous studies indicated that the internal transcribed spacer (ITS) showed higher species resolution than the concatenated rbcL and matK sequences in the case of Halophila ovalis and closely related species. In this study, 26 ITS, two rbcL and two matK consensus sequences from 18 seagrass taxa belonging to four families collected in India, Vietnam, Germany, Croatia and Egypt were processed. Molecular ITS analysis resolved five clades. The results also indicate that the Cymodoceaceae family might be a non-monophyletic group. In conclusion, ITS could be applied as a DNA barcode for seagrasses instead of the rbcL/matK system previously proposed.     

Composition of lipids, fatty acids and sterols in Okinawan corals

A survey of lipid composition was made for 15 cnidarians from Okinawa, Japan. Eleven zooxanthellate scleractinian corals, an azooxanthellate scleractinian coral Tubastrea sp., a soft coral Lobophytum crassum, a hydroid coral Millepora murrayi and a sea anemone Boloceroides sp. were examined to elucidate the total lipid content, fatty acid composition for each lipid class and sterol composition. All specimens contained monoalkyldiacylglycerol which migrated between the triacylglycerols and esters on thin layer chromatography (TLC). Analysis by high performance thin layer chromatography (HPTLC) and Gas chromatography-mass spectrometry (GC-MS) revealed that these cnidarians were rich in wax ester and triacylglycerol, and that palmitic acid (16:0) was the most abundant fatty acid component of these lipid classes, followed by stearic (18:0) and oleic (18:1, n-9) acid in order of concentration. Of 11 sterols separated, four sterols were identified. It is suggested that sterol composition may be more useful for the biochemical classification of these cnidarians than fatty acid composition.