Influence of nitrogen deficiency on biochemical composition of the green alga <Emphasis Type="Italic">Botryococcus</Emphasis>

A study has been carried out to investigate the influence of nitrogen deficiency on intracellular lipid composition, including total fatty acid composition of lipids, polar lipids, and triacylglycerols, of the alga Botryococcus braunii Kütz IPPAS H-252 in batch culture. Under nitrogen limitation, the alga accumulates lipids as triacylglycerols and the total fatty acid (FA) composition changes: trienoic acids decrease (from 52.8–57.2 to 19.5–24.7% of the total FAs) and the oleic acid increases (from 1.1–1.2 to 17.1–24.4%) as does the saturated acids (from 23.7–26 to 32.9–46.1%). A similar rearrangement in the FA spectrum occurs at later times in the control culture, but it is less pronounced. Under nitrogen limitation, considerable changes in the polar lipid FAs are registered at day 13: saturated acids increase (from 28.6–35.5 to 76.8%) and all polyenoic acids markedly decrease (from 56.9–64.1 to 6.8%). Changes in the triacylglycerol fatty acid spectrum are seen on day 7: the oleic acid increases (from 14.7 to 34.2%) and remains at a high level till the end of the culture. In the control, triacylglycerols with large contents of oleic acid are detected at day 13, the total lipids and triacylglycerols still remaining unchanged.     

Oleosomes (Spherosomes) from Daucus carota suspension culture cells

Isolated oleosomes from Daucus carota L. cells are lipid droplets consisting mainly of triacylglycerols (>97%) and very little protein (1–2%). The boundary between the lipid phase and the cytosol, which is visible on electron micrographs, is not built up by a true phospholipid-containing unit or half unit membrane. Enzymatic activities of lipid metabolism were not found to be associated with oleosomes with the exception of very low (contaminating) acyl-CoA:1,2-diacylglycerol acyltransferase (EC 2.3.1.20) and relatively high acyl-CoA hydrolase (EC 3.1.2.2) activities. The triacylglycerols exhibited a half life time of about 70 h, which is below the generation time of the cells (80–90 h). The fatty acid pattern of triacylglycerols was very similar to that of polar cellular membrane lipids.     

The lipid content of the diabetic kidney of the rat

Rats were made diabetic by intravenous administration of streptozotocin, 100 mg/kg. Six groups of animals were studied: normal; animals given a supplement of 100% corn oil margarine; insulin-treated normoglycemic diabetic; hyperglycemic nonacidotic diabetic; ketoacidotic diabetic; and NH4Cl acidotic. The kidneys were removed from anesthetized animals. The renal cortex was separated from the medulla, freeze-clamped, and homogenized. Total lipids were extracted and measured gravimetrically. Lipid fractions were determined by thin-layer chromatography. Fatty acids of triacylglycerols and of phospholipids were analyzed by gas chromatography. Plasma triacylglycerols were elevated in hyperglycemic nonacidotic rats and more so in ketoacidotic animals. Total kidney lipids were 18% higher in nonacidotic hyperglycemic rats and 56% higher in ketoacidotic diabetic rats. This was due to accumulation of triacylglycerols while the phospholipid and cholesterol fractions did not change. Examination of long-chain fatty acids of kidney cortex triacylglycerols revealed that palmitate rose in a significant fashion while linoleate fell. This pattern was similar in all three groups of diabetic animals. The present data characterize the lipid content of the experimental rat diabetic kidney. They establish that the accumulation of lipids in the renal cortex during diabetes is related to triacyclgycerols and their palmitate content. Our study also provides a clear profile of plasma triacylglycerols during diabetes mellitus in the rat.     

Composition and role of tapetal lipid bodies in the biogenesis of the pollen coat of Brassica napus

The composition of the two major lipidic organelles of the tapetum of Brassica napus L. has been determined. Elaioplasts contained numerous small (0.2–0.6 μm) lipid bodies that were largely made up of sterol esters and triacylglycerols, with monogalactosyldiacylglycerol as the major polar lipid. This is the first report in any species of the presence of non-cytosolic, sterol ester-rich, lipid bodies. The elaioplast lipid bodies also contained 34- and 36-kDa proteins which were shown by N-terminal sequencing to be homologous to fibrillin and other plastid lipid-associated proteins. Tapetosomes contained mainly polyunsaturated triacylglycerols and associated phospholipids plus a diverse class of oleosin-like proteins. The pollen coat, which is derived from tapetosomes and elaioplasts, was largely made up of sterol esters and the C-terminal domains of the oleosin-like proteins, but contained virtually no galactolipids, triacylglycerols or plastid lipid-associated proteins. The sterol compositions of the elaioplast and pollen coat were almost identical, consisting of stigmasterol > campestdienol > campesterol > sitosterol ≫ cholesterol, which is consistent with the majority of the pollen coat lipids being derived from elaioplasts. These data demonstrate that there is substantial remodelling of both the lipid and protein components of elaioplasts and tapetosomes following their release into the anther locule from lysed tapetal cells, and that components of both organelles contribute to the formation of the lipidic coating of mature pollen grains. Received: 4 December 1998 / Accepted: 9 February 1999     

Determinants of echolocation click frequency characteristics in small toothed whales: recent advances from anatomical information

1. The pulse-like clicking sounds made by odontocetes for echolocation (biosonar) can be roughly classified by their frequency characteristics into narrow-band high-frequency (NBHF) clicks with a sharp peak at around 130 kHz and wide-band (WB) clicks with a moderate peak at 30–100 kHz. Structural differences in the sound-producing organs between NBHF species and WB species have not been comprehensively discussed, nor has the formation of NBHF and WB clicks.
2. A review of the sound-producing organs, including the latest findings, could lead to a new hypothesis about the sound production mechanisms. In the current review, data on echolocation click characteristics and on the anatomical structure of the sound-producing organs were compared in 33 species (14 NBHF species and 19 WB species).
3. We review interspecific information on the characteristics of click frequencies and data from computed tomography scans and morphology of the sound-producing organs, accumulated in conventional studies. The morphology of several characteristic structures, such as the melon, the dense connective tissue over the melon (the ‘porpoise capsule’), and the vestibular sacs, was compared interspecifically.
4. Interspecific comparisons suggest that the presence or absence of the porpoise capsule is unlikely to affect echolocation frequency. Folded structures in the vestibular sacs, features that have been overlooked until now, are present in most species with NBHF sound production and not in WB species; the vestibular sacs are therefore likely to be important in determining echolocation click frequency characteristics. The acoustical properties of the shape of the melon and vestibular sacs are important topics for future investigations about the relationship between anatomical structure and sound-producing mechanisms for echolocation clicks.

     

Elemental composition, total lipid content, and lipid class proportions in zooplankton from the benthic boundary layer of the Beaufort Sea shelf (Canadian Arctic)

Biochemical analyses such as lipid class and elemental composition can inform us about a species’ role in community energetics and nutrient cycling. The accumulation of lipid-rich energy stores affects the elemental composition and stoichiometry of animal tissues, and this relationship is especially relevant to zooplankton at higher latitudes due to increased seasonal lipid storage. However, due to sampling difficulties, the elemental composition and energy storage capabilities of polar, benthic boundary layer zooplankton are poorly known. We determined elemental and lipid class compositions for 26 taxa of benthic boundary layer zooplankton from the Beaufort Sea shelf. Elemental composition as a percentage of dry weight ranged 21–56% for carbon (C), 4–11% for nitrogen (N), and 0.1–1.1% for phosphorus (P) across all taxa. C concentration and C:N were positively correlated with the storage lipids triacylglycerols (TG) and wax esters/steryl esters (WE/SE) and negatively correlated with membrane lipids (phospholipids and sterols). Most taxa had high levels of storage lipids, generally TG. High levels of WE/SE were found in the copepod Calanus hyperboreus (>90% of total lipid) and the chaetognath Eukrohnia hamata (72%). In contrast, the chaetognath Parasagitta elegans had only minor proportions of both TG and WE/SE. The high levels of storage lipids in most taxa indicate that feeding behavior of benthic boundary layer zooplankton on the Beaufort Sea shelf is tightly linked with seasonal pulses of epipelagic production. This is the first report on the biochemical composition of most of the amphipod and mysid taxa presented here.     

Evaluation of swimming performance for fish passage of longnose dace Rhinichthys cataractae using an experimental flume

The swimming performance of longnose dace Rhinichthys cataractae, the most widely distributed minnow (Cyprinidae) in North America, was assessed in relation to potential passage barriers. The study estimated passage success, maximum ascent distances and maximum sprint speed in an open‐channel flume over a range of water velocities and temperatures (10·7, 15·3 and 19·3° C). Rhinichthys cataractae had high passage success (95%) in a 9·2 m flume section at mean test velocities of 39 and 64 cm s^–1, but success rate dropped to 66% at 78 cm s^–1. Only 20% of fish were able to ascend a 2·7 m section with a mean velocity of 122 cm s^–1. Rhinichthys cataractae actively selected low‐velocity pathways located along the bottom and corners of the flume at all test velocities and adopted position‐holding behaviour at higher water velocities. Mean volitional sprint speed was 174 cm s^–1 when fish volitionally sprinted in areas of high water velocities. Swimming performance generally increased with water temperature and fish length. Based on these results, fishways with mean velocities <64 cm s^–1 should allow passage of most R. cataractae. Water velocities >100 cm s^–1 within structures should be limited to short distance (<1 m) and structures with velocities ≥158 cm s^–1 would probably represent movement barriers. Study results highlighted the advantages of evaluating a multitude of swimming performance metrics in an open‐channel flume, which can simulate the hydraulic features of fishways and allow for behavioural observations that can facilitate the design of effective passage structures.     

Intestinal absorption of specific structured triacylglycerols

To clarify the intestinal absorption pathway of medium-chain fatty acids from MLM-type structured triacylglycerols containing both medium- and long-chain fatty acids, we studied the lymphatic transport of 1,3-dioctanoyl-2-linoleoyl-sn-glycerol (8:0/18:2/8:0), 1,3-didecanoyl-2-linoleoyl-sn-glycerol (10:0/18:2/10:0), and 1,3-didodecanoyl-2-linoleoyl-sn-glycerol (12:0/18:2/12:0) in a rat model. Safflower oil was used in the absorption study in order to compare the absorption of medium-chain fatty acids and long-chain fatty acids. The triacylglycerol species of lymph lipids were separated on a reversed-phase high performance liquid chromatograph (RP-HPLC) and identified by atmospheric pressure chemical ionization mass spectrometry. The composition of triacylglycerols was quantified by RP-HPLC with evaporative light scattering detection. The intact MLM-type triacylglycerols were detected in the lymph lipids after administration of the specific structured triacylglycerols (STAG). The recoveries of 8:0/18:2/8:0, 10:0/18:2/10:0, and 12:0/18:2/12:0 were 0.6%, 12%, and 5%, respectively. Several new triacylglycerol species were detected in the lymph lipids, including MLL-, LLL-, and MMM-type triacylglycerols.From the present study we conclude that the medium-chain fatty acids from STAG, in addition to absorption into the portal blood as free fatty acids, are absorbed by the same pathway as the conventional long-chain triacylglycerols, that is, they are hydrolyzed into free fatty acids, absorbed and activated into CoA, and reacylated into triacylglycerols in the enterocyte. The hydrolysis of MLM-type STAG is predominantly partial hydrolysis, whereas part of the STAG can also be hydrolyzed to free glycerol and free fatty acids.     

The lipid,fatty acid and amino acid composition of ratite eggs from three different species of kiwis Apteryx australis mantelli,A. haasti and A. oweni bred in captivity on the same diet

The lipid composition of the eggs obtained from three different species of New Zealand kiwis (Apteryx australis mantelli, A. haasti and A. oweni) were investigated and compared. Although those of A. australis mantelli were known to have high levels of triacylglycerols and Iow levels of phospholipids (83% and 8% respectively), the other species had reduced quantities of triacylglycerols (65–69%) but compensated with increased levels of phospholipids (23–24%). These findings were similar to those of the domestic hen eggs. As regards to the proportion of lipid to protein in the kiwi eggs, A. australis mantelli and A. haasti contained similar ratios of 1.00–0.51 but A. owenihad higher levels of lipids, 1.00–0.38. The distribution of amino acids in each case was similar.     

Lipid biosynthesis in developing mustard seed: formation of triacylglycerols from endogenous and exogenous Fatty acids

Cotyledons of developing mustard (Sinapis alba L.) seed have been found to synthesize lipids containing the common plant fatty acids and very long-chain monounsaturated (icosenoic, erucic, and tetracosenic) and saturated (icosanoic, docosanoic, and tetracosanoic) fatty acids from various radioactive precursors. The in vivo pattern of labeling of acyl lipids, either from fatty acids synthesized `endogenously' from radioactive acetate or malonate, or from radioactive fatty acids added `exogenously', indicates the involvement of the following pathways in the biosynthesis of triacylglycerols. Palmitic, stearic, and oleic acid, synthesized in the acyl carrier protein-track, are channeled to the Coenzyme A (CoA)-track and converted to triacylglycerols via the glycerol-3-phosphate pathway. Pools of stearoyl-CoA and oleoyl-CoA are elongated to very long-chain saturated and monounsaturated acyl-CoA, respectively. Most of the very long-chain saturated acyl-CoAs acylate preformed diacylglycerols. Very long-chain monounsaturated acyl-CoAs are converted to triacylglycerols, partly via phosphatidic acids and diacylglycerols, and partly by acylation of preformed diacylglycerols.     

Changes in lipids containing long- and very long-chain polyunsaturated fatty acids in cryptorchid rat testes

The aim of the present study was to examine the effects of experimental cryptorchidism on rat testicular phospholipids and neutral lipids that contain long-chain (C(18)-C(22)) and very long-chain (VLC) (C(24)-C(32)) polyunsaturated fatty acids (PUFA). The weight of the cryptorchid testis was nearly half that of the contralateral control at postsurgical Days 7-10 owing to the depletion of germ cells. Concomitantly, the amounts of major glycerophospholipids (GPL) and sphingomyelin (SM) per testis decreased. Both these lipids lost their characteristic long-chain and very long-chain PUFA, notably 22:5n-6 and 28:4n-6, respectively, which suggests that these species are linked to the membranes of germ cells. In contrast, the amounts and concentrations of triglycerides (TG; triacylglycerols and 1-O-alkyl-2,3-diacylglycerols) and cholesterol esters (CE) increased several fold in the surviving cells (mainly Sertoli cells) in the cryptorchid testis. All these neutral lipids, but especially CE, accumulated large amounts of the major PUFA of the testis, 22:5n-6, as well as pentaenes with longer carbon chains (i.e., 24:5n-6 in TG and 28:5n-6 in CE). This accretion suggests that neutral lipids may store preformed PUFA coming from dying germ cell GPL and also VLCPUFA no longer needed as a source of PUFA destined to assemble new germ cell GPL. The lipid adjustments observed in cryptorchidism suggest a possible role for Sertoli cell CE in the turnover and conservation of PUFA within seminiferous tubules.     

On the Compartmentation of Triacylglycerol Synthesis in Developing Seeds of Brassica napus

Compartmentation of storage lipid biosynthesis in developing erucate-rich rapeseeds during the period of rapid triacylglycerol accumulation has been investigated by labelling acyl residues and the glycerol backbone in endomembrane lipids of isolated embryos with radioactive precursors, either before (“in vivo”) or after (“in vitro”) subcellular fractionation. In contrast to the low light environment within the pod under normal environmental conditions, the photosynthetic and lipid synthesizing capacities of the embryos were significantly stimulated by their illumination in the isolated state. Both ways of demonstrating “de novo” synthesis of triacylglycerols and erucic acid in endomembrane vesicles show their significantly higher accumulation in oil bodies than in microsomal fractions, where membrane lipids predominate. The increased diacylglycerol acylation in erucate-rich rape embryos appears to be coupled to an alternative elongation mechanism for oleic acid, with another immediate acyl donor than 18:1-CoA. The present results are interpreted as a spatial separation of triacylglycerol formation, with very long-chain fatty acids obtained from residual lipid synthesis and fatty acid elongating capacity located on the endoplasmic reticulum.     

Lipid composition and trophic relationships of krill species in a high Arctic fjord

Our study deals with the lipid biochemistry of the krill community in the ecosystem of the high Arctic Kongsfjord (Svalbard). During the last decades, Kongsfjord experienced a change in krill species composition due to recent increased advection of Atlantic water masses carrying characteristic boreal as well as subtropical-boreal euphausiids into the ecosystem. The lipid biochemistry and trophic relationships of the species recently inhabiting the Arctic water masses are scarcely known, although a change in a krill population may have a significant impact on the ecosystem. A comparison of nutrition and energy storage strategies, stable isotopes, lipid profiles and fatty acid compositions showed remarkable differences between the krill species. These reflected the diverse feeding behaviours and specific adaptations to the environments of their origin: the boreal Meganyctiphanes norvegica and subtropical Nematoscelis megalops appear more carnivorous and have significantly lower mean lipid contents (29 and 10 %, respectively) and a different energy storage pattern (triacylglycerols and polar lipids, respectively) than the arcto-boreal Thysanoessa inermis, which consists of up to 54 % of lipids mainly stored as wax esters (>40 %). These differences may have significant implications for the rapidly changing marine food web of Kongsfjord—especially for higher trophic levels relying on the nutritional input of animal lipids.     

Evidence contrary to the existence of storage lipid in leaves of plants inhabiting cold climates

Abstract In a study of the lipid composition of the upland Empetrum nigrum subspp. hermaphroditum and Empetrum nigrum subspp. nigrum with a lowland distribution, no evidence was found to support the suggestion that lipids (triacylglycerols) play a major energy storage role in the leaves of alpine species. On a quantitative basis the triacylglycerols constituted less than 5% of the total lipid in both species and the lowland species possessed the higher levels of total lipid, neutral lipid and triacylglycerols. It is suggested that the presence of a well-developed waxy cuticle might account for the high total lipid levels encountered in dwarf evergreen shrubs.     

Improved separation and quantification of neutral and polar lipid classes by HPLC–ELSD using a monolithic silica phase: Application to exceptional marine lipids

An improved HPLC method is presented, which allows separation and quantification of a broad range of lipid classes of marine zooplankton with special regard to neutral lipids. Marine zooplankton species often produce high amounts of exceptional lipids, especially at high latitudes, in order to cope with the harsh environmental conditions and strong seasonality in food supply. Major neutral lipid classes are wax esters, triacylglycerols, diacylglycerol ethers, free fatty alcohols and sterols. Neutral and polar lipids were separated and identified on a monolithic silica column (Chromolith^®Performance-Si) using high performance liquid chromatography (HPLC) with an evaporative light scattering detector (ELSD). The method resolves a broad spectrum of lipids, varying in polarity from squalene to lysophosphatidylcholine in a single run. The total run time was 35 min including column re-equilibration. The calibration was made at levels of 0.1–60 μg lipid/injection, but a 10–15-fold greater amount can be injected if single lipid classes need to be separated, e.g. for further determination of individual fatty acids. The method was applied to representative Arctic zooplankton species (copepods, pteropods, euphausiids and ctenophores) that are known to biosynthesize in particular neutral lipids like diacylglycerol ethers and free fatty alcohols.     

Lipids noncovalently associated with keratins and other cytoskeletal proteins of mouse mammary epithelial cells in primary culture

Lipids noncovalently associated with cytoskeletal (CS) proteins of mouse mammary epithelial cells (MMEC) grown in primary culture were analyzed. A CS fraction, preapred by subjecting MMEC to 1.5 KCl and 1% Triton X-100 in phosphate buffered saline (pH 7.4), was extracted 4–6 times with chloroform/methanol. Thin-layer chromatography (TLC) indicated that in comparison to whole cell lipid extracts, CS lipids consisted mostly of neutral lipids, especially triacylglycerols and, possibly cholesteryl esters. TLC analysis of chloroform/methanol CS extracts prepared from MMEC that had been incubated 4 h in [³H]palmitate revealed similar results, with the majority of label appearing in triacylglycerols and other neutral lipids. By autoradiography of sodium dodecyl sulfate polyacrylamide gels, all of the major CS proteins appeared labelled. The major regions of autoradiographic density of the gel were excised, the protein solubilized, and the lipids extracted and subjected to TLC. Most of the radiolabel appeared at the origin and ion front and resolved as neutral lipids. In contrast, keratins of 54–55 kDa and 46 kDa appeared to be associated noncovalently with a higher ratio of polar lipids (possibly phospholipids) to nonpolar (neutral lipids). Very little radioactivity, mostly neutral lipid, was associated with actin. A previously unidentified CS component of 30 kDa had primarily noncovalently bound neutral lipid. The results are discussed in terms of the apparent interactions of keratin filaments with the plasma membrane, nuclear envelope and cytoplasmic organelles.     

高产油小球藻的筛选及其油脂分析

小球藻广泛分布于各种生境,特别是淡水环境中,适应性强。其同化产物主要是淀粉,但在环境胁迫条件下可显著积累中性脂,其脂肪酸类型主要为C16和C18,适合作为生物柴油的原料。我们从中国部分地区水体中分离纯化到若干株小球藻,通过薄层层析比较分析了21株产油小球藻的油脂含量,筛选到一株三酰基甘油含量较高的藻株Chlorella sp.NMX37N。其适宜生长温区为15—35℃,在25℃时生长速率最快,比生长速率为0.53/d,生长的最适光强为250μmol photons/(m2.s)。批量培养实验显示,藻细胞的三酰基甘油含量随培养时间延长而增加,并在培养的稳定期达到最大值,此时培养液中氮基本被耗尽。在批量培养条件下培养Chlorella sp.NMX37N约40d,藻细胞中总脂含量可达到33%左右,与此相比通过两步培养方式,将培养至对数后期(约20d)的藻细胞缺氮处理48h后,得到的总脂产率相当。通过两步培养方式可以大大缩短培养时间,使得该藻细胞快速有效积累油脂。另外,气相色谱分析显示,该藻的总脂和三酰基甘油的脂肪酸均以C16∶0和C18∶2为主,占总脂肪酸的70%以上,且不含C20以上的长链脂肪酸,可以作为优质的生物柴油原料。     

Application of atmospheric pressure chemical ionization liquid chromatography–mass spectrometry in identification of lymph triacylglycerols

Atmospheric pressure chemical ionization liquid chromatography–mass spectrometry was used in the identification of triacylglycerol molecular species in lymph samples from rats given either a structured lipid or safflower oil. The structured lipid was MLM-type (M, medium-chain fatty acid; L, long-chain fatty acid) and manufactured from caprylic acid (8:0) and the oil (safflower oil or high-oleic sunflower oil). The triacylglycerol composition of lymph varied significantly between structured triacylglycerols and safflower oil. Diacylglycerol fragment ions were found for all triacylglycerols and we could also observe the ammonium adduct molecular ion [M+NH₄]⁺ for all the triacylglycerols at the selected conditions. Protonated molecular ions were formed from triacylglycerols containing unsaturated fatty acids, and fatty acid fragment ions were also observed in the case of strong fragmentation. The lymph triacylglycerols were identified from their ammonium adduct molecular ions and diacylglycerol fragment ions. In addition to the intact MLM-type structured triacylglycerols, the MLL- and LLL-type triacylglycerols were also identified. The absorption pathway of MLM-type structured triacylglycerols is most likely the same as that of conventional long-chain triacylglycerols, i.e. they were hydrolyzed into 2-monoacylglycerol and medium-chain fatty acids, which were then used for resynthesis of triacylglycerols. The present study thereby also demonstrates the possibility to study the absorption pathway of triacylglycerol via identification of triacylglycerol species in biological samples.     

Morphology of the melon and its tendinous connections to the facial muscles in bottlenose dolphins (Tursiops truncatus)

The melon is a lipid‐rich structure located in the forehead of odontocetes that functions to propagate echolocation sounds into the surrounding aquatic environment. To date, the melon's ability to guide and impedance match biosonar sounds to seawater has been attributed to its unique fatty acid composition. However, the melon is also acted upon by complex facial muscles derived from the m. maxillonasolabialis. The goal of this study was to investigate the gross morphology of the melon in bottlenose dolphins (Tursiops truncatus) and to describe how it is tendinously connected to these facial muscles. Standard gross dissection (N = 8 specimens) and serial sectioning (N = 3 specimens) techniques were used to describe the melon and to identify its connections to the surrounding muscles and blubber in three orthogonal body planes. The dolphin forehead was also thin‐sectioned in three body planes (N = 3 specimens), and polarized light was used to reveal the birefringent collagen fibers within and surrounding the melon. This study identified distinct regions of the melon that vary in shape and display locally specific muscle‐tendon morphologies. These regions include the bilaterally symmetric main body and cone and the asymmetric right and left caudal melon. This study is the first to identify that each caudal melon terminates in a lipid cup that envelopes the echolocation sound generators. Facial muscles of the melon have highly organized tendon populations that traverse the melon and insert into either the surrounding blubber, the connective tissue matrix of the nasal plug, or the connective tissue sheath surrounding the sound generators. The facial muscles and tendons also lie within multiple orthogonal body planes, which suggest that the melon is capable of complex shape change. The results of this study suggest that these muscles could function to change the frequency, beam width, and directionality of the emitted sound beam in bottlenose dolphins. The echolocation sound propagation pathway within the dolphin forehead appears to be a tunable system. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Distribution,abundance, and density of harbor porpoises in Hood Canal,Washington

Harbor porpoises (Phocoena phocoena) are the only cetaceans routinely sighted in Hood Canal, a narrow fjord that comprises the western edge of Puget Sound, Washington, USA. Harbor porpoises are sensitive to anthropogenic sounds, including noise from recreational and commercial vessel traffic, and the United States Navy, which conducts military training and testing within Hood Canal that can include underwater sound sources. This study was funded as part of the Navy monitoring program to assess potential impacts of naval activities on cetaceans. We conducted vessel-based line-transect surveys for harbor porpoises in Hood Canal in 2022–2023 to derive seasonal estimates of abundance and density. We carried out surveys over 37 days and surveyed the entire canal twice per season totaling 2,176 km of on-effort track line. We recorded 809 on-effort harbor porpoise groups and 1,385 individuals. Seasonal abundance estimates were lowest in winter (308 animals, 95% CI = 189–503) and gradually increased through spring and summer to a peak of 1,336 animals (95% CI = 826–2,160) in fall. Overall porpoise density was highest in central Hood Canal, an area that includes a designated United States Navy training range, though porpoise sightings were notably absent in a 21-km² area adjacent to the naval submarine base within this otherwise high-density region. Though we collected only a single year of data, these results suggest that harbor porpoise abundance in Hood Canal increased significantly since it was last estimated (2013–2015). The notable seasonal fluctuation of harbor porpoise abundance suggests Hood Canal may host a larger percentage of the overall Washington Inland Waters stock during the fall season, raising important management considerations.