Spanish salt lakes: Their chemistry and biota

A large number of small saline lakes are distributed throughout Spain. Four main lake districts occur from sea level to 1000 m.a.s.l. Most lakes are temporary because of the arid conditions in the Spanish endorheic areas. Many lakes are situated in Tertiary depressions in NE. and S. Spain. Lake basins were formed in karstic areas by hydrologic and aeolian erosion. Saline lakes in NE. Spain occupy areas isolated between river basins. The major ions encountered in these lakes are usually sodium-chloride and magnesium-sulphate; sodium carbonate or sodium-sulphate rich waters also occur.The biota of Spanish salt lakes is related to that of a larger biogeographical region which includes the Mediterranean countries. The main types of salt lakes in Spain include: (1) temporarily mineralized but not highly saline lakes, salinity is less than 7 g l^-1. Chara canescens, C. aspera, Zanichellia palustris, Daphnia atkinsoni, Mixodiaptomus incrassatus and Arctodiaptomus wierzejskii are the most characteristic organisms. (2) Temporary salt lakes, salinity fluctuates between 7 and 300 g l^-1. Chara galioides, Lamprothamnion papulosum, Daphnia mediterranea, Arctodiaptomus salinus and Cletocamptus retrogressus are the most common species. (3) Permanent salt lakes, Ruppia maritima, Najas marina and Artemia salina are the characteristic organisms.     

Trace fossils and rhizoliths as a tool for sedimentological and palaeoenvironmental analysis of ancient continental evaporite successions

Recognition of evaporite formations from continental Tertiary basins of Spain provides evidence that trace fossils (including rhizoliths) can be abundant in some saline lake systems and their study helps in palaeoenvironmental interpretation of ancient continental evaporite sequences. Six main types of trace fossils have been distinguished and include: (1) networks of small rhizoliths; (2) large rhizoliths; (3) tangle-patterned small burrows; (4) isolated large burrows; (5) L-shaped traces; and (6) vertebrate tracks. Rhizoliths were related to both marginal areas of hypersaline lakes and lakes of moderately high saline waters. In these settings, pedoturbation resulted from colonization by grasses and bushes of distinct lake subenvironments. The activity of burrowing invertebrate faunas was especially intense in lakes of moderately concentrated brines from which gypsum was the main evaporite mineral deposited. A specific gypsum lithofacies (‘bioturbated gypsum deposits') forming thick, massive beds has a widespread occurrence in many of the basins. Tangle-patterned small burrows and minor isolated large burrows constitute the typical trace fossil types within the gypsum. The traces are interpreted as having been caused by burrowing insect larvae, probably chironomids, coleopterans and annelids. The behaviour of these organisms in recent lake environments yields information about the salinity range of lake waters from which gypsum precipitated. Concentration values averaging 100–150 g/l may be thus deduced though some organisms involved in the formation of the traces can tolerate higher salinities. The combined analysis of lithofacies and trace fossils from the lacustrine evaporite sequences contributes to the study of distinct saline lake subenvironments as well as changes in the sedimentary evolution of the lake systems. Consequently, trace fossils can provide valuable insight for palaeoenvironmental analysis of at least some evaporite formations that accumulated in continental settings.     

The distribution,structure, and composition of freshwater ice deposits in Bolivian salt lakes

Freshwater ice deposits are described from seven, high elevation (4117–4730 m), shallow (mean depth <30 cm), saline (10–103 g l^-1) lakes in the southwestern corner of Bolivia. The ice deposits range to several hundred meters in length and to 7 m in height above the lake or playa surface. They are located near the lake or salar margins; some are completely surrounded by water, others by playa deposits or salt crusts. Upper surfaces and sides of the ice deposits usually are covered by 20–40 cm of white to light brown, dry sedimentary materials. Calcite is the dominant crystalline mineral in these, and amorphous materials such as diatom frustules and volcanic glass are also often abundant.Beneath the dry overburden the ice occurs primarily as horizontal lenses 1–1000 mm thick, irregularly alternating with strata of frozen sedimentary materials. Ice represents from 10 to 87% of the volume of the deposits and yields freshwater (TFR <3 g l^-1) when melted. Oxygen isotope ratios for ice are similar to those for regional precipitation and shoreline seeps but much lower than those for the lakewaters. Geothermal flux is high in the region as evidenced by numerous hot springs and deep (3.0–3.5 m) sediment temperatures of 5–10°C. This flux is one cause of the present gradual wasting away of these deposits. Mean annual air temperatures for the different lakes probably are all in the range of -2 to 4°C, and mean midwinter temperatures about 5°C lower. These deposits apparently formed during colder climatic conditions by the freezing of low salinity porewaters and the building up of segregation ice lenses.     

Upper Pleistocene and Holocene lakes in the An Nafud,Saudi Arabia

Summary Two major lake periods were discovered in the sand sea of An Nafud and the surrounding areas. In Upper Pleistocene large lakes occurred around the dune area and in the interior of the sand sea. Their deposits were formed between 34 000 and 24 000 BP. The lakes were not conformous to the present dune relief. They had an extension of several km² and a depth of ca. 10 m. Holocene lakes (8 400–5 400 BP) were of minor extension and restricted to the interdune depressions. Lake sediments consist of cemented sand, calcareous crusts and diatomites. Upper Pleistocene lakes were fresh water lakes, the Halocene lakes were mostly swamps depending on rising and falling aquifers in the dunes. Plant remains as pollen and macro rests show that the environmental changes didn't exceed the system of semidesert comparable to the modern plant cover. However, the Upper Pleistocene lake deposits contain some more soudanian elements as the Holocene sediments in the pollen spectra. Climatically the lake formations are interpreted as depending on a stronger influence of the mediterranean cyclones or an interaction of them with monsoonal air masses.     

Mongolian salt lakes: some features of their geography,thermal patterns,chemistry and biology

There are >3500 lakes of area >0.1 km² in Mongolia. Most have salinities >1 g 1^–1 Of these saline lakes, 12 have areas > 50 km² each, 10, areas > 100 km², and 2, areas > 1000 km². Limnological investigations of salt lakes include morphometric studies, and investigations of bottom sediments, thermal regimes, chemical features, and biological (including fish) characteristics. Data from these investigations now provide a much clearer picture of the limnology of saline lakes in central Asia.     

Comparative limnology of Sambhar and Didwana lakes (Rajasthan,NW India)

Two alkaline saline inland lakes of Indian arid region were studied during 1984 and 1985, to assess functioning and interaction of various environmental and biological factors. Changes in physical and chemical variables, planktonic composition, chlorophyll content and phytoplankton primary productivity were examined.Salinity in both lakes fluctuated from almost fresh water (1.80), to hypersaline (300) and acted as the main controlling factor for almost all the biotic parameters. Maximum total alkalinities were 2162 mg l^–1 and 2090 mg l^–1, respectively in Sambhar and Didwana lakes. Dissolved oxygen ranged from completely anoxic conditions to maxima of 11.68 and 7.29 mg 1^–1, respectively in Sambhar and Didwana lakes. Nutrient enrichment in the lakes was low.The phytoplankton species composition of Sambhar lake was reduced from an earlier reported 20 genera to only 11 (Nostoc, Microcystis, Spirulina, Aphanocapsa, Oscillatoria, Merismopedia, Nitzschia, Navicula, Synedra, Cosmarium and Closterium). Phytoplankton of Didwana was composed of only 9 genera including Anabaena and Nodularia. Sambhar lake, which once contained Artemia, is now totally devoid of them. On the other hand, Artemia was the most dominant zooplankter in Didwana lake at a salinity range of 15–288. Other zooplankters such as Moina, Cyclops and Brachionus flourished at lower salinity levels in Didwana lake. The seasonal quantitative and qualitative phyto- and zooplankton changes in relation to salinity are documented.     

The microbe–mineral environment and gypsum neogenesis in a weathered polar evaporite

Evaporitic deposits are a globally widespread habitat for micro‐organisms. The microbe–mineral environment in weathered and remobilized gypsum from exposed mid‐Ordovician marine evaporite beds in the polar desert of Devon Island, Nunavut, Canadian High Arctic was examined. The gypsum is characterized by internal green zones of cyanobacterial colonization (dominated by Gloeocapsa/Aphanothece and Chroococcidiopsis spp. morphotypes) and abundant black zones, visible from the surface, that contain pigmented cyanobacteria and fungi. Bioessential elements in the gypsum are primarily provided by allochthonous material from the present‐day polar desert. The disruption, uplift and rotation of the evaporite beds by the Haughton meteorite impact 39 Ma have facilitated gypsum weathering and its accessibility as a habitat. No cultured cyanobacteria, bacteria and fungi were halophilic consistent with the expectation that halophily is not required to persist in gypsum habitats. Heterotrophic bacteria from the evaporite were slightly or moderately halotolerant, as were heterotrophs isolated from soil near the gypsum outcrop showing that halotolerance is common in arctic bacteria in this location. Psychrotolerant Arthrobacter species were isolated. No psychrophilic organisms were isolated. Two Arthrobacter isolates from the evaporite were used to mediate gypsum neogenesis in the laboratory, demonstrating a potential role for microbial biomineralization processes in polar environments.     

Effects of Cd++ on short-circuit current across epithelial membranes

Summary Cadmium ion (Cd⁺⁺) significantly increased potential difference (PD) and short-circuit current (SCC) across isolated frog skin when added to the outside Ringer's solution at 10^–4, 10^–3 and 5×10^–3 m concentration. Resistance was reduced by 10^–4 m Cd⁺⁺ but not significantly changed by the higher concentrations. When SCC was first stimulated by vasopressin, 10^–4 and 10^–3 m Cd⁺⁺ produced additive stimulation which was reversible by washing with Cd⁺⁺-free Ringer's. If SCC was first stimulated by Cd⁺⁺, further stimulation by vasopressin was additive with 10^–4 m Cd⁺⁺ but completely inhibited by 10^–3 m Cd⁺⁺. Elevating the calcium ion (Ca⁺⁺) concentration of the outer Ringer's from 10^–3 m to 5×10^–3 m or 10^–2 m prior to Cd⁺⁺ treatment did not reduce the magnitude of SCC stimulation by Cd⁺⁺. Removal of Ca⁺⁺ from the outside Ringer's with 2×10^–3 m EDTA increased SCC as predicted. Subsequent addition of 5×10^–3 m Cd⁺⁺ drastically reduced SCC below control levels while equimolar concentrations of Cd⁺⁺ and EDTA reduced SCC only to control levels. These results suggest that Cd⁺⁺ interacts with the components of the apical plasma membranes of epithelial cells which are associated with the stimulation of SCC by vasopressin and Ca⁺⁺ removal and may be a useful probe for elucidating these components.     

Response of sugarcane to different types of salt stress

Summary Due to climatic conditions and prevailing water regime the yield and sucrose recovery in sugarcane are high in South Western India. However, excessive irrigation, poor drainage and luxuriant use of fertilizers have resulted in conversion of large fertile areas into saline lands. The salinity is due to the excess of Na⁺, Ca⁺⁺, Mg⁺⁺, SO₄ ^– and Cl^– ions. Individual salts of NaCl, Na₂SO₄, MgCl₂ and MgSO₄ were employed in culture experiments to study salt stress effect on sugarcane variety Co 740. It was observed that sulphate salinity was more toxic to sugarcane than the chloride one. Sulphate salts caused more inhibition of growth, chlorophyll synthesis, PEPCase activity, decreased the uptake of K⁺ and Ca⁺⁺ ions but stimulated nitrate reductase. The stress did not result in proline accumulation in the sugarcane cultivar Co 740. The degree of toxicity of different ions in decreasing order in sugarcane cultivar Co 740 is SO₄ ^–>Na⁺>Cl^–>Mg⁺⁺.     

Sulfte-reduction process in sediments of Lake Kinneret,Israel

Monomictic Lake Kinneret is stratified during summer and autumn, resulting in a hypolimnion rich in H₂S (3–7 mg 1^–1). In winter and spring every year a bloom of dinoflagallate Peridinium gatunense produces an average biomass of 150000 ton wet weight. Part of this biomass sinks to the hypolimnion and sediments where it is decomposed and mineralized, with some of the mineralization due to the activity of sulfate-reducing bacteria (SRB). The sulfate-reduction potential of the upper sediment layer at the deepest part of the lake (42 m) was measured. The activity of the enzyme arylsulfatase was also monitored. Rates of sulfate-reduction ranged from a minimum of 12 nmoles SO_f4 ^p2–-reduced cm^–3 day^–1 in December before lake overturn to a maximum of 1673 nmoles SO_f4 ^p2– reduced cm^–3 day^–1 in July during stratification. These rates are considerably higher than those recorded from other freshwater lakes in the world and are probably limited more by the availability of organic matter than by sulfate concentrations.     

Contribution to high altitude limnology of the Himalayan system I. Limnology and primary productivity of the plankton community of Nilnag Lake,Kashmir

The Nilnag (alt. 2180 m) situated in the Kashmir Himalayas, marks the beginning of the dimictic lake series of this region. The high turbidity of water (t : % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGadiiEayaara% aaaa!3703!\[\bar x\] = 1.16) as a result of accelerated particle movement from the adjoining terrestrial ecosystem, has affected the sensitive macroflora which was recorded five decades ago. The lake water chemistry depicts a cation pattern which is dominated by divalent calcium (Ca⁺⁺ > Mg⁺⁺ > Na⁺ > K⁺) and the anions by a carbonate-bicarbonate system (HCO₃ > SO₄ > Cl). The ionic composition of the lake water comes close to the World Standard for freshwater lakes. The levels of ortho-phosphate and nitrate-nitrogen are not very high, indicating moderate fertility of the lake. The phytoplankton production, as measured by ¹⁴C isotope technique, ranged from 120–562 mgC_assim m^–2 d^–1 during the ice-free period (1975–76) with an annual estimated yield of 90–100 gC m^–2. The vertical distribution of production is suggestive of plankton rich lake water. In its general limnological features, the Nilnag resembles mesotrophic lakes of the Kashmir valley.Formed a part of thesis for which Ph.D. was awarded to MAK by Kashmir UniversityFormed a part of thesis for which Ph.D. was awarded to MAK by Kashmir University     

The microbial plankton of freshwater lakes in the Vestfold Hills,Antarctica

Summary The plankton of twelve freshwater and slightly saline lakes in the Vestfold Hills, Antarctica was sampled in February 1991. All of the lakes are oligotrophic. The chlorophyll a concentrations in the lakes ranged from 0.10–2.69 g · 1^–1. The majority of the phytoplankton were flagellates or picoplanktonic cyanobacteria with the species composition varying between the lakes. Cyanobacteria were found in five of the lakes. Five to 6 species of ciliated protozoa occurred, among them oligotrichs, including the mixotrophic species Strombidium viride. The concentrations of protists and bacteria were an order to several orders of magnitude lower than reported from lower latitude oligotrophic lakes. Low species diversity and low numbers in the plankton characterise these eastern Antarctica lakes which reflects their low nutrient status and isolation.     

Two calcium currents in the somatic membrane of mollusc neurons

Two new types of calcium channels were discovered during research in ionic currents in the somatic membrane ofHelix pomatia neurons, using an intracellular perfusion technique. Apart from the principal calcium current described in the literature with a holding potential of about –110 mV, an additional calcium current was observed activated at depolarizations of –40 to –80 mV and was not reduced when the cell was perfused with solutions containing fluoride anions. The kinetics of this current were well described in the context of the Hodgkin and Huxley model with a time constant of activation of 6–8 msec and of inactivation of 300–600 msec. It increased in amplitude as the Ca⁺⁺ rose in the cellular environment but was reduced by extracellular addition of the Ca⁺⁺ antagonists Co⁺⁺, Ni⁺⁺, and Cd⁺⁺, and the organic blockers nifedipine and verapamil. The association constants of these substances with corresponding channels determined from the maximum of the current-voltage relationship were 2 (Ca⁺⁺), 3 (Co⁺⁺), 0.06 (nifedipine), and 0.2 mM (verapamil). The properties detected in this component of calcium conductance are compared with those of calcium channels in other excitatory formations and its possible functional role is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 627–633, September–October, 1985.     

A new species of cormorant (Aves: Phalacrocoracidae) from the Pleistocene of Olduvai Gorge,Tanzania

Phalacrocorax owrei nov. sp. is a small cormorant from the Lower Pleistocene of Olduvai Gorge. Osteological proportions are established for the four subgenera of Phalacrocorax, and P. owrei is assigned to the subgenus Stictocarbo. The species was the most abundant bird in the Bed I deposits and is also represented by a few specimens in the middle part of Bed II. Its last known appearance coincides with a change in the local environment when the climate became more arid and the Olduvai Lake became more saline and more alkaline. At other localities in Bed II the extinct P. tanzanice occurs, as well as P. africanus and P. corbo, which breed on the African lakes and seacoast today.     

Physico-chemical limnology of eleven,mostly saline permanent lakes in western Victoria,Australia

Major physico-chemical features of eleven, mostly saline permanent lakes situated on volcanic terrain in western Victoria, Australia, are described. All are large (1.1 to 251 km² in area), and most are shallow (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabeOEayaara% aaaa!3702!\[{\text{\bar z}}\]= <6 m). Mean salinities were 0.3 to 56.6 g 1^–1, and seasonal differences were slight. Major ion dominances were Na > Mg > Ca K : Cl > HCO₃ + CO₃ > SO₄. Generally, pH was 8.0 to 9.0. Nitrogen not phosphorus appeared to be a limiting plant nutrient. The shallow lakes were often highly turbid and had low secchi disc transparencies (sometimes < 5 cm).     

The major ion chemistry of some southern African saline systems

Africa south of about 23° S has few natural athalassic lakes, saline or freshwater. South Africa, however, is rich in temporary pans, many of which are saline, while permanent saline springs occur along the coastal strip of the Namib Desert in Namibia. This paper examines the chemistry of the major ions in 67 Namibian waters, 47 of which have not previously been reported in the literature, and compares them with 66 South African waters, five of which have not previously been reported, and with saline lakes in East Africa.The highest value for total dissolved solids in South African waters was 276 g l^–1 (Koekiespan, south-western Cape) and the highest for Namibian waters were 160 g l^–1 (Hosabes, a small spring on a gypsous crust) and 302 g l^–1 (a salt pan at Oranjemund at the mouth of the Orange River). The dominant ions in fresh waters in the region are Ca²⁺ and HCO _inf3 ^– /CO _inf3 ^2– in the interior and in Namibia, and Na²⁺ and Cl⁺ on the south and east coasts. Regardless of the geochemistry of their substrata, the dominant ions in the saline waters throughout the region are Na⁺ and Cl^–. Thus differential precipitation of CaCO₃ and CaSO₄, as a result of evaporative concentration at high salinities, appears to be the determinant of the proportions of the major ions in these systems.The permanent springs on gypsous crusts along the coast of Namibia, although dominated by Na⁺ and Cl^– ions, contain considerable quantities of both Ca²⁺ and SO ₄ ^2– ions.     

Effects of soil-added Cl on growth ofAndropogon scoparius and possible implications for heavy metal research

Soil additions of Cl^–, as NaCl, over the 0 to 400 ppm Cl^– range did not affect germination forAndropogon scoparius. Height and top dry weight were significantly reduced by 300 ppm soil added Cl^–. Although not conclusive, these results did indicate that growth and germination effects reported for Cd⁺⁺, added as CdCl₂, are probably due to Cd⁺⁺ rather than to a Cl^– or salt effect. Reported Pb⁺⁺ effects, where Pb⁺⁺ is added as PbCl₂, however may be at least partially due to a Cl^– or salt effect.Contribution from Purdue University Agricultural Experiment Station, West Lafayette, Indiana 47907. AES Journal No. 6934. This work was supported by federal funds from the National Science Foundation—RANN Program.     

Benthic invertebrates of some saline lakes of the Sud Lipez region,Bolivia

The benthic invertebrates fauna of most of the saline lakes of the Sud Lipez region (Bolivia, Altiplano) has been until now quite unstudied. Samples collected during an extensive survey of 12 lakes and two small inflow rivers allow a first list of the main macroinvertebrates living in these biotopes.The heterogeneous nature of these saline lakes with their freshwater springs and phreatic inflows offers a variety of habitats to macroinvertebrates. The benthic fauna in lakes with salinities > 10 g l^–1 is not so low in density but includes few species and is dominated by Orthocladiinae and Podonominae larvae. In contrast, the freshwater springs and inflows are colonized by a diverse fauna, with a mixture of both freshwater and saline taxa, but dominated by Elmidae and Amphipoda. The lakes are quite isolated and, apart from some cosmopolitan organisms, their fauna can be quite distinctive.     

Role of external calcium in sodium and chloride transport in the gills of seawater-adaptedMugil capito

Summary When the mulletMugil capito is transferred to medium lacking Ca⁺⁺ (either Ca⁺⁺-free seawater or distilled water) the passive permeability of the gill to Na⁺ and Cl^– is increased and the activating effect of external K⁺ on the Na⁺ and Cl^– effluxes in hyposaline media is inhibited. The permeability of the gill increases progressively in proportion to the time of Ca⁺⁺ deprivation; it declines when Ca⁺⁺ is added again to the external medium. The active mechanisms for ion excretion are not reversible. At external Ca⁺⁺ concentrations from 0.1 to 10 mM the Na⁺ permeability is constant but the activation of Na⁺ efflux by K⁺ shows a maximum at a Ca⁺⁺ concentration of about 1 mM. For activation of Cl^– efflux external bicarbonate must be present, in addition to Ca⁺⁺, suggesting the existence of a Cl^–/HCO ₃ ^– exchange. The mechanism by which Ca⁺⁺ controls the passive branchial permeability is thus probably different from that involved in K⁺ activation of ion excretion. The Ca⁺⁺ effect on the K⁺ sensitive ionic excretory mechanisms seems to be related to intracellular Ca⁺⁺ movements. Thus, on the one hand, substances such as Ruthenium Red and La⁺⁺⁺ which both inhibit Ca⁺⁺ exchange, in media containing Ca⁺⁺ and HCO ₃ ^– also inhibit K⁺ activation of Na⁺ and Cl^– effluxes; on the other hand, the ionophore A 23187, a stimulator of Ca⁺⁺ exchange, when added to these media, activates the Na⁺ and Cl^– effluxes; its maximal effect on the Na⁺ flux occurs at 2 mM Ca⁺⁺.Abbreviations ASW-Ca artificial seawater minus calcium - DW deionised water - DWCa deionised water with 1 mM Ca⁺⁺ added - DWCaHCO ₃ DW with calcium plus bicarbonate - DWHCO ₃ DW with 1 mM sodium bicarbonate added - FW freshwater (tap water) - FWK freshwater with K⁺ added - P. D. potential difference - SW seawater The experiments reported in this paper were done with Jean Maetz who tragically died in August 1977. It is the last report about several years of friendly collaboration     

A histocytochemical study of the macrophages present in tissue responses to adult Onchocerca volvulus

Summary Immunocytochemical and histochemical properties of macrophages present in the subcutaneous chronic inflammatory responses surrounding adultOnchocerca volvulus (nodules) in human tissues were examined. Macrophages with strong non-specific esterase (NSE) and acid phosphatase (AcPase) activities but weak adenosine triphosphatase (ATPase) activity and HLA-DR expression (NSE⁺⁺⁺, AcPase⁺⁺⁺, ATPase^–/+, HLA-DR^–/+) were present in the centre of nodules. Many of the cells adhering to the surface of worms were NSE⁺⁺⁺, AcPase⁺⁺⁺, ATPase^–, HLA-DR⁺⁺⁺. The inner zone of the fibrous capsule of nodules contained macrophages with the profile NSE⁺⁺⁺, AcPase^–, ATPase^–/+, HLA-DR^–/+. A fourth type, NSE⁺⁺⁺, AcPase^–/+, ATPase^–/+, HLA-DR⁺⁺⁺, was located in the outer zone of the capsule, frequently within perivascular accumulations of macrophages, lymphocytes and plasma cells. Active fibroblasts were identified at the inner edge of the fibrous capsule by alkaline phosphatase staining. A feature of all nodules examined was the presence of lipid-filled macrophages, demonstrated by Oil Red O stain; these cells were usually situated in zones adjacent to the centre of nodules, and were of the NSE⁺⁺, AcPase⁺⁺, ATPase^–/+, HLA-DR^–/+ type. Lipid accumulation was not found to be related to the clinical status of the patients studied. The origin and functional significance of this lipid is unknown.