Ephydra Hians Research Articles

External morphology of the larvae of Ephydra (Hydropyrus) hians (Diptera: Ephydridae).

Scanning electron microscopy is used to describe the ultrastructure of morphological features related to feeding, locomotion, respiration, and pigmentation in second- and third-instar larvae of Ephydra hians (Ephydridae: Diptera). Using larvae fixed with the head extended, the ultrastructural details of the mandibles, maxillary papilli, and antennae are described for the first time. The larvae possess finger-like projections at the anterior spiracle and a distensible bifurcated siphon at the posterior spiracle. Slit-like openings are found on each. The second- and third-instar larvae can be differentiated on the basis of dorsal pigmentation associated with extensive patches of spines. The larvae have regional specializations in spine distribution, particularly on the ventral and dorsal body surfaces, and the prolegs. © 1994 Wiley-Liss, Inc.

Concentrated Excretion of Sulfate by the Anterior Colon of the Brine Fly, Ephydra hians

The larvae of Ephydra hians in saline Mono Lake drink the hyperosmotic medium to gain water lost by osmosis. The larvae take most of the sulfate ions ingested into the hemolymph at the midgut. The Malpighian tubules and rectum do not contribute significantly to sulfate transport in this insect. The colon, particularly the anterior half shows sulfate transport capacities exceeding those required to remove the sulfate from the hemolymph. The process of sulfate excretion in the colon is considered to be active because (1) a large concentration gradient for sulfate is established across the epithelium of the colon (i.e., the sulfate concentration is higher in the lumen), (2) the transepithelial electrical potential opposes sulfate excretion, with the lumen approximately -6 mV relative to the bath, and (3) there is a high dependency for oxygen in the transporting tissue. The results of anoxic and cyanide experiments suggest that the colon epithelium does not have a high passive permeability to sulfate ions. It is clear, therefore, that the very impressive capacities of these larvae to osmoregulate in water containing more than 150 mM sulfate reside in their ability to move sulfate from the midgut into hemolymph and then to rapidly remove this sulfate from the hemolymph. The removal of sulfate involves an active and highly concentrative sulfate-pumping mechanism located in the anterior half of the colon.

A population model for the alkali fly at Mono Lake: depth distribution and changing habitat availability

A population model for the alkali fly at Mono Lake: depth distribution and changing habitat availability

Taxonomy and Distribution of Benthic Diatoms from Mono Lake, California, U.S.A.

The benthic diatom flora of Mono Lake is described from samples taken from three localities at depths of approximately 1, 5, and 10 meters on rock and sediment substrates. Relative abundances of 30 taxa were recorded from duplicate counts of 500 valves from each of 18 samples. Dominant taxa included Navicula crucialis, Nitzschia frustulum, N. latens, N. reimerii sp. nov., N. monoensis, sp. nov. and Anomoeoneis sphaerophora var. minor var. nov.; taxonomy, morphology, and distribution of these taxa are considered. Navicula crucialis, previously recorded from saline lakes in North Africa and highly variable in outline, was most abundant in sediment samples. Anomoeoneis sphaerophora var. minor, Nitzschia reimeri, and N. monoensis were most abundant in deeper waters whereas both N. latens and N. frustulum occurred most frequently in collections from shallow waters. Smaller individuals of N. latens were broader than larger specimens, and some N. frustulum cells resembled N. austriaca. Nitzschia monoensis has numerous girdle bands and prominent external distal raphe ends. Navicula crucialis, A. sphaerophora var. minor, and Nitzschia monoensis were observed with internal valves. Mono Lake, located at the western edge of the Great Basin (Fig. 1), is a hypersaline (95 g/L in 1990) and alkaline (pH 10.0) (Herbst, unpublished data) remnant of Pleistocene Lake Russell. At a current surface elevation of 1,943 m, the lake has fluctuated considerably in the late Holocene (Stine, 1990). During the past 50 years, the lake has undergone a net decline of 14 m and a doubling of salinity, both attributable to diversion of tributary streams by the city of Los Angeles (National Academy of Sciences, 1987). The major ion content is dominated by sodium, with high anion concentrations of bicarbonate in addition to carbonate, chloride, and sulfate (Herbst, 1988). The benthic environment is composed of sand and organic-rich mud sediments over much of the basin. Hard substrates occur as localized calcareous tufa formations, pumice and alluvial granite cobble, and gravel along the west, north, and south shores (Herbst, 1990). The high salinity of Mono Lake restricts macrofaunal diversity to eight known benthic insects, all dipteran larvae (Herbst, 1988) and a single zooplankton species, Artemia monica Verrill. The dominant benthic insect is the alkali fly Ephydra hians Say (Ephydridae), a herbivore that grazes epilithic algae and epipelic microbial mats. Benthic algae from Mono Lake with which diatoms are known to occur include Ctenocladus circinnatus Borzi (Chlorophyceae) ' Portions of this study and support for D. B. H. were provided by a grant from the University of California Water Resources Center. We thank T. J. Bradley for informative discussions and C. W. Reimer for use of the Diatom Herbarium, Academy of Natural Sciences of Philadelphia. Publication costs, in part, are being met by a grant from the Darbaker Fund of the American Microscopical Society. TRANS. AM. MICROSC. Soc., 111(4): 338-355. 1992. ? Copyright, 1992, by the American Microscopical Society, Inc. This content downloaded from 207.46.13.64 on Sat, 03 Sep 2016 04:09:50 UTC All use subject to http://about.jstor.org/terms VOL. 111, NO. 4, OCTOBER 1992

Distribution and abundance of the alkali fly (Ephydra hians) Say at Mono Lake, California (USA) in relation to physical habitat

The distribution and abundance of larval, pupal, and adult stages of the alkali fly Ephydra hians Say were examined in relation to location, benthic substrate type, and shoreline features at Mono Lake. Generation time was calculated as a degree-day model for development time at different temperatures, and compared to the thermal environment of the lake at different depths.

A Malpighian Tubule Lime Gland in an Insect Inhabiting Alkaline Salt Lakes

ABSTRACT The alkali fly, Ephydra hians Say, inhabits alkaline salt lakes which can contain concentrations of dissolved carbonate and bicarbonate as high as 500 mmol l−1. Larvae of the alkali fly possess two pairs of Malpighian tubules. The posterior pair has a morphology similar to that of the tubules of most other insects, but the anterior pair is modified into an enlarged gland containing white microsphere concretions. We describe the ultrastructure of all cell types in both pairs of tubules. Using scanning electron microscope (SEM) X-ray microanalysis and chemical CO2 quantification, we demonstrate that the concretions in the lime glands are composed of nearly pure calcium carbonate. Isolated preparations of lime gland tubules accumulate 45Ca significantly more rapidly than do normal tubules. Although similar to the lime concretions found in the Malpighian tubules of other Diptera, the lime glands of this insect may function to regulate the high concentrations of carbonate and bicarbonate encountered in their aquatic environment. It is proposed that the mechanism of this regulation may be chemical precipitation of carbonate/bicarbonate with calcium in the lumen of these specialized lime gland tubules.

Osmoregulation in an alkaline salt lake insect, Ephydra (Hydropyrus) hians Say (Diptera: Ephydridae) in relation to water chemistry

Larvae of the alkali fly Ephydra hians, from Mono Lake (California), were exposed to osmotic concentrations ranging from distilled water to over 6000 mOsm of either alkaline Mono Lake water, or non-alkaline sea water/sodium chloride solutions. Larvae were capable of both hyper- and hypo-osmotic regulation of haemolymph osmolality (at around 300 mOsm) in Mono Lake water, but this ability was less effective in sea water/sodium chloride. In addition, higher mortality rates in sea water/sodium chloride suggest larvae are less tolerant of this chloride-dominated water chemistry. Pre-acclimation of larvae in sea water/sodium chloride did not improve survival in higher concentrations of this solution relative to larvae acclimated to Mono Lake water. At and above 200 g/l total dissolved solids (about 4800 mOsm) of Mono Lake water, larval survival is severely reduced, in association with osmotic dehydration. Sodium and chloride are the major haemolymph osmolytes, comprising about 70% of the total osmotic concentration. The results suggest that this species is alkali-adapted, and that restriction in habitat distribution from non-alkaline chloride waters and salinities above 200 g/l has a physiological basis.

Ecology of migrant Black‐necked Grebes Podiceps nigricollis at Mono Lake, California

Autumnal migrant Black‐necked or Eared Grebes Podiceps nigricollis begin arriving in large numbers at Mono Lake, California, in August. Juveniles appear to arrive later than adults, and the number of grebes at Mono Lake peaks in September and October. The grebes leave by November or December. Stomachs of 73 grebes collected in the Autumns of 1980 and 1981 reveal that brine shrimp Artemia monica comprise over 90% of the diet. The remainder of the diet is composed of the larvae, pupariaand adults of a brine fly Ephydra hians and small numbers of shore bugs Saldula arenicola and 5. opiparia and other terrestrial arthropods. The grebes do not feed at night but rest instead in large nocturnal aggregations over deep water. Grebe fat stores and total body‐weight increase from August to October, and adults moult their regimes in August and September. In late autumn brine shrimp densities decline dramatically and the grebes leave the lake.

Sanctuaries of the Bird Islands of Great Salt Lake

GREAT SALT LAKE in the north-central part of Utah is the second largest body of water within the confines of the United States, being eclipsed only by Lake Michigan. It has the highest saline content of any other similar lake. At average level the specific gravity of the water is about 1.13 but this year, since the level has dropped below the lowest recorded mark, the specific gravity has a corresponding increase and now is about 1.2. It is essentially a saturated salt solution and the large square crystals of sodium chloride are being deposited on the sand of the bottom, on the hulls of the boats and on any foreign substance placed in the water. Ecologically the waters of the lake constitute a physiological desert. No large animals and only a few small forms have been able to adapt themselves to the unusual environment and so far as known no parasites have been able to follow them into the brine. The flora is restricted to one of the blue-green algae (Aphanothece utahensis) a few unicellular green algae and a few diatomes. The former occurs in considerable amount and is the principle source of food supply. The most notable organism is the brine shrimp (Artemia gracilis) which passes its entire development to sexual maturity in the briny waters propagating parthenogenetically as well as by fertilized eggs. Two brine flies (Ephydra hians and Ephydra gracilis), have strictly aquatic eggs, larvae and pupae, the larvae having the breathing tube transformed into tracheal gills so that they need not come to the surface to breathe. The masses of floating pupae may be seen as brownish streaks in the water and when they collect along the shores great windrows, often many inches thick, are formed. They are used as food by birds, such as the migrating flocks of Northern Phalarope, the Eared Grebe, California Gull, certain Ducks and others. These extensive collections of fly pupae along the shores are mentioned in the writings of the early explorers and the Indians formerly collected them for food. The gnats, of course, are liberated on the surface of the water and collect in large swarms along the shore and for some distance inward and furnish food for some birds and the common spiders of the region. The larger islands are arranged in two longitudinal groups. Fremont and Antelope Islands form an extension southward from the Promontory Ridge

Animal Relationships of Great Salt Lake

The Great Salt Lake, with its saline content approaching saturation, presents a hostile environmnent to most living organisms, both within the water and upon the niearby shores. Those who would survive the rigors of this aquatic desert must either be equipped to meet the exactions imposed or to avoid them. The problem of meeting the peculiarities of the environment is largely physiological-that of extracting moisture from a salt solution. This problem varies not only from time to time with the rise and fall of the lake level and its consequent dilution and concentration but also from place to place wlhere dilution occurs by the inpouring of fresh-water streamns and underground seepage. The paucity of life forms actually living within the lake water is undoubtedly due to these severe restrictions. The principal food-makers of the lake are blue-green algae including several colonial forms of the genus Aphanothece which produce salmon colored gelatin-like masses, especially near shore, diatoms of the genera Navicula and Cymbella, two flagellates of the genus Chlamydolonas, and several others of lesser importance. These are undoubtedly the food base for a very limited fauna of protozoans and invertebrates which can withstand immersion in the water of the lake. A rhizopod of the genus Ainoeba and a ciliate of the genus Uroleptus are reported to occur, undoubtedly in vasL numbers although invisible to the eye. Of the visible forms, the brine shrimp, Artemia gracilis Verrill, and two brine flies, Ephydra gracilis Packard and Ephydra hians Say are common inhabitants of the lake. So far as known, no parasites have been able to follow them into the brine. Freed from parasites, these arthropods have been enabled to multiply with little or no molestation to the limit of the food supply,