Showing papers in "American Midland Naturalist in 1969"

Reproductive Modes and the Number and Sizes of Ova in the Urodeles

Abstract: Three major reproductive modes are described among the salamanders, one associated with abandoning the eggs in still waters, another with nesting in running waters, and a third with direct development in terrestrial sites. Correlations are examined between adult body size, ovum size, clutch size, hatchling size, and metamorphic size. All are found to be interrelated. Very simply, larger animals produce larger ova and more of them per reproductive cycle and, furthermore, metamorphose at larger larval sizes. Larger ova result in larger hatchlings regardless of reproductive mode. These data are examined in the light of theoretical considerations concerning the kinds of selection pressures that can operate on ovum and clutch size.

An ecological study of the swift fox (Vulpes velox) in the Oklahoma Panhandle.

Abstract: Swift foxes studied in Beaver Co., Oklahoma, in 1965 and 1966 used dens throughout the year. Most dens had multiple entrances and were placed in open situations. Additional entrances were added prior to whelping. Location of dens seems to depend on properties of the soil including its friability. Dens in cultivated fields were temporary, infrequently used, and relatively shallow; those in pastures deeper and more permanent. Breeding begins in late December and most whelps are born around 1 April, average 5 (3 to 6) per litter. Family groups remain together until late August, when first-year individuals have attained adult size. Swift foxes probably pair and mate in their first year. Early growth rates are the same for both sexes, but adult males are larger than females. Adult foxes were heavily parasitized by fleas, ticks, cestodes and nematodes. The cestode Taenia multiceps and the tick Ixodes kingi are here first reported from swift foxes. The composition of 488 scats examined indicates that Sylvilagus sp. comprise over half the bulk of food consumed in early spring. Other important prey included birds, jack rabbits, and various rodents. Mammals other than lagomorphs account for 82% of the biomass represented in an autumn sample of scats. Remains at dens were those of larger prey species and hence were not a true representation of the food habits. Predation by swift foxes seems to be random and non-selective. Insects comprised the largest percentage of individuals represented in scats and stomachs, but are not significant in terms of biomass.

Ecological Factors and the Distri6ution of Cladophora glomerata in the Great Lakes

Abstract: Nutrient enrichment in the Great Lakes has provided fertile areas for growth of algal nuisances. One of these species, Cla- dop,hora glomerata, has become a major problem for many cities border- ing the Great Lakes. Ecological factors concerning its growth in Milwau- kee's Harbor were studied, and its distribution in the Great Lakes deter- mined. Phosphorus levels appear to be closely linked with Cladophora increases.

The Submerged Aquatics of University Bay: A Study in Eutrophication

Abstract: The submerged aquatic plants of University Bay, Lake Mendota, Dane Co., Wisconsin, were sampled using the line intercept method. Twenty-one lines, perpendicular to the shoreline and extending into the bay to the depth at which growth of submerged aquatic plants ceased were sampled. All plants intercepting the line were recorded within consecutive half-meter segments of the line. The data were used to construct a contour map of the vegetated portions of the bay and to delimit the plant communities. Six plant communities were found. Data on plant height and standing crop were obtained from quadrat samples taken at biweekly intervals from four regions within the bay. The data were compared with studies made in 1922. Marked changes in quantitative composition have occurred since 1922, with the most marked difference being the great increase in Myriophyllum exalbescens and the complete disappearance of several species that were formerly major components of the vegetation.

Limnological Features of a Northern Brown-water Stream, with Special Reference to the Life Histories of the Aquatic Insects

Abstract: Aquatic invertebrates of a northern brown-water stream of west central Alberta, the Bigoray River, were studied for 2 years. The stream drains extensive muskeg terrain, but the pH of the water is always on the alkaline side; water temperatures are near 0 C for 6 months of the year, and the stream is completely ice-covered for 5 months; there is progressively less flow during the winter months. During dry winters, water freezes into the substrate, causing considerable mortality to riffle- inhabiting insects. The stream supports a large and diverse mayfly (Ephemeroptera) fauna, Leptophlebia cupida (Say) and Baetis tri- caudatus Dodds accounting for over 50% of the total yearly fauna by numbers and also volume biomass. Life history data are presented for 11 aquatic invertebrates. Compared to faunas of other streams, the Bigoray River has the following pertinent features: (1) a fauna with a restricted emergence period; (2) a short period (5 months) of seasonal succession and a long period (7 months) when the fauna changes very little; (3) various seasonal growth patterns exhibited by individual species, but the fauna as a whole growing most intensely in autumn; (4) a relatively large number of temporary (or summer) mayfly species; and (5) a winter species fauna having extensive delayed hatching.

Ecology of Limnetic Bluegill (Lepomis macrochirus) Fry in Crane Lake, Indiana

Abstract: In Crane Lake, Indiana, bluegill fry (Lepomis macrochirus Raf.) abandon littoral spawning areas shortly after yolk sac absorption and migrate to the limnetic zone of the lake. The ecology of the fry during their residence in the limnetic zone was studied utilizing data derived from fry captured in plexiglass fry traps. The distribution of the fry in the epilimnion is patchy, suggesting that they are aggregated, possibly in schools. They feed upon crustacean zooplankters, selecting copepods in preference to other plankters. They demonstrate a diel periodicity in their activity with low activity during the day, peak activity at dusk, low activity at night, and a secondary peak of activity at dawn. They remain in the limnetic zone for approximately a month and a half, growing at a rate of 0.4 mm/day. After achieving a size of 22 to 25 mm, they return to the littoral zone. In 1965 the brief period of limnetic residence for bluegill fry suggested that the duration of successful spawning had been very short, although nest-building activity extended from May to August.

Behavioral Aspects of Feigned Death in the Opossum Didelphis marsupialis

Abstract: Behavioral aspects of feigned death were studied in captured opossums (Didelphis marsupialis). Feigned death was induced by grabbing and shaking the opossums by "predators" (either human or dogs). It is a stereotyped behavior pattern characterized by a ventral flexure of the body, flexure of the digits, and grasping of lhe substrate. The opossum lies on its side with its feet visible. Corncrs of the mouth are retracted initially and then usually relaxed. The eyes remain open. During sleep, in contrast, the opossum keeps the mouth and eyes closed and its dorsum uppermost with the feet out of sight. Sham attacks rarely caused opossums to feign death; almost invariably tactile stimula- tion (grabbing) was necessary. Opossums feigning death may twitch the ears at sharp noises, retract the lips when prodded, or claw the air when picked up by the tail. Opossums raised in cages could not be induced to feign death even by grabbing. But when females with pouch young were captured and kept in a large indoor enclosure, their young showed the ability to feign death at 120 days of age. The feigned death response develops near the time of weaning. When six animals were stimulated daily, all continued to feign death for at least 12 days and one was still responding at 60 days. Generally the duration of feigned death increased with daily stimulation. Adult opossums responded less readily than ones under 8 months of age.

Plant Communities of Saline Soils at Lincoln, Nebraska

Abstract: The plant communities and their relationships to saline soils are described. A relationship is shown between an increase in salinity and decrease in cover of several species. Field observations indicate that the species which tolerate the highest salinities are capable of growing normally in low to nonsaline environments. This study area represents the southernmost extension of a stable Salicornia rubra community in the prairie region of the United States. A theory of tolerance to extreme environments is presented.

The Lodgepole Pine Zone in Colorado

Abstract: Vegetation and habitat characteristics are described in lodgepole pine forests on the east slopes of the Colorado Front Range where invasion by Douglas fir, subalpine fir, or Engelmann spruce has not occurred after 65-100 years of pine dominance. Absolute mortality of Douglas fir seedlings on plots cleared of pine litter was observed in 1967, and absolute mortality on uncleared plots was observed in 1966 and 1967. The lack of advanced reproductive stages of trees normally considered climax in adjacent Douglas fir and Spruce-Fir forest zones suggests that a lodgepole pine zone can be recognized between these other zones. Stands of lodgepole pine occurring on deep soils and normal relief within this zone may be climax or in a prolonged seral stage under present environmental conditions.

Mating Choice in Crosses between Geographic Populations of Drosophila pseudoobscura.

Abstract: Data are presented for mating choices in crosses between originate in two stages. The first stage involves geographic separation and the accumulation of genetic differences in the course of adjust- ment to different environments. The second stage involves selection for stronger isolation should the populations become sympatric (see Grant, 1966 for a review). The populations must become sufficiently different while allopatric so that crosses between them are less frequent or less successful' than crosses within each population. The most efficient mechanisms of isolation are those, such as sexual preference, which act before mating; they lessen the wastage of gametes in unsuccessful matings or lower the production of less fit hybrids. It is of interest to know how often mating preferences arise through genetic divergence in allopatric populations. Only in the genus Drosophila have a substantial number of species been tested. The tests of mating preference are made in the laboratory, of course, and do, not represent fully what occurs in nature. However, laboratory experiments do provide an indication of the situation in nature, and with this in mind, we have reviewed the literature to find tests of mating behavior in crosses between allopatric strains of Droso-phila species. The, review was intended to be representative, not exhaustive. Crosses between subspecies were excluded, since in Drosophila, unlike many other animal groups, named subspecies are likely to be well advanced toward full speciation. We are interested in mating preferences among popula- tions at the beginning of possible speciation. The data from the literature are summarized in Table 1.

Patterns of Genetic Similarity Between Larrea divaricata of North and South America

Abstract: Seeds of Larrea divaricata were collected from four Argentina and 34 United States sites, and certain morphological, anatomical, physiological, and cytological characteristics of the fruit and of seedlings grown from seed in a uniform environment were noted. The three warm deserts of the United States in which Larrea occurs exhibit an east-west cline of increasing aridity, with the Argentinian climate being overall most similar to the Chihuahuan. Mitotic chromosome counts made from root tips of seedlings in- dicated that a different chromosome race exists in each of the three United States deserts. Of some 16 other characteristics which showed significant desert differences, 15 exhibited east-west clines in the United States. Argentinian plants were overall most similar to 'Chihuahuan plants. It is difficult to say whether the strong east-west pattern of genetic divergence indicates adaptation to divergent environments, path of historic plant migration, or both. A hypothesis was developed that the present disjunct range of Larrea divaricata originated by Larrea of the Chihuahuan and Argentinian types evolving from a common trans- tropic prototype which later became extinct. The prototype was hypoth- esized to have been a minor element of the early Madro-Tertiary flora.

Effects of Diazinon Contamination on an Old-field Ecosystem

Abstract: A uniform 14-acre field on the Piedmont of New Jersey was abandoned following treatment of one half with a soil application of 14 lb active ingredients of diazinon per acre in May, 1966. Ecological parameters were used to assess the consequences of insecticide contamination in the treated half as compared to the untreated half of the field. In the first post-treatment growing season species diversity, total density, and net production of herbs were greater in the treated area than in the untreated control. Faunal simplification accompanied by ultimate resurgence in numbers occurred among the insects in the treated area. Soil microarthropod density in the treated area was depressed almost to zero during the summer of 1966 but recovered during the fall. Despite this, the disappearance rate of organic detritus was greater in the treated area. By the second year of abandonment, the contaminated area largely had equilibrated with the untreated area and no, differences persisted among the herbs or insects. Soil microarthropods, however, experienced mild resurgence and this apparently speeded the rate of disappearance of litter in the treated area. By utilizing an ecosystem approach to the pesticide problem it was possible to relate factors which rrmost studies of single components of the ecosystem have not done. The responses of the insects were found to be intimately related to those of the vegetation and resurgence apparently was more a consequence of changes in floristics induced by the insecticide than of reductions in natural enemies of the herbivores, as is commonly thought to be the case. The insecticide influenced rates of succession among both herbs and insects and an important consequence of contamination was an increase in floral diversity. Perhaps equally important was the apparent increase in rates of nutrient cycling induced by the diazinon.

Home Range of Crayfish Orconectes juvenalis

Abstract: Observations were made every 5 hours on five radioactively tagged crayfish, Orconectes juvenalis, in an intermittent Kentucky stream for three and one half weeks. Home areas range from 9.7 to 60.4 m2 in area and from 9.4 to 47.0 m in length. The differences do not appear to be directly related to size or sex. The female that was in berry when tagged was found to remain under one rock unless disturbed while carrying eggs, later to change her position as much as the other crayfish. The tendency to stay in one area, often under one rock was shown by all crayfish studied. For each individual, there were at least two sites at which it stayed or to which it returned for at least six observations or 30 hrs. Flooding did not result in loss of marked crayfish; no tendencies to be washed downstream or to migrate upstream are evident. INTRODUCTION Little is known about the home range of crayfish. Camougis and Hichar (1959) studied Orconectes virilis by trapping and marking them in a small pond in Massachusetts and concluded that the animals either do not have a limited home range or it is very large, over 30 m in length. Black (1963) worked with the stream-dwelling crayfish (Procambarus penni Hobbs and Procambarus bivittatus Hobbs) in Louisiana. By study-group marking and electric-shock collecting methods, he concluded that these invertebrates possess a home range of approximately 30 m in length. Merkle (1967), studying the home range of Orconectes juvenalis in a Kentucky stream by trapping and marking, generally recaptured the individuals within 30 m of their original capture sites but found that some occasionally ranged up to 60 m. The above studies all suffer bias because of faults in methodology. Camougis and Hichar used baited minnow traps, which likely affected the natural movement patterns of the animals by attracting animals to the bait and by preventing travels while the animals were in the traps. Also their failure to give distinguishing marks to the animals precluded the possibility of studying individual movements. Black (1963) captured his crayfish by shocking sections of a stream which he had separated by nets. He studied movements from one section of the stream to others. His method was such that he knew neither from what part of the enclosed section an animal was originally captured nor from what part it was later retaken. Also all animals were lumped and marked by sections; individuals were not followed. Merkle (1967) tagged 'her crayfish with different markings for each individual and thus was able to trace individual movements. However, baited minnow traps were used at scattered stations along the stream Present address: 32 Weskora Avenue, Pleasantville, New York 10570. 228 This content downloaded from 207.46.13.71 on Fri, 21 Oct 2016 05:02:33 UTC All use subject to http://about.jstor.org/terms 1969 MERKLE: HOME RANGE OF CRAYFISH 229 and these traps would affect the normal behavior of the crayfish. Therefore, the present project was designed to study the home range, movements and activity of crayfish with a minimum of disturbance to their normal behavior. METHODS AND MATERIALS Five crayfish (Orconectes juvenalis) were tagged in an intermittent third-order stream, Clemons Fork, Breathitt Co., Kentucky, for a 932-week period (17 May to 23 July 1967). A reference specimen has been deposited in the U. S. National Museum. Clemons Fork flows in a westerly direction, and depending on the amount of flow, varies from 1 to 5 m in width and from 5 to 100 cm in depth. During the time of the study there was a constant flow of water, and on 1 June 1967 a heavy rain caused the stream to flood, becoming 60 cm or more deep in all places. High waters started receding after two days. Although predation on small crayfish by Natrix and large fish was observed, none of the tagged individuals was lost during the main course of the experiment. Each crayfish was tagged with a 0.7 X 2.5 mm piece of Co60 alloy wire with an activity of about 55 microcuries. The tag was inserted into the ventral abdominal muscle by means of a hypodermic needle and plunger. The animals were individually marked by small triangles clipped out of the different uropods, and the cephalothorax length was taken for each individual. All crayfish were located every 5 hours for a 3V/2-week period (17 May to 8 June 1967) with a Thyac II survey meter with earphones, shoulder strap and scintillation probe. By walking carefully in the stream and sweeping the probe back and forth, the tagged individuals could be located from distances of 1.2 to 1.5 m, depending on the depth of the water and thickness of rock. New sites were marked with aluminum-foil-covered stones and, at the end of the study, the distances and directions of these sites, from one point were measured and plotted. Two further observations were made after this concentrated study, one 2 weeks later (24 June) when all but Crayfish 3 were relocated, and one 6 weeks later (23 July) when Crayfish 5 and 6 were relocated and removed from stream and the tag from Crayfish 2 was recovered. The shape and area of the home range of each individual were then determined by the modified minimum area method (Harvey and Barbour, 1965). RESULTS Crayfish 1, a second form male, was the smallest individual studied, with a cephalothorax length (from the tip of the rostrum to the posterior margin of the carapace) of 26 mm. He was located the farthest downstream in a pool 6 m wide and 15 to 75 cm deep. This individual has a home range with an area of 53 m2, and a length of 26 m. The range seems to be divided into two areas, with the larger section being used most frequently (Fig. 1). This individual remained, This content downloaded from 207.46.13.71 on Fri, 21 Oct 2016 05:02:33 UTC All use subject to http://about.jstor.org/terms 230 THE AMERICAN MIDLAND NATURALIST 81(1) with intermittent departures, at site 1 for 30 observations. During the flood of 1 June, this individual stayed at sites 10 and 11 and not until the water level had dropped considerably was he found downstream at site 12. Only toward the end of the study did Crayfish 1 travel upstream for a total of five observations. Two weeks later, he had returned to the periphery of the original area but he was not located one month later at the final check. Crayfish 2 was a female with a cephalothorax length of 33 mm. The tag of this individual was inserted into the dorsal abdominal muscles because she was in berry from the time of capture 19 May until 3 June (sites 1 through 8). She was located approximately 75 m upstream from Crayfish 1 in a shallow channel usually 1.4 m wide. The home range area of Crayfish 2 is 60.4 m2, the largest studied, and the total length of the range is 26.5 m (Fig. 2). While carrying eggs and young, this individual tended to stay in one place for extended

Ecological distribution of Hydracarina in north central Colorado

Abstract: Ninety-nine species of Hydracarina were collected in an extensive survey of streams, lakes, ponds, and hot springs of north central Colorado during 1965, 1966, and 1967; 72 are new for Colorado and three are new for continental North America. The faunas of lentic and lotic habitats are distinct, with only four species contributing appreciably to both faunas. The stream fauna is composed of 44 species. When the 29 most common stream species are analyzed on the basis of their altitudinal distributions and their habitat ranges for bound carbonates, ash content, organic content, and temperature, four groups are evident: euryzonaleuryokous species, with wide altitudinal and habitat ranges; euryzonalstenokous species, with wide altitudinal but narrow habitat ranges; altitudinally restricted-euryokous species; and altitudinally restrictedstenokous species. The ecological basis for these groups is the variable adaptability of the water mites coupled with the physical-chemical characters of Rocky Mountain streams. The effects of substrate, stream velocity, and pollution on the distribution of Hydracarina were found to be significant, but highly localized; aquatic plants exert a negligible influence. The maximum number of species was found between 2450 and 2700 m, where faunas from higher and lower elevations overlap and where numerous small streams provide a great diversity of habitats. Zoogeographic affinities of stream species are with faunas to the north and west, suggesting colonization of this region by northern species. The fauna of hot springs consists of only two species: Thermacarus nevadensis, a species common in hot springs; and Tyrrellia circularis, not previously reported from hot springs. Lakes and ponds yielded 66 species; their low frequencies and low abundance reflect their haphazard passive dispersal and their sensitivity to environmental factors. The common lentic species also form four distinct groups: plains species, tolerant of high concentrations of dissolved salts and high temperatures; relatively stenokous montane species; alpine species, largely high-altitude stream forms that have invaded lakes; and euryzonal species, which are highly euryokous. Aquatic plants play a significant but highly localized role in the distribution of lentic Hydracarina. The greatest number of species occurs in nonalkaline plains lakes where a great variety of habitats are available and montane and plains faunas slightly overlap. Most species of lentic Hydracarina have a wide Holarctic and Nearctic distribution; there is a considerable overlap of eastern and western faunas, and a close affinity with the northwestern fauna in some genera. A comparison of lotic and lentic faunas indicates that their major differences are the product of the divergent nature of the two types of habitat, while similarities reflect characters common to the Hydracarina as a group. INTRODUCTION Though the Hydracarina live in a wide variety of aquatic habitats throughout the world, we know few details of their ecological distribu1 Contribution No. 52, Limnology Laboratory, University of, Colorado. 2 Present Address: Biology Department, Southwest Texas State College, San Marcos, Texas 78666.

Effects of Change of Characters and of Number of Characters in Numerical Taxonomy

Abstract: Information on 214 morphological characters for 30 taxospecies of the genus Salix, willows, was obtained. Ten analyses were made using different subsets of these characters. The purpose of these analyses was to determine whether different analyses yield different results. Each analysis used the same coefficient of distance in Eu,clidean space to obtain similarities among the taxospecies. The unweighted pair group method (averages) was, used for cluster analysis. Results reveal different clusters of taxospecies with each analysis, although certain groups remained invariant in most of the analyses. In the absence of other information, those analyses using all available data are judged to estimate best the phenetic relationships among taxospecies in the context of all possible characters. The potential value of numerical taxonomy in biosystematics is indicated by its ability to, serve as an efficient context for the generation of hypotheses of biosystematic value. INTRODUCTION Crovello, (1968a) investigated the effect of change of number of OTU's (operational taxonomic units; see Sokal and Sneath, 1963) on the results of clustering in numerical taxonomy. I found a significant effect, which motivated the present study. The purpose of the present paper is to investigate the effect of change of characters and of number of characters in numerical taxonomy. Katz and Torres (1965) carried out an analogous study but they varied the statistical index. In zoology Boyce (1964), Minkoff (1965), Michener and Sokal (1966), and Ehrlich and Ehrlich (1967) have made somewhat similar analyses. The present investigation will also, serve as a test of the hypotheses of nonspecificity and of the matches asymptotes (Sokal and Sneath, 1963). The primary concern of the present study is analysis of part of the methodology of numerical taxonomy to, ascertain its value for plant systematics. The particular species used in the present study serve as a context in which results of the different taximetric analyses can be observed. Although increased knowledge about these species is a natural by-product, the evaluation of the present results in terms of formal taxonomy for the group, is the subject of another paper. MATERIAL AND METHODS Crovello (1966) obtained data on the willows of California as a by-product of a study of the taxonomy of section Sitchenses of the genus Salix. Measurements were made on 372 plants representing the 30 taxospecies of the genus Salix in California. The total number of morphological characters measured was 214. Details of sampling and of the methods of character state coding can be found in Crovello (1966, 1968b). Table 1 lists the 30 taxospecies of California recog-

A Comparison of Microtus pennsylvanicus Home Ranges As Determined by Isotope and Live Trap Methods

Abstract: Microtus pennsylvanicus were systematically live-trapped to gain recapture data for home range determination. Using this information, trap-revealed home ranges were plotted by several currently used methods. The same animals were then subjected to isotopic tracing. The location of each of the eight study animals was determined at approximately 45-minute intervals. These data were used to calculate isotope-revealed home ranges. Trap-revealed and isotope-revealed home ranges were then compared. This study indicates that the home ranges determined by the isotope method reflect more accurately the true situation than did those ascertained from live-trapping methods. Home ranges estimated by live-trapping methods gave a false impression of the location and actual size of the true home ranges. A study of the sequence and positions of recapture of some of the study animals indicated a shift of home range over a relatively short period of time, thus showing that time is a vital factor in the interpretation of any home range study.

Studies on monogenetic trematodes. XXXIX. Exotic species of Monopisthocotylea with the proposal of Archidipkctanum gen.n. and Longi-haptor gen.n.

Abstract: The family Diplectanidae Bychowsky, 1957, and the genera Ancylodiscoides Yamaguti, 1937, Heteroncocleidus Bychowsky, 1957, and Trianchoratus Price and Berry, 1966, are emended. Archidiplectanum gen. n. and Longihaptor gen. n. are proposed and the following new species are described: Ancylodiscoides caecus from an unidentified fish (USNM No. 202610), Thailand; Archidiplectanum archidiplectanum from Gnathonemus petersi (Gunther), western Africa; Heteroncocleidus gracilis from Colisa labiosa (Day), India; Longihaptor longihaptor from Cichla ocellaris Bloch and Schneider, Brazil; Urocleidoides amazonensis and U. catus (both) from Phractocephalus hemiliopterus (Bloch and Schneider), Brazil; U. megorchis from Sorubim lima (Bloch and Schneider), La Plata Drainage to the Magdalena, S. A.; U. robustus from an unidentified South American catfish; and U. variabilils from Symphysodon discus Heckel, Brazil. Trianchoratus acleithrium Price and Berry, 1966, is redescribed. Conspicuous survival of immediately ancestral and liaison species of some Monopisthocotylea is suggested by present information, part of which is contributed by this investigation. Such information implies that the barriers between different genera, subfamilies, and even families are becoming less formidable and in some cases apparently are disappearing. It is postulated that when a comprehensive number of monopisthocotylean species are described, genera and higher taxa may insensibly intergrade with cne another as segments in a continuous succession of species that differ radically only at remotely separated points. On a generic level this phenomenon is illustrated in the Ancyrocephalinae by the originally disjunct genera Cleidodiscus Mueller, 1934 (Mizelle and Hughes, 1938), Urocleidoides Mizelle and Price, 1964 (Mizelle, Kritsky and Crane, 1968), and Urocleidus Mueller, 1934 (Mizelle and Hughes, 1938). Cleidodiscus and Urocleidus, being typically Nearctic genera, occur on fishes very different from those in the Neotropical Region that harbor species of Urocleidoides. The genus Cleidodiscus is characterized by a sinistral vagina (when present) and a proximally articulated cirrus and accessory piece. Urocleidoides is distinguished principally by a sinistral or ventral vagina (when present) and usually a proximally nonarticulated cirrus (coiled shaft) and accessory piece. Principal characteristics of Urocleidus are a 1 Present address: Department of Zoology, University of Illinois, Urbana

Ecology of Aspen in Gunnison County, Colorado

Abstract: The ecology of quaking aspen was studied in Gunnison County, Colorado. In the study area, aspen stands often take the form of small islands surrounded by fescue grasslands. At its upper altitudinal limits, aspen generally abuts the spruce-fir forest. The greatest number of trees were 4- to 7-in DBH with only a few being greater than 10-in DBH. Aspen reproduction is evident, but many of the trees below 4-in DBH were dead. The aspen understory is very lush and is characterized by many tall herbaceous species. The disjunct distribution of several understory species does not seem related to soil or aspect conditions. Aspen soils are generally more fertile than adjacent spruce-fir or fescue grassland soils. All soils possessed several characteristics of immature soils: 1) little variation in silt and clay content throughout the profile, 2) little horizon and structural development, and 3) little variation in per cent base saturation throughout the profile. Aspen seed retained good viability after cool storage for 1V/2 years. The pattern of morpho- logical characteristics, site conditions, and leafing times is much more complex than that reported in other areas in the central Ro,cky Moun- tains. Aspen appears to be successional to, spruce-fir in the present study area, although in local sites that may be inaccessible to a spruce-fir seed source the present mosaic pattern of aspen groves within fescue grassland or sagebrush may persist.

Studies on monogenetic trematodes. XL. New species from marine and freshwater fishes.

Abstract: This paper presents descriptions of new species as follows: Anacanthorus brevis from Brycon melanopterus (Cope) ; Dactylogyrus navarroensis from Hesperoleucas navarroensis Snyder; Diplectanum jaculator and D. toxotes from Toxotes jaculator (Pallas) ; Parahaliotrema affinis from Chaetodon auriga Forskal and C. lunula (Lacepede); P. brevis from Acanthostracion quadricornis (Linnaeus); P. cornutus from Bodianus pulchellus Poey; P. grandis from Chaetodon auriga, C. lunula and C. setifer Bloch; P. pacificus from Chaetodon nigrorostris (Gill); and P. zebrasoma from Zebrasom.a veliferum (Bloch). All hosts were frozen initially for a minimum of 48 hours except Brycon melanopterus (Cope), which was placed directly into 10% formalin. Further preparation concerning mounting, observation, measurement, illustration, and descriptions including nomenclature were employed as given by Mizelle and Kritsky (1967), Kritsky and Mizelle (1968) and Mizelle, Kritsky and Crane (1968). All measurements are in microns. Acknowledgments.-The authors are indebted for aid in the collection of host specimens to the following (all California): M. R. Brittan, Sacramento State College, for Brycon melanopterus (Cope); J. Wittmer Crane, University of California, Davis, for Hesperoleucas navarroensis Snyder; R. P. Dempster, Steinhart Aquarium, California Academy of Sciences, San Francisco, for Bodianus pulchellus Poey, Chaetodon auriga Forskal, C. lunula (Lacepede), C. nigrorostris (Gill), C. setifer Bloch, Acanthostracion quadricornis (Linnaeus), Toxotes jaculator (Pallas) and Zebrasoma zelifer (Bloch). Especial thanks are due S. H. Weitzman, U.S. National Museum, Washington, D.C., for aid in the identification of fishes. This investigation was supported by the National Science Foundation (GB 6455). Anacanthorus brevis sp. n. (Figs. 21-23) Host and locality.-Brycon melanopterus (Cope) (Characidae), Rio Xeruiny near Terra Preta, Amazonas, Brazil, S. A. Location on host.-Gills. Type specimens.-Holotype, USNM Helm. Coll. No. 70967. Paratypes in authors' collections. Description (based on three specimens).-Dactylogyridae, Ancyrocephalinae. Length 386 (382-389), width 122 (93-152). Cephalic lobes poorly developed; head organs and cephalic glands inconspicuous. Eyespots four, anterior pair smaller, distance between members of pairs variable; accessory eyespot granules in trunk, peduncular and cephalic areas. Pharynx broadly ovate, width 30 (23-37); gut normal. I Present address: Department of Zoology, University of Illinois, Urbana

A Method for Estimating Age in the California Vole, Microtus californicus

Abstract: Several methods for estimating age are developed for Microtus californicus, based on cranial and body measurements taken from 373 known-age individuals varying in age from 14 to 1058 days, all of which were born and raised in the laboratory. Ten measurements, selected from an initial sample of 17, were subjected to a multiple regression analysis. Six regression formulae gave estimates of age with mean errors that varied from 9.2 days for males less than 100 days old to 38.5 days for males more than 100 days old. An alternative method utilizes growth curves for the characters found to be most useful in age estimation. It combines estimates made from each variable by means of formulae that weight each variable according to its predictive power. Average estimation errors varied in this case from 10.9' days for males less than 100 days old to 52.0 days for females over 100 days old. The second method permits ageing of older individuals not covered by the regression formulae and also accommodates missing measurements. Schemata are provided which permit objective choice of the most appropriate ageing formula for each unknown-age individual. Mean estimation errors were plotted against estimated age; expected errors increase linearly to 100 days at one year estimated age. A group of 24 known-age individuals permitted limited testing of the applicability of the methods to field populations. Accurate estimates were achieved for those individuals not subjected to stunting for more than three months (age range: 40 to 325 days). Individuals stunted for three months or more had their ages underestimated in proportion to the length of time in which they lived under stunting conditions (age range: 138 to 412 days). We conclude that the methods proposed are sufficiently accurate for many ecological studies. INTRODUCTION The age distribution of a particular population is a fundamental variable in demographic studies. In spite of its importance, however, our ability to estimate the ages of individual organisms remains a chronic problem for most species. This inability is particularly troublesome in microtine rodents because of their hypsodont dentition, sometimes marked sexual dimorphism, and variable individual growth patterns. Nevertheless, microtines are frequently the subject of intensive ecological study. This is in part due to their widespread distribution in the Holarctic, their abundance over large areas, their importance in community food webs, and the three to four-year population density oscillations exhibited by many species. Our objective in this study has been to determine to what extent various cranial and body dimensions can be used to estimate age in the California meadow vole, Microtus californicus. We wanted to know, for example, what measurements carried the most information about age and over what age ranges they were most useful. If unacceptably large errors were associated with age estimates based on these features, then attempts to use such measurements in ageing

A Limnological Study of a Tennessee Cold Springbrook

Abstract: A one-year limnological investigation was conducted on an unnamed cold springbrook in Putnam County, Tennessee. The study was undertaken to analyze the components of invertebrate biocoenoses, to record population fluxes, and to determine possible factors affecting abundance and interactions between members of the communities of a relatively uniform habitat. Fifty-nine taxa of invertebrates were recorded. Relative abundance was greatest in February and lowest in July. The surrounding deciduous forest was determined to have the greatest effect on species composition and abundance of the fauna of the springbrook.

Digestive anatomy of terrestrial Isopoda: Armadillidium vulgare and Armadillidium nasatum

Abstract: The digestive tract of Armadillidium is essentially a straight tube, and consists of a foregut, a midgut, and a hindgut. The foregut is differentiated into an esophagus and cardiac and pyloric stomach chambers. The triturating mechanism, the gastric mill, is de- rived from the chitinous intima, and is the most conspicuous aspect of the cardiac stomach. The intima of the pyloric stomach forms a strain- ing apparatus. The hindgut is short, and opens by way of a terminal anus. The foregut and the hindgut are histologically similar, their walls consisting of a chitinous intima, a mucosa of columnar epithelium, con- tinuous bands of circular muscle, and scattered bundles of longitudinal muscle. The midgut possesses two pairs of hepatopancreatic caeca, a dorsal longitudinal typhlosole, and a midgut sphincter. The structure of the midgut wall includes a folded chitinous intima, a syncytial mucosa with intraepithelial muscle fibers, and a basement membrane. The mid- gut muscularis forms a segmented checkerboard pattern of spaced inner circular bands and spaced outer longitudinal bands. The hepatopan- creatic caeca are hollow blind tubes composed of large columnar cells with one or two nuclei near their bases and conspicuous vacuoles near their lumen surfaces.

Differential Burning Response of Poa pratensis Fields and Andropogon scoparius Prairies in Central Wisconsin

Abstract: The Buena Vista Marsh on the central Wisconsin sand plains was converted from sedge meadow and tamarack on peat to agricultural uses by drainage and peat fires 50 years ago. Today, the exposed sandy soils support a cover of predominantly bluegrass. Periodic burning is being used on a small scale to maintain conditions favorable for the only major remaining population of prairie chickens in Wisconsin. This study investigates the differences in response to fire of (i) bluegrass and (ii) a cover of native prairie vegetation, both considered on ridges and depressions within the gentle topography. Unlike the results reported by several authors, these studies show that on favorable sites bluegrass density and fruiting can be greatly stimulated. The native grass, little bluestem, is not always favored by burning; on ridge sites no, increase in standing crop occurred with burning. It is concluded that the burning has a highly desirable effect on the drymatter production of prairie species on mesic sites, is detrimental to bluegrass on dry sites, and creates a favorable open habitat for the spread and establishment of drought-tolerant native species on the extreme ridge sites. INTRODUCTION The response of native prairie species to fire has been reported by Aldous (1934), Curtis and Partch (1948), Aikman (1955), Kucera and Ehrenreich (1962), Ehrenreich and Aikman (1963), Hadley and Kieckhefer (1963), Brown (1967), and others. Many of these papers have emphasized fire in relation to the management of prairie vegetation. On Buena Vista Marsh in central Wisconsin, however, fire is used on bluegrass (Poa pratensis) fields to discourage invasion of woody species. This maintenance of open habitat is part of the prairie chicken management project on the Marsh (Hamerstrom et al., 1957). Since fire is often detrimental to Poa pratensis (Aldous, 1934; Ehrenreich and Aikman, 1963; Hadley and Kieckhefer, 1963), and since its use as a management technique on Buena Vista Marsh is still on a trial basis, field experiments were carried out to assess the effects on both prairie and bluegrass vegetation within the management lands. The work was financed by the Davis Fund in 1966, and by a grant from the Wisconsin Alumni Research Foundation in 1967. The authors wish to acknowledge Dr. F. N. Hamerstrom for his helpfulness throughout the study and Dr. P. H. Zedler for criticism of the manuscript. STUDY AREA Buena Vista Marsh is an area of about 50,000 acres (20,235 ha) located in southwestern Portage Co., Wisconsin. Prior to drainage in 1 Present address: Department of Botany, University of Missouri, Columbia, Missouri 65201.

The Use of Artificial Substrates in Pollution Surveys

Abstract: Artificial substrates were constructed from pressed Masonite board and suspended in the Minnesota and Mississippi Rivers during the summer of 1965. The benthos recovered from the Mississippi River substrates reaffirmed the zones of water quality defined by results from conventional bottom sampling techniques, and analysis of chlorophyll-a indicated a progressive increase in periphyton crop below the major contributors of organic pollution. The numbers and kinds of benthic animals gathered from the Minnesota River substrates differed from results obtained from conventional bottom sampling methods, and suggest that the factor limiting river biota is a lack of suitable natural habitats rather than chemical quality.