Comparative ecology of Sarcobatus baileyi and Sarcobatus vermiculatus in estern California

Greasewood ( Sarcobatus ) is a succulent-leaved, halophytic shrub of North American origin. The genus comprises 2 species: Sarcobatus baileyi and Sarcobatus vermiculatus. Sarcobatus vermiculatus is common throughout much of western North America, but S. baileyi is much more limited in distribution and was previously thought to be endemic to Nevada. Here we document and describe a S. baileyi population in eastern California, comparing its morphology and ecology to an adjacent S. vermiculatus population. Morphologically, S. baileyi is smaller in stature but produces larger seeds; however, fewer S. baileyi seeds germinated and survived a 20-day laboratory incubation compared to seeds of S. vermiculatus. Sarcobatus baileyi has higher leaf Na concentrations and operates at much lower plant water potentials than S. vermiculatus under field conditions; however, no significant differences were observed between the 2 species in long-term water-use efficiency as measured by leaf δ13C. Leaf Na concentrations were very low in both species. Overall, these species differ greatly in a number of traits that are consistent with the upland, nonphreatophytic character of S. baileyi, which is in stark contrast to the phreatophytic character of S. vermiculatus. Both species, however, are very salt tolerant and have low leaf N concentrations, indicating the low nutrient availability and the potentially high salinity of their extreme habitats. Further investigation of comparable desert ridge environments should be conducted to determine the extent of S. baileyi in eastern California, and common garden comparisons of the 2 species should be conducted to compare their ecophysiological traits. El ";greasewood” ( Sarcobatus ) es un arbusto halofítico de origen norteamericano con hojas suculentas. El género consta de dos especies: Sarcobatus baileyi y Sarcobatus vermiculatus. Aunque S. vermiculatus es común en gran parte del oeste de Norteamerica, S. baileyi tiene una distribución mucho más limitada. Se pensaba anteriormente que S. baileyi era endémico a Nevada, pero aquí documentamos y describimos una población en el este de California, comparando su morfología y ecología con las de una población adyacente de S. vermiculatus. Morfológicamente, S. baileyi es más pequeña de altura, pero produce semillas más grandes. Sin embargo, menos semillas de S. baileyi germinaron y sobrevivieron a una incubación en laboratorio de 20 días, comparado con S. vermiculatus. Sarcobatus baileyi opera con potenciales de agua mucho más bajos que los de S. vermiculatus en condiciones de campo y tiene mayores concentraciones de Na en sus hojas. No obstante, no se observaron diferencias significativas en la eficiencia del uso de agua a largo plazo, medida en términos de δ13C entre las 2 especies. Las concentraciones de N en las hojas fueron muy bajas en ambas especies. En general, estas especies difieren mucho en varios rasgos que son consistentes con el carácter no freatofítico de S. baileyi de tierras altas, el cual contrasta claramente con el carácter freatofítico de S. vermiculatus. Ambas especies, sin embargo, son bastante tolerantes a la sal y tienen concentraciones bajas de N en hojas, lo cual indica la baja disponibilidad de nutrientes y la potencial alta salinidad en sus hábitats extremos. Investigaciones adicionales en ambientes comparables de bordes desérticos deberán llevarse a cabo para determinar la extensión S. baileyi en el este de California, además de comparaciones de las dos especies en jardín para comparar sus rasgos ecofisiológicos.     

Effects of osmotic potential, potassium chloride, and sodium chloride on germination of greasewood ( Sarcobatus vermiculatus )

Greasewood ( Sarcobatus vermiculatus [Hook.] Torr.) (Chenopodiaceae) typically grows on salt-affected soils where its germination requirements may reflect characteristics necessary for establishment in saline environments. The objective of this study was to determine the effect of osmotic potential and specific ions on the germination of seeds from three populations of greasewood. Seeds were germinated at 20 C in solutions of polyethylene glycol with water potentials ranging from –0.3 to –2.2 MPa that contained 0 to 68480 µmol·L –1 sodium chloride (NaCl) or 0 to 53640 µmol·L –1 potassium chloride (KCl). Germination of two populations was reduced by increasing salt concentration and decreasing osmotic potential; germination of one population was reduced by declining osmotic potential. No seeds germinated at an osmotic potential lower than –1.6 MPa. For all populations, days to 50% of final germination increased and abnormal germination decreased as osmotic potential declined. Comparison of our results with those from other studies suggests geographic ecotypic development in response to osmotic potential and NaCl and KCl concentrations during germination.     

The ploidy races of Atriplex confertifolia (Chenopodiaceae)

Previous accounts of polyploidy in the North American salt desert shrub Atriplex confertifolia (shadscale) have dealt with the distribution of polyploidy and the morphological and secondary chemical differences between races. The present study amplifies these studies and reveals additional ploidy-flavonoid races, with ploidy levels known to extend from 2x to 12x, and all except 2x and 12x represented by races with and without 6-methoxylation of flavonol compounds. Results of this study show that diploids across their range have about 113% as much DNA per genome as do polyploids and that parallel variation in monoploid genome size between diploids and accompanying polyploids can be shown in different parts of the species’ range. Polyploidy, therefore, appears to have developed independently in several areas of the western United States. Hexaploids are generally not as common as octoploids in shadscale, which could be an indication of diploidization of older tetraploid races. Informes anteriores sobre la poliploidía en el arbusto Atriplex confertifolia (“shadscale”) del desierto de sal norteamericano, han tratado la distribución de la poliploidía, las diferencias químicas secundarias y las diferencias morfológicas entre razas. El presente estudio amplía los estudios previos y revela razas ploidía-flavonoides adicionales, con niveles de ploidía que se sabe que van de 2x a 12x, y todos, con excepción de 2x y 12x, están representados en razas con y sin 6-metoxilación de compuestos de flavonoles. Durante el estudio descubrí que los diploides a lo largo de su rango de distribución tienen alrededor del 113% más ADN por genoma que los polploides. También descubrí que la variación paralela en el tamaño del genoma monoploide entre los diploides y sus poliploides correspondientes, se puede manifestar en diversas partes del rango de distribución de la especie. La poliploidía, por lo tanto, parece haberse desarrollado de forma independiente en varias regiones del occidente de los EE.UU. Los hexaploides son generalmente menos comunes que lo octoploides en el shadscale, lo cual podría ser indicio de diploidización de razas tetraploides más antiguas.     

High nitrogen availability does not improve salinity tolerance in Sarcobatus vermiculatus

Natural and anthropogenic changes in basin lake levels in the western U.S. expose saline, alkaline substrates that are commonly colonized by shrubs in the Chenopodiaceae. On a chronosequence of recently exposed substrates at Mono Lake, California, Sarcobatus vermiculatus has greatest biomass accrual, seed production, seedling establishment, and leaf N at younger sites where soils are extremely saline and alkaline. These field observations and an understanding of the role of N-containing compatible solutes in salinity tolerance of halophytes led to our prediction that Na and N interactions stimulate Sarcobatus performance. To test this, we grew Sarcobatus juveniles for 2 years in the greenhouse at 4 levels of NaCl (5, 100, 300, and 450 mM) and 3 levels of N (0.04, 0.4, and 8 mM) in a randomized, complete-block design. Contrary to our expectations, high N availability did not induce salt-stimulated growth nor did it increase salinity tolerance in Sarcobatus . Increased N nutrition also had no significant effect on leaf cation ratios or selectivity. Plants grown at high salinity had significantly lower leaf K:Na, Ca:Na, and Mg:Na ratios than plants grown at lower salinity. However, plant selectivity for the macronutrient cations remained high, even at 450 mM NaCl. Without such high selectivity, the cation nutrition of Sarcobatus would decline to even lower levels, resulting in severe nutrient deficiencies. This study suggests that the ability of Sarcobatus to attain high leaf N, rather than an interaction between Na and N, enhances its performance at saline sites. In addition, the ability of Sarcobatus to maintain high macronutrient cation selectivity despite high salinity allows its distribution to extend to extremely saline and alkaline substrates in this arid system.     

Comparative habitat and community relationships of Atriplex confertifolia and Sarcobatus vermiculatus in central Utah

Thirty-four study sites were established in shadscale ( Atriplex confertifolia [Torr. & Frem.] Wats.) and greasewood ( Sarcobatus vermiculatus [Hoov. Torr. in Emory) communities bordering Utah Lake in central Utah. Differences in species composition, vegetation, and soil characteristics were assessed. Significant differences in soil factors between the two communities were found for sand, calcium, manganese, zinc, and copper. Soluble salts and sodium concentrations were generally higher in the greasewood type, but differences were not significant. Major differences were found in understory species, with burr buttercup ( Ranunculus testiculatus Grantz) showing significantly greater cover in the shadscale community and cheatgrass ( Bromus tectorum L.) showing significantly greater cover in the greasewood community.     

Taxonomic revision of Steganacarus (Steganacarus) magnus (Nicolet, 1855) (Acarida,Oribatida)

The classical taxon, Steganacarus (Steganacarus) magnus (Nicolet, 1855) is redescribed on the basis of topotypic material. The study and the comparison of many European and North African populations reveals a variation in the size of the anterior notogastral tectum and consequently enables another classic entity, S. (Steganacarus) anomalus (Berlese, 1883), to be put into synonymy. These two different ecophenotypes, in the authors' opinion, seem to be linked to the presence of xeric low-altitude southern environments (S. (S.) magnus f. anomala) or cool higher-altitude mid-northern environments (S. (S.) magnus f. magna).     

A new species of Protocladorchis (Paramphistomidae,Dadaytrematinae) from Pangasius nasutus (Bleeker, 1863) in Thailand

Protocladorchis chinabutae sp. nov. from Pangasius nasutus in Thailand differs from Protocladorchis burmanicus mainly in the size, shape and position of the testes and from P. pangasii in body shape, egg size and the shape of the pharyngeal sacs. The genus has not previously been reported from Thailand.     

Palpal loss,single palp copulation and obligatory mate consumption in Tidarren cuneolatum (Tullgren, 1910) (Araneae,Theridiidae)

Males of Tidarren cuneolatum (Tullgren, 1910) amputate one of their palps a few hours after the penultimate moult, like T. sisyphoides (Walckenaer, 1841) from the USA (Branch, 1942). Hence adult males, which are minute, have only one palp, either left or right randomly. This palpal organ is not oversized, when compared with other small spiders. During courtship females are unusually active, signalling receptivity by continuous twanging with legs II. Males construct a mating thread. Copulation involves one insertion, which lasts ca 4 min. Thus, only one receptaculum is inseminated during copulation. With the advance of insertion the male's prosoma becomes shrunken. Copulation regularly ends in mate consumption. In copulation with a virgin female the palp was inserted contralaterally. Females taken in the field had both receptacula filled with sperm and therefore were polyandrous. Re-mating was also observed in the laboratory. Remarkably the second male performed an ipsilateral insertion, if it possessed the same palp as the previous male. Probably the virgin receptaculum was recognized. Postembryonic development is rapid in males, which moult three times and mature ca 41 days after hatching from the cocoon. Females need four or five moults and ca 69 days to reach maturity and then survive ca 2-4 months.     

The juvenile stages of Parastacus brasiliensis (von Martens, 1869) (Crustacea,Decapoda, Parastacidae)

The family Parastacidae consists of the freshwater crustaceans popularly known as crayfishes or crawfishes. Only the genus Parastacus occurs in Brazil, with P. brasiliensis (von Martens, 1869) endemic to the state of Rio Grande do Sul in southern Brazil. Parastacids have direct development, ecloding as juveniles. In laboratory‐reared specimens, juvenile I stage is similar in morphology to the adult, with no setae on most appendages, absence of uropods and presence of a hook on the dactyl of pereiopods 4 and 5. The juvenile II retains juvenile I characteristics but has more setae, which are more varied in morphology. The juvenile III possesses setae as the adults, fully formed uropods and the hooks on pereiopods 4 and 5 are substituted by an apical rectilinear dactylus.     

Foraminiferan (Protozoa) epizoites on the anthuridean (Crustacea,Isopoda) Calathura brachiata (Stimpson)

Foraminiferan epizoites were studied on the isopod Calathura brachiata (Stimpson). Most individuals found belonged to the genus Cibicides. The foraminiferans were either rare or quite frequent on Calathura brachiata, indicating patchy occurrence of living foraminiferans. They were most frequent on the anterior part of the body (head, first pereonites) and the first two pairs of legs (pereopods). This pattern, which is unusual among foraminiferan epizoites on isopods, is explained by habitat selection of the foraminiferans and the behaviour of the isopod, which presumably rests between feeding with the anterior part of the body held in an upward position, allowing foraminiferans to settle on mouthparts and on the legs (first two pereopods) used in grasping prey. The size range of the foraminiferans indicates that settling of foraminiferans from the water column is more important for the development of foraminiferan epibiosis on Calathura than migration of individuals from the bottom and this may be the general pattern for most isopod species.     

Observations on courtship,mating and sexual maturity in Portunus pelagicus (L., 1766) (Crustacea,Portunidae)

Summary

Larvae of Alpheus heterochaelis from North Carolina hatch from large eggs as advanced zoeae, usually moult three times, and exhibit almost no linear growth during a short (4 days at 25°c) larval development. Stage I lasts 6 hours at most and is sometimes skipped; III lasts about twice as long as II. Individuals simultaneously exhibiting characteristics of Stage III and the postlarva were occasionally seen. The three zoeal stages and postlarva are described in detail and illustrated. Stages in embryonic and juvenile development and the hatching process are briefly described.

An ‘extended’ pattern of larval development, characteristic of most alpheid species, is described in a general way, and the ‘abbreviated’ development of A. heterochaelis compared to it. At hatching, A. heterochaelis larvae bear rudimentary pereiopods and pleopods; other structures are at the same level of development in both patterns, but subsequent morphogenesis is faster in A. heterochaelis. Larval development of Synalpheus spp., some of which exhibit extreme abbreviation or direct development, is briefly described with reference to the A. heterochaelis pattern.     

Copepodid stages of laboratory-reared Astericola asterinae (Bocquet, 1952) (Copepoda,Poecilostomatoida, Lichomolgidae), a copepod associated with Asterina gibbosa (Pennant, 1777) of Lake Faro (Messina)

We describe the five copepodids of Astericola asterinae (Bocquet, 1952) a poecilostomatoid copepod (family Lichomolgidae), reared in the laboratory. It shows only very slight sexual dimorphism in the third segment of C5 maxilliped. Our study of the copepodid development, together with the observations of Carton (1964), Bocquet et al. (1970) and Conradi et al. (1993), support the separation of A. asterinae from its sister species A. clausi (Rosoll, 1889).