Chrysophycean stomatocysts from the postglacial sediments of a High Arctic lake

1988 ◽  
Vol 66 (6) ◽  
pp. 1117-1128 ◽  
Author(s):  
Katharine E. Duff ◽  
John P. Smol
Keyword(s):  
Species Composition ◽  
Light Microscopy ◽  
High Arctic ◽  
Ellesmere Island ◽  
Arctic Lakes ◽  
Ecological Research ◽  
Stratigraphic Analysis ◽  
Morphological Detail ◽  
Electron And Light Microscopy ◽  
Scanning Electron

Twenty-six chrysophycean stomatocyst morphotypes were described from the postglacial sediments of a small, rock basin lake near Baird Inlet, Ellesmere Island. Scanning electron and light microscopy were used to classify the stomatocysts, following the guidelines of the International Statospore Working Group. None of the stomatocysts could be related with certainty to the chrysophyte species that produced them, but sufficient morphological detail is present in most of the stomatocysts to allow for taxonomic differentiation. A stratigraphic analysis of the dominant stomatocyst morphotypes revealed that chrysophyte species composition changed most markedly during the lake's early development but then remained relatively constant. This study demonstrated that chrysophycean stomatocysts provide useful paleoecological information in High Arctic lakes, but further taxonomic and ecological research is required to fully exploit these microfossils.

Setal morphology of grooming appendages in blue crabs Callinectes sapidus Rathbun, 1896 and stone crabs Menippe mercenaria (Say, 1818) (Decapoda: Brachyura: Portunidae, Menippidae)

2019 ◽  
Vol 39 (4) ◽  
pp. 357-377
Author(s):  
Jen L Wortham ◽  
Stephanie Pascual
Keyword(s):  
Light Microscopy ◽  
Functional Morphology ◽  
Sensory Input ◽  
Callinectes Sapidus ◽  
Time Budget ◽  
Activity Level ◽  
Body Regions ◽  
Electron And Light Microscopy ◽  
Insight Into ◽  
Scanning Electron

Abstract Respiration, sensory input, movement, and molting rely on crustacean body regions being free of fouling. While the grooming appendages of shrimps have been described, few studies have documented the functional morphology of grooming appendages in brachyuran crabs. Because shrimps and brachyurans have very different body morphology and grooming behaviors, their grooming setae may vary. The morphology of grooming appendages of blue (Callinectes sapidusRathbun, 1896) and stone (Menippe mercenaria (Say, 1818)) crabs were investigated to gain better insight into their efficiencies in decreasing fouling. Callinectes sapidus is an active swimmer, migrates through currents across estuaries, spends less time grooming, and is exposed to more environmental variants in contrast to M. mercenaria, which has a lower activity level and spends more time grooming. To compensate for this higher activity level and lower grooming time budget, C. sapidus was predicted to have more setal types on its grooming appendages as compared to M. mercenaria. Thirteen different body appendages/regions involved in grooming are described in both species by using scanning electron and light microscopy. We documented the morphology, presence or absence of setal patches, and types of setae in 104 different grooming appendages and groomed body regions. Of 25 types of setae, nine are unique to C. sapidus, rejecting the hypothesis that C. sapidus have more diverse grooming setae. Menippe mercenaria has denser setal patches and less fouling than C. sapidus. Nine new setal types are described. Fouling, setal diversities, and functions that correspond to grooming behaviors are discussed.

ZOOPLANKTON OF LAKE HAZEN, ELLESMERE ISLAND, AND A NEARBY POND, WITH SPECIAL REFERENCE TO THE COPEPOD CYCLOPS SCUTIFER SARS

1964 ◽  
Vol 42 (4) ◽  
pp. 613-629 ◽  
Author(s):  
I. A. McLaren
Keyword(s):  
Special Reference ◽  
Standing Crop ◽  
Dry Weight ◽  
High Arctic ◽  
Ellesmere Island ◽  
Arctic Lakes ◽  
Net Production ◽  
Daphnia Middendorffiana ◽  
Ice Conditions ◽  
Cyclops Scutifer

Zooplankton was studied in the large, high-arctic Lake Hazen and in a small nearby pond. Primary (O2) production in Lake Hazen may have occurred largely before the ice began to melt, but was unmeasurable in summer. Primary production in the pond was about the same as in other small arctic lakes, Cyclops scutifer was overwhelmingly dominant in Lake Hazen. C. scutifer and Daphnia middendorffiana were commonest in the pond. C, scutifer is annual in Scandinavia, often with coexisting spring-born and fall-born generations. On Ellesmere Island the pond appears to contain alternating annual and biennial generations, whereas the species is strictly biennial in Lake Hazen. Numbers of C. scutifer in Lake Hazen were greatly reduced as a result of summer ice conditions between 1958 and 1961, while the rotifer Keratella hiemalis increased. Estimated mean standing crop (96 mg/m2) and net production (1.0 mg/m2 day) in dry weight ol C. scutifer in Lake Hazen during the summer of 1958 were extremely low. In early August the crop of this species in the pond was abont the same as in Lake Hazen, but net production was sonic 15 times as large, and other zooplankters added considerably to crop and production of the pond.

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