Search results for "Crustacea"

Accumulation of Tetradifon in an Algae ( Nannochloris oculata ) and the Cladoceran, Daphnia magna

1996

Heading which way? Y-maze chemical assays: not all crustaceans are alike

2015

In a world full of chemicals, many crustaceans rely on elaborate olfactory systems to guide behaviors related to finding food or to assess the presence of conspecifics and predators. We analyzed the responses of the isopod Saduria entomon to a range of stimuli by which the animal is likely to encounter in its natural habitat using a Y-maze bioassay. In order to document the efficiency of the experimental design, the same bioassay was used to test the behavior of the crayfish Procambarus fallax whose ability to track odors is well documented. The crayfish performed well in the Y-maze and were able to locate the source of a food-related odor with high fidelity. The isopod S. entomon reacted i…

Hemocyte types and some plasmatic properties of two edible crabs Cancer borealis and Cancer pagurus

2015

Cancer pagurus and Cancer borealis and are edible crabs produced by economically relevant aquaculture. In this study the hemocytes and some plasmatic parameters of Cancer borealis and Cancer pagurus were examined. The cell features of the hemocytes were observed using light and scanning electron microscopy (SEM). Granulocytes, semigranulocytes and hyalinocytes were mainly identified on the basis of size, presence/absence and quantity of the cytoplasmic granules and the nucleus-to-citoplasma (N/C) ratio. SEM observations were useful for disclosing the surface features of these cells, and the same characteristics were found in both crab species. A smooth surface distinguishes elongated hyalin…

A hidden species becoming visible : biogeography and ecology of Rhynchotalona latens (Cladocera, Anomopoda, Chydoridae)

2019

A long hidden chydorid (Chydoridae, Cladocera) taxon, first found as fossil specimens and recently redefined as Rhynchotalona latens (Sarmaja-Korjonen et al., Hydrobiologia 436: 165-169, 2000) is investigated for its biogeography and ecology. Late Holocene sediment sequence from Lake Sylvilampi, NE Finnish Lapland, and R. latens spatial distribution in relation to limno-climatic attributes in Finland were examined. Principal component analyses of fossil cladoceran communities showed that R. latens is mostly affiliated with Alonella excisa-Alonopsis elongata-Alonella nana species pool. Generalized linear modeling of R. latens responses to limno-climatic variation indicated that it prefers ac…

Cuticle: Formation, Moulting and Control

1984

The relative rigidity of the arthropod exoskeleton makes it impossible for body size to increase continuously during the postembryonic development of these animals. Once they have hatched from the egg, they grow in steps, passing through a variable number of (larval) stages (Fig. 1 a). Apart from a few exceptions, there are between 3 and 10 such stages in the arachnids, 3–20 in the crustaceans, and 3–10 in the insects. In many cases a metamorphosis stage intervenes (some crustaceans; holometabolous insects) (Fig. 9b, c).

Factors affecting abundance of Triaenophorus infection in Cyclops strenuus, and parasite-induced changes in host fitness.

2000

Factors affecting the abundance of Triaenophorus crassus and Triaenophorus nodulosus procercoids in their copepod first intermediate host, Cyclops strenuus, and effects of infection on feeding behaviour, reproduction and survival of the host were studied experimentally. When exposed to the same number of coracidia, copepods harboured considerably less procercoids in the trials where ciliates or Artemia salina nauplii were given as alternative food items. The prevalence of infection was higher in adult copepods as compared with copepodite stage IV and stage V, and higher in stage V than in stage IV. The prevalences in adult females and males did not differ significantly from each other. The …

New data on the early development of Hysterothylacium aduncum (Nematoda, Anisakidae).

1998

This note reports on incidental observations of the early development of the third-stage larvae of Hysterothylacium aduncum from gadid fishes. Gravid H. aduncum females were collected from Pollachius virens, Pollachius pollachius. Gadus morhua, and Molva molva in Norwegian waters. The eggs were incubated at 20 per thousand salinity and 5 C. Spontaneous hatching of third-stage larvae was observed 10-25 days after egg deposition. These larvae were long lived and could infect Acartia tonsa copepods, the infections being maintained for up to 34 days. The morphology of the third-stage larvae in the copepods and some traits of the life cycle were similar to those reported in previous studies. How…

Potential predation pressure of littoral mysids on herring (Clupea harengus membras L.) eggs and yolk-sac larvae

2008

The predation potential of littoral mysid shrimps (Mysidacea) on Baltic herring (Clupea harengus membras L.) eggs and yolk-sac larvae was studied experimentally. The results showed that littoral mysids feed actively on both eggs and yolk-sac larvae. It was shown that Neomysis integer preys on eggs, which are not attached to the substrate. Alternative food (yolk-sac larvae or zooplankton) did not decrease feeding rate on eggs. Only gravel as a bottom material lowered the ingestion rate to nearly zero. The largest of the mysid species Praunus flexuosus ate yolk-sac larvae more than other mysids and most efficiently. Mysids switched to feed on eggs when larvae and eggs were offered simultaneou…

Light-mediated host searching strategies in a fish ectoparasite, Argulus foliaceus L. (crustacea: branchiura).

2000

Argulus foliaceus, an obligate fish ectoparasite, can search for its hosts in both light and dark conditions and uses vision in the light. We have examined what searching mode is used at night, when the infection rate was at its highest, and which stimuli produced by the fish are most important. A change of illumination produced a clear difference in the searching behaviour of adult Argulus females. The mean swimming speed and the area explored were 3-4 times higher in the dark, when the parasite employed a cruising search strategy. This changed to an ambush (hover-and-wait) strategy in the light. The swimming activity is accompanied by changes in metabolic costs; the activity of the electr…

Molecular phylogeny of the Notostraca

2012

Abstract We used a combined analysis of one nuclear (28S rDNA) and three mitochondrial markers (COI, 12S rDNA, 16S rDNA) to infer the molecular phylogeny of the Notostraca, represented by samples from the six continents that are inhabited by this group of branchiopod crustaceans. Our results confirm the monophyly of both extant notostracan genera Triops and Lepidurus with good support in model based and maximum parsimony analyses. We used branchiopod fossils as a calibration to infer divergence times among notostracan lineages and accounted for rate heterogeneity among lineages by applying relaxed-clock models. Our divergence date estimates indicate an initial diversification into the gener…