Sun, 20 May 2012 02:09:18 +0000 1800 This is the RSS feed of the last ten file submissions accepted into our database. This RSS feed is always up to date as it is dynamically updated. processes. In crustaceans, male sexual differentiation is controlled by the male-specific androgenic gland (AG). An AGspecific
insulin-like gene, previously identified in the red-claw crayfish Cherax quadricarinatus (designated Cq-IAG), was
found in this study to be the prominent transcript in an AG cDNA subtractive library. In C. quadricarinatus, sexual plasticity is
exhibited by intersex individuals in the form of an active male reproductive system and male secondary sex characters,
along with a constantly arrested ovary. This intersexuality was exploited to follow changes caused by single gene silencing,
accomplished via dsRNA injection. Cq-IAG silencing induced dramatic sex-related alterations, including male feature
feminization, a reduction in sperm production, extensive testicular degeneration, expression of the vitellogenin gene, and
accumulation of yolk proteins in the developing oocytes. Upon silencing of the gene, AG cells hypertrophied, possibly to
compensate for low hormone levels, as reflected in the poor production of the insulin-like hormone (and revealed by
immunohistochemistry). These results demonstrate both the functionality of Cq-IAG as an androgenic hormone-encoding
gene and the dependence of male gonad viability on the Cq-IAG product. This study is the first to provide evidence that
silencing an insulin-like gene in intersex C. quadricarinatus feminizes male-related phenotypes. These findings, moreover,
contribute to the understanding of the regulation of sexual shifts, whether naturally occurring in sequential hermaphrodites
or abnormally induced by endocrine disruptors found in the environment, and offer insight into an unusual gender-related
link to the evolution of insulins.]]> Fri, 09 Sep 2011 13:27:29 +0000 430 New South Wales, Australia. Euastacus morgani is found living sympatrically with two more common species,
E. dangadi Morgan, 1997 and E. neohirsutus Riek, 1956. Systematically, the species belongs in the
‘simplex’ complex of the genus that includes E. simplex Riek, 1956, E. clarkae Morgan, 1997, E. maccai
McCormack and Coughran 2008 and E. morgani. Th is new species diff ers from its nearest congenor, E.
simplex, in having three mesial carpal spines. A key to the ‘simplex’ complex is presented.]]> Sat, 12 Mar 2011 19:51:37 +0000 429 Spain feeding mainly on the recently introduced red swamp crayfish (Procambarus clarkii ). In control colonies, where
crayfish was absent, plasma was collected for comparison. Our objective was to determine whether the astaxanthin
contained in the crayfish reached the blood, accumulated in fat, and finally was deposited in the red-colored bill and legs.
If that was true, the visual cues provided by those tegumentary areas would be altered, with potential behavioral
consequences. Plasma carotenoids were directly extracted with acetone, whereas skin and fat samples needed harsher
conditions, i.e. grinding, sonication and extraction with diethyl ether. The extracts were analyzed by thin-layer
chromatography (TLC) and UV:Vis spectroscopy. In crayfish-eating storks, astaxanthin was confirmed to be the
dominant pigment in all analyzed tissues. This red pigment was absorbed unchanged in the gut, and was responsible for
the red color of plasma and the abnormal orange pigmentation of the feather-covered skin. It was also present in large
quantities in the exposed bill and tarsi, which are typically red-colored in the stork. Control storks with no crayfish in
the diet only presented lutein in their plasma.]]> Sat, 15 Jan 2011 10:34:19 +0000 428
Very interesting stuff.]]> Sat, 08 Jan 2011 22:41:36 +0000 427 orangey-red hue to sea animals such as the
pink flesh of salmon, and the exoskeletons of
crayfish – or Astacidea from where it was first
identified - shrimps. …and boiled lobster. Is it
astaxanthin that gives lobsters their blue-green
color in the first place? Yes. Why lobsters turn
red when boiled is a question which the
American biologist George Wald (1906-1997)
had already raised over half a century ago.]]> Sat, 08 Jan 2011 22:28:23 +0000 426 Excavation of burrows, Norrocky burrowing crayfish trap (NBCT), and burrowing crayfish mist nets (BCN) were simultaneously
compared for capture efficiency and trap efficacy. Additional research goals were to evaluate patterns in capture rates with changes in
seasonal activity, influence of burrow diameter size to capture success, relationships between differences in morphological characteristics
of species and capture success, and capture success and habitat quality. Excavation caught significantly more burrowing crayfish than the
other two methods (40.7%), but the NBCT (5.2%) was not significantly different from the BCN (4.5%) in trap efficiency. The relative
percent efficacy success adjusted for effort of each method was 2.61% for the NBCT and 2.24% for the BCN. Positive correlations
between habitat quality and increasing NBCT (rs¼0.414, P¼0.023) and increasing BCN (rs¼0.447, P¼0.013) trap efficiency success
were found, while no significant linear relationship (rs ¼0.134, P ¼ 0.479) was observed between the Qualitative Habitat Evaluation
Index score for habitat quality and excavation success. No significant correlation was observed between NBCT (rs¼0.273, P¼0.144) or
BCN (rs¼0.286, P ¼ 0.125) and annual date; however, a significant linear relationship was observed for excavation (rs¼0.372, P ¼
0.043) and annual date of collection. Individuals of Cambarus (Tubericambarus) polychromatus and Cambarus (Lacunicambarus) species
‘‘A’’ that were collected were significantly different in size; however, this was not a result of gear bias. A positive correlation was observed
between C. polychromatus size and habitat quality indicating longer lived individuals occur in higher quality habitats.]]> Sat, 08 Jan 2011 22:27:07 +0000 425 analyzed for blue color phase variants of the crayfish populations in North Twin and
South Twin Lake, Otsego County, Michigan. Crayfish were collected with baited minnow
traps, growth was determined by size frequency analysis of the total catch, and mortality
analyzed by use of sequential mark and recapture population estimates. The results
suggest that growth is density dependent, survival between blue and normally brown
color phases is not different and that the percentage of blue color phase variants in these
populations does not exceed one percent of the total population. The lack of difference in
mortality rates between the olive brown and blue color phases and the lack of blue crayfish
in the stomachs of the fish in these lakes does not support the thesis of selective mortality
on the conspicuous blue color phase.]]> Sat, 08 Jan 2011 22:19:31 +0000 424 has been spreading across the globe for the past decade.
We compare this crayfish directly to two other cambarids, Procambarus
fallax and P. alleni, that have been suggested to be
related or even identical to the Marmorkrebs. Using external
morphology and sequences of two mitochondrial genes we
show clear correspondences between Marmorkrebs and P. fallax,
a species found natively throughout peninsular Florida,
USA. Based on these congruent results we suggest that the Marmorkrebs
is the parthenogenetic form of P. fallax. This finding
has potential evolutionary and ecological implications at several
levels. The Marmorkrebs might be a type of geographical parthenogenesis,
but a natural population in the wild is so far unknown.
Furthermore, challenges arise in regard to the respective
species status of the Marmorkrebs. Taxonomically we suggest
that the Marmorkrebs is treated as ‘parthenogenetic form’ of P.
fallax. Last but not least, the identity of this animal and its ecology
has an impact for considering potential spread and effects of
this species across the globe.]]> Tue, 04 Jan 2011 05:06:04 +0000 423
cheers
Paul]]> Tue, 23 Nov 2010 09:12:20 +0000 422 (Astacus astacus), the narrow-clawed crayfish (Astacus leptodactylus), and the North-
American signal crayfish (Pacifastacus leniusculus) species. Probably only noble crayfish
are native and migrated into the country after the last glaciation. Narrow-clawed crayfish
has also been present at least since the beginning of the 20th century. In total there are
current information on crayfish from 258 localities in Latvia. Most of these localities are
lakes (175), but many crayfish populations are also found in river and streams (66). A few
populations are found in reservoirs, ponds and gravel-pits.]]> Tue, 19 Oct 2010 23:02:50 +0000 421