1,721,013 research outputs found
Redescription of Pleuretra hystrix, an endemic alpine bdelloid rotifer
No full textPleuretra hystrix Bartoš, 1950 is a peculiar bdelloid rotifer unrecorded for more than 50 years since its description.
We found this species in the western Italian Alps and we redescribe it, confirming the validity of this species. New
morphological details are described from scanning electron micrographs. Variability in spines on the trunk is great;
their adaptative significance in bdelloid rotifers is discussed
Trophi structure in bdelloid rotifers
No full textBdelloids show a rather uniform morphology of jaws (trophi), named ramate. The most recognizable feature is the presence of a series of teeth forming unci plates. The unci are not uniform in size; each plate has 1-10 major median teeth. Using SEM pictures of trophi and data from the literature, we analyzed the number of major unci teeth in relation to trophi size, total number of teeth, and environmental features. Variability in the number of major unci teeth in bdelloids is not related to trophi size or to total number of unci teeth, while total number of unci teeth and trophi size seem to be related to each other: larger trophi in general have more teeth than smaller trophi. Few major teeth are more common in species living in water bodies where they possibly eat unicellular algae, while more major teeth are more common in species living outside water bodies, among mosses and lichens, where they possibly eat bacteria
Bdelloid rotifers from lakes above 1700 m in western Italian Alps, with taxonomic notes on Dissotrocha macrostyla
No full textBenthic and periphytic bdelloid communities from 16 alpine lakes from 1700 to 2850 m in above sea level in Sesia Valley (Piedmont region, North-western Italy), sampled during summer 2001 and 2002, were analyzed. Seventeen species were identified from these species-poor communities, with 1 to 6 species each. Dissotrocha macrostyla and Philodina citrina were the most common species, present in 10 lakes while 9 species were collected from one lake only. New morphological details from S.E.M. pictures of Dissotrocha macrostyla revealed that Dissotrocha macrostyla tuberculata (GOSSE, 1886) is only a seasonal morphotype. Its different appearance is due to the presence of locally distributed microscopic mucous bubbles (diameter 1.41 +/- 0.18 mum) on the trunk surface, produced by the rotifer itself under stressful conditions
Postembryonic development oh hard jaws (trophi) in a species belonging to the Brachionus plicatilis complex (Rotifera, Monogononta) : a morphometric analysis
No full textThe presence of hard jaws (trophi), with species-specific shape and size, is a taxonomic
feature of Rotifera, a group of microscopic metazoans. Since trophi are used to discriminate
among species, it is important to know whether these structures change in taxonomically important
ways during postembryonic development. Using both SEM and optical images, we analyzed more
than 100 individuals of a single clonal lineage of a monogonont rotifer, Brachionus plicatilis, in order
to describe body and trophi development after hatching. Body size, expressed as lorica width and
length, was isometrically related to age of the animals only during preadult stages. Trophi size,
expressed as length of the different parts, was unrelated to either age or body size. Therefore, trophi
elements do not grow after hatching in B. plicatilis. Despite the dimensional invariance with age,
some differences in trophi size among individuals of the same clone were recorded. No difference in
left–right asymmetry of the trophi was shown; the asymmetric elements of the trophi named rami
consistently had the right ramus longer than the left. This constancy is in contrast to the reported
trophi asymmetries in bdelloid rotifers, in which left–right asymmetries are not constant within clonal
lineages. In conclusion, we suggest that also trophi size, constant within the analyzed clone, may
be used as an additional taxonomic feature to help in the discrimination of taxa within the B. plicatilis
complex of cryptic species
On some rotifers new for the Italian fauna
No full textFaunistic data concerning rotifer species not previously cited for the Italian fauna are reported. They are all found in the northwestern part of the country and belong to 24 genera, seven of which are new for Italy: Cyrtonia, Didymodactylos, Eosphora, Mikrocodides, Pleuretra, Proalinopsis, and Taphrocampa. For some of these species, data on rearing in laboratory cultures, dimensions, and SEM pictures of trophi or whole animals are given
Do rotifer jaws grow after hatching?
No full textThe hard articulated jaws of some pseudocoelomte metazoans were recently used in reconstructing their phylogenetic relationships, but we still do not know if these structures could change in size and shape during the life of individuals, and experimental data are lacking on their post-embryonic development. Rotifers are one of the groups in which hard articulated jaws, called trophi, are well known, and are widely used taxonomically. Here we report on SEM study of trophi of rotifers of different ages, to determine if the trophi structures change in shape and/or in size during post-embryonic development. We used linear measurements and geometric morphometrics analyses from scanning electron microscopic pictures of trophi of Cupelopagis vorax, Dicranophorus forcipatus, Macrotrachela quadricornifera, Notommata glyphura, Rotaria macrura, R. neptunoida, and R. tardigrada. Results for these species show that trophi do not change after hatching, either in size or in shape. In contrast, data on Asplanchna priodonta reveal trophi growth after hatching
Morphology of Floscularia ringens (Rotifera, Monogononta) from egg to adult
No full textFloscularia ringens is a cosmopolitan, sessile rotifer (class Monogononta) that lives inside a tube it constructs from numerous small, rounded pellets. Adults of F. ringens produce parthenogenetic eggs that are retained within the tube. Upon hatching, juveniles remain within the maternal tube for a short time completing their development before swimming away. The free-swimming juvenile has a conical body, short foot, small corona, and mastax with trophi, but appears unable to feed. After a short time (<1 day), the young rotifer attaches permanently to a substrate and its morphology changes radically: the corona develops 4 wide lobes and the foot elongates, becoming slender and retractable. Once the corona has developed, the young animal begins to feed by producing filtering currents, and also starts to build its own tube. Here we report 4 new morphological details regarding this species. (1) A specialized epidermal groove is present on the trunk in front of the cloaca. (2) A small hole is located in the center of the inner surface of each pellet of the tube. (3) The muscles inside the foot are U-shaped in transverse section. (4) The size of the trophi remains unchanged during growth of the juvenile into an adult
Phylogenetic constraints in the muscular system of rotifer males: investigation on the musculature of males versus females of Brachionus manjavacas and Epiphanes senta (Rotifera, Monogononta)
No full textSexual dimorphism is characteristic of monogonont rotifers, but at present, most
investigations on the evolution of morphology within Monogononta have focused
exclusively on females, with only minor taxonomic comments on the male
structure. Here, we make the first detailed comparison of female and male
morphology by examining their muscular organization, with the aim of understanding
how factors such as phylogeny, habitat and the structural rigidity of the
body wall determine the muscle arrangement patterns. We compare the musculature
of both females and males in Brachionus manjavacas and Epiphanes senta.
Generally, rotifer males have a similar ecology that may be different from the
conspecific females. Thus, we analysed muscles of conspecific females and males
with different ecology, namely habitat and/or different stiffness of the lorica.
Females of B. manjavacas are loricate and planktic, while E. senta females are
illoricate, can be found in the plankton, but have a lifestyle much related to a
substrate. Males are in both species free swimmers and without a stiff lorica.
Visceral muscles are present in the digestive (only in females) and reproductive
apparatus (only in males). Somatic musculature comprises inner longitudinal and
outer circular muscles. Major differences are discernible among circular muscle
states: B. manjavacas has dorsoventral bands, while E. senta possesses muscles that
are ventrally incomplete. The same condition occurs in both sexes. Results from
analyses on female rotifers support that the circular arrangement is a variable trait
that mainly reflects morpho-ecological adaptations, potentially related to the
development of a lorica. The presence of an identical condition in the conspecific
males, independently of their ecology, suggests, however, that this variability may
be limited by evolutionary and developmental constraints. Further investigations
should be required to clarify whether males have different arrangements from their
females, and thus whether their musculature may be informative for phylogeny
within monogononts
Marine rotifers from the Northern Adriatic Sea, with description of Lecane insulaconae sp. nov. (Rotifera: Monogononta: Lecanidae)
No full textDuring a survey of the marine rotifers of the Northern Adriatic Sea, Italy, we found a total of 20 taxa, including a new species
of Lecane. This novelty, Lecane insulaconae sp. nov., occurred in the interstitial area of sandy sediment in the outlet of the
Isonzo River, at a salinity of 30‰ and is therefore the first exclusively marine representative of this diverse (~200 species)
genus. It is characterized by unique sets of anterolateral projections on the ventral and dorsal lorica. Here, we present the
description of the species, together with scanning electron microscopy pictures of trophi of this and some other species, and
an account of the marine rotifers encountered during the survey
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