Skeletal characters for identification of juvenile Ophiactis resiliens and Amphiura constricta (Echinodermata): cryptic ophiuroids in coralline turf habitat

2006 ◽  
Vol 86 (5) ◽  
pp. 1199-1207 ◽  
Author(s):  
I. Falkner ◽  
M. Byrne
Keyword(s):  
Larval Stage ◽  
Early Stage ◽  
Skeletal Development ◽  
Algal Turf ◽  
Disc Diameter ◽  
Planktonic Larval Stage

Skeletal development of Ophiactis resiliens and Amphiura constricta was examined to determine characters that could be used to identify the juveniles of these species, which co-occur in algal turf habitat. Juvenile O. resiliens recruit to turf after a planktonic larval stage while A. constricta recruit through release from brooding adults. Skeletal development in O. resiliens and A. constricta is typical of most ophiuroids with diagnostic adult characters taking some time to appear. The main characters that can be used to distinguish the two species from an early stage are the number and arrangement of the oral papillae and the presence of disc spines. In O. resiliens diagnostic adult skeletal characters developed at 1.5 mm disc diameter. In A. constricta most identifying adult characters were evident at 700 μm disc diameter. Identification of juvenile O. resiliens is assisted by the presence of disc spines and thorny arm spines, features that disappear as the juveniles grow. Juvenile A. constricta did not develop disc spines or thorns on the arm spines.

The taxonomic position of the pelagic ‘staurozoan’ Tessera gemmaria as a ceriantharian larva

Zootaxa ◽  
2011 ◽  
Vol 2971 (1) ◽  
pp. 49 ◽  
Author(s):  
CAROLINA S. RODRIGUEZ ◽  
ANTONIO C. MARQUES ◽  
SÉRGIO N. STAMPAR ◽  
ANDRÉ C. MORANDINI ◽  
ERNESTO CHRISTIANSEN ◽  
...  
Keyword(s):  
Larval Stage ◽  
Early Stage ◽  
Atlantic Coast ◽  
Molecular Data ◽  
External Morphology ◽  
Taxonomic Position ◽  
Southwestern Atlantic ◽  
Incertae Sedis ◽  
Long Time ◽  
Planktonic Larval Stage

Based on 16 specimens from the Southwestern Atlantic coast (Argentina and Brazil) we reinterpret the taxonomic position of Tessera gemmaria Goy, 1979, a stauromedusa considered as incertae sedis for a long time. Using external morphology, histological preparations and molecular data (16S and COI) we conclude that T. gemmaria is an early stage of a cerinula, the long-lived planktonic larval stage of the Ceriantharia (Anthozoa).

Phoronida

2017 ◽  
Author(s):  
Judith Fuchs
Keyword(s):  
Life Cycle ◽  
Small Group ◽  
Larval Stage ◽  
Intertidal Zone ◽  
Marine Invertebrates ◽  
Tree Of Life ◽  
General Morphology ◽  
Family Level ◽  
Planktonic Larval Stage

This chapter describes the taxonomy of Phoronida, a small group of exclusively marine invertebrates found in most of the world's oceans from the intertidal zone to about 400 metres depth. Phoronids are meroplanktonic with a planktonic larval stage usually less than 2 mm in length and a benthic adult whose length ranges from a few cm up to 50 cm. The chapter covers their life cycle, ecology, and general morphology. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

scholarly journals Developmental effect of polyamine depletion in Caenorhabditis elegans

1998 ◽  
Vol 333 (2) ◽  
pp. 309-315 ◽  
Author(s):  
Madhu MACRAE ◽  
Debora L. KRAMER ◽  
Philip COFFINO
Keyword(s):  
Larval Stage ◽  
Brood Size ◽  
Early Stage ◽  
Complex Medium ◽  
Slight Reduction ◽  
Free Medium ◽  
Developmental Effect ◽  
Stage Of Development ◽  
Deficient Medium ◽  
Well Differentiated

Ornithine decarboxylase (ODC) catalyses the conversion of ornithine to putrescine, an obligate precursor to the polyamines spermidine and spermine. We reported previously that homozygous odc-1 (pc13) worms have no detectable ODC activity. Despite their inability to make polyamines, these mutant worms appear normal, but with a slight reduction in total brood size, when grown in complex medium that presumably contains polyamines. We now show that when ODC-deficient worms are transferred to polyamine-free medium, they show a strong phenotype. odc-1 worms have two different fates, depending upon the developmental stage at which polyamines are removed. If the polyamines are removed at the L1 larval stage, the mutant animals develop into adult hermaphrodites that produce very few or no eggs. In contrast, if mutant larvae at the later L4 stage of development are transferred to polyamine-deficient medium, they develop and lay eggs normally. However, approx. 90% of the eggs yield embryos that, although well differentiated, arrest at early stage 3. Either maternal or zygotic expression of ODC provides partial rescue of embryonic lethality. Supplementing deficient medium with the polyamine spermidine allows ODC-deficient worms to develop as on complex medium. Together, these findings suggest that ODC activity is most critically required during oogenesis and embryogenesis and, furthermore, that exogenous polyamines can override the requirement for ODC activity.

Skeletal development and abnormalities of the vertebral column and fins in larval stage of hatchery-reared American shad,Alosa sapidissima

2018 ◽  
Vol 49 (7) ◽  
pp. 2376-2392 ◽  
Author(s):  
Xiao-Qiang Gao ◽  
Zhi-Feng Liu ◽  
Chang-Tao Guan ◽  
Bin Huang ◽  
Bao-Liang Liu ◽  
...  
Keyword(s):  
Larval Stage ◽  
Vertebral Column ◽  
Skeletal Development ◽  
American Shad ◽  
Alosa Sapidissima

Spiral torsion in Taenia taeniaeformis (Batsch, 1786) caused by the knotting together of two worms

Parasitology ◽  
1952 ◽  
Vol 42 (1-2) ◽  
pp. 114-124
Author(s):  
Gwendolen Rees
Keyword(s):  
Larval Stage ◽  
Adult Stage ◽  
Early Stage ◽  
The Body ◽  
Detailed Account ◽  
Spiral Growth ◽  
Surface Layers ◽  
Nervous Systems ◽  
Internal Structures ◽  
Taenia Taeniaeformis

The larval stage of Taenia taeniaeformis, namely, Cysticercus taeniae-taeniaeformis, has recently been described by the writer (1951), a detailed account being given of the musculature and of the excretory and nervous systems of the scolex and strobila. In addition, some abnormalities in structure were noted, chief of which was the spiral torsion observed in some specimens and which involved the musculature, excretory and nervous systems of the strobila but not the surface layers. A search was then made for some adult specimens in order to find whether the same abnormality could be seen and to ascertain what the effect of such a torsion would be on the genitalia in the mature and gravid regions. Several adult specimens, from the intestine of a cat, were given to the writer by Mr L. E. Hughes, veterinary investigation officer. Unfortunately, none of these specimens showed the identical spiral torsion found in the larva, but two of them had become knotted together, presumably at an early stage, and were considerably distorted in the regions involved in the knot. This distortion was again of a spiral nature but involved the entire proglottid and not only the internal structures as was found in the type of spiral torsion common in the larval stage of this species. The condition was not merely a turning over of the strobila but an abnormal spiral growth brought about by the continued constriction on the body where the two worms were twisted around one another. So here again, in the adult stage, spiral torsion is evident but from a different cause and involving the whole of the relevant segments from the surface layers to all the contained organs.

scholarly journals THE LITTLE BIVALVE Planktomya UNMASKED

2016 ◽  
Vol 13 ◽  
Author(s):  
Donald R. Moore
Keyword(s):  
Larval Stage ◽  
Western Atlantic ◽  
Fossil Species ◽  
The Family ◽  
Planktonic Larval Stage

The enigmatic bivalve Planktomya henseni has masqueraded as a holoplanktonic animal for nearly a century. Allen and Scheltema (1972) showed that all the evidence pointed to a benthic clam with an unusually long planktonic larval stage. This benthic clam has finally been found in the tropical western Atlantic, and appears to be a member of the Family Sportellidae. Comparison with fossil species in this family shows a trend toward a large prodissoconch and apparently a long planktonic larval stage

Early Devonian calymenid larvae (Trilobita) from the Bissounel Formation (Montagne Noire, France)

2007 ◽  
Vol 178 (3) ◽  
pp. 197-200 ◽  
Author(s):  
Rudy Lerosey-Aubril
Keyword(s):  
Larval Stage ◽  
Morphological Characteristics ◽  
Developmental Strategy ◽  
Two Stage ◽  
Early Devonian ◽  
Montagne Noire ◽  
Middle Member ◽  
Planktonic Larval Stage ◽  
Late Emsian ◽  
Comparable Size

AbstractThe late Emsian middle Member of the Bissounel Formation (Montagne Noire, France) has yielded a highly diverse silicified trilobite fauna. Among the thousands of disarticulated sclerites discovered, two protaspid specimens were found that display morphological characteristics of planktonic larvae of calymenid trilobites. The presence of calymenid protaspides within a non-calymenid trilobite fauna is noted. The two specimens are very similar to the first planktonic larval stage of the Ordovician Flexicalymene senaria (Conrad, 1841), and are of comparable size. This indicates that, as in F. senaria, a second planktonic larval stage might have occurred in the ontogeny of this undetermined calymenid. Thus, some post-Ordovician calymenids might have retained the ancestral developmental strategy with a two-stage planktonic period. The discovery of these two protaspides constitutes the first evidence of a calymenid trilobite in the Devonian of the Montagne Noire.

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