WMU MEDICAL SCHOOL RESEARCH

Grant for Medical School Research

Medical research at the Dr. Homer Stryker Medical School of Western Michigan University and at its two collaborating teaching hospitals of Borgess Health and Bronson Healthcare will benefit from a two million dollar bequest given by Martha Parfet's estate.  She is a granddaughter of the founder of the Upjohn Company, Dr. W. E. Upjohn.  Kalamazoo has benefited greatly by the generosity of numerous relatives and friends of both of the doctor’s families.

Clinical research will benefit from the bequest, as well as basic research using tissue culture and cells and animals that share functions in ways more accessible than in human subjects.  Such non-clinical studies can speed, reduce cost, and sometimes simplify the discovery of things beneficial in modern medicine.

BACTERIA share many biochemical features of all more advanced organisms.  In particular, they contributed greatly to understanding DNA related details.  Their beneficial roles as well as the diseases some caused will encourage continued searches for new antibiotics when resistance to old ones develop.

The bacteria of today and ourselves share some of our biochemical processes as a result of our common ancestry over two billion years in the past.  As organisms share more recent common ancestry with us, they are expected to share more features with us although they may lose some and gain others unique to themselves and their descendants.

The figure above is just to suggest what happens many times during the ancestral history of organisms.  There is no precision to it, but the internal lines show continuity in one or both branches (multiple branches may also occur at the same time) and it may take very many generations that may include the beginning or end of new or old features.  The short blue line on the right branch could be repeated in many times and places for numerous other extinct groups from the past.

INVERTEBRATE animals range from protozoans and simple sponges to complex ones, some of which, especially the giant squid, reach large size.   Invertebrates began leaving an abundant fossil record of great diversity about 500 million years ago.

VERTEBRATE animals of today share a common ancestry with echinoderms, perhaps lophophorate animals, and a few degenerate annelid-like worms that gave rise to early pre-vertebrate chordates that diverged from the other advanced invertebrates (annelids, mollusks, and arthropods) near the beginning of the Cambrian.  The following figure is intended to represent an educated guess of some of the ancestral tree major relationships.

The tree of life is to graphically show the central role of the annelids leading to the two main branches of coelomate animals (protostomes left, deuterostomes right with the pogonophorans linking them to the other line) with the vertebrates upper right and the arthropods, upper left.  Plants in green are are lower left, and nematodes are on the blue and red left middle main branch.

Why are organisms important in medical research?

1.      Shared system features of physiology, structure, and biochemistry are likely to be most similar when the distances (or perhaps generations) from one group to another along the branches of the ancestral tree of life are shortest (or fewer).

2.      Some organisms have feature comparable in some ways to ours, but in a more accessible or larger form.  For example, the transmission of nerve impulses was made understandable by studying the giant nerve fibers of squids.  Fruit-fly larvae have giant chromosomes that led to some genetic discoveries.

3.      Basic toxicity studies of proposed drugs can be on simple organisms after or in place of initial tissue culture or other studies.  Such tests may be much less costly in time and/or money.

Where should medical research start?

1.      Most likely it will start as you work with a senior medical researcher using you as an assistant performing work for which you are trained.

2.      A first step that should become a habit is studying the research literature in the library, on-line, in appropriate journals, and attending meetings of your research group.  Especially, attending related research being reported at local, state, or national conferences.  Often, verbal presentations of research include clues of value to apply in your research.

How is evolution important in medical research?

It may not always be important to you if you are a specialist is some aspect of a research project.  If you are planning research it may help you select organisms for non-human aspects of research such as in the first list above.  Keep abreast of new developments, even the most unlikely organisms may teach us things of value.

Although animals greatly separated from us on the tree of life may share some identical features with us, they are expected to have greater differences than ones that are more recently separated.  The pogonophorans clue us in on where differences in biology are more likely to be greater in some instances and less in others.

The pogonophorans are a bottleneck where they branch off from the annelids, losing the spiral cleavage of the three big invertebrate groups - the annelids, mollusks, and arthropods – as well as loss of much of the gastrointestinal system and skeletal functions.   In spite of the latter, cartilage of the squid seems indistinguishable from vertebrate cartilage with casual microscopic examination.

Many biochemical features survived the pogonophoran link bottleneck.  Hemoglobin is the blood pigment of vertebrates as well as some invertebrates across the pogonophoran divide.  Aspects of delivery of pituitary hormones in our endocrine system show remarkable similarities in mammals and arthropods.  Peculiar intercalated disks of our heart muscle are also seen in some mollusks.

If you find commonalities of another organism and humans, don’t use the just stated facts as reason to change your experimental animals.  But consider the discussion as an aide to picking new ones if evidence warrants it.  Selective evidence was used to put nematode worms in a major cluster with arthropods when most evidence indicated otherwise.  The post -

  http://evolutioninsights.blogspot.com/2017/10/evolution-nematode-worms.html  

- and the post on May 31, 2013 indicate otherwise, Ecdysozoa is not a valid related group.  Both posts provide references supporting that statement.  I write this with hope that it may be of some benefit to the researchers the grant will fund in the university from which, twenty-two years ago, I retired.

Joseph Engemann   Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan           March 6, 2018

EVOLUTION: NEMATODE WORMS

Nematode worms are typically long, round, unsegmented, gradually tapered at both ends.

"Nematodes have many species with relatively little difference in body form.  Many are parasitic and it is thought that most species of vertebrates may have one or more parasitic nematode species unique to them.  Nematodes parasitize many other groups of animals and plants.  Many live in the intestines of animals.  One free-living nematode species lives in organic rich soil but can also live as a parasite in humans. Rotting organic matter in soil is not so different from the intestinal contents of some animals.  Both are rich in bacteria that the nematodes can feed upon.  Adapting to the rich soil made them somewhat "pre-adapted" to life as an intestinal parasite. This adaptation included an ability to live in environments with oxygen so limited many other animals could not survive." (from my unpublished 2010 manscript)

The similarity of structure of different species disappears when the mouth end, and often the anal end, are examined microscopically.  Three jaws are present in some.  The pharanyx may have a muscular bulb that probably helps ingestion of food without losing pressure, the body contents act as a hydrostatic skeleton.  The cuticular covering of the body is molted or shed typically several times in early development.  During the process of development portions of the chromosomal material can be ejected from the chromosomes; this is perhaps a result of selection for the small size of ancestors living among the sand grains of soils. In one species the ejection of chromatin occurs in all cells except the stem cell until the 32 cell stage.  Body cells of many achelminths other than nematodes also seem to have the loss of ability to regenerate that is thought to be a result of the reduced chromosomal material in body cell nuclei (or nuclei when tissues are syncytial).  Near constant number of nuclei or cells of the species are present in the tissues of many aschelminths.

I was reviewing some of Libbie Hyman's work on Aschelminthes (not accepted as a valid cluster by many zoologists), but unfortunately she did not have the benefit of knowing about gnathostomulids (first described in 1956) which were later.  Gnathostomulids seem to be descendents of the simple early flatworms that are not flat, but are adapted to living in sediments that are often anoxic.  Reidel, 1969, suggests the gnathostomulids can be placed in either the Platyhelminthes or the Aschelminthes.  The gastrotrichs may be the connecting link to rotifers.  Nematodes may have been the termination of a line orginating early in the cluster of achelminth groups; but they have a complete lack of cilia, a fact that makes them unlikely to have given rise to any other groups since arthropods also lack cilia but are so clearly derived from annelids that do have cilia.  Thus the lack of cilia in nematodes and arthropods is an analagous, not homologous, trait.

The reason I referred to Hyman was to find out about the adhesive glands or pedal glands, commonly paired on most ashelminths' posteriors, but absent in the gnathostomulids.  The glands are very small and difficult to see, especially in nematodes.  I did not see them in some nematodes I had watched in water on a microscope slide at low magnification, but those nematodes were clearly adhering by their tail as the writhed around.  One researcher (Chitwood) divided nematodes into two groups depending on whether they had phasmids at their posterior.  The mouth area and anal areas of nematodes show great variation in microcopic details not conducive to casual observation.

Such fine details can be a great help in identifying species and often show revealing variation suitable for showing evolutionary relationships.  The October 20, 2017, issue of Science has a research report detailing such a fact with feather-like hairs on water-strider feet.  In the case of water-striders, the details are limited to very close relatives.  In arthropods, similar microscopic comparisons can be made of structures limited to closely related species of the same genus and sometimes of different orders.

When the very small and the very large features match, relationship seems more likely.  To determine evolutionary relationships, neither can be ignored.  Over-dependence on one may lead to error and demonstrate why the novice or student may see things the specialist or teacher does not see, a relationship affecting creativity as noted by Tinbergen.

Among the larger features distinctive for nematodes, that show them as a terminal group in an evolutionary sense, are the muscle cells of the body of the intestinal parasite, Ascaris.  All are longitudinal and each passes a muscle cell process to the nerve enervating the muscle.  Other lines of evidence that the Ecdysozoa are an invalid group are indicated by some of the references appended.

Ascaris can grow to a foot long during it time in the intestine.  It has a simple life cycle with transmission of eggs, typically ingested with fecal contaminated food, hatching in the intestine and larve going through tissue and blood to the lungs where they break out and get coughed up, swallowed, and then comlete their life in the intestine.  Another nematode parasite of humans is thought to be the fiery serpent mentioned by Moses.  It has a big name, Dracunculus medinensis, and is known as the guinea worm.  The adult female can be as much as a meter long and live in the subcutaneous tissue under the skin.  The larvae are discharged through a hole in the skin and, if ingested by an aquatic microcrustacean named Cyclops, complete their larval development and, if Cyclops is ingested by a human, eventually reach their location under the skin.

The great variations in size, number of host species needed to complete life cycles, and adaption to a single or limited number of final hosts of most vertebrates, as well as many invertebrates, seems to indicate an ancient origin for nematodes.

Joseph G. Engemann    Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan   October 30, 2017

REFERENCES (comments added)

Aguinaldo, Anna Marie A., James M. Turbeville, Lawrence S. Linford, Maria C. Rivera, James R. Garey, Rudolf A. Raff, and James A. Lake.  1997.  Evidence for a clade of nematodes, arthropods and other moulting animals.  Nature, 387:489-493. Unfortunately, textbooks have picked up their grouping of nematodes with arthropods and some other molting animals in a group they named Ecdysozoa; based on 18s ribosomal DNA sequences, it is inadequate to support such a group.  They even say “It was unexpected to find nematodes contained within the Ecdysozoa because in previous molecular studies they diverged deep in the protostome tree, even before the deuterostome-protostome bifurcation.”   -page 491 has discussion of unequal rates found in other nematode studies (documented and ignored) and their search for and choice of slowly evolving representatives [almost guaranteed to put an outgroup in where it doesn’t belong]

Fraser, Hunter B., Aaron E. Hirsh, Lars M. Steinmetz, Curt Sharfe, and Marcus W. Feldman.  2002.  Evolutionary rate in the protein interaction network.  Science, 296:750-752.  (26 Apr 2002)  “We show that the connectivity of well-conserved proteins in the network is negatively correlated with their rate of evolution.”  “interacting proteins evolve at similar rates.” - used “putatively orthologous sequences between Saccharomyces cerevisiae and the nematode Caenorhabditis elegans.” 

Halanych, Kenneth M.  1996.  Testing hypotheses of chaetognath origins: long branches revealed by 18S ribosomal DNA.  Syst. Biol., 45(223-246.   Well-done study but long branches and small sample size make result of relationships beyond the nematode-chaetognath affinity somewhat dubious.

Halanych, Kenneth M., John D. Bacheller, Anna Marie A. Aguinaldo, Stephanie M. Liva, David M. Hillis, and James A. Lake.  1995.  Evidence from 18S ribosomal DNA that the lophophorates are protostome animals.  Science, 267:1641-1643.  “we propose the node-based name (16)[K. de Queiroz and J. Gauthier, Syst. Zool. 39, 307 (1990)] Lophotrochozoa, which is defined as the last common ancestor of the three traditional lophorate taxa, the mollusks, and the annelids, and all of the descendants of that common ancestor.”  Note 10 includes the following statement “Regions that could not be readily aligned were excluded from the analyses.”  Their proposal is ridiculous when all data are considered.

Halanych, Kenneth M., and Yale Passamaneck.  2001.  A brief review of metazoan phylogeny and future prospects in Hox-research.  Amer. Zool., 41:629-639.  maintain Hox gene research supports the earlier ridiculous proposals of ecdysozoans and lophotrochozoans.  Has numerous references.

Hobert, Oliver, and Gary Ruvkun.  1998.  A common theme for LIM homeobox gene function across phylogeny?  Biol. Bull., 195:377-380.  neurogenesis regulatory genes and transcription factors are very similar in vertebrates, insects, and nematodes

Hobmayer, Bert, Fabian Rentzsch, Kerstin Kuhn, Christoph M. Happel, Christoph Cramer von Laue, Petra Snyder, Ute Rothbackerm, & Thomas W. Holstein.  2000.  WNT signaling molecules act in axis formation in the diploblastic metazoan Hydra.  Nature, 407:186-189.  the WNT signaling pathway had been found in nematodes, insects and vertebrates.

Kappen, Claudia.  2000.  Analysis of a complete homeobox gene repertoire: implications for the evolution of diversity.  Proc. Natl. Acad. Sci. USA, 97:4481-4486.  used the nematode, C. elegans

Sarnat, Harvey B.  1984.  Muscle histochemistry of the planarian Dugesia tigrina (Turbellaria: Tricladida): implications in the evolution of muscle.  Trans. Am. Microsc. Soc., 103(3):284-294.  Says striated muscle is in every metazoan phylum except Porifera and adult Platyhelminthes. (oblique striations in nematodes – Rosenbuth 1965, 67  Wright 62) 

Van Auken, Kimberly, Daniel C. Weaver, Lois G. Edgar, and William B. Wood.  2000.  Caenorhabditis elegans embryonic axial patterning requires two recently discovered posterior-group Hox genes.  Proc. Natl. Acad. Sci. USA, 97:4499-4503.  “essential embryonic patterning in C. elegans requires only Hox genes of the anterior and posterior paralog groups, raising interesting questions about evolution of the medial-group genes.” Three Hox genes in the nematode

LUTHER THEN AND NOW

Today's paper

A Washington Post article by Jonathan Kay, “Nobody Listened to Luther at first. That’s why he succeeded”, published in the Kalamazoo Gazette October 29, 2017, deserves reading to see an example of how momentous ideas develop.  Some similar circumstances surrounded Darwin’s ideas about natural selection.

Non-conformists may face problems

Today such factors as rapid communication and professional networks can, Kay writes, “make us more cautious, since we know that any new idea can expose us to instant censure from complete strangers in other parts of the world………. – This phenomenon goes by different names – group think, political correctness, herd mentality.  But in every form, it serves the interest of the orthodox and frustrates the heretic.” 

I sometimes feel like I am a group of one in terms of my findings.  I don’t expect to be in a group with Luther or Darwin, but I am not aware of much acceptance of what I thought were my best ideas about evolution.  I do appreciate the fact that my post about the coelom has received so many views.

An early post of mine-  http://evolutioninsights.blogspot.com/2014/02/creativity-brainstorming.html  has had zero page views. The post makes suggestions for solitary brainstorming that can substitute to some degree for the benefits of group brainstorming.

Nematodes

I have begun a draft of a post on nematodes.  It is hoped to be helpful in understanding the antiquity of their origin, far before the time the erroneous Ecdysozoa implies.  I was reviewing some of Libbie Hyman’s invertebrate volumes and will leave most related comments to the forthcoming post.  But the last two paragraphs of the post http://evolutioninsights.blogspot.com/2015/03/abandoned-theories-and-libbie-hyman.html  said some of the things I might have repeated.

Christian Unity

Today, about the 500^th anniversary of the event most associate with Luther’s long campaign, there is a mood that seems to have developed in recent years, of Protestants recognizing that Catholics have gotten past such blemishes as selling indulgences and killing heretics, and of Catholics thinking that Protestants have selectively departed from teachings of Jesus.  There is recognition of a common bond for many on both sides of the former divide; and if it has not been there before, that all humans are created by, and loved by, God.

Joseph Engemann      Kalamazoo, Michigan   October 29, 2017

THE TREE OF LIFE

REVISED TREE OF LIFE

The revised tree of life described in the previous post lacked any illustration to aide understanding.  The transfer of files to a new computer, operating system and associated software (Windows Vista to Windows 10) has delayed production of something suitable.  I was eventually able to find Paint embedded in 10.  But my attempt to modify the diagram below with color to clarify the protostome and deuterostome groupings left an illustration dangling somewhere in a jpg file that I have not been able to migrate to this blog.

 The protostomes began with platyhelminthes, the flatworms ancestral to other protostomes, and eventually deuterostomes via annelids.  The anthropocentric view showing primates upper right as the ultimate chordates is only for illustration of our lineage.  Every living group could have an illustration showing their group at the peak.  Some hint of this is shown with wasps and flies being groups of insects at the upper left.  And at the far left the cephalopods are perhaps the ultimate mollusks.

The boldface names in the above diagram represent groups in the direct ancestral line to primates.  All animals with a eucoelomate body cavity are included in the annelids and those above them in he diagram.  Phylum names are in all capital letters.  Polychaetes are probably the ancestral annelids for other annelids (oligochaetes and their descendants the leeches), mollusks, and arthropods, as well as the pogonophorans.  Echinoderms and lophophorates were probably each derived from ancestors intermediate between polychaetes and hemichordates; echinoderms perhaps being farther along the line to chordates in their origin.

The various other groups are not all fairly treated in showing how advanced they are in an evolutionary sense.  Their position is generally more an estimate of the antiquity of their origin.

OLDER VERSIONS OF THE TREE OF LIFE

A.  Prior to the erroneous Lophotrochozoa and Ecdysozoa proposals the "Tree of Life" would have looked much like the version presented above with the following evident.
 1. a separate origin of the deutrostomes from much earlier connecting the Hemichordates via unknown intermediates to the platyhelminthes.
2. a consequence is the assumption of a separate origin of coelom and blood vascular system of deuterostomes and advanced protostomes.
3. inexplicable cellular, histological, and moleular similarities in advanced protostomes and deuterostomes.

B.  The Lophotrochoza error may some value as an assessment of lophophorate invertebrates but is not much use as showing relationships to vertebrates and some other phyla.

C.  The Ecdysozoa error is made worthless by trying to make nematodes an important part of the evolutionary history of other some other phyla.  Nematodes, as partially indicated in the diagram above, are probably part of an aschelminth group derived from turbellarian flatworms miniaturized by selection for adaptation for life in the interstices of marine, then freshwater and terrestrial sediments.  The extreme specialization of nematodes did not provide a good base for selection of new groups.  The superficial resemblance of their outer covering with the exoskeleton of arthropods is misleading.  Surprisingly or fortunately, they did not make reptiles part of the group for shedding their skin.  The post of May 31, 2013 should make it evident why the molecular data they used as a basis for Ecdysozoa is worthless.

D.  Other versions of the "tree of life" based on symmetry and other features such as segmentation are not in vogue today, although the data used for them may have application in limited portions of "the tree of life".  The antiquity of brachiopods and bryozoans as well as considerable differences in the lophophores would seem to argue for separate origins, perhaps from somewhere along the polychaete to pogonophora line.

E.  The ancient annelid theory (over 100 years old) can be tweaked by insertion of the pogonophora to explain several things as shown elsewhere in the blog and indicated by the above diagram.
1. How the pogonophora turned an annelid arrangement of systems in to the chordate pattern.
2. How the anterior nervous system could fuse into a brain without an esophagus penetrating it.
3. How the drastic embryological changes of spiral to radial cleavage were simply made.
4. How molecular homologies of chordates and advanced protostomes came about.


Joseph G. Engemann   Emeritus Professor of Biological Science, Western Michigan University, Kalamazoo, Michigan     May 16, 2016

Disclaimer: All errors, mistakes, and omissions are my own and not the responsibility of Michigan State University, The University of Tasmania, nor Western Michigan University, nor the U. S. Fulbright Agency; although their assistance was valuable enabling me to make them.  jge

MUSCLES AND EVOLUTION

MUSCLES

Muscles are almost the definition of the animal kingdom.  The larger the animal the larger its proportion of muscle.  It is a consequence of the strength of a muscle being proportional to its cross-sectional area which increases in amount with the square of lineal dimensions.  The strength needed to move its mass increases with the cube of the lineal dimensions.  Thus muscles scale up in size with increasing animal size faster than do most animal organs.

Two types of muscle are found in vertebrates and most other advanced groups of animals.  Striated muscle, often referred to as skeletal muscle in vertebrates, is usually the most abundant.  Intestines and blood vessels are the major locations of smooth muscle.  The sliding filaments of actin and myosin are aligned in the fibrils of the muscle fiber so striations are evident, keeping their orientation as they contract or relax and lengthen as the biochemical reactions powering the movement is regulated by control by voluntary nerves.  Smooth muscle is the other type of muscle and is controlled mostly by nerve fibers of the autonomic nervous system.  Smooth muscle is the muscle type responsible for contraction of veins and intestines.  Like skeletal muscle it works only by contracting.

A special type of striated muscle, not associated with the skeleton, is found in the heart and called cardiac muscle.  Cardiac muscle fibers branch and fuse forming a network.  The network probably is needed to prevent blood from separating fibers and pushing through the wall of the heart.  The fibers of cardiac muscle are partitioned at intervals by intercalated disks.  Intercalated disks are also found in some protostome hearts thus providing some evidence supporting the annelid ancestry of advanced protostomes and deuterostomes.

MUSCLE ATTACHMENTS

Bone
Skeletal muscles, which do their work by contracting as do all muscles, have an origin on a bone at one end and an insertion at the other end on an adjacent bone that is moved when the muscle contracts.  To move the bone back to its original position and opposing muscle must contract on the other side of the bones and joint.

Soft tissue
So how do we stick out our tongue.  We do it by contracting other muscles within the tongue oriented in directions other than the length of the tongue in which muscles are relaxing.  If they relax more on one side the tongue will curve more to the other side.

Hydrostatic or hydraulic skeletons
The earthworm provides a good example of this type of skeleton.  Under the cuticle and epidermis, the outer layer of muscle is circular muscle.  The soft tissue and fluid in the coelom is forced by contractions of the circular muscle into lengthening the worm as it gets thinner in the segments containing the contracting muscle.  Interior to the circular muscles are longitudinal muscles that lengthen.  If all the segments lengthen, the worm gets long and thin, the total worm volume remains the same.  Conversely, when the longitudinal muscles contract the worm shortens and gets much thinker, but total volume remains the same.

The leech also is dependent on the muscular system using the transmission of fluid and flexible soft tissue moved by the opposing contractions of outer circular and inner longitudinal muscles.  But the body is flattened by transverse muscles connected to dorsal and ventral surface tissues.  Thus movement involves less lengthening and shortening but more up and down bending to either swim by undulations of the body or move along surfaces my bringing the posterior sucker up close to the attached anterior sucker which is then released as the body straightens its bend to attach it further forward.

The photo above is a cross-section of a portion of a leech showing the thin layer of circular muscles under the cells of the epidermis.  Bundles of longitudinal muscles underlie the circular muscles.  A few transverse muscles are shown as dark tracts, some with lighter connections passing between longitudinal muscle bundles to tissue associated with the circular muscles.  The coelom is mostly filled with soft organs.

Hydras do much the same, but the interior of the hydra is fluid filled and the body has the circular muscle fibrils of the gastrodermal cells inside the longitudinal fibrils of the epidermal cell where the fibrils are in more of a network.  The fibrils of both layers of the layers are in close association with the thin layer of connective tissue separating the two cell layers.

Resolving the evolutionary switch from outer longitudinal to outer circular muscle

It is evident that the cnidarian medusa to planarian flatworm suggested in earlier posts and illustrated in [ http://evolutioninsights.blogspot.com/2015/03/evolution-quiet-pre-cambrian-genes.html ] provides a plausible mechanism for the transition.

I gained some insight into the functioning of hydra's hydrostatic skeleton when I had students study the feeding reaction of hydra.  When a weak solution of glutathione is introduced into the water near a hungry hydra it will start moving its tentacles toward its mouth in the same manner it would do if a small crustacean had been captured by a tentacle.  I was amazed to see that the mouth was wide open.  I was thinking it was impossible for it to maintain its posture if the fluid in the gastrovascular cavity was not prevented from exiting the open mouth.  Examination of hydra sections, in particular the tentacles, showed the gastrodermal cells were very large, almost balloon like, and the cavities in the tentacles were almost non-existent.

It made sense that each gastrodermal cell had a single circular muscle fibril so that contraction would be most directly applied to the cell and not slip between cells.  And the thick gasterodermis near the mouth allowed longitudinal fibers of the epidermis to open the mouth more efficiently.

Although the bloated gastrodermal cells may be a more important part of hydra's hydrostatic skeleton, large anthozoan anemones do utililize the fluid filling the gastrovascular cavity to a much greater extent.  Many have one or two siphonoglyphs which are ciliated grooves of the gastrodermis extending from near the mouth to near the basal disk.  Siphonoglyphs enable the anemone to remain inflated and/or reinflate itself after major contractions reducing size for self-protection.

Nematode muscles and evolution

The muscular system of large nematodes such as Ascaris is unique in that the muscles of the body wall are all longitudinal muscles.  The fibrils are enclosed in cells that are long tapering tubes with the nuclei containing part projecting into the pseudocoel.  From the bulbous part containing the nucleus, a slender tubular extension runs to one of two major nerves extending the length of the worm in dorsal or ventral positions; the synaptic connection to the nerve is made at the nerve by the muscle cell rather than at the muscle as in most organisms.  The muscular pharynx is a characteristic of nematodes important in maintaining fluid volume of the worm enabling its hydrostatic skeleton to function.  The cuticle is strong enough to keep the fluid retained for its function as a skeleton.  As a result, when the muscles of dorsal and ventral halves of the worm alternate contractions, the nematode bends or undulates up and down.

The peculiarity of the muscular system of nematodes and their lack of motile cilia are reason enough to reject the Ecdysozoa as a legitimate phylogenetic group.  The molecular basis for its formation is unsustainable if the evidence presented in [ http://evolutioninsights.blogspot.com/2013/05/science-screw-up-no-1.html  ]  is known.

Joseph G. Engemann     Kalamazoo, Michigan     January 28, 2016