A new phylum of Animalia ---Eucestoda n.p.

Cheng Gong-Huang*1 Cheng Caigui2, Liu Chuwu1, Wu Zaohe1
1. Fisheries College，Zhanjiang Ocean University, Guangdong,524025,China
2. Dept. Vector Biology,Institute of Microbiology and Epidemiology,AMMS,Beijing,100071,China
* is the correspondence author, Email: ghcheng@sohu.com

The cestodes are a group of the most specialized parasites in the world, it is special in the kingdom of animal world. There are 2 very special outstanding characteristics for a group in these animals: one is segmentation, the other is the animals without an intestine or gut. Therefore they do not resemble to any animals in the group-- helminthus they were put, and these should be discussed carefully.
With the speciallised characteristics we think this group of animal should be divided into two groups as it was done: the Cestodaria and the Eucestoda. The first group should be put in the earlier position they occupied because they almost resemble to those trematodes except without gut. but the Eucestoda should be elevated as a new phylum of the Animalia.
Key words: Taxonomy, Cestoda, new Phylum, Eucestoda

1. The basic view of the new Phylum—Eucestoda n.p.
In the years of study the authors found these specialized characteristics, which are with segmentation and with no gut, of the Subclass Eucestoda by surprise. When we compared them with other phylum of Animalia（Table 1.） we find no one is exactly the same group of Eucestoda: (Barnes, 1980) therefore we suggest setting a new phylum of Animalia that is Phylum Eucestoda n.p.
Here, we should first discuss about the metamerism of cestoda：untrue(Upton,1999) or truly segmentation. What kind of segmentation is untrue: maybe that should be some kind of Acanthocephalus that only have grooves on the tegument but no segment at all. For an Eucestode with several segments from the neg to the tail—how can it be untrue tagmosis? As in ancient we know cestode just by their segments not the whole worm, cestode was called “Zunbai Chong” in ancient China(means “white inch worm”, this maybe the earliest record of cestoda. Xu, 1984), so it must be thoroughly metamerism. As it is known that the annelids develop a trochophore larva and after its changing form then become an adult. In the metamorphosis of trochophores their larvae pass through stages in which larval structures are replaced by those characteristics of the adult.(Hichman, 1973) One stage is polytroch with several segments, however this resembles an adult cestode extremely. This is to say they have almost the same development experiences in segmentation. By comparison the segment(Schmidt, 1984) with human segmentation(Marieb, 1985) we shall find they amazingly resemble: The head—the scolex<0>; the cervical columns—the neck<1>; the thoracic columns—the germinal segments<2>; the lumbar columns—the immature proglottids<3>; the sacrum—the mature proglottids<4>; the coccyx—the progravid proglottids<5>.(Each columns of human imply certain segments) All these segment are almost the same when they are together and they just change a little gradually, for both human and Eucestodes. So how can we say Eucestoda is with a untrue metamerism?(Fig 1)
By comparison the Annelid, arthropod and Eucestode we may found that they have great differences and similarities too(Tab 1) but they are belonging 3 different groups( phyla). Because of the primitive characteristics (i.e. intersegment septa, without coelom and so on) and differentiated metamerism, which is much higher characteristics in Animalia, of Eucestoda n.p. we put this new Phylum between Annelida and Arthropoda

Table 1. Annelid- arthropod- Cestode comparison
Trait
Annelid
Eucestode
Arthopod
Determinate cleavage
Present
Present
Present
Tagmosis
Few species
Ubiquitous
Ubiquitous
Intersegmental septa
Present
Present
Absent
Coelomic cavity
Present
Absent
Reduced
Cilia
present
No, with microtriches
Absent
Circulatory system
Closed
Closed
Open
Chitinous exoskeleton
Absent
Absent
Present
Jointed appendages
Absent
Absent
Present
External segment
Present
Present
Present
Segmental muscle layout
Present
Present
Present
Tagmosis
Few species
Ubiquitous
Ubiquitous
Gut
Present
Absent
Present
(Sorry, this cannot be shown as a table, but you may know it by carefully reading)

And the characteristics of the Phylum Eucestoda are as follows: 1. Bilateria that is very common after the Phylum Platyhelminthes according to systematic development; 2. With 3 embryo layers; 3. With no guts; 4. With no body cavity; 5. With segmentation; 6. hermaphrodite; 7.Mostly with holdfast organs. 8. All inside parasites.

More detailed materials about them are below:
Most are parasites of vertebrates (only a couple of genera parasitic in invertebrates).
General morphologic structures
linear series of reproductive structures of both sexes (in most species): monecious.
composed of a scolex (head), neck (germinal region), and body (termed a strobila)
most species with segments, termed proglottids
craspedote (one proglottid overlaps another)
acraspedote (proglottids do not overlap)
new proglottids added at neck; termed strobilation
as new proglottids form, they move back and gradually mature; copulate with other proglottids (or those of other worms); eggs develop; become gravid and rupture/break off (apolysis)
scolex (head) at anterior end
holdfast organs : suckers, hooks, spines, grooves, sucker-like structures, acetabulum, cup-shaped, muscular, usually 4; sometimes 1 or 2, bothridia, muscular, highly mobile leaf-like structures, usually 4; project from scolex, bothria, shallow pits or grooves, usually 2; up to 6
hooks are keratinized, often in a circle (1-more circles), often on (often) protrusible, dome-shaped area on scolex termed a rostellum
glands: modified tegumental cells, produce adhesive material, sometimes form discrete apical organ
tegument: absorbs all nutrients since cestodes have no gut, covered by tiny projections to increase surface area (microtriches), covered by glycocalyx (carbohydrate containing molecules), enhances host amylase activity.
Nerves: unmyelinated, acetylcholinesterase a main neurotransmitter; some 20 different types of neuropeptides also noted, sensory nerves throughout body, ganglia in scolex; highly innervated, longitudinal nerves proceed posteriorly
excretion and osmoregulation: most have 2 pair osmoregulatory canals running posteriorly, dorsal and ventral pairs, unite in scolex, protonephridia embedded throughout each proglottid
basic metabolism: mainly anaerobic, absorbed across tegument, glucose (also galactose) most important; overally, many other not metabolized, amino acids actively transported inside, purines and pyrimidines facilitated diffusion, fatty acids, monoglycerides, and sterols absorbed
Reproductive structures: most monecious with 1 set of male and 1 set of female reproductive structures; few dioecious, few with 1 set of male and 2 sets of female reproductive structures, proglottids gradually mature as the move back, usually male reproductive organs mature first and sperm stored (i.e. after insemination) until ovary matures (protandry or androgyny) or in some, female organs mature first (protogyny or gyandry), sperm transfer usually from cirrus to vagina of some segment, or between adjacent strobila. If no vagina, then hypodermic impregnation.

2. Discussion:
About the systematic of lives it was determined according to the embryo development and dissected of every systematic group of lives that is to say the anatomic characteristics of them as well as morphology.
The Eucestoda is quite differentiated from other phyla even those of the “same” phylum Platyhelminthes as we stated it above. we strongly suggested to set a new phylum of “Eucestoda”. We do not use a new name because of too much name may cause diffusion in systematics. There should be a lot of new problem after a new phylum is established, for example—how to define the Class. As we stated here Eucestoda is tagmosis so the Caryophyllidea should be belong to these phylum.
Here we give a suggestion for classes in Eucestoda n. p.: Trypanorhyncha new class; Bothrida new class; Suckera new class and Deformida new class.
These Classes are for groups divided mainly by morphology of scolex: Trypanorhyncha, new class—almost the same “order” as before, it has four armed tentacles; Bothrida n.c. is for those who has bothridia or bothria; Suckera n. c.: for those with one or more sucker(s); and Deformida n. c.: for those who have deformed scoleces and do not belong to the above classes.

Reference
Hickman, C. P. 1973 Biology of the Invertebrate. The C.V. Mosby Company. Saint Louis: 426-440.
Marieb, E. N. 1985, Human Anatomy and Physiology Laboratory Manual. Fetal Pig Version, 2nd Edition, The Benjamin / Cumming Publishing Company, Inc. PP66-70
Barnes R. D. 1980 Invertebrate Zoology, Saunders College/HRW
Schmidt, G，D. 1984 Handbook of Tapeworm Identification. CRC Press INC, Boca Ratom, Florida. USA.
Steve J. Upton,1999, Animal Parasitology, Kansas State University—internet course.
Xu Bingkun(Chief Editor). 1984 Human Parasitology. Beijing:People’s Medical Publishing House,2nd edition:113.

(The figure is on another document)
Fig 1. Comparison of Metamerism of Human and Eucestoda new Phylum