Proporus minimus (An der Lan, 1936) (citation) Steinbock O 1935 (citation)- mentions this species as Archiproporus - compares with his Protomacrostomum groenlandicum - says he brought this back from Groenlad and it was found among his acoels. An der Lan, 1936 (citation)- describes as Archiproporus minimus. Westblad E 1945 (citation)- moves from Archiproporus to include in Proporus. Westblad E 1948 (citation)- p 33, notes simple reproductive organs. Steinbock O 1966 (citation)- mentions p 134, 135 calls it Archiproporus and discusses. Dorjes J 1968 (citation)- lists as good species. p 370 - see note on this species as treated by Westblad- he disagrees. Dorjes J 1971 (citation)- lists as (An der Lan, 1936) - described by An der Lan as Archiproporus minimus- describes and illustrates- p 117-121. Diagnosis p 133. Karling TG 1974 (citation)- says this should be a separate genus- Dorjes J, Karling TG 1975 (citation)- Greenland and North Sea- SMNH. Smith JPS 1981 (citation)- mentions Dorjes description of epithelium in digestive tract.
[translated from Doerjes 1971]
Proporus minimus (An der Lan 1936)
Archiproporus minimus An der Lan 1936
Proporus minimus Westblad 1945, 1948
Pr. m. Dorjes 1968
localities:
Diskobay, southern Godhavn, 250 (-300) m deep on muddy bottom (Steinbock Aug 1926)
Droebak, Norway, depth ?, sediment ? (E Westblad July 1935)
material:
sections of Westblad in Natural History Museum Stockholm, wrongly labeled as Haploposthia viridis.
because Westblad based his placing this species into Proporus solely on literature,
Doerjes adds this account of the sections:
epidermis thickly condensed, insunk in front end;
reaches twice thickness in mid-body
gradually reduces to original thickness in posterior
vacuolated
from insunk anteriorly to intraepithelial posteriorly
mucous glands eosinophilous and finely granulated
no distinct arrangement; An der Lan wrote of regular distribution
glands into peripheral parenchyma with voluminous gland body
open with fine necks between cilia
no rhabdite glands
frontal organ only weakly developed
body-wall musculature forms inner border to epid.
layering typical of acoels (inner longitudinal)
inner-body musculature exceptionally well developed
strong longitudinal fibers, weak dorsoventral fibers with distinctive functions
2 retractors insert on front end and
run in diagonal direction to ventral and dorsal body-wall musculature
2 other longi- bands reach into body
ventral longitudinal end at level of inner pharynx opening w/o tying w/ pharynx muscles
dorsal longitudinal muscles reach far into inner body
and surround what An der Lan (1936) called a gut-like space, corresponding gut lumen
in hind portions, these fan horse-tail-like and protrude into gut epithelium
besides these powerful muscle bands,
numerous circular surround gut lumen and
fixators run from gut musculature to body-wall muscles
large number of muscles insert into brain, dispersing shortly into parenchyma
nervous system
brain cross-form, sunk into body, ensheaths statocyst
nerves: two clear frontal- and two lateral-nerves to front body pole
and to lateral body periphery
longi nerves in body are followed by the powerful inner longitudal muscles
parenchyma
peripheral parenchyma is exceptionally spongy
vacuolated consistency is thicker in front than posteriorly
appears lamellate through distinct muscle fibers through it
round nuclei relatively small, strongly cyanophilic
and frequently in peripheral layers of the tissue
gut
reminiscent of gastrodermis of other (non-acoel) turbellarians:
peculiar structure in delimiting region between marginal parenchyma and gut lumen
basal layer is set off by numerous circular and longitudinal muscles
which form a special gut musculature
that is linked to body-wall muscles by cross-fibers
gut musculature sits proximal to epithelial binding tissue
which is overlain by numerous villi in central lumen
no digestive glands or ciliation like those in Nemertoderma and Meara
digestion apparently by form of holocrine secretion
numerous cell groups loose from epithelium in central digestive cavity
supports An der Lan's statement that "regular spaces corresond to true gut lumen"
Doerjes skeptical about lack of limit betwen peripheral parenchyma and gut
because of clear membranous & muscular layer
mouth opening ventral between first and second body fifths
pharynx tube ciliated, projects inward from mouth dorsally and slightly posteriorly
= simplex type, simple inturning of epidermis inward
weak longi- and circular muscles over its entire length
continue at inner end partly as gut musculature, partly as dilators toward bodywall musc.
pharyngeal glands finely granulated, insunk in peripheral parenchyma
not regularly distributed over length of pharynx, more at mouth and inner end
male reproductive organs
germ cells in unpaired testes in peripheral layers of peripheral parenchyma
in region from first to second body third
into small, few-celled follicles
formation center not visible (An der Lan described as behind brain)
dorsal testicular string widens posteriorly, reaches body wall at its end
here, the follicles are tightly appressed, borders not clear
sperm club-shaped, no synchronous dev't
sperm, sermatogonia, and spermatids mixed together, reaching right to copulatory organ
copulatory organ unremarkable
opens with very short antrum masculinum on hind body pole
consists of outer glandular vesicle [vesicula granulorum] covered with muscles +
inner vesicula seminalis into which the short muscular cirrus is invaginated;
ciliated atrial portion narrows toward body to an unciliated ductus ejaculatorius
in front of whose proximal end lie additional eosinophilous gland cells
these glands are different from those of glandular vesicle in distal part of ves. sem.
secretions of these glands stop off the lumen of the penis
mature sperm penetrate through canal that binds sperm vesicle with endbranch of testes string
and into vesic. sem.
female reproductive organs
no female accessory organs
medial ventral egg string, with no hint of pairing in fully mature animal
(so differs from observations of An der Lan who studied younger animals)
oogonia formed in wide area in front portion of middle third of body
at first are united as thickly granulated oogonia
climb toward midbody and come together to a compact egg field
mature eggs reach diameter of 3/4 of body height
protrude into gut space by end of their development
uptake of nutrients by osmosis [pinocytosis] (no lobopodia seen)
Notes from synonyms
Notes for Archiproporus minimus
An der Lan H 1936 (citation)- p 322-3 describes and illustrates, figure 4 and 16. Westblad E 1945 (citation)- p 43 says Archiproporus minimus = Proporus minimus. Westblad E 1948 (citation)- p 58 says he has eliminated this genus. Dorjes J 1971 (citation)- also places minimus in Proporus. Karling TG 1974 (citation)- says Dorjes considers this a valid genus. Dorjes J, Karling TG 1975 (citation)- lists.
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