Weldon WFR 1889 (citation)- Bohmig L 1895 (citation)- lists of 7 species described here. Long description of anatomy and histology in the genus- definition p 35, key p 35, 37. Also p 39, 43, and 45. Graff L v 1904 (citation)- definition of Graff L v 1905 (citation)- "Proporidae without a bursa seminalis. The mouth usually lies on the ventral side or behind this, the pharynx is very short or completely wanting. Body flattened, plate shaped. the frontal gland is a little more strongly developed than in other Acoela and openings lie scattered on the anterior end in such a way that no frontal organ is formed. Moreover the arrangement of this latter appears to be of specific significance. In one alleged instance (H. piger) one finds also a statocyst which lies on the dorsal side of the brain, while eyes appear to be lacking. The genital opening occurs ventrally shortly before the posterior end of the body. The testicular follicles are scattered thickly dorsally either in a single median egg-shaped mass or (H. obtusus) in two longitudinal rows. Neither the testes nor the two ventral ovaries possess a membrane. All species contain xooxanthellae. The flattened body (described many times as naked in preserved specimens) has a circular to oval or leaf shaped outline. 0.8-2.5 mm." Pelagic only one species parasitic. Teirreich - Graff 1905, p 6. Bohmig L 1908 (citation)- p 3 lists in family Proporidae, mentions p 6. Lohner L 1910 (citation)- comment on type of digestive parenchyma in a species of this genus. Wilhelmi J 1913 (citation)- mentions p 36, 67, 103, 113 lists p 12 in Family Proporidae. Westblad E 1948 (citation)- p. 12- comment on epithelium in, p 56- in key. Hyman LH 1951 (citation) -vol 2, p 129- notes these are pelagic and habits poorly known. Steinbock O 1966 (citation)- mentions testes in p 85, 138. Dorjes J 1968 (citation)- lists this way in literature review- places in family Convolutidae p 85- definition and description of species- 7 species Haplodiscus piger Weldon 1888 Haplodiscus acuminatus Bohmig 1895 Haplodiscus obtusus Bohmig 1895 Haplodiscus orbicularis Bohmig 1895 Haplodiscus ovatus Bohmig 1895 Haplodiscus weldoni Bohmig 1895 Haplodiscus ussowi Sabussow 1896 Dorjes J 1970 (citation)- description of new species Haplodiscus bocki and summary of genus. Long description and literature review p 261-265. Lists species as above but H. orbicularis is uncertain, also H. scutiformis and H. ussowi. Also, p 255, 257, 259, 261-5, and diagnosis p 265. Yamasu T, Okazaki A 1987 (citation)- Haplodiscus sp in faunal list.
from Doerjes (1970) (citation) Haploplodiscus bocki spec. nov.,....
all Haplodiscus species are pelagic
Lebensform characters with this life-style:
broad-bodied, often disc-shaped
numerous symbiotic algal cells
(but body form of certain species and absence of statocyst in H. piger should be discussed:)
H. piger absence of statocyst
Weldon (1899) described H. piger as a neotenic cestode or trematode larva
so no statocyst described
Bohmig doubted this, but had communication from Weldon that was actual absence
Graff (1904-08) speculated that statocyst easily overlooked in Weldon's material
Doerjes had difficulty finding statocyst in H. bocki, so overlooking in H. piger understandable
other acoels without statocyst:
Amphiscolops sargassi Hyman (1939)
A. evelinae Marcus (1947)
but Bohmig (1895: 37) right in synonymyzing H piger with H orbicularis
shape
H piger is the only species to have been studied alive (by Weldon)
therefore, whether body form described for others, studied only in fixed
preps, is applicable to live animal, is in question
same applies to length and breadth measurements
data from sections provides only vague results:
insunk brain
simple mouth opening (even in H ovatus--i.e., not pharynx simplex here)
penis tube terminal, invaginated in a muscular bell
ovaries paired
epidermis partially or wholly insunk
parenchyma strongly spongy, vacuole-rich
ovary position distinctive
in second body third
(except in H. bocki, where are in forebody back to second body third;
and H. ussowi, where are in third body third)
ovary fields
hang together in H. ussowi, H. scutiformis, H obtusus
but eggs separated by broad interspace in H. piger, H. acuminatus, H bocki
unknown in incompletely mature specimens of H ovatus, H. orbicularis
which is certainly true of H. weldoni
bursa seminalis
known only in H. bocki
simply built, probably overlooked in other species
(e.g., Sabussow (1896) mentions unpaired sperm mass between copulatory organ and ovary)
(for this reason Doerjes did not establish separate genus for H. bocki)
testes unpaired except in H. bocki and H. obtusus
germ center in dorsal peripheral parenchyma in middle body third
copulatory organ similar in all spp
ventro-caudal body wall invaginated into tube into body
bounded by more or less loose or bell-shaped muscle tissue
both organ parts tightly bound together
lengths appear not to be significant (contrary to Bohmig (1895))
because judged so far only in fixed material
Bohmig (1895) distinguished 2 groups:
with or without an antrum masculinum
but certain only for H. ovatus (w/o) and H. acuminatus (with)
...
muscle sheath of copulatory organ functions as sperm reservoir
i.e., serves as sem. ves.
this applies as well to H. ussowi, H. bocki
H. piger, according to Weldon 1889, with sperm assembling in peripheral parenchyma
proof of a sem. ves. lacking for this species
brain insunk in all species
5 prs of longitudinal nerves at most
large number of frontal and marginal nerves and around statocyst
but apparently lacking in H. piger
no nerve connection between brain and statocyst/sense-cell complex
in H. bocki; embedded in a circle of finely granular cells
(this sensory complex is in position Bohmig and Sabussow described
a postcerebral cell concentration, though this appears more like
germ-cell center, according to Doerjes)
key to species of Haplodiscus difficult because of uncertainty of characters
H bocki with
ovary beginning in front end
bursal organ
mouth opening in hind body third
statocyst
H obtusus
paired testes
H piger
lack of statocyst
length/breadth relationship unique
otherwise identical to H orbicularis
H. orbicularis / H. ussowi difficult to distinguish
...
Return to Convolutidae Haplodiscus