Sample Pages “Sea Urchins III” Echinophyces” )

Sample Pages “Sea Urchins III” (
Cidaroida Cidaridae Ctenocidarinae
Specimens of an unusual species previously thought to be infected by
Mortensen 1909 recorded specimens of Rhynchocidaris triplopora with
unusual morphological modifications:
1. The test is conspicuously lower and, including the podia, more darkly
pigmented than the normal specimens.
2. The pedicellarian epithelium is thickened and also darker pigmented.
3. The primary spines are set with filaments originating in the innermost part
of the layers.
4. In females the genital plates are not pierced by a gonopore, but the
gonoducts lead downwards each forming an opening at the adoral median
suture of the interambulacra or at the edge of the peristome. In males the
gonoduct leads to an opening midway down the test in the interambulacrum.
Mortensen assumed that these “abnormal” echinoids were infected by a
parasite which he described as Echinophyces mirabilis. However, he was
not able to explain how the parasite, housing in the calcareous primary
spines, could cause such drastic modifications in soft tissues and especially
in the inner bauplan.
Fig. 1684. Right: Pedicellaria of an “unusual specimen”: The epithelium of the pedicellaria is strongly
thickened and pigmented. Scale 500µ. Mortensen 1909
Literature: Th. Mortensen 1909; 1910; 1928, 1950 Th. Mortensen & K. Rosenvinge 1910; R.
Koehler 1902, 1912a,b; F.J. Fell 1976 (unpubl. thesis); S.J. Lockhart 2006 (unpubl. thesis and
unpubl. data).
Fig. 1685. Female of an “unusual specimen”.
Diameter of test 19 mm, Scotia Sea. ZMUH
(as “Rhynchocidaris triplopora”.)
Above left: Aboral side: No gonopores at all are
developed in the genital plates.
Above right: Oral side: The lower interambulacra are
pierced by gonopores (arrows) and the peristomial
membrane is strongly depressed.
Left: Side view: The test is very low.
Cidaroida Cidaridae Ctenocidarinae
Further examinations by Mortensen (1909) revealed that the
tubular filaments, first thought to be typical to Echinophyces,
were actually normal structures being part of the spine
cortex often developed in cidarid spines. (Fig. 1686.)
S.J. Lockhart confirmed this fact by her molecular analyses
(unpubl. thesis 2006).
Mortensen (1909) found a single plasmodial cell on one
spine of one of the specimens with these “abnormal”
modification, which he attributed to the parasite
Echinophyces mirabilis. No other plasmodium of
Echinophyces was ever found again.
And there is no evidence that it infests all these “unusual
specimens” nor that it does not infest other Antarctic
Consequently Echinophyces does not appear to be
responsible for the morphological changes.
S.J. Lockhart (unpubl. thesis 2006) proposed that the cell
found by Mortensen (1909) may belong to a member of the
Fig. 1686. Right: Primary spine of an unusual specimen. The
enlarged filaments originate from the spine cortex of the cidarid.
They were previously thought to be typical for an infection with the
parasite Echinophyces mirabilis (arrow above). Clusters of small
spots show the position of broken filaments. (arrow below).
Scale 1 mm.
Fig. 1687. Position of the crosssection in fig. 1688.
Fig. 1688. Above left: Cross-section of an “unusual specimen”: The gonads in A III, A IV and A V are visible.
They consist of eggs of various size, indicating that the reproduction is continuous. The eggs are not released
through gonopores in the genital plates in the apical system but the gonoducts lead downwards to an opening on
the oral side or at the peristomial edge. (Modified after the drawing of R. Mooi in S.J. Lockhart 2006 unpubl.
It is self-evident that the position of the gonopores on the oral side is advantageous for the success of
reproduction, because the perilous transfer of the eggs from the gonopores on the apical side to the
brood chamber on the peristome is avoided. Thus it is very likely that these modifications are a sign of
natural evolution as S.J. Lockhart 2006 pointed out.
Specimens with such drastic morphological changes were found not only amongst Rhynchocidaris
triplopora but also living sympatrically amongst samples of Ctenocidaris perrieri, C. speciosa and C.
Recent morphological and molecular examinations by S.J. Lockhart (unpubl. thesis 2006) revealed
that the “unusual specimens” represent a phylogenetic clade of its own with well-defined
characteristics distinctive from the other ctenocidarids.
Cidaroida Cidaridae Ctenocidarinae
Fig. 1689. “Unusual specimen”. Diameter of test 30 mm, South Georgia. ZMUC (as Ctenocidaris speciosa).
This specimen is anomalous in having six columns of ambulacra and interambulacra and in consequence six
genital and ocular plates in the apical disc and six gonopores on the oral side.
Above left: Aboral side: There are no traces of gonopores in the genital plates.
Above right: Side view: The test is conspicuously low with flattened aboral and oral sides.
Below: Oral side: Five of the gonopores open into notches at the peristomial edge positioned at the median line
of the interambulacra; the sixth opens more distant from the edge in the median suture. (The holes in the
peristomial ambulacra are likely to be artefacts.)
Cidaroida Cidaridae Ctenocidarinae
There exists a rather vague original description of Koehler (1902) on Aporocidaris incerta. Although
the type material is lost or damaged consisting of five specimens of less than 15 mm from the
Bellingshausen Sea at 100 – 300 m, S.J. Lockhart proposes that they actually belong to this clade and
the newly erected genus she called Miracidaris.
Test very low, 40 – 50% of horizontal diameter, hardly exceeding 30 mm; flattened above and below;
apical system: ocular plates widely exsert, genital plates large, gonopores in females not piercing the
genital plates, but the median sutures on the oral side or even the peristomial edge in median
interambulacral position; gonopores in males small, transferred midway down the test in the median
sutures of the interambulacra ;
Colour: Preserved specimens are dark brown. Alive, they are bright red, spreckled with black (i.e. the
darkly pigmented pedicellariae).
Distribution: Living on the island shelves of the Scotia Sea from the South Shetland Islands to the
Shag Rocks (S.J. Lockhart 2006 unpubl. thesis), off the East coast of Antarctica and Ross Sea and
also in the Bellingshausen Sea and off the Antarctic Peninsula (Koehler 1912 a,b).
Biology: The specimens live sympatrically amongst their presumed respective conspecifics. Their
reproduction is staggered and continuous in contrast to the single-cohort brood in the other
ctenocidarines and in Austrocidaris (S.J. Lockhart 2006). Apparently the reproduction is also more
successful as there occur distinctly more female individuals with brood in a population than in the
other groups.
The species name is listed as Miracidaris incerta (Koehler 1902) in Kroh & Mooi 2010 World Echinoid
Database. (WED 2010).
Fig. 1690. “Unusual specimen”. Diameter of test 21 mm; Scotia Sea. AWI
The primary spines are set with tiny filaments (see fig. 1686.).
2011 copyright Heinke & Peter Schultz Partner
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