Sample Pages “Sea Urchins III” ( www.sea-urchins.com) Cidaroida Cidaridae Ctenocidarinae 983 Specimens of an unusual species previously thought to be infected by “Echinophyces” 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. 984 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 cidarids. 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 Orthonectida.. 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. thesis) 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. spinosa. 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 985 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.) 986 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). http://www.marinespecies.org/echinoidea 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 For more information: www.sea-urchins.com