Pycnotheca Stechow, 1919

Agís, José Ansín, Vervoort, Willem & Ramil, Fran, 2014, Hydroids of the families Kirchenpaueriidae Stechow, 1921 and Plumulariidae McCrady, 1859 (Cnidaria, Hydrozoa) collected in the Western Pacific Ocean by various French Expeditions, Zoosystema 36 (4), pp. 789-840 : 794-798

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Pycnotheca Stechow, 1919


Genus Pycnotheca Stechow, 1919 View in CoL View at ENA

Pycnotheca mirabilis ( Allman, 1883) View in CoL ( Fig. 2 View FIG ; Table 3)

Diplocheilus mirabilis Allman, 1883: 49 View in CoL , pl. VIII, figs 4-7. — Stechow 1913: 9, 88, figs 55, 56.

Kirchenpaueria mirabilis – Mulder & Trebilcock 1909: 34, pl. I, fig. 8. — Hodgson 1950: 50, figs 81, 82.

Plumularia mirabilis – Billard 1910: 37.

Diplocheilus (Kirchenpaueria) mirabilis View in CoL – Bedot 1923: 221, figs 14, 15.

Plumularia (Diplocheilus) mirabilis – Jäderholm 1919: 23.

Pycnotheca mirabilis View in CoL – Totton 1930: 216, fig.55b-e. — Rho 1967: 350, fig. 11A, B, pl. I, figs 2, 3. — Millard 1975: 377, fig. 120D-G. — Hirohito 1995: 256, fig. 86a- e. — Vervoort & Watson 2003: 366, fig. 89D-J. — Moazzam & Moazzam 2006: 230, fig. 7b, c.

Kirchenpaueria (Diplocheilus) mirabilis – Stechow 1925:241.

Pycnotheca mirabilis var. mirabilis View in CoL – Ralph 1961: 50, fig. 7a, b.

MATERIAL EXAMINED. — New Caledonia. CHALCAL 2, stn DW 80, 23°26.70’S, 168°01.80’E, 160 m, 31.X.1986, small colony composed of two plumes rising from stolon GoogleMaps ; no gonothecae ( MNHN).

DISTRIBUTION. — Species with a wide distribution in the Indian and western Pacific Oceans, with isolated records from the Atlantic Ocean ( Vervoort & Watson 2003). Reported from coastal waters of South Africa, Mozambique, Pakistan, India, Korea, Japan, Australia and New Zealand. In the Atlantic it is known only from Vema Seamount and South Africa (False Bay).

The presence of P. mirabilis in California should be confirmed with new data because the previous records [ Torrey 1902 as Halicornaria producta (Bale, 1882) ; Torrey 1904 as Diplocheilus allmani Torrey, 1904 ] were included by some authors ( Hirohito, 1995; Bouillon et al., 2006) in P. mirabilis , but in P. producta by Totton (1930) and Vervoort & Watson (2003).

Bathymetrical distribution extends from littoral zone to 732 m (400 fathoms).

The present material was collected from a single locality in New Caledonia at 160 m.


Hydrorhiza tubular, composed of tubules adhering to substrate, with short apophyses supporting a monosiphonic and unbranched axis.Basal part of the axis has one or two internodes with transverse septa and without nematothecae.Rest of stem composed of athecate internodes with oblique nodes (type hingejoints). Stem internodes with one to four apophyses, typically two, alternately directed left and right, with one or two nematothecae between two successive apophyses. Axis nematothecae monothalamic, immobile, with deeply scooped adcauline wall.

Each apophysis with a well developed mamelon on upper surface and one axial nematotheca with structure identical to that stem nematothecae.

Hydrocladia composed of a succession of thecate internotes separated by oblique nodes, including proximal oblique node separating apophyses from first thecate internode. Each internode bearing one hydrotheca, one mesial nematotheca and a naked sarcostyle behind the hydrotheca.

Hydrotheca with adcauline wall almost fully adnate, with exception of distal border. Abcauline wall moderately convex at the basal part and concave distally. Hydrothecal aperture tilted forwards, rim smooth, circular and slightly deepened laterally. Intrathecal cavity with strong septum arising near



Height of colony (in mm) 250

Stem internode, length 980-3430 Diameter at node 250-440

Length thecate hydrocladial 240-290 internodes Diameter at node 60-90

Hydrotheca Length abcauline wall 100-120 Diameter at rim 95-110

Mesial nematotheca, length 80-95 Diameter at rim 40-50

Lateral nematotheca, length 70-90 Diameter at rim 35-40

the end of abcauline wall, visible in lateral view as a triangle with upturned top pointing towards interior of hydrotheca.

Mesial inferior nematotheca not reaching hydrothecal base, immobile, monothalamic, with deeply scooped adcauline wall. Sarcostyle in axil between free part of adcauline hydrothecal wall and internode, with basal part invested by shallow hyaline cup.

No gonothecae observed.


Watson & Vervoort (2003) consider that the differences between Pycnotheca mirabilis ( Allman, 1883) and Pycnotheca producta (Bale, 1882) , are based on variable characters and not clearly established, but they recognise both as valid species.Our material agrees with the descriptions given in the literature for Pycnotheca mirabilis , and therefore it is included in this species.

Family PLUMULARIIDAE McCrady, 1859 Genus Cladacanthella Calder, 1997

Cladacanthella scabra ( Lamarck, 1816) View in CoL ( Figs 3 View FIG , 4 View FIG ; Table 4)

Plumularia scabra Lamarck, 1816: 127 View in CoL . — Billard 1913: 47. — Watson 2000: 52, fig. 40A-E. — Schuchert 2003: 212, fig. 61A-D.

Plumularia effusa Busk, 1852: 400 View in CoL . — Kirchenpauer 1876: 46, pl. I, fig. 4, pl. V, fig. 4. — Bale 1884: 129, pl. XVIII, fig. 5.

Acanthella effusa – Allman 1883: 27, pl. VI, figs 1-4. — Stechow & Müller 1923: 474.

Cladacanthella scabra View in CoL – Bouillon et al. 2006: 365, 366, fig. 172 C-F.

MATERIAL EXAMINED. — Philippines. MUSORSTOM 3, stn CP 142, 11°47.0’- 11°47.3’N, 123°01.5’- 123°03.0’E, 27- 26 m, 06.VI.1985: Many broken colonies GoogleMaps ; fragments up to 150 mm; no gonothecae ( MNHN), ( RMNH).

DISTRIBUTION. — Cladacanthella scabra is known from the Indo-Pacific: Indonesia, Philippines, Singapore and Australia ( Schuchert 2003).

Bathymetrical range varies between 15 and 1270 m.

Our material originates from one station in the Philippines and was collected at 26-27 m depth.


Hydrorhiza formed by a mass of intertwining tubules supporting a monosiphonic strongly ramified hydrocaulus with several internal coenosarcal canals. Lateral branches with a short basal internode with five nematothecae, one mamelon on upper surface and one apophysis supporting a hydrocladia. Rest of branch divided into internodes by oblique nodes like main stem, and with apophyses placed alternately directed left and right. Axis divided into internodes by oblique nodes, each internode with a varied number of apophyses and without nematothecae.

Apophyses in older parts arranged in three or four rows (not in true verticils) and in younger parts alternately directed left and right and slightly frontally, not in the same plane. Each apophysis with one mamelon on superior surface and three nematothecae: two longer in the axil and one impaired distal. All nematothecae bithalamic, movable, and distal chamber with scooped margin. Node between apophyses and first hydrocladial internode oblique.

Hydrocladia composed of a succession of thecate internodes with oblique nodes, each with one hydrotheca and three nematothecae: one mesial inferior and two lateral. Hydrotheca cup-shaped, placed on middle of internode, adcauline wall fully


Height of colony (in mm) 35

Length thecate hydrocladial internodes 790-940

Length athecate hydrocladial 245-330


Diameter at node 60-80

Hydrotheca, depth 260-330

Length abcauline wall 260-330

Length adcauline wall 260-320

Diameter at rim 150-160

Mesial nematotheca, length 85-90

Diameter at rim 30-40

Lateral nematotheca, length 80-90

Diameter at rim 30-40

adnate, abcauline wall sinuous, slightly convex on basis and strongly concave in the distal half; hydrothecal margin smooth and with two broad rounded lateral lobes.

Mesial nematotheca born immediately below hydrothecal base and reaching middle of hydrotheca. Lateral nematothecae inserted below hydrothecal margin. All nematothecae conical, movable and two chambered, basal chamber long and apical chamber with scooped rim.

Thecate internodes of basal part of hydrocladia with four internal perisarc rings, two at both extremities and two behind hydrotheca. Internal perisarc ring lacking on distal hydrocladial internodes or thin and little developed.

At distal part of branches hydrocladia replaced by thorn-like projections bearing several nematothecae.

Gonothecae not observed in the studied material.


In older parts of colonies modified hydrocladia with atrophied hydrotheca may occur, in which case the internodes have three nematothecae and a mamelon.


Schuchert (2003) and Vervoort & Watson (2003) include this species in the genus Plumularia , but Bouillon et al. (2006) place it in Cladacanthella Calder, 1997 , an opinion followed in this work.


Museum National d'Histoire Naturelle


National Museum of Natural History, Naturalis












Pycnotheca Stechow, 1919

Agís, José Ansín, Vervoort, Willem & Ramil, Fran 2014

Cladacanthella scabra


Pycnotheca mirabilis var. mirabilis

RALPH P. M. 1961: 50

Pycnotheca mirabilis

MOAZZAM N. & MOAZZAM M. 2006: 230
VERVOORT W. & WATSON J. E. 2003: 366
HIROHITO 1995: 256
MILLARD N. A. H. 1975: 377
RHO B. J. 1967: 350
TOTTON A. K. 1930: 216

Kirchenpaueria (Diplocheilus) mirabilis

STECHOW E. 1925: 241

Diplocheilus (Kirchenpaueria) mirabilis

BEDOT M. 1923: 221

Plumularia (Diplocheilus) mirabilis

JADERHOLM E. 1919: 23

Plumularia mirabilis

BILLARD A. 1910: 37

Kirchenpaueria mirabilis

HODGSON M. 1950: 50
MULDER J. F. & TREBILCOCK R. E. 1909: 34

Diplocheilus mirabilis

STECHOW E. 1913: 9
ALLMAN G. J. 1883: 49

Acanthella effusa

STECHOW E. & MULLER H. C. 1923: 474
ALLMAN G. J. 1883: 27

Plumularia effusa

BALE W. M. 1884: 129
BUSK G. 1852: 400

Plumularia scabra

SCHUCHERT P. 2003: 212
WATSON J. E. 2000: 52
BILLARD A. 1913: 47
LAMARCK J. B. P. A. 1816: 127
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