Orthopyxis mollis ( Stechow, 1919 )

Gil, Marta & Ramil, Fran, 2025, Hydroids (Cnidaria, Hydrozoa) from Guinea Bissau, Zootaxa 5577 (1), pp. 1-89 : 29

Orthopyxis mollis ( Stechow, 1919)

( Fig. 5A–B ; Table 3)

Clytia mollis Stechow, 1919: 44–45 , fig. L.

Orthopyxis mollis : Picard, 1951b: 344–346, fig. 3.

non Orthopysis mollis : Ralph, 1957: 840, fig. 7E–K.— Vervoort & Watson, 2003: 440–441, fig. 107I–T.— Galea, 2007: 86–88, fig. 20E, F (= Campanularia lennoxensis Jäderholm, 1903 ).

Material examined. BISSAU-0810, stn BS191, 10º18'25"– 10º19'20"N, 16º08'47"– 16º08'47"W, 24–25 m, 3-XI-2008: 63 colonies (one with male gonothecae), up to 11 mm high, of which 23 growing on bryozoans, 11 on Idiellana pristis , six on Diphasia digitalis , two on Eudendrium capillare , two on crustaceans, one on Bimeria vestita and one on Tridentata loculosa .

BISSAU-0810, stn BS194, 10º21'59"– 10º22'36"N, 16º13'23"– 16º14'03"W, 21–24 m, 3-XI-2008: 13 colonies (two with male gonothecae), 19–39 mm high, of which six growing on bryozoans, one on Eudendrium sp. , one on Halecium sp. and one on Idiellana pristis .

Description. Colonies arising from filiform hydrorhiza adhering to substrate, composed of scattered pedicels, each bearing apically a hydrotheca. Pedicels usually long, irregularly undulated and never ramified. Undulations more pronounced in some parts than in others with, sometimes, transverse nodes, indicating breakage followed by regeneration. A sub-hydrothecal spherule between the hydrotheca and its corresponding pedicel.

Hydrothecae deeply campanulate, smooth-walled, tapering towards base. Basal part rounded, with diaphragm formed by an annular thickening delimiting a small basal chamber. Hydrothecal rim circular, with 10 to 12 low rounded cusps separated by U-shaped incisions of equal dimension.

Male gonothecae given off from stolon, long, elliptic, borne on short, undulated pedicels. Aperture circular, located at distal end. Female gonothecae not seen.

Remarks. The synonymy of this species given by Vervoort & Watson (2003) proved partly erroneous, with several South-American records reassigned to either Campanularia lennoxensis Jäderholm, 1903 (see Galea et al. 2009: 16–17) or Campanularia hartlaubi (El Beshbeeshy, 2011) (see Galea & Schories 2012a: 59). Consequently, it is assumed that the records of O. mollis by Ralph (1957) and Vervoort & Watson (2003) likely belong to different species, based on their geographically remote areas of occurrence.

Our material agrees well with those described by Stechow (1919) and Picard (1951b) in terms of colony structure and measurements.

However, O. mollis has only been recorded from the Mediterranean Sea and seems to be a species restricted to shallow waters. The present authors have studied abundant material collected from West Africa and have never recorded this species, possibly because their materials originated from deep waters. Ansín Agís et al. (2001) and Gil & Ramil (2017a) have highlighted the importance of the Atlantic-Mediterranean species in West Africa, emphasising the importance of the current systems in the southward dispersion of sessile epifauna (Van Soes 1993). It is therefore not surprising that this first record of O. mollis for Guinea Bissau, stands also for the West Africa, as well.

Biology. This species has been found growing on algae ( Stechow 1919, as Clytia mollis ; Picard 1951b). In the northern hemisphere gonothecae have been found in August ( Stechow 1919; Picard 1951b).

In our material, most of the colonies were growing on bryozoans and the hydroids I. pristis , T. loculosa , D. digitalis , E. capillare , B. vestita , Eudendrium sp. and Halecium sp. ; however, two colonies were also found growing on crustaceans. Gonothecae were found in November.

Distribution. This species has only been collected from the Mediterranean, and its distribution seems to be restricted to shallow waters ( Picard 1951b).

Our colonies were collected from Guinea-Bissau at depths between 21–25 m.

Figures

FIGURE 5. A–B. Orthopyxis mollis (Stechow, 1919) (stn BS194): portion of colony with hydrotheca and two gonothecae (A); portion of colony with two hydrothecae (B). C–D. Clytia linearis (Thornely, 1900) (stn BS191); hydrotheca (C); gonotheca (D). E–F, Laomedea calceolifera (Hincks, 1871) (stn BS131); hydrotheca (E); female gonotheca (F). Scales: a–f, 0.5 mm.