Chelonicola costaricensis Majewska, De Stefano & Van de Vijver, 2015

Majewska, Roksana, Kociolek, J. P., Thomas, Evan W., Stefano, Mario De, Santoro, Mario, Bolaños, Federico & Vijver, Bart Van De, 2015, Chelonicola and Poulinea, two new gomphonemoid diatom genera (Bacillariophyta) living on marine turtles from Costa Rica, Phytotaxa 233 (3), pp. 236-250 : 242-243

Chelonicola costaricensis Majewska, De Stefano & Van de Vijver , sp. nov. ( Figs 1–12 )

Frustules wedge-shaped in girdle view showing conspicuous septa at both poles. Valves small, heteropolar, typically clavate with a broadly rounded, non-protracted headpole and an acutely terminating footpole. Septa visible in LM and SEM on both poles. Valve dimensions (n=50): length 6.0–17.5 μm, width 1.7–3.1 μm. Axial area very narrow, not discernible in LM. Central area very small. Raphe filiform, straight with simple, indistinct proximal raphe endings. Distal raphe endings not discernible in LM. Striae almost parallel throughout the entire valve, very faintly visible in LM, 36–47 in 10 μm.

Type:— COSTA RICA. Olive ridley sea turtle, 9º 59’ 23.7” N, 85º 41’ 52.6” W, M. De Stefano, 27 October 2013 (holotype BR! stub 4420).

Scanning Electron Microscopy:—( Figs 1–12 ) Frustules isovalvar, clavate in girdle view, attached by the footpole on short mucilaginous stalks ( Fig. 3 ). Valve face flat in both valves with a clear angle to the very shallow mantle ( Figs 3 , 7 ). The mantle is equally high in its distal and proximal part but larger in the central part ( Fig. 7 ). Pseudosepta absent ( Figs 9, 10, 12 ). Axial area very narrow, linear ( Figs 4–6 ). Central area very small, bordered on one or both sides by one slightly shortened central stria ( Figs 4–7 ). Fascia never present ( Fig. 5 ). External raphe branches almost straight to very weakly curving ( Figs 4–6 ). External proximal raphe endings slightly expanded, unilaterally weakly deflected ( Fig. 5 ). External distal raphe fissures elongated, weakly deflected, continuing shortly onto the mantle on both poles ( Figs 6 , 7 ). Striae uniseriate, equally spaced throughout the entire valve, composed of a series of 3–5 slightly transapically elongated areolae ( Figs 4–7 ). Areolae bordering the axial area being the largest ( Fig. 6 ). Striae continuing without interruption onto the shallow mantle ( Figs 4–7 ). Apical pore field absent on both poles ( Figs 4, 6 , 8 ). Internally, raphe straight to weakly curved, positioned asymmetrically in a raised raphe sternum ( Figs 9–12 ). Primary side of the sternum thickened, opening the raphe in a lateral position ( Figs 9–12 ). Proximal raphe endings covered by a silica flap and distal raphe endings straight, terminating on weakly developed helictoglossae ( Figs 9–12 ). Areolae internally slightly sunken between thickened interstriae, covered by hymenes ( Figs 11, 12 ). Cingulum composed of a large number (up to 12) of open copulae, each with one row of apically elongated, slit-like poroids in the advalvar position ( Figs 3, 4 & 7 ). First band, the valvocopula, with a small, but distinct septum at the head pole ( Fig. 9 ). Second copula with a small septum at the footpole ( Fig. 10 ). Other copulae lacking a septum.

Etymology:—The specific epithet refers to the geographical locality, Costa Rica, where the species was first observed.

Figures

FIGURES 1–6. Chelonicola costaricensis. SEM pictures taken from the holotype population from the olive ridley sea turtle carapace collected on Ostional Beach, Costa Rica. 1. Three frustules of Chelonicola attached to the substrate together with one frustule (upper one) of Poulinea. 2. Several valves of Chelonicola attached to the substrate showing their valve face and the girdle composition. 3. One frustule attached to the substrate by a mucilaginous stalk. The girdle structure composed of at least 10 bands is shown. 4. Valve face view showing the head pole with the distal raphe fissure continuing onto the mantle. 5. External detail of the central area showing the lack of fascia and the stria structure. 6. External detail of a head pole showing the distal raphe fissure. Scale bar represents 10 μm except for Figs 5, 6 where scale bar = 1 μm.

FIGURES 7–12. Chelonicola costaricensis. SEM pictures taken from the holotype population from the olive ridley sea turtle carapace collected on Ostional Beach, Costa Rica. 7. External valve face view showing the mantle and the areolae. 8. External detail of a footpole showing the absence of an apical pore field and the distal raphe fissure continuing onto the mantle. 9 & 10. Internal views of an entire valve showing the raphe sternum, the septate girdle bands and the covered areolae. 11. Internal detail of the central area. 12. Internal detail of the footpole with helictoglossa. Scale bar represents 1 μm.