Poulinea lepidochelicola 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 : 243-247

Poulinea lepidochelicola Majewska, De Stefano & Van de Vijver , sp. nov. ( Figs 13–31 )

Frustules wedge-shaped in girdle view showing conspicuous septa at both poles. One valve slightly concave while other valve flat. Valves small, heteropolar, typically clavate with acutely rounded, non-protracted headpole and footpole. Septa visible in LM and SEM on both poles. Valve dimensions (n=50): length 5.2–10.0 μm, width 1.6–2.8 μm. Axial area very narrow, not discernible in LM. Central area forming a wide fascia. Raphe filiform, curved with expanded proximal raphe endings. Distal raphe endings not discernible in LM, typically covered by a silica flap on both poles, only visible in SEM. Striae weakly radiate near the central area, almost parallel throughout the rest of the valve, very faintly visible in LM, 25–36 in 10 μm, composed of only two, transapically elongated areolae, only discernible in SEM.

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 4421).

Scanning Electron Microscopy: —( Figs 13–31 ) Frustules heterovalvar, wedge-shaped in girdle view ( Fig. 15 ), attached by the footpole to the substrate by a mucilaginous pad ( Figs 13, 14 ). Valve face flat in one valve and slightly concave in the other ( Fig. 15 ). Valve face gently sloping towards the mantle margin ( Fig. 26 ). Mantle height largest near the valve middle becoming shallower towards both poles ( Figs 15, 16 , 26 ). Pseudosepta absent ( Figs 27–29 ). Axial area narrow, linear, narrowing towards the apices ( Fig. 21 ). Central area small, forming a rectangular fascia that widens towards the valve margins ( Figs 21, 24 , 26, 27 ). Occasionally shortened striae present in the central area ( Figs 15, 16 , 21 ). External raphe branches differing in length with branch in upper half (headpole) shorter than in lower halve of the valve ( Figs 16 , 21 ). Branches almost straight to curving ( Fig. 21 ). External proximal raphe endings spatulate, unilaterally weakly deflected ( Fig. 24 ). Distal raphe fissures elongated, unilaterally bent, terminating near the valve poles, covered on the headpole and footpole by silica flaps, conspicuously thickened on the footpole ( Figs 21–23 ). Striae uniseriate, equally spaced on most of the valve, but somewhat denser near the poles ( Figs 21–23 ), composed of 1–2 (very rarely 3, Figs 27–29 ) transapically elongated areolae ( Fig. 25 ). Both rows of areolae separated by a larger hyaline area, formed by the valve face/mantle junction ( Figs 25 , 26 ). Apical pore field absent on both poles, but one series of elongated areolae surrounding the distal raphe ending present at the footpole ( Fig. 23 ). Internally, raphe straight, located on a raised raphe sternum ( Fig. 27 ). Proximal raphe endings covered by a silica flap ( Figs 30, 31 ). Evident in oblique view, proximal raphe endings terminating on a slightly raised central nodule ( Fig. 31 ). Distal raphe endings straight, terminating on weakly developed helictoglossae ( Figs 28, 29 ). Areolae internally slightly sunken between interstriae, covered by hymenes located in the middle of the areolar canal ( Figs 28–30 ). Cingulum composed of a large number (up to 12) of open copulae ( Fig. 20 ), each with one row of apically elongated, slit-like poroids in the advalvar position ( Figs 15–18 ). Near the footpole, a double row of poroids often present on the copulae ( Fig. 17 , arrow). First band, the valvocopula, with a small, but distinct septum at the head pole ( Figs 19 & 20 ). Second copula with a small septum at the footpole ( Fig. 19 ). Other copulae lacking a septum.

Etymology:—The specific epithet lepidochelicola refers to the habitat of the new species, living (Latin - cola) on

Lepidochelys olivacea .

Phylogenetic analysis

A total of four most parsimonious trees of 97 steps was recovered in the cladistics analysis. From these four trees, a strict consensus tree was computed and is presented in figure 32 and had a consistency index of 0.443 3 and retention index of 0.597 0. The strict consensus tree shows a monophyletic clade with Chelonicola sister to Poulinea . This group is sister to Cuneolus , and together that group of three genera is sister to Tripterion . Other taxa suggested to be part of the Rhoicopheniaceae are found in widely divergent places in the tree, either sister to gomphonemoid diatoms ( Rhoicosphenia and Gomphoseptatum ) or ‘monoraphid’ diatoms (Gomphonemopsi s and Gomphosphenia are sisters and then related to a clade of Achnanthidium and Cocconeis ).

Figures

FIGURES 13–20. Poulinea lepidochelicola. SEM pictures taken from the holotype population from the olive ridley sea turtle carapace collected on Ostional Beach, Costa Rica. 13. Several frustules attached to the substrate showing how the population is organised. 14. Five frustules attached to the substrate showing the headpoles and the girdle bands. 15. External girdle view of an entire frustule showing the girdle bands and the mantle. 16. External girdle view of an entire valve showing the mantle, the distal raphe fissures and the doubling of the perforation of the girdle bands near the footpole. 17. External detail of the footpole. The arrow shows the doubling of the poroids. 18. External detail of the headpole. 19. Internal view of an entire valve showing the raphe sternum, the septate girdle bands and the covered areolae. 20. Second copula with the typical septum at the footpole. Scale bar represents 10 μm, except for Figs 17, 18 where scale bar = 1 μm.

FIGURES 21–25. Poulinea lepidochelicola. SEM pictures taken from the holotype population from the olive ridley sea turtle carapace collected on Ostional Beach, Costa Rica. 21. External view of an entire valve showing the raphe structure, the striae composed of two enlarged areolae and the fascia with only one reduced stria. 22. External detail of a headpole with the siliceous covering of the distal raphe fissure and the lack of an apical pore field. 23. External detail of a footpole with the thickened siliceous covering of the distal raphe fissure and the presence of several areolae surrounding the apex. 24. External detail of the central area showing the spatulate proximal raphe endings. 25. External detail of the striae. Note the hymenate coverings in the areolae canals. Scale bar represents 1 μm except for Fig. 21 where scale bar = 10 μm.

FIGURES 26–31. Poulinea lepidochelicola. SEM pictures taken from the holotype population from the olive ridley sea turtle carapace collected on Ostional Beach, Costa Rica. 26. External oblique view of an entire valve showing the shape of the mantle. 27. Internal view of two entire valves without girdle elements showing the raphe sternum and the covered areolae. 28. Internal detail of the headpole showing the helictoglossae and a few areolae surrounding the headpole. 29. Internal detail of the footpole with the helictoglossae and several rows of areolae surrounding the footpole. 30. Internal detail of the central area with the siliceous covering of the proximal raphe endings. 31. Internal detail of the central area. The siliceous flap covering the proximal raphe endings has been removed showing the raphe endings. Scale bar represents 1 μm except for Fig. 27 where scale bar = 5 μm.