Two new genera (Paracatenula and Wallaceago) with seven new species from coral reefs of Java and Sulawesi Islands

NEWS - Researchers explored marine benthic diatoms from coral reef areas and reported 2 new genera with 7 new species: Paracatenula porostriata sp. nov., Wallaceago porostriatus sp. nov., Catenula boyanensis sp. nov., Catenula komodensis sp. nov., Catenula decusa sp. nov., Catenula densitystriata sp. nov. and Catenulopsis baweana sp. nov.

Catenulaceae was originally described by Mereschkowsky (1902) for Catenula pelagica and later moved Navicula adhaerens Mereschkowsky to Catenula. The name Catenulaceae comes from the Latin words catēna and ula which literally mean small chain.

Indonesia is recorded as an area with high marine biodiversity, especially when considering three large tropical ecosystems: seagrass beds, mangrove forests and coral reefs. Samples for this study were taken from remote areas of Bawean Island and Tomini Bay in Central Sulawesi.

False catenula diatom (Paracatenula Witkowski, Luthfi & M.Rybak, gen. nov.) gets its name from its resemblance to Catenula. “Para” in Greek means beside, near, resembling, apart from and abnormal, referring to the superficial resemblance to Catenula but not to the type genus: C. pelagica Mereschkowsky. Paracatenula means resembling Catenula.

Frustules strongly dorsiventral attached with valve faces to form short chains, plastid unknown. In girdle view, several bands perforated with one or two rows of small pores. Valves asymmetrical about the apical axis with dorsal margin gently arched and ventral margin straight usually with apices slightly deflected towards the ventral side.

Raphe sternum positioned close to the ventral margin, raphe slits externally almost straight with simple proximal and apical ends. Striae on valve face usually absent or observed as shallow transapical grooves filled in with silica.

On the dorsal mantle, solitary pore-like areolae are present, whereas on the dorsal mantle, short striae are usually composed of several small poroids. The valve face is internally hyaline without any areolae, and the valve mantle has a row of areolae along the valve margin, which is occluded by the hymen.

Internally, raphe slits are bent toward the dorsal margin and proximally terminate in a simple somewhat raised end, whereas apically, they terminate in oblique helictoglossae. Present sulcus in apical area. The sulcus clearly found in the internal view of the diatom valve after the distal ending.

Porous lines diatoms (Paracatenula porostriata Luthfi, Witkowski & M.Rybak) are consistently found in coral debris specimens from Gili Iyang and MHD harbors, Bawean Island, East Java, Indonesia.

The epithet 'porostriata' is a combination of the Latin words porus meaning pore or punctum and striatus meaning striped or having stripes to indicate that this species consists of porous stripes on the mantle and cingulum.

The valves are semi-lanceolate, apices broadly rounded, protracted and rostrate, which tends to deflect to the ventral side. The ventral margin is straight, and the dorsal side is smoothly arched or curved. Raphe slits are observed on the valve face as short lines. Valve length 10.1–25.4 µm (n = 25) and width 1.7–4.7 µm (n = 25). Striations are parallel in the middle and then slightly radial near the ends.

Alfred Wallace diatom (Wallaceago Witkowski, Arsad, Luthfi & M.Rybak, gen. nov.) is dedicated to Alfred Russel Wallace in recognition of his contribution to the biogeography of the Indonesian Archipelago. The suffix “-ago” is used to indicate an explorer or traveler.

Frustules strongly dorsiventral, plastid unknown, and girdle not observed. Valves asymmetrical about the apical axis. The sternum raphes are close to the ventral side along the apical axis. Raphe slit straight with externally simple proximal and apical ends that bend towards the ventral margin.

Transapical striae are absent in the valve face, but short striae are present on the ventral margin, which is composed of a series of small areolae. On the ventral side, a distinct, rhomboidal central nodule is observed. Valve face internally flat, central nodule with distinct siliceous deposition.

Areolae occluded by hymenate structures. Internal raphe slits, exhibiting slight dorsal curvature; proximally elevated above central nodule deposition, terminating apically in indistinct helictoglossae.

Porous lines Wallace diatom (Wallaceago porostriatus Arsad, Witkowski, Luthfi & M.Rybak, sp. nov.) has so far only been found in Tanjung Perak, Poso Pesisir Regency, Central Sulawesi, Tomini Gulf. This species was dedicated to Alfred Russel Wallace as a thank you for his contribution in exploring the Indonesian archipelago. The term porostriatus is a Latin adjective meaning having a porous ridge.

The valves are dorsiventral, apices dull without protracted ends. The narrower valves are weakly protracted. Valve length 7.1–14.8 µm (n = 17) and width 1.6–3.1 µm (n = 17). Raphe branches cannot be found. The central area is resolvable with LM, marked by a light color in the middle of the ventral margin.

Boyan diatom (Catenula boyanensis Luthfi, Witkowski & M.Rybak, sp. nov.) was found in sand and coral boulders on a coral reef in Gili Iyang harbor, Bawean Island, East Java, Indonesia. The name of this species comes from the local inhabitants of Bawean Island who call it Boyan.

The valves are semi-lanceolate, dorsiventral. The raphe is clearly observed through the ventral area with proximal raphe endings distant from each other and distal raphe endings distant to apices. Valve length 8.2–22.2 µm, n = 29 and width 2.1–4.9 µm, n = 17. Transapical striae can be observed on the dorsal face. Apices obtusely rounded with distinct helictoglossae.

Decorative diatom (Catenula decusa Luthfi, Witkowski, Arsad & M.Rybak, sp. nov.) was collected on sand and coral reefs in Gili Iyang harbor, Bawean Island, East Java, Indonesia. The species name is derived from the Latin word decus which literally means ornament, decoration, or decoration. The new species shows a distinctive central area.

The valves are semi-lunate or semi-lanceolate dorsiventrally. Thickening silica in the central area is very clear under LM. A row of linear areolae can be distinguished in the dorsal margin. Valve length 8.2–16.5 µm, n = 18 and width 1.9–2.9 µm, n = 17. Apices broadly rounded with indistinct, dot-like helictoglossae. The frustule is rectangular in girdle view, 1.1 µm depth. Raphe slits observed in ventral area.

Komodo diatom (Catenula komodensis Witkowski, Risjani, Yunianta, M.Rybak & Luthfi, sp. nov.) was collected on sand and coral reef rocks in Gili Iyang harbor, Bawean Island, East Java, Indonesia. The species name is derived from the Komodo dragon which is endemic to 4 islands: Komodo, Rinca, Flores and Gili Motang in East Nusa Tenggara.

The valves are lanceolate, dorsiventral to linear-lanceolate with straight to less convex margins. The apices are narrowly pointed. Thickened silica in the central area was clearly observed on some valves under LM. Valve length 8.3–15.6 µm, n = 13 and width 1.7–2.6 µm, n = 13.

Solid lines diatom (Catenula densestriata Luthfi, Witkowski, M.Rybak & Arsad, sp. nov.) was found in sand and coral rubble in Daun, Bawean Island, East Java, Indonesia. The species name is derived from the Latin word for "solid." The species has dense lines dorsally.

The frustules are rectangular in girdle view, 1.8 µm deep, joining each other on the valve face. Valves exhibit asymmetry and are dorsiventral, characterized by a curved dorsal margin and a straight ventral margin. Some dorsal margins are slightly flat in the middle, as semi-lanceolate.

Valve apices cuneate with dot-like helictoglossae. Raphe slits positioned on the ventral side close to the margin. The terminal raphe ends are closed. Valve length 10.7–17.5 µm, n = 15 and width 1.8–3.5 µm, n = 14. The striae on the dorsal side are indistinct.

Bawean diatom (Catenulopsis baweana Luthfi, Witkowski, M.Rybak & Kryk, sp. nov.) was found in sand and coral rubble in Gili Iyang harbor, Bawean Island, East Java, Indonesia. The species name is derived from the geographical location of the habitat on Bawean Island. Bawean means sunlight in Sanskrit.

Valves are asymmetrical, dorsiventral, with the dorsal margin curved and the ventral margin straight. Valves are 10.7–16.1 μm long (n = 19) and 1.8–3.1 μm in width (n = 19). The apices look subcapitate when focusing on multiple planes using LM; the helictoglossae appear as a darker grey spot.

A white line appearing near the ventral margin is a raphe. The frustule in girdle view is rectangular or widely rectangular because it consists of several cingula. Transapical striae are difficult to resolve with LM.

This study expands and introduces 7 new catenuloid species from the Indonesian marine environment. These discoveries enhance our understanding of the biodiversity of Catenulaceae, particularly in the understudied Indonesian archipelago.

Ongoing research further supports the notion of diverse diatom communities in the archipelago, as evidenced by the identification of additional amphoroid species that will soon be described as new members of Catenulaceae.

These findings collectively highlight the unexplored potential for discovering novel diatom taxa in Indonesia’s vast and ecologically complex coral reef ecosystems.

Original research

Luthfi OM, Arsad S, Kryk A, Risjani Y, Yunianta, Rybak M, Peszek Ł, Wróbel RJ, Pappas JL, Bąk M, Witkowski A (2024). New genera and new species of Catenulaceae (Bacillariophyta) from Coral Reef habitat of two Indonesia islands—Bawean and Sulawesi—A morphological approach. PhytoKeys 248: 263-291, DOI:10.3897/phytokeys.248.131839

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