A new species of Ochthebius (Cobalius) (Coleoptera: Hydraenidae: Ochthebiinae) inhabiting marine rockpools of NW Sicily

Figures & data

Figure 1. Holotype of O. (Cobalius) senczuki sp. n.; (a) dorsal habitus; (b) head and pronotum. Scale bars: a = 0.3 mm; b = 0.1 mm.

Figure 2. Aedeagus of O. (Cobalius) senczuki sp. n.; (a) (male holotype from Riserva Naturale Orientata dello Zingaro, Sicily, Italy), ZEISS® Axio Zoom V16 microscope photo, lateral view; (b) accurate drawing of the same (BX50 OLYMPUS® upright microscope, 400×), better evidencing the structure of the distal mobile lobe of the aedeagus (drawn slightly darker than reality, to better highlight its structure) and of a paramere. Scale bar: 0.1 mm.

Figure 3. Habitat of Ochthebius (Cobalius) senczuki sp. n. (a) Cala Capreria, Riserva Naturale Orientata dello Zingaro, Sicily, Italy; (b) Terrasini, Lungomare Peppino Impastato, Sicily, Italy.

Table I. Genus Ochthebius Leach 1815, subgenus Cobalius Rey, 1886: list (in roughly phylogenetic order) of 18 included putative species, with recognized synonymies or homonymies (indented), as well as data on their geographic distribution. Refer to the main text for the here proposed re-evaluation at the specific rank of the three supposed subspecies of O. adriaticus throughout the Mediterranean. All known species are associated with marine rockpools, particularly those shallow (2–10 cm deep), small (20–70 cm wide) and positioned relatively farther from the sea (ca. up to 10 m high and inland from the sea), with the exception of the isolated O. serratus, present in southern Spain and northern Morocco in salty coastal wetlands and along backwaters of coastal salty streams.

Species	Distribution
Ochthebius (Cobalius) subinteger Mulsant & Rey, 1861 Ochthebius (Cobalius) aspectabilis d’Orchymont, 1932*	Central and Western Mediterranean coasts, NW Greece, Crete Island*, coasts of W Black Sea*, ?Andaman Islands**
Ochthebius (Cobalius) lejolisii Mulsant & Rey, 1861	Atlantic coasts of Scotland, Wales, SW Ireland, France, Iberian Peninsula, and Morocco, Mediterranean coasts of SE Spain and NW Morocco
Ochthebius (Cobalius) senczuki sp. n.	NW Sicily
Ochthebius (Cobalius) celatus Jäch, 1989	Italy, Sicily, Balkan Peninsula, NE Mediterranean
Ochthebius (Cobalius) asper Sählberg, 1900	Southern continental Greece
Ochthebius (Cobalius) adriaticus Reitter, 1886	Coasts of Adriatic Sea, southern Italy, E (and W***) Sicily
Ochthebius (Cobalius) pleuralis Reitter, 1886 (stat. n.)	Near East (Syria, Lebanon, Israel), Crete Island
Ochthebius (Cobalius) moreanus Pretner, 1929 (stat. n.)	Peloponnese (Southern Greece), Crete Island, Samos and Rhodes Islands (SE Greece, close to the W Turkey coast),
Ochthebius (Cobalius) algicola Wollaston, 1871	Island of Madeira (Portugal)
Ochthebius (Cobalius) lanthanus Ribera & Foster, 2018	Island of Gran Canaria (Spain, Canary Islands)
Ochthebius (Cobalius) freyi d’Orchymont, 1940	Azores (Portugal)
Ochthebius (Cobalius) balfourbrownei Jäch, 1989 Ochthebius lindbergi Balfour-Browne, 1976, nec Janssens, 1961
Ochthebius (Cobalius) gorgadensis Villastrigo, Hernando, Millán & Ribera, 2020	Cabo Verde Islands (Ihla de Santiago)
Ochthebius (Cobalius) biltoni Jäch & Delgado, 2017	W and S Sicily
Ochthebius (Cobalius) cortomaltese Villastrigo, Hernando, Millán & Ribera, 2020	Island of Gozo (Maltese Islands)
Ochthebius (Cobalius) evae Villastrigo, Hernando, Millán & Ribera, 2020	Coasts of SW Spain and of NW Morocco
Ochthebius (Cobalius) anzar Villastrigo, Hernando, Millán & Ribera, 2020	Island of Lanzarote (Spain, Canary Islands) and SW Morocco
Ochthebius (Cobalius) serratus Rosenhauer, 1856	Southern Spain, N Morocco

*We have thus far not analyzed molecularly and morphologically the populations of O. aspectabilis (d’Orchymont 1932), described from Crete, as well as those from any eastern Mediterranean and Pontic coastal areas attributed to O. subinteger; however, the possible synonymy of this taxon with the W Mediterranean populations of O. subinteger was confirmed by Hernando et al. (2017).

**On the contrary, as correctly believed by Ghosh et al. (2022), the records of O. subinteger from Indian Ocean (Andaman and Nicobar Islands, S India) reported by Jäch (1989), Hansen (1998) and recently also listed by Ghosh et al. (2022), could refer very likely to a new, undescribed cryptic species of the same complex, unless these data are based on a mistake in labeling the original material. Should new records confirm the presence of Cobalius sp. in the Andaman Islands, these data could introduce an interesting biogeographic scenario, including the Asian areas bordering the ancient Tethys in the range of the species of this subgenus. Other unpublished species of this lineage could therefore be discovered at least in the coastal regions of the northern Arabian Peninsula, of southern Iran and of the NW Indian subcontinent.

***As discussed in the text, it is likely that the purported W Sicilian population of O. adriaticus cited by Sabatelli et al. (2021b) should be referred to a distinct, undescribed species of this same complex.

Table II. Comparative table of the main diagnostic characters of Ochthebius (Cobalius) senczuki sp. n. In relation to other members of the more closely related Mediterranean species or species complexes (the subinteger and adriaticus complexes) of Cobalius. O. (C.) celatus, which based on external morphology should be attributed to the O. (C.) subinteger complex (Jäch 1989), exhibits quite distinct male genitalia more recalling those of members of the O. (C.) adriaticus complex (Jäch 1989; Villastrigo et al. 2020b), as well as a molecular positioning fully confirming its closer genetic relationships with the latter complex (Villastrigo et al. 2020b; Sabatelli et al. 2021b). For these combined reasons it is here considered separately from both the subinteger and adriaticus complexes. For our estimated values of COI genetic distances among the same taxa, see table S1 herein.

Characters	senczuki	subinteger complex	celatus	adriaticus complex
1	Outer lateral edges of pronotum with only barely distinct, small and obtuse teeth (Figure 1)	Outer lateral edges of pronotum with a series of distinct, very small triangular teeth	Outer lateral edges of pronotum with a series of distinct, very small triangular teeth	Outer lateral edges of pronotum without distinct teeth, almost simple
2	Lateral sides of elytra with a moderately wide flattened area, its middle portion ca. 0.8–0.9× as wide as width of the last antennomere (Figure 1)	Lateral sides of elytra with a rather narrow flattened area, its middle portion ca. 0.6–0.7× as wide as width of the last antennomere	Lateral sides of elytra with a rather narrow flattened area, its middle portion ca. 0.6–0.7× as wide as width of the last antennomere	Lateral sides of elytra with a wide flattened area, its middle portion ca. 1.0 up to ca. 1.5× as wide as width of the last antennomere
3	Lateral sides of pronotum with a wide, rather flattened area, also partially extended in posterior fourth (Figure 1)	Lateral sides of pronotum with a moderately wide, rather flattened area in anterior two thirds, not also extended posteriorly	Lateral sides of pronotum with a moderately wide, rather flattened area in anterior three fourths, not also extended posteriorly	Lateral sides of pronotum with a wide, rather flattened area, also partially extended posteriorly
4	Pronotum usually with space between punctures distinctly smooth and shiny (Figure 1)	Pronotum usually with space between punctures at least to some extent distinctly shagreened and dull	Pronotum usually with space between punctures at least to some extent distinctly shagreened and dull	Pronotum usually with space between punctures predominantly or entirely smooth and shiny
5	Pronotum usually with punctures fine and shallow, separated from one another by a distance markedly wider than their diameter (Figure 1)	Pronotum usually with punctures rather variable, coarse and granulose, sometimes even hardly distinct from one another, or separated from one another by a distance slightly wider than their diameter	Pronotum usually with variable punctures, sometimes rather coarse and granulose, sometimes separated from one another by a distance slightly wider than their diameter	Pronotum usually with punctures fine and shallow, separated from one another by a distance markedly wider than their diameter
6	Dorsal color usually dark brown to blackish, with only barely distinct metallic-green hues (Figure 1)	Dorsal color usually with markedly distinct metallic-green hues	Dorsal color usually with markedly distinct metallic-green hues	Dorsal color usually dark brown to blackish, rarely with barely distinct metallic-green hues
8	Posterior tibiae in both sexes rather slender, ca. 8.5× as long as wide (Figure 1), their length ca. 0.9× the maximum width of the head (Figure 1)	Posterior tibiae in both sexes moderately slender, ca. 7.5× as long as wide,^(1) their length ca. 0.9× the maximum width of the head	Posterior tibiae in both sexes moderately slender, ca. 7.5× as long as wide,^(2) their length ca. 0.9× the maximum width of the head	Posterior tibiae in both sexes markedly slender, ca. 9.0–9.5× as long as wide, their length ca. 1.0–1.1× the maximum width of the head
9	Mobile lobe of the aedeagus in males digitiform, more or less distinctly narrowed distad, and never curved dorsally if observed in lateral view (Figure 2)	Mobile lobe of the aedeagus in males digitiform, more or less distinctly narrowed distad, and never curved dorsally if observed in lateral view (Figs 5–6 in Jäch 1989)	Mobile lobe of the aedeagus in males widely sickle-shaped and subtruncated distad, very distinctly widened before apex, and rather strongly flat-widened and curved dorsally if observed in lateral view (Fig. 7 in Jäch 1989)	Mobile lobe of the aedeagus in males sickle-shaped, more or less distinctly widened distad, and more or less distinctly curved dorsally if observed in lateral view (Fig. 1 in Jäch 1989)
10	Body length: 1.7–1.90 mm	Body length: 1.7–2.0 mm	Body length: 1.7–2.0 mm	Body length: 2.0–2.8 mm

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