Ochthebius (Cobalius) lanthanus, 2018

Ribera, Ignacio & Foster, Garth N., 2018, Report of Frank Balfour-Browne’s collecting in Gran Canaria and Madeira (1932 - 1933), with the description of Ochthebius (Cobalius) lanthanus sp. nov. (Coleoptera, Hydraenidae), Zootaxa 4524 (1), pp. 65-76 : 68-75

Ochthebius (Cobalius) lanthanus sp. nov.

( Figs 2–7 )

Type locality. Rockpools in Charco las Palomas, Arucas, Gran Canaria, Canary Islands, Spain (28°9'13.7"N 15°31'49.3"W).

Type material. Holotype male (MNCN): “9 Gran Canaria 13.3.2018 / Arucas: Charco las Palomas, rockp. /

28°9'13.7"N 15°31'49.3"W / Millán, Ribera & Villastrigo leg.”, “DNA-voucher / IBE-AN173”, plus printed red

holotype label. DNA aliquots are deposited in the tissue & DNA collections of the IBE and MNCN; the COI-3’ sequence has been deposited in the ENA database with accession number LS997917 .

Paratypes (64 exx): 11 exx. ( IBE) 4 exx. ( EAM) same data as holotype, with red paratype labels; 25 exx. ( IBE, GNFC, MNCN, NMW) 5 exx. ( UM) “1 Gran Canaria 12+ 14.3.2018 / rockpools in Taliarte, lighthouse / 27°59'34.7"N 15°22'10.9"W / Millán, Ribera & Villastrigo leg.”, with printed red paratype labels (one male used for DNA extraction and sequencing and for SEM observation, with label “DNA- voucher / IBE-AV169”). Most of the specimens collected in 2018 were immature. A total of 19 paratypes are held in Frank Balfour-Browne’s collection at the National Museums Collection Centre ( RSM) in two shallow trays, one 60 x 44 mm with a label for the tray “ Ochthebius subinteger Muls. & Rey & var. lejolisii M & R Grand Canary 3iii.1932 ” [F-BB handwriting] with 15 exx “Gd Canary 3.III.32 ” [F-BB handwriting], “Balfour-Browne NMSZ.1962.23.xx” [printed, where “xx” is 7–17 and 29–32], plus printed red paratype labels ( Fig. 1 ); the genitalia and abdomen of specimen 10 have been dissected and glued on the same card with water-soluble adhesive. A second tray 44 x 31 mm ( RSM) holds five cards, four of them occupied by paratypes with the same labels as before numbered 1–4, plus printed red paratype labels .

Description. Habitus as in Fig. 2 . Length: 1.70–1.90 mm; width: 0.65–0.75 mm (females larger on average); body form slender. With a greenish metallic hue, some specimens darker (almost black); palpi brown, antennae yellowish except for the brown club, legs yellowish-brown, knees and apical tip of tarsi darker brown.

Upper surface of head ( Fig. 3 ) with irregular, adpressed fine whitish setae. Labrum transverse, anteriorly sinuated, surface smooth. Frontoclypeal suture distinct, strongly arched. Surface of head partly reticulated, with a shagreened appearance, especially around two depressed fovea on vertex; each fovea with a deep pit, visible clearly only with SEM imaging. Eyes large, with small, recumbent setae among ocelli. With two very small ocelli between pits and anterior margin of pronotum.

Pronotum ( Fig. 4 ) transverse, wider than long (length/width ratio: 0.8); surface covered with same type of setae as on head, more densely distributed, margins with longer and more robust setae; anterior margin straight in middle; anterior angles rounded; lateral margin serrate in middle. Hyaline membrane narrow at anterior and

posterior margins, wider at posterior corners. Surface very densely punctate; disc with a shallow median groove and well defined lateral furrows.

(1) Green, filamentous algae.

Elytra elongate (length/width ratio: ca 1.5), subparallel-sided; with regular rows of punctures, less regular at base; at apex surface becomes somewhat granulated, with space between punctures elevated forming apparent ridges; surface between punctures at base and elytral disk almost flat ( Fig. 5 ); with a strong, adpressed seta on anterior part of each puncture. Lateral rim strongly serrate, with a seta facing backwards at each dent. Membranous wings well developed.

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3

Recorded taxa current names 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0

1 Agabus biguttatus A. biguttatus (Olivier, 1895) 1 1 1 1 1 1

2 Agabus nebulosus A. nebulosus (Forster, 1771) 1 1 1 1 1 1 1 1 1 1 1 1 1 1

3 Anacaena haemorrhous A. haemorrhoa (Wollaston, 1864) 1

4 Aulonogyrus striatus A. striatus (Fabricius, 1792) 1

5 Bidessus minutissimus B. minutissimus (Germar, 1823) 1 1 1 1 1 1

Coelambus (Herophydrus)

6 Hygrotus musicus (Klug, 1834) 1

musicus

7 Coelambus confluens Hygrotus confluens (Fabricius, 1787) 1 1 1 1 1 1 1 1 1 1 1 1

8 Cybister tripunctatus C. tripunctatus africanus Laporte, 1835 1 1 1

9 Cyclonotum orbiculare Coelostoma hispanicum (Küster, 1848) (1) 1 1 1

10 Deronectes canariensis Nebrioporus canariensis (Bedel, 1881) 1 1 1 1 1 1

11 Gyrinus dejeani G. dejeani Brullé, 1832 1 1 1 1 1 1 1 1 1

12 Gyrinus urinator G. urinator Illiger, 1807 1 1 1

13 Haliplus lineatocollis (2) H. lineatocollis (Marsham, 1802) 1 1 1

14 Hydroporus delectus Woll : Graptodytes delectus (Wollaston, 1864) 1 1 1

15 Hydroporus pubescens (3) H. errans Sharp, 1882 1 1 1 1 1 1

16 Hyphydrus crassus H. maculatus Babington, 1841 1 1 1 1 1 1

17 Laccobius gracilis Muls. (4) L. praecipuus Kuwert, 1840 1

18 Laccobius regularis (5) L. atrocephalus canariensis d’Orchymont ,

1

1940

19 Laccobius (5) 1 1 1 1

20 Laccophilus inflatus L. hyalinus (De Geer, 1774) 1 1 1 1 1 1 1 1 1 1 1 1 1

21 Meladema coriacea M. coriacea Laporte, 1834 1 1 1 1 1

22 Ochthebius lejolisii Ochthebius lanthanus sp. nov. 1

23 Ochthebius meridionalis (6) O. subpictus subpictus Wollaston, 1857 1

24 Ochthebius pygmaeus (7) O. rugulosus Wollaston, 1857 1 1 1 1 1 1 1 1

25 Ochthebius quadricollis (8) O. heeri (Wollaston, 1854) 1

26 Ochthebius quadrifoveolatus O. quadrifoveolatus Wollaston, 1854 1 1 1 1 1

27 Parnus Dryops gracilis (Karsch, 1881) (9) 1

28 Philhydrus maritimus Enochrus bicolor (Fabricius, 1792) 1 1 1 1 1 1 1

29 Philhydrus politus Enochrus politus (Küster, 1849) 1 1 1 1 1 1 1 1 1 1

Total 7 8 3 1 1 4 2 1 1 6 4 6 5 5 7 2 5 2 1 2 6 2 1 3 6 6 7 3 0 1

(1) F. Balfour-Browne’s Gran Canaria collection in the RSM holds seven specimens of C. hispanicum collected 7 March, 1932.

(2) Recorded as a dark form.

(3) H. pubescens Gyllenhal, 1808 is not present in the Canaries ( Gutiérrez-Álvarez et al. 2014), the records must be referred most likely to H. errans .

(4) L. (Microlaccobius) gracilis Motschulsky, 1855 is not present in the Canaries, the only Microlaccobius present in the islands is L. praecipuus ( Gutiérrez-Álvarez et al. 2014) . One female in the collection in the RSM, collected 7 March, 1932

(5) L. regularis Rey, 1885 is currently a synonym of L. obscuratus Rottenberg, 1874 , not present in the Canaries. Some of the captures were first recorded in the journal as “ Laccobius regularis ”, but subsequently “ regularis ” was crossed out. F. Balfour-Browne’s Gran Canaria collection in the RSM holds 27 specimens (including six dissected males) of L. a. canariensis , collected mainly on 7 March, 1932. We thus assume all the captures correspond to this species, the only species of Laccobius recorded from Gran Canaria in addition to L. praecipuus ( Gutiérrez-Álvarez et al. 2014) .

(6) O. meridionalis Rey, 1885 is not present in the Canaries. The only species of the O. marinus group recorded from the islands is O. subpictus Wollaston, 1857 , which would represent a new record for Gran Canaria ( Gutiérrez-Álvarez et al. 2014).

(7) Ochthebius pygmaeus (Paykull, 1798) is currently a synonym of O. (Asiobates) minimus (Fabricius, 1792) , not present in Gran Canaria. The only species of Asiobates recorded from the island is O. (A.) rugulosus (Gutiérrez- Álvarez et al. 2014), also in the minimus group ( Villastrigo et al. 2019).

(8) “This is a small form, named by Wollaston as 4 foveolatus distinctly smaller than the Spanish specimens”

(9) No specimen of Dryops could be found in F. Balfour-Browne’s Gran Canaria collection in the RSM, but this is the only species of the genus recorded from the island ( Gutiérrez-Álvarez et al. 2014).

(1) Note that Parnus (= Dryops ), recorded from this locality, was not considered a water beetle! has been re-interpreted. See Table 3 for details on the localities.

(1) F. Balfour-Browne’s Madeira collection in the RSM holds four males of L. atricolor collected 4 March, 1933, and one female collected 11 March, 1933

(2) The only species of Ochthebius (Cobalius) recorded from Madeira (see main text).

(3) Ochthebius pygmaeus (Paykull, 1798) is currently a synonym of O. (Asiobates) minimus (Fabricius, 1792) , not present in Madeira. The only species of Asiobates recorded from the island is O. (A.) rugulosus ( Hughes et al. 1998; Borges et al. 2008), also in the minimus group ( Villastrigo et al. 2019).

(4) This is the only species of the genus recorded from Madeira ( Hughes et al. 1998; Borges et al. 2008). No specimen of Dryops could be found in F. Balfour-Browne’s Madeira collection in the RSM (see also Table 2).

Legs short and robust, with rows of strong spine-like setae, without natatorial setae.

Ventral surface with a uniform shagreened appearance, covered with fine, dense uniform pubescence ( Fig. 6 ). Margins of metaventrite and abdominal sternites with longer setae, more orderly disposed.

Aedeagus ( Fig. 7 ) with main piece evenly curved, with uniform width. Distal lobe tubular, finger-like, apex sinuate, hyaline. Parameres inserted near median part of main piece, not reaching its apex.

Etymology. lanthanus , a Latinised adjective derived from the Ancient Greek λανΘάνω, to be unnoticed, to escape detection; a reference to the fact that the species remained unnoticed despite Balfour-Browne’s (1958) book being widely read, and the beetle fauna of Gran Canaria being well known. The specific name is an adjective in nominative singular.

Distribution. So far only known from Gran Canaria, but its possible presence in other Canarian islands should be investigated.

Habitat. Found in two series of small rockpools over volcanic substratum and devoid of algae or other vegetation ( Figs 8, 9 ), away from the shore and in company of O. heeri .

Remarks. Both in external morphology and in the aedeagus O. lanthanus sp. nov. is virtually indistinguishable from O. algicola from Madeira. The median lobe of O. lanthanus sp. nov. seems slightly more robust, with a uniform thickness and without any narrowing in the medial part, while in the studied O. algicola the medial part of the median lobe is slightly narrower. These are, however, very small differences, and not enough material has been studied to discard the possibility of intraspecific variation. Despite the morphological similarity, both species differ by ca 11% in the barcode fragment and 10% in the 3’ end of the COI gen, both well within the range of differences between other well characterised sister species of Ochthebius ( Villastrigo et al. 2019) .

Morphological differences with O. freyi d’Orchymont, 1940 from the Azores, also in the same clade, are more pronounced: the pronotum of O. freyi has a continuous, regularly oval outline, with very shallow fossae and the surface completely shagreened. The head also has a shagreened surface, without marked fossae. The aedeagus is also very different, with a sinuated median lobe and a short and trapezoidal mobile piece. Both the external morphology and aedeagus of O. lanthanus sp. nov. are more similar to those of O. serratus Rosenhauer, 1856 , even although this is the most distant species of the lineage (sister to the rest, Villastrigo et al. 2019). None of the three described Macaronessian species of Cobalius seems to be present in the Moroccan Atlantic coast (from Sidi Ifni to Tangier), which species of the subgenus are more related to the true O. lejolisii and some Mediterranean lineages (unpublished molecular data).

Figures

FIGURE 1. One of the two trays with Balfour-Browne specimens of “Ochthebius lejolisii” collected in Gran Canaria deposited in the Royal Scottish Museum (RSM), containing 15 paratypes of O. lanthanus sp. nov.

FIGURE 2. Habitus of the holotype of Ochthebius (Cobalius) lanthanus sp. nov., voucher IBE-AV173.

FIGURES 3–6. SEM photographs of Ochthebius (Cobalius) lanthanus sp. nov., paratype voucher IBE-AV169. 3) head; 4) pronotum; 5) elytral disc; 6) abdominal ventrites.

FIGURE 7. Aedeagus of Ochthebius (Cobalius) lanthanus sp. nov., lateral view.

FIGURES 8–9. Habitat of Ochthebius (Cobalius) lanthanus sp. nov. 8) rockpools in Taliarte; 9) rockpools in Arucas (Gran Canaria) (photos: IR).