Peschetius nilssoni, Sheth & Ghate & Dahanukar & Hájek, 2021

Sheth, Sayali D., Ghate, Hemant V., Dahanukar, Neelesh & Hajek, Jiri, 2021, Integrative taxonomic review of the genus Peschetius (Coleoptera, Dytiscidae, Hydroporinae) from India with description of two new species, Arthropod Systematics & amp; Phylogeny 79, pp. 535-553 : 535

3.3.2. Peschetius nilssoni sp. nov.

Figs 5B , 6B , 7B , 8B

Peschetius andrewesi Balfour-Browne 1946: 104 (partim.)

Peschetius toxophorus : Vazirani 1977c: 126 (partim.)

Specimens examined.

Holotype: INDIA • ♂; Maharashtra, Pune, Ane; 19°09′47″N, 74°14′4″E; 800 m a.s.l.; 15 Sep. 2016; S. D. Sheth leg; pond; Indian Council of Agricultural Research , Bengaluru, India [ICAR] . Paratypes: INDIA - Maharashtra • 3 ♂♂, 3 ♀♀; same data as holotype; UASB • 1 ♂, 1 ♀; Pune, Jejuri ; 18°16′39″N, 74°9′22″E; ca 750 m. a.s.l.; 22 Feb. 2014; S. D. Sheth leg.; reservoir; HVGC • 1 ♀, Nashik, Igatpuri , 19°42′13″N, 73°34′30″E, ca 600 m. a.s.l., 17 Jan. 2014, S. D. Sheth leg.; reservoir; ZSIP • 1 ♀; Pune, Talegaon ; 18°42′58″N, 73°41′18″E; ca 600 m. a.s.l.; 16 Feb. 2014; reservoir; S. D. Sheth leg.; ZSIP • 1 ♀; Pune, Panshet ; 18°22′57″N, 73°37′17″E; ca 600 m. a.s.l.; 7 June 2014; S. D. Sheth leg.; pond; HVGC • 1 ♂; Satara, Mahardara ; 17°40′59″N 73°58′23″E; ca 750 m. a.s.l.; 16 Jul. 2014; S. D. Sheth leg.; pond; HVGC • 2 ♂♂; 120 km NE of Mumbai, Igatpuri env.; 19°42.17′N 73°33.06′E [19°42′11″N, 73°33′4″E]; ca 600 m. a.s.l.; 1 Aug.-12 Aug. 2002; P. Šípek and M. Fikáček leg.; NMPC • 1 spec.; 4 km S of Lonavala, Bushi [Bhushi] dam env.; [18°42′8″N, 73°25′3″E]; 500 [ca 600] m.a.s.l.; 12 Oct.-15 Oct. 2005; J. Bezděk leg.; NMPC • 1 ♂; Western Ghats Mts., Amboli env., 50 km W Belgaum, Daudki ; [15°51′4″N, 74°29′52″E]; [ca 800 m. a.s.l.]; 21 May-23 May 2006; V. Ryjáček leg.; drying up river; NMPC . - Rajasthan • 1 ♀; Alwar di., Naranimata env.; 27°08′22″N 76°20′38E [27°8′21″N, 76°20′39″E]; 460 [ca 450] m.a.s.l.; 6.-7.2002; P. Šrámek leg.; NMPC • 1 ♂; NW of DUNGARPUR; 23°52′N 73°41′E [23°51′60″N, 73°40′60″E]; ca 250 m. a.s.l.; 1 Jul.-2 Jul. 2006; Z. Kejval leg.; along river; NMPC. Other material: INDIA - Madhya Pradesh • 3 ♀♀; Hoshangabad Dist., Bandrabhan, ca. 60 km SSE Bhopal, ca. 5 km NE Hoshangabad , Riv. Narmada ; 22°47′29″N, 77°46′50″E; ca 280 [ca 300] m.a.s.l.; 23 Feb.-24 Feb. 2008; M. Jäch, S and P Sharma leg.; NHMW • 1 ♀; Hoshangabad Dist., River Denwa, ca. 8 km SSE Matkuli, Satpura range; 22°34′29″N, 78°29′43″E; ca 400 m. a.s.l.; 28 Feb. 2008; M. Jäch S and P Sharma leg.; NHMW • 1 ♀; Hoshangabad Dist., Sona, Bhadra [stream], northern part of Satpura NP, head of River , Denwa , Reservoir , Satpura Range , Lagdha Beta ; 22°31′38″N, 78°11′18″E; 365 [ca 350] m.a.s.l.; 29 Feb. 2008; M. Jäch, S and P Sharma leg.; NHMW . - Maharashtra • 3 spec.; Khandesh ; [20°59′60″N, 75°32′60″E]; [229 m. a.s.l.]; T.R. Bell leg.; BMNH [paratypes of P. andrewesi ] • 1 ♀; Igatpuri ; [19°40′60″N, 73°32′60″E]; 2000ft [ca 600 m. a.s.l.]; H.L. Andrewes leg.; BMNH [paratype of P. andrewesi ].

The specimens listed in other material agree well with the type material of P. nilssoni but in absence of the male, we prefer not to designate them as paratypes.

Description of male holotype.

Habitus: Body elongate, oblong oval, widest before midlength of elytra; outline discontinuous with distinct angle between pronotum and elytra; elytral keels prominent; dorsal surface submatt (Fig. 5B ). - Colouration: Head black except testaceous occipital part posterior to eyes, appendages testaceous. Pronotum testaceous with bilobed black band near posterior margin extending to posterior corners. Elytron blackish with typical testaceous markings consisting of two subbasal spots, two premedian spots, postmedian transverse band and preapical spot. Ventral side overall ferruginous. Prosternum darker along anterior margin, prosternal process with black border. Posterior margins of abdominal ventrites dark. Legs testaceous. - Head: transverse, eyes slightly emarginate. Antennae with all antennomeres slender, club-shaped. Width across eyes 1.8X the width between eyes. Clypeus arcuate. Labrum deeply emarginate with series of setae on anterior margin. Punctation of head dense, distance between punctures smaller than puncture diameter. Punctures fine on clypeus, becoming progressively coarser posteriorly on frons, occipital part posterior to eyes impunctate. Setiferous punctures present in well-developed fronto-clypeal depressions and as a row along inner margin of eyes. Reticulation consisting of polygonal, slightly transverse meshes present on clypeus and in anterior part on frons; posterior part of frons smooth. Impunctate occipital part coarsely microreticulate. - Pronotum: Transverse. Anterior margin straight, sides evenly rounded, posterior margin gently sinuate; anterior corners acute, posterior angles obtuse. Pronotum with distinct depressions between disc and sides, mediolaterally between disc and posterior margin. Pronotal disc strongly vaulted. Punctation dense, distances between punctures smaller than puncture diameter. Punctures setiferous, finer on disc, becoming coarser on margin and sides. Surface between punctures microreticulate with shallowly impressed, polygonal meshes. - Elytra: Widest before midlength, keels prominent. Punctation dense, distance between punctures approximately equal to puncture diameter. Punctures finer along suture, costae and lateral margin, coarser on disc. Surface between punctures microreticulate, reticulation similar to that of pronotum. - Legs: Tibiae club-shaped, dorsally with long natatorial setae; pro- and mesotarsi broadened, dorsally with long natatorial setae, ventrally with adhesive setae; metatarsi with long natatorial setae on both sides. - Ventral side: Prosternum sinuate on anterior margin, area between procoxae narrowed. Prosternal process elongate, flat basally, laterally compressed posteriorly, convex with short keel apically, apex tuberculate, posteriorly narrowed, without transverse depression (Fig. 7B ). Mesoventrite bifurcated on anterior margin, posterior margin rounded. Metaventrite densely punctate with coarse punctures, distance between puncture approximately equal to puncture diameter. Surface microreticulate with shallowly impressed polygonal meshes. Anterior border of metaventrite with two prominent depressions below mesocoxae. Metacoxal plate with punctation and reticulation similar to that of metaventrite. Metacoxal lines raised. Abdomen with five ventrites (V1 to V5); V1 with 8-10 macropunctures in one row and V2 with 8-10 macropunctures in two rows on either side; punctures on V2 prominent while those on V3 to V5 shallow; V3 to V5 with lateral depression shallow; V3 longitudinally obtusely keeled; reticulation of V2 to V5 consists of polygonal meshes. Punctures on ventral surface setiferous.- Male genitalia: Median lobe broad at base, narrowed towards apex, evenly curved or ‘C’ shaped, and with basal process (Fig. 6Ba). Parameres with extended setae in apical half, apex rounded (Fig. 6Bb).

FEMALE. Identical to male in habitus, dorsal surface reticulation more impressed, thus beetles appearing matt. Apex of prosternal process non-tuberculate. Pro- and mesotarsi less broadened. Spermatheca as in (Fig. 8B )-spermathecal spine curved.

Measurements (N =22). Body length 2.60-3.15 mm (holotype: 2.75 mm), and maximum width 1.64-1.74 mm (holotype: 1.64 mm). See also Supplementary file 4.

Variability.

The species slightly varies in body size and width. The shape of sub-basal yellow spot on elytra varies within species.

Differential diagnosis.

With the black head, and the prosternal process convex with a short apical keel, and the general shape of the male genitalia, Peschetius nilssoni sp. nov. is very similar and undoubtedly closely related to P. toxophorus . This fact is confirmed also by the raw genetic distance as measured by the cox1 gene, which is 2.7-3.3%-the least differentiated within Indian Peschetius . The two species can be easily recognised based on the shape of the testaceous premedian transverse band on elytra, which is always interrupted between elytral costae in P. nilssoni sp. nov. forming lateral longitudinal spot (Fig. 5Ba) and discal transverse spot (Fig. 5Bb) while the band is always uninterrupted in P. toxophorus (Fig. 5Da). Additionally, the body shape of P. nilssoni sp. nov. is more elongate and narrower (Fig. 5B ), while it is broader in P. toxophorus (Fig. 5D ). These differences in body shape were also confirmed with the multivariate morphometric analysis (Fig. 3 ). Further, the median lobe of P. nilssoni sp. nov. is gently and evenly curved (Fig. 6Ba), while that of P. toxophorus is more strongly and unevenly curved (Fig. 6Da). Parameres are gradually narrowing to their apex in P. nilssoni sp. nov., (Fig. 6Bbx) but they are distinctly tapered subapically in P. toxophorus (Fig. 6Dbx). Finally, the spermathecal spine in P. nilssoni sp. nov. (Fig. 8Ba) is curved unlike compared to other Indian species.

Etymology.

The new species is dedicated to Dr. Anders N. Nilsson ( Mullsjö, Sweden) for his immense contribution to aquatic Coleoptera . The name is a noun in the genitive case.

Collection circumstances.

The species was collected in ponds with mud and rock as substratum. It was frequently found sympatrically with P. quadricostatus and sometimes with P. toxophorus .

Distribution.

The distribution of the new species is confined so far to north-western, central and western India, namely Rajasthan, Madhya Pradesh and Maharashtra States. Some of the previous records of P. toxophorus , especially those from northern half of India, may actually also represent P. nilssoni sp. nov. and their revision is necessary.

Figures

Figure 3. Multivariate analysis of morphometric data of four Indian species of Peschetius. A Scatter plot of factor scores of between-group PCA (values in parenthesis are percentage variation explained by each PCA axis) B Overall PERMANOVA indicated that at least one of the species has significantly different centroid C Pairwise PERMANOVA between species suggested that all species are morphometrically significantly different even after sequential Bonferroni correction (the F values are provided above diagonal and p values are provided below diagonal in grey cells).

Figure 5. Dorsal habitus of Indian Peschetius. A P. bistroemi sp. nov. (Holotype) B P. nilssoni sp. nov. (Paratype- a longitudinal spot, b transverse spot; Amboli, Maharashtra) C P. quadricostatus (Amboli, Maharashtra) D P. toxophorus (a uninterrupted transverse band; Kotagiri, Tamil Nadu). (Body length: A 3.04 mm, B 3.15 mm, C 3.40 mm, D 3.35 mm).

Figure 6. Male genitalia of Indian Peschetius (a. median lobe; b. paramere; bx. tapering of paramere). A P. bistroemi sp. nov. (holotype) B P. nilssoni sp. nov. (holotype) C P. quadricostatus (Jejuri, Maharashtra) D P. toxophorus (Satara, Maharashtra). Scale bars: 100 µm (A, B, C, D).

Figure 7. Prosternal process of Peschetius. A P. bistroemi sp. nov. (paratype; Mukkada, Kerala) B P. nilssoni sp. nov. (paratype; Jejuri, Maharashtra). Scale bars: without scale.

Figure 8. Female spermatheca of Indian Peschetius. A P. bistroemi sp. nov. (paratype; Mukkada, Kerala) B P. nilssoni sp. nov. (a spermathecal spine; paratype; Ane, Maharashtra) C P. quadricostatus (Ane, Maharashtra) D P. toxophorus (a spermathecal spine; Satara, Maharashtra). Scale bars: 100 µm (A, B, C, D).