Serratella palatovi Martynov, Selvakumar & Jacobus, 2021

Martynov, Alexander V., Selvakumar, C., Subramanian, K. A., Sivaramakrishnan, K. G., Vasanth, M., Sinha, Bikramjit & Jacobus, Luke M., 2021, Overview of Indian Hyrtanellini (Ephemeroptera: Ephemerellidae), with new species and records from related regions, Zootaxa 4975 (3), pp. 451-482 : 454-461

publication ID	https://doi.org/ 10.11646/zootaxa.4975.3.2
publication LSID	lsid:zoobank.org:pub:222B81FA-E0F5-43A9-960D-5C9ACC2ADD0A
DOI	https://doi.org/10.5281/zenodo.4926482
persistent identifier	https://treatment.plazi.org/id/1D7287CD-FFD1-D679-FF09-0A520E01FDDC
treatment provided by	Plazi
scientific name	Serratella palatovi Martynov, Selvakumar & Jacobus
status	sp. nov.

Treatment

Serratella palatovi Martynov, Selvakumar & Jacobus , sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 ; Jacobus & McCafferty 2008: fig. 14)

Serratella uenoi ( Allen & Edmunds, 1963) sensu Jacobus & McCafferty, 2008 View in CoL partim (nec Allen & Edmunds, 1963: 18)

Type material. Holotype: larva (slide # 623, mounted with Canada balsam), THAILAND, Chiang Mai Province, Chom Thong District, stream—main source of the Klang Phat River, 18.577542°N, 98.527056°E, h ~ 1370 m a.s.l., 18.xi.2009, Palatov D.M. &Chertoprud M. V. leg.— IN Thai10Sersp [ NMNH NASU]. Other material: INDIA: 1 larva, Arunachal Pradesh, Lower Subansiri District, Tale Valley, 27.537201°N, 93.959883°E, h ~ 2370 m a.s.l., 14.iv.2015, Coll. K. A. Subramanian—Reg. No. 5603/H13 [ ZSI]. NEPAL: 1 larva, Nawakot & Sindu Districts, 1/ 2 mi north of Gulbhanjyang (on lower trail), 18.ix.1968, Coll. C Wiens [ PERC] (previously reported as Serratella uenoi ( Allen & Edmunds, 1963) by Jacobus & McCafferty 2008).

Description. Larva: Body length 5.0– 5.3 mm; caudal filaments 4.5–4.8 mm. Body pale brown ( Fig. 2A View FIGURE 2 ).

Head: With pair of small suboccipital tubercles and pair of distinct, blunt, occipital protuberances ( Fig. 2B View FIGURE 2 ) bearing short, stout setae with divergent margins and feathered apices ( Fig. 2C, D View FIGURE 2 ). The same scattered stout setae cover head surface, they also presented on compound eyes, but they are smaller. Genae moderately developed. Mouthparts: Labrum ( Fig. 3C View FIGURE 3 ) densely covered with long, hair-like setae; anterior margin with numerous feathered and hair-like setae; anteromedian emargination shallow. Median part of mandibles with numerous, long, hair-like setae; basal part of lateral margin with smaller number of middle-sized and short, hair-like setae. Right mandible ( Fig. 3A View FIGURE 3 ): outer incisor trifurcate, inner incisor bifurcate; prostheca consisting of dorsal process, smaller than on left mandible, and bunch of long and short hair-like setae; row of 10–15 long, stout, hair-like setae under mola; bunch of short, hair-like setae above mola. Left mandible ( Fig. 3B View FIGURE 3 ): outer incisor trifurcate, inner denticle small; inner incisor with two central denticles and one small lateral denticle; prostheca consisting of process and bunch of relatively long and short hair-like setae; inner surface with distinct denticles near mola. Maxilla with two dentisetae ( Fig. 3F View FIGURE 3 ), their inner margins serrate. Apex of maxilla with group of long, thin and stout, hair-like setae; apical part of inner margin with row of long, stout, hair-like setae; base of galea-lacinia with group of 4–6 long, stout, pointed, not bifurcated or bifurcated, hair-like setae. Maxillary palp 3-segmented ( Fig. 3E View FIGURE 3 ), short; segment III elongate, narrowed from middle, rounded apically; segment I somewhat broader than segments II and III; apex of segment III with several fine setae. Superlinguae of hypopharynx with long, stout, hair-like setae on apices, dorsal and ventral surfaces with fine setae, short and hair-like setae, and stout and hair-like setae; apex of lingua convex, with hair-like setae on dorsal and ventral surfaces ( Fig. 3D View FIGURE 3 ). Labial palp 3-segmented ( Fig. 3G View FIGURE 3 ); segments I and II subequal in length; surfaces, inner and outer margins of segment I and II covered with long, thin, hair-like setae and less numerous long, stout, hair-like setae. Segment III distinctly elongated (length/width ratio in last larval instar = 2.19–2.45). Glossae rounded; apices of paraglossae and glossae covered with long, stout, hair-like setae.

Thorax: Pronotum without anterolateral and posterolateral projections ( Fig. 2E View FIGURE 2 ); with one pair distinct submedian tubercles and three pairs small indistinct tubercles ( Fig. 2F View FIGURE 2 ). Mesothorax with two pairs of indistinct protuberances and ridges, and one distinct protuberance between wingpads. Protuberances and ridges of prothorax and mesothorax, veins of wingpads covered with short, stout setae with divergent margins and feathered apices.

Femora of legs moderately flattened (length/width ratio in last larval instar: forefemur 2.04–2.05; middle femur 2.39–2.49; hind femur 2.38–2.57) ( Fig. 4A–C View FIGURE 4 ). Femora longer than tibiae, and tibiae longer than tarsi. Dorsal surfaces of all femora covered mainly with short, feathered, usually bifurcate, stout setae ( Fig. 4E–H View FIGURE 4 ) (most numerous on middle and hind femora), and with scattered short or middle-sized hair-like setae; also, irregular rows of middle-sized, hair-like setae situated along inner margins. Distal tips (distal margins and adjacent areas of dorsal surfaces) of all femora with groups of short, feathered, sometimes bifurcate, setae. Dorsal surface of forefemur with irregular rows of middle-sized and long, hair-like setae along outer and inner margins; with group of 4–5 mainly long, rounded or pointed, stout setae; most of these stout setae located near outer margin ( Fig. 4A, D View FIGURE 4 ). Outer margin of forefemur with few different-sized hair-like setae and few short, feathered, sometimes bifurcate, setae and two chalazae bearing long, pointed or rounded, stout setae. Inner margin of forefemur with short, hair-like setae only. Outer margins of fore tibia and tarsus with a few thin, long hair-like setae. Inner margin of fore tibia with several short stout setae along margin and group of several elongated setae near distal end, some with serration of one margin. Inner margin of fore tarsus with middle-sized and long, pointed stout setae; their number increases towards claw.

Outer margins of mid- and hindfemora with long hair-like setae (most numerous and forming regular row in basal part), few short, feathered, sometimes bifurcate, setae and row of 6–9 long, pointed or rounded apically, stout setae; some chalazae forming serration of margins ( Fig. 4B, C View FIGURE 4 ). Inner margins of mid- and hindfemora with no stout setae or chalazae.

Setation of middle and hind tarsi as those on fore leg. Dorsal surface of middle and hind tibiae of row of few stout setae continue on inner margin of tibiae; setae bluntly pointed of rounded apically; on hind tibia setae more numerous and longer. Inner margin of tibiae also with group of several elongated stout setae (some with one serrated margin) near distal end. Outer margin of middle and hind tibiae with few hair-like setae only; hind tibia additionally bears few long stout setae along margin.

Tarsal claw with 5–7 denticles, distal one largest, and up to 5 subapical setae ( Fig. 4I, J View FIGURE 4 ).

Abdomen. Pairs of projections present on terga III–IX, with those on terga IV–IX more developed; largest on tergum VIII ( Fig. 5A–C View FIGURE 5 ). All projections with spatulate, stout setae; most apical, stout setae grouped in bunches ( Fig. 5A, B View FIGURE 5 ). Dorsal surfaces of terga IV–IX with areas of short, stout setae above projections. Lateral surfaces of paired projections of tergum VIII and adjacent part of posterior margin with greatly elongated, apically rounded, stout setae ( Fig. 5A–C View FIGURE 5 ). Posterior margin of tergum IX (excluding area between projections) with several spatulate, stout setae with rounded apices. Distinct posterolateral projections on segments IV–IX; lateral margins covered with spatulate, stout setae. Sterna VIII–IX and lateral areas of sterna IV–VII covered with short, stout setae.

Gills ( Fig. 5D–G View FIGURE 5 ). Gill III with elongate posterolateral angle; with well-defined, brown, trilobed pattern; somewhat truncate; and without medial transverse band of weakened membrane ( Fig. 5D View FIGURE 5 ). Ventral lamellae of gills III–VI bifurcate and multifoliate; medial cleft of gills VI ventral lamella deep.

Caudal filaments subequal in length ( Fig. 2A View FIGURE 2 ). Segments with rows of elongated, rounded apically, stout setae on posterior margins alternate with segments bears rows of long, stout, hair-like setae on posterior margins; all these setae shorter than corresponding segment ( Fig. 5H View FIGURE 5 ).

Adult: Unknown

Egg. Chorion smooth, without reticulations ( Jacobus & McCafferty 2008: fig. 14; Nepal specimen herein).

Diagnosis. The species can be distinguished from larvae of other Serratella Edmunds, 1959 species by the following combination of characters: (i) head with pair of small suboccipital tubercles and pair of distinct, blunt, suboccipital protuberances ( Fig. 2A, B View FIGURE 2 ); (ii) pronotum without anterolateral and posterolateral projections ( Fig. 2E View FIGURE 2 ), with one pair distinct submedian tubercles and three pairs small indistinct tubercles ( Fig. 2F View FIGURE 2 ); (iii) mesothorax with two pairs of indistinct protuberances and ridges, and one distinct protuberance between wingpads; (iv) two pairs of head protuberances, protuberances and ridges of prothorax and mesothorax, veins of wingpads covered with short, stout setae with divergent margins and feathered apices (as in Figs 2C, D View FIGURE 2 , 4F, G View FIGURE 4 ); (v) maxilla with short 3-segmented palp ( Fig. 3E View FIGURE 3 ); third palpal segment elongated; (vi) tarsal claw with 5–7 denticles, distal one largest, and up to 5 subapical setae ( Fig. 4I, J View FIGURE 4 ); (vii) pairs of projections present on terga III–IX, with those on terga IV–IX more developed; largest on tergum VIII ( Fig. 5A–C View FIGURE 5 ); (viii) all paired projections of terga with spatulate, stout setae; most apical, stout setae grouped in bunches ( Fig. 5A, B View FIGURE 5 ); (ix) lateral surfaces of the paired projections of tergum VIII and the adjacent part of the posterior margin (excluding area between projections) with greatly elongated, apically rounded, stout setae ( Fig. 5A–C View FIGURE 5 ).

Despite this new species being assigned to Serratella , it should be noted that similar tergum VIII setation is present in Quatica paradinasi (Gonzalez del Tanago & Garcia de Jalon, 1981), but the setae are much shorter (fig. 2 in Studemann & Tomka 1987).

Etymology. This species is named in honor of Dr. Dmitry M. Palatov, friend of the first author and specialist in aquatic invertebrates of the Palearctic and Indomalayan realms, who collected this species in Thailand.

Distribution. Thailand, India-China border region, and Nepal.

Habitats. In Thailand, the new species was collected from a stream that is a main source of the Klang Phat River. The stream is situated in forest, has a high current velocity and rapids, and has sandy and stony bottom ( Fig. 20B View FIGURE 20 ). In India, the species was collected from a first order stream in Rhododendron and Bamboo forest. The stream has a sandy bottom and rapids in some sections ( Fig. 20C View FIGURE 20 ). The Nepal specimen is covered with sandy silt, suggesting a similar habitat.

Remarks. Initially Serratella uenoi ( Allen & Edmunds, 1963) was described as a representative of the subgenus Drunella Needham, 1905 (then part of the genus Ephemerella Walsh 1862 ) by Allen & Edmunds 1963, based only on description and illustrations of “ Ephemerella sp. ” by Ueno (1955), as the whereabouts of Ueno’s specimen was then—and remains—unknown. Later, a second species, Ephemerella (Acerella) undatella Allen, 1971 , was described based on the same specimen (or rather description and illustrations). Subsequently, the name was recognized as an objective junior synonym ( Allen 1973). Ephemerella (Drunella) uenoi ( Allen & Edmunds, 1963) was transferred to other genera ( Allen 1986; Paclt 1994) before being placed most recently in Serratella Edmunds, 1959 based on phylogenetic analysis of morphological data ( Jacobus & McCafferty 2008: fig. 98). The characters used to analyze the species’ relationships were scored from a single specimen from Nepal and from historical literature ( Jacobus & McCafferty 2008). During the course of this study, we discovered that the specimen from Nepal differed from the species described by Ueno (1955), especially in regards to the morphology of the maxilla ( Ueno 1955: figs 6, 6b); the two also differ considerably in size, with Ueno’s species being larger, even though the Nepal specimen is a mature female with black wingpads. Intraspecific variation in body size and maxillary palp development has been assumed for many ephemerellid species (e.g., Jacobus et al. 2004); however, in this case, the discovery of additional material reveals that the characters in question show little variation between individuals. Thus, we specifically reject the intraspecific variation hypotheses previously implied for S. uenoi and therefore no longer consider the Nepal specimen to be conspecific with Ueno’s species. Therefore, the operational taxonomic unit (OTU) labeled “ uenoi ” by Jacobus & McCafferty (2008) should be considered an erroneous amalgamation, and the species hypothesis that it represents is rejected.

In light of this, we restrict the name Serratella uenoi ( Allen & Edmunds, 1963) to the specimen described by Ueno (1955). Very clear illustrations of the species show some differences from other species of the genus Serratella , especially: the apex of the maxilla, the length ratio and shape of segments of the labial palp; the number of head tubercles; the shape of projections on terga (posterolateral and paired); setation of all femora; and presence of anterolateral projections (medially notched) on mesonotum. Modalities of some characters of S. uenoi are unusual for Hyrtanellini , and more typical of some Ephemerellini , viz. representatives of the genera Notacanthella Jacobus & McCafferty, 2008 , Spinorea Jacobus & McCafferty, 2008 , Ephacerella Paclt, 1994 , Adoranexa Jacobus & McCafferty, 2008 , and Cincticostella Allen, 1971 . As part of the tribe Ephemerellini , each of the latter five genera have a ventral lamella of gill VI that lacks a deep medial cleft.The original illustration of S. uenoi shows a distinct cleft on the ventral lamella of gill VI (fig. 18 in Ueno 1955), which excludes it from Ephemerellini . Although we find it reasonable to question the generic placement of S. uenoi , we leave it in Serratella until fresh material from the type locality, as precisely indicated by Ueno (1955), can be examined in detail.

Serratella fusongensis (Su & You, 1988) (north-east of China) and Serratella longipennis (Zhou, Gui & Su, 1997) ( China, east-central mainland) are the only species of Serratella from East and Southeast Asia unknown in the larval stage, and based on biogeography, we consider them unlikely to be conspecific with our new species, which is unknown as alates.

Serratella palatovi sp. nov. is the third representative of the genus known from the Indomalayan realm; the two others are S. uenoi , which has a questionable generic position, and S. brevicauda Jacobus, Zhou & McCafferty, 2009 , a species whose generic placement was provisional ( Jacobus et al. 2009). Thus, it is clear that more data, especially for the male adults, are needed for these species and the genus in the region.