Tychepsephus Waterhouse, 1876

Shepard, William D. & Barr, Cheryl B., 2023, A revision of the Chilean water penny genus Tychepsephus Waterhouse, 1876 (Coleoptera, Psephenidae, Eubriinae), with description of a second species and two larval morphotypes, and notes on other Chilean Psephenidae, ZooKeys 1164, pp. 23-61 : 23

Genus Tychepsephus Waterhouse, 1876

Tychepsephus Waterhouse, 1876: 15.

Ectopria (Chilectopria) Pic, 1947: 3-4, syn. nov.

Tychepselaphus : Philippi, 1887: 665, lapsus calami.

Tychepsephenus : Zaitzev, 1910: 4, lapsus calami.

Tychepsephenus : Blackwelder, 1944: 274, lapsus calami.

Tychepsephenus : Artigas, 1963: 6, lapsus calami.

Tychepsephenus : Moroni, 1985: 173, lapsus calami.

Tychepsephenus : Ashworth & Hoganson, 1987: 879, lapsus calami.

Tychepsephenus : Passos et al., 2018: 598, lapsus calami.

Type species.

Tychepsephus felix Waterhouse, 1876, by monotypy.

Etymology.

Waterhouse (1876) did not explain the etymology of the genus. However, Tyche (Gr.) refers to the goddess of fortune; and the suffix, - psephus, from psephenos (Gr.), meaning "dark, obscure," has been used as the stem for multiple psephenid genera.

Adult diagnosis.

The following characters used to distinguish Tychepsephus from the neotropical eubriine genera Dicranopselaphus , Eubria , and Neoeubria are for the most part taken from Lee et al. (2007, 2016): 1) antenna of the male weakly serrate (pectinate in Neoeubria ); 2) pronotum with serrate lateral margins (not serrate in Dicranopselaphus and Eubria ); 3) mesoventrite with a median longitudinal sulcus (absent in Eubria and some Dicranopselaphus ); and 4) metaventrite with a transverse suture (vestigial in other eubriines except Sclerocyphon ). For the original characterization of adults of Tychepsephus , see Waterhouse (1876: 15-16).

Tychepsephus and the Australian genus Sclerocyphon are closely related sister genera which, in the adult stage, do not have many good characters to separate them. One obvious difference is that in Tychepsephus the apical margins of abdominal ventrites 2-4 are entire, whereas in Sclerocyphon they are serrate. Of course, there is also the geographical difference with each occurring on different continents: Tychepsephus in South America and Sclerocyphon in Australia.

Adult description.

Waterhouse (1876) described the genus Tychepsephus in English, unlike the type species description which is in Latin. His description is adequate for identifying the genus. However, since Waterhouse had only a female specimen, he did not know that his species, T. felix , is sexually dimorphic, with males having a distinctive patch of setae on the abdominal venter. This character is also present in T. cekalovici sp. nov. The dorsal patterning also differs between the sexes of both species.

Remark, adult males.

A new morphological note is that males have a sperm pump composed of a heavily muscularized ejaculatory duct which is situated medially, anterior to the aedeagus, bent around itself in an S-shape and coming from the juncture of the paired testes. The sperm pump is as short as or shorter than the aedeagus.

Larval diagnosis.

The following characters used to distinguish Tychepsephus from the neotropical eubriine genera Dicranopselaphus , Eubria , and Neoeubria are for the most part taken from Lee et al. (2007, 2016): 1) antennomere 1 subequal to antennomere 2 (much shorter in other eubriines except Sclerocyphon ); 2) maxillary and labial palpi with 4 and 3 palpomeres, respectively ( Dicranopselaphus and Eubria with 3 and 2, respectively); 3) longitudinal medial suture from thorax to abdominal segment VII (not in other eubriines except Sclerocyphon ).

Larval characters separating Tychepsephus from its Australian sister genus Sclerocyphon include the following: 1) setae on the posterior margin of the thoracic and abdominal tergites hair-like in Tychepsephus and absent in Sclerocyphon ; 2) paired longitudinal rows of setae or sensillae near the dorsal midline in Sclerocyphon , but not in Tychepsephus ; and 3) gin traps on the abdominal tergites of Sclerocyphon , but not on Tychepsephus .

Larval descriptions.

Tychepsephus larvae were previously well-described by Lataste (1897a) and Artigas (1963). Our collections revealed the presence of two distinct larval morphotypes (Figs 1 , 2 ) which have not been associated with adults and are therefore unnamed. Artigas (1963) illustrated a larva that corresponds to our larval morph 2, below.

Tychepsephus larval morph 1 (Fig. 1 ). Body shape elongate-oval; color brown and red-brown with variable yellow patterning; tergites darker than paratergites. Body margined with a long, dense fringe of golden yellow, white-tipped setae. Dorsal surface with very small, scattered cuticular beads. Longitudinal medial suture from middle of pronotum to AB VIII tergite. Mesothoracic tergite to AB VII tergite each with a pair of large, prominent, dark tubercles straddling the medial suture. Abdominal tergite VIII clasping AB IX laterally; AB VIII with a pair of large, spiracular tubercles on posterior margin at bases of paratergites. Abdominal tergite IX subquadrate, flattened, apex rounded. Paratergites generally rectangular, more than twice as wide as long, anterolateral margin curved. Ventral surfaces lacking tubercles and cuticular beads. Abdominal ventrites I-VIII with sternopleural sutures. Operculum as long as wide, widest just anterior to apex; apex broadly rounded.

Tychepsephus larval morph 2 (Fig. 2 ). Body shape elongate-oval; color brown to red-brown with yellow areas of variable size, shape, and position, often along midline of tergites and base of paratergites. Body margined with a long, dense fringe of yellow-brown, white-tipped setae. Dorsal surface sculptured with shallow, irregularly shaped depressions of varying sizes; cuticle with numerous, round, dark, flat-topped tubercles arranged in curvilinear shapes often encircling the depressions. Longitudinal medial suture from middle of pronotum to AB VII tergite. Tergites without pairs of prominent tubercles at the midline. Abdominal tergites each with an irregular, transverse line of tubercles; paratergites often with a longitudinal line of tubercles near the midline. Abdominal tergite VIII with a pair of large spiracular tubercles on posterior margin at base of paratergites. Abdominal tergite IX subelliptical, convex, sometimes sculptured and laterally angulate. Paratergites I-VIII paddle-shaped, twice as wide as long, narrower at base than apex, anterolateral margin curved. Abdominal ventrites with anterior and posterior transverse lines of small, faint, brown tubercles. Abdominal ventrites I-VIII with sternopleural sutures. Operculum nearly circular from midline to apex.

Remarks, larvae.

The most obvious differences between the larval morphs are: 1) the presence on the dorsum of numerous dark tubercles, some in curvilinear patterns (morph 2); 2) the presence of pairs of large, prominent tubercles at the midline (morph 1); 3) the shape of AB IX tergite; and 4) the shape of the operculum. The dorsal morphology of larval morph 2 is quite variable in regard to the number and arrangement of tubercles and the amount of sculpturing. Because of this, it would not be surprising if another undescribed species is discovered with further sampling of the adult habitat.

Some larvae have an abundance of peritrich protozoans attached to the venter in a scattered fashion on both sclerites and membranes.

Pupal description

(pupa of larval morph 2) (Figs 3 , 4 ). Pupa (Fig. 3 ) under exuvium of last larval instar (Fig. 4 ). Exuvium 8.3 mm long; entire dorsum intact; venter with abdominal ventrites anterior to AB II separated from tergum and reflexed, remainder of exuvium intact. Pupa 7.1 mm long, exarate, unsclerotized, color golden yellow. Pronotum projecting anteriorly, covering head; entire margin with very long setae. Elytra and abdominal segments I-IX with long setae on lateral margins. Abdominal tergites I-VIII each with two faint, transverse rows of round tubercles, at anterior 1/3 and near posterior margin, lateral to midline on each side. Abdominal tergite IX with apical margin nearly truncate, each posterolateral angle with a short spine. Paratergites separate; I reduced; II larger, projecting weakly anteriorly; III-VI each longer than II, projecting posteriorly, each with an anterobasal spiracular tubercle; VII similar but with a lateral spiracular tubercle. Ventrally, AB II-VI with sternopleural sutures; II-VIII each with a faint, transverse row of round tubercles near posterior margin.

Remarks, pupa.

This rare specimen was provided to WDS by Tomás Čekalović who collected it as a larva at Estero Nonguén in Concepción Province ( Región VIII, Bío Bío) on 27 January 1996. He kept it alive for more than nine months until it pupated on 10 November 1996.

In comparison with sister genus Sclerocyphon , pupal characters separating the two genera include the following: 1) gin traps in Sclerocyphon but absent in Tychepsephus ; 2) spiracle on abdominal paratergite II reduced in Tychepsephus but not in Sclerocyphon ; 3) spiracles on all paratergites located at the anterior base in Tychepsephus but mid-dorsally in Sclerocyphon ; 4) paratergites in Sclerocyphon much longer than in Tychepsephus ; and 5) apex of abdominal segment IX with a median projection in Sclerocyphon but lacking in Tychepsephus . The latter two characters probably aid the pupa of Sclerocyphon in crawling out from under the larval exuvium ( Smith 1981; Davis 1986). The pupa of Tychepsephus remains under the larval exuvium until the adult emerges.

Tychepsephus geographic and seasonal distribution

In Chile, published localities describe Tychepsephus occurring from Peñaflor ( Región Metropolitana) in central Chile ( Lataste 1897a), south to Chillán, Tomé and Arauco ( Región VIII, Bío Bío; Región XVI, Ñuble) ( Artigas 1963), and west of Puerto Varas ( Región X, Los Lagos) ( Ashworth and Hoganson 1987). Data records from the MNNC include adult specimens from the Andes and foothills in Reserva Nacional Altos de Lircay ( Región VII, del Maule), Cordillera Chillán ( Región XVI, Ñuble), Parque Nacional Conguillío ( Región IX, Araucanía) and Parque Nacional Vicente Pérez Rosales ( Región X, Los Lagos), as well as specimens from near the Pacific Coast in Quirihue ( Región XVI, Ñuble) and Valdivia ( Región XIV, Los Ríos) (M. Elgueta, in litt.). See Appendix 2 for detailed locality information regarding the above records. Collections by the authors of adult and larval Tychepsephus , from regions VIII ( Bío Bío) through XI ( Aysén), plus regions XIV (Los Ríos) and XVI ( Ñuble), are listed in Appendix 1.

Larval records from Provincia del Neuquén, Argentina, indicate that Tychepsephus also occurs on the east front of the Andes. Wais (1990, 1995) reported T ychepsephus (listed as Chilectopria grandis ) from the Rio Meliquina in the Rio Negro Basin north of San Carlos de Bariloche. Nicolás Román (N. Román, in litt.) has more recently reported finding a larva (morph 2) (Fig. 5 ) near San Martin de los Andes. More surprisingly, in the EMEC there is a larval eubriine from French Guiana (Fig. 6 ) that greatly resembles the larva of Tychepsephus . If this is actually a Tychepsephus larva, the geographic distribution of the genus would be significantly expanded (see Discussion).

A summation of the locality data for adults and larvae reveals a geographic distribution of Tychepsephus in the middle third of Chile, including both the Andes and the Coast Range, and on the eastern front of the central Andes in Neuquén Province, Argentina (Appendices 1, 2). The distribution map (Fig. 7 ) represents species-verified adult records only.

The adults examined for this study were collected from November through January, during the austral summer. Larvae are present year-round. Tomás Čekalović collected larvae in January and August, and Fierro et al. (2012) reported collecting larval T. felix in all seasons except winter.

Tychepsephus habitat

We have collected larvae and/or adults of Tychepsephus across an elevational range of 15-1685 m at streams and rivers in Chile. In general, these watercourses were small to medium-sized and rather shallow, with moderate current, and with clear or often brown, tannin-stained water. This is in contrast to Zarges et al. (2019) who reported them from areas with "high slope and high water currents." Label data from specimens collected by Tomás Čekalović show larvae living in temperatures of 10-14 °C. Surprisingly, some them were found in humus under Chusquea quila [Kunth ( Poaceae ) bamboo], 2-3 m from a river.

Examples of the small to medium-sized streams and small, shallow rivers in which adult Tychepsephus have been collected by the authors, described below, include Río Colegual, Río Contaco, Río Oroco, and an unnamed tributary of the Río Blanco (Figs 8 , 9 , 11 ).

Río Colegual (Fig. 8 ), located west of Puerto Varas at an elevation of ~ 200 m, is a medium-sized stream with moderate to slow flow over cobble and gravel coated with brown algae. Pools with laminar water flow are interrupted by areas of shallow riffles. Riparian vegetation overhangs some of the banks. At the time of sampling, the water was cool, clear, and brown-stained (Fig. 8b ). The watercourse is situated in mostly flat terrain bordered by cleared fields (Fig. 8a ) and is partly shaded at the collection site near the bridge. Adults of two species were readily collected by sweeping and beating the riparian vegetation, which consisted of willows, streamside grasses and forbs. Blacklight sampling yielded no specimens. Many larvae were present in the substrate of the riffles, including both morphs.

Río Contaco (= Río Tranallaquín) (Fig. 9 ), located west of Osorno at an elevation of ~ 160 m, is a medium-sized stream with clear water, moderate flow, and a substrate of sand, gravel and rubble with submerged mosses. Larvae were very abundant in the substrate of the riffles, as they also were at a small tributary of the Río Contaco at Puente El Avion (Fig. 10 ).

Río Oroco at Puente Hondo, located east of Puerto Montt at an elevation of ~ 30 m, is small and shallow, with cool, brown-stained water and a sand and cobble substrate with aquatic moss.

An unnamed tributary of Río Blanco (Fig. 11 ), located between Caleta Gonzalo and Caleta Santa Bárbara (north of Chaitén) at an elevation of ~ 160 m, yielded one adult and a small number of larvae. The stream is small, clear, and very cold with moderate current, shallow riffles, and knee-deep pools. It has a substrate of cobbles and sandy gravel with some aquatic moss present.

Figures

Figure 7. Map of Chile with enlarged section showing the geographic distribution of species-verified adult Tychepsephus specimens: T. cekalovici, yellow triangles; T. felix, violet squares; both species, red circles.

Figures 1, 2. Tychepsephus larvae 1 morph 1 a dorsal view b ventral view 2 morph 2 a dorsal view b ventral view.

Figures 3, 4. Tychepsephus pupa and larval exuvium 3 pupa a dorsal view b ventral view 4 exuvium of last larval instar, ventral view.

Figures 5, 6. Non-Chilean larvae 5 Tychepsephus larva from Argentina a dorsal view b ventral view. Images provided by Nicolas Roman (CONICET) 6 larva from French Guiana, possibly Tychepsephus a dorsal view b ventral view. Images provided by Robert Sites (UMC).

Figures 8 - 11. Tychepsephus habitat 8 Rio Colegual, T. cekalovici type locality a stream with riffle-pool morphology flowing through a mixture of forest and pasture land b streamside shrubby vegetation, adult habitat 9 Rio Contaco 10 stream at Puente El Avion 11 tributary Rio Blanco.