Cabecar serratus, Baumgardner & Ávila, 2006

Baumgardner, David E. & Ávila, Socorro, 2006, Cabecar serratus, a new genus and species of leptohyphid mayfly from Central America, and description of the imaginal stages of Tricorythodes sordidus Allen (Ephemeroptera: Leptohyphidae), Zootaxa 1187 (1), pp. 47-59 : 49-54

Cabecar serratus n. sp. Baumgardner and Ávila

Mature Larva: Body length 3.5–4.0 mm; caudal filaments 2.0–3.0 mm. General color reddish­brown, frequently covered with extensive black maculations.

Head: Reddish brown with variable black maculations; small genal projections present; tubercles absent; compound eyes small and widely separated; three ocelli present; antennae pale, approximately two times length of head capsule. Mouthparts: Labrum ( Fig. 1 ): dorsally with filiform setae along lateral margin; two rows of acuminate setae recessed from anterior margin; ventrally with one longitudinal row of acuminate setae near mid­line, with interspersed filiform setae; anterior margin with filiform setae. Right mandible ( Fig. 2 ): outer incisor three lobed, with robust setae at base; inner incisor two lobed; prostheca and molar region as in figure 2; scattered filiform setae on dorsal surface. Left mandible ( Fig. 3 ): outer incisor four lobed, mostly fused; inner incisor two lobed, mostly fused; prostheca arising at base of inner incisor, with filiform setae projecting towards molar region; molar region as in figure 3; mandible with scattered filiform setae on dorsal surface. Hypopharynx ( Fig. 4 ): lingua apically truncate; numerous filiform and acuminate setae present on anterior margin; superlinguae oval, with numerous filiform and acuminate setae along anterior and lateral margins. Maxilla ( Fig. 5 ): palp elongate, twosegmented, with an elongate terminal seta; two subapical setae on inner apical margin; cluster of filiform setae on outer apical surface; filiform and acuminate setae along base of outer margin. Labium ( Fig. 6 ): postmentum moderately developed, with regularly­spaced acuminate setae along lateral margins; ventrally with numerous robust setae most abundant near midline; prementum ventrally with numerous filiform setae; labial palp three­segmented with numerous filiform setae; glossae and paraglossae subequal, fused except distally, with smooth outer margins; glossae slightly recessed, rounded, and with robust setae; paraglossae with numerous filiform setae.

Thorax: Reddish brown, often with extensive black maculations; pronotum with a pair of distinctive, sharp projections on anterior lateral margin ( Fig. 7 ); mesonotum with a pair of small, rounded anterolateral tubercles ( Fig. 7 ). Femur reddish brown with extensive dorsal black maculation; tibia reddish brown to black with pale maculation basally and apically; tarsus reddish­brown. Profemur ( Fig. 8 ): dorsal surface with a transverse row of five or six chalazae, apical setae elongate with apices serrate; a second and slightly basal row of five or six chalazae also present, with apical setae elongate; two chalazae with apical setae elongate, with apices serrate, near center of femur; anterior and posterior margins of femur with numerous acuminate and elongate chalazae, becoming shorter towards apex of femur; filiform setae along basal anterior and posterior margins. Tibia and tarsus: margins with numerous acuminate and filiform setae; tibia with numerous, multi­branched robust setae distally; tarsal claw with a single row of four or five denticles, basal denticle very small; remaining denticles similar in shape and size with equal spacing ( Figure 9 ). Meso­ and metaleg femur ( Fig. 10 ): dorsal surface with distinct median longitudinal row of four or five chalazae with apical setae elongate with apices serrate ( Fig. 11 ); anterior and posterior margins with numerous acuminate chalazae, becoming shorter towards apex of femur. Tibia ( Fig. 10 ): acuminate setae present along anterior and posterior margins; row of 10­12 elongate setae present on dorsal surface; distally with numerous multi­branched robust setae (visible under high magnification). Tarsus: four to six acuminate setae along inner margin. Claw ( Fig. 12 ): with five or six denticles; apical denticles larger and more flattened than smaller, more sharply pointed, basal denticles.

Abdomen: Reddish brown; some individuals with extensive black maculations; a median longitudinal pale line running length of terga; posterior margins of terga I­X with numerous acuminate setae; filiform setae present along lateral margins of terga I­X; posterolateral margins of abdominal segments VII­IX greatly expanded; segments VII and VIII, reaching approximately mid­point of next segment; segment IX projecting beyond posterior margin of segment X. Dorsal lamella of operculate gill ( Fig. 13 ) on abdominal segment two subovate, reddish brown with extensive scattered black maculations; acuminate setae present along inner and apical margins; robust setae present along basal third of outer margin; gill formula (after Molineri, 2003): 2/3/4/4/2. Cerci with whorls of acuminate setae at each annulation.

Male imago. Body length: 2.5–3.5 mm. Forewing length 2.5–3.5 mm. Hindwing absent. Cercus and median caudal filament length 11.0–12.0 mm.

Head: brown with black maculation posterior to ocelli and lateral to compound eyes; vertex pale brown; compound eyes small, widely separated; diameter of one eye less than distance between eyes; lateral ocelli black at base, clear in distal one­third; median ocellus mostly clear; antenna pale; scape enlarged, remaining segments filiform.

Thorax: tergum and sternum pale brown, contrasing strongly with the pale gray pleuron; tergum and pleuron with moderate to extensive black shading, most extensive on the pronotum.; membranous filaments on mesoscutellum (plumidium) absent. Femur: pale brown with very limited black maculation; foretibia purplish, dark brown at base; foretarsus purplish, three­fourths length of foretibia; meso­ and metatibia pale reddish brown, dark brown at base; foreclaws similar and blunt; middle and hind claws dissimilar, one blunt, one pointed; hindfemur slightly shorter than hindtibia and handtarsus combined. Forewings ( Fig. 14 ): translucent, margin opaque; costa, subcosta, and R1 purplish black for one­half to three­quarters their length, heavily pigmented purplish­black beyond margin of vein; vein ICu 1 joined basally with vein CuP; vein CuP present, not converging with vein AA; vein ICu 2 joined basally with ICu 1.

Abdomen: tergites and sternites pale gray with moderate to extensive black overshading, mostly confined to medial region of tergites; cerci pale gray, bases with black stippling. Genitalia ( Fig. 15 ): penes broad, fused for most of their distance, with shallow distomedial emargination; subgenital plate with moderately deep emargination; forceps three segmented, second segment with a basal swelling; segment one of forceps about as long as segments two and three combined.

Female imago. Body length: 3.0–4.0 mm. Forewing length 3.0–3.5 mm. Hind wing absent. Cercus length 3.0–3.5 mm. Median caudal filament 2.5–3.0 mm.

Head: as in male, except darker brown.

Thorax: tergum and sternum dark red­brown with extensive overshadings of black dorsally and laterally; pleural region pale brown. Legs: dark reddish­brown with extensive black stippling; base of tibia with black ring. Forewings as in male, except with extensive black maculation at wing base.

Abdomen: pale yellowish­brown, with extensive black stippling; subgential plate with posterior margin rounded; cercus and median pale gray; basal segments reddishbrown.

Etymology: The specific epithet of this species is an adjective from the Latin word serratus (m), meaning serrated. It alludes to the serrated appearance of the margin of the femur.

Discussion: The only significant variation observed in the larvae was the degree to which black maculations covered the body. Some larvae were entirely reddish brown with almost no black maculation, while other larvae were extensively covered with black. No morphological differences could be discerned between these two color variants, both of which were observed for both sexes. This variable coloration is likely a developmentallyinfluenced character, as is typical with many species of mayflies. A similar situation has also been observed in Leptohyphes zalope Traver , in which mature larvae may become very dark in appearance ( Baumgardner and McCafferty 2000) as they near emergence to the adult stage.

Distribution and Biology: Cabecar serratus is currently known only from low­land costal regions of both the Atlantic and Pacific slopes of Nicaragua, Costa Rica, and Panamá. Larvae were collected from leaf packs and the surface of rocks and woody debris found in the slower regions of small streams. Their bodies were frequently covered by thick periphyton biofilm.

HOLOTYPE: Mature Female Larva — COSTA RICA: Limón Province, unnamed creek at Hwy 32, ca. 3 km W Pocora (10º10'38"N, 83º37'03"W, elev. 110 m), 10.vi.2001, DE Baumgardner ( DB 01­29 ), deposited in the Texas A & M University Insect Museum, College Station , Texas.

PARATYPES: Same data as holotype, 1 mature female larva ( FAMU) ; COSTA RICA: Puntarenas.: Río Barú at Barú , ca. 5 km NE Dominical, 22.vi.2001, 3L, 1 slide (#DB 02i2002), DEB ( DB 01­49 ) ( TAMU) ; Río Balsar at Hwy 34, ca. 8 km NW Palmar Norte (08º59'05"N, 83º31'07"W; elev. 65m), 22.vi.2001, 1L, DEB ( DB 01­53 ) ( PERC) . Golfito , Quebrada Km. 20, 21.iii.2005, 1♂ subimago (reared), S. Avila ( TAMU) . Río Claro, Quebrada Chiricanos , puente de C.I.A., 12.iii.2005, 1♂ (reared), 1♂ (slide #DB 05x2101), 1♀, S. Ávila ( TAMU) . Golfito, Río Claro, Golfito , Queb. Lagarto , 21.iii.2005, 2♂, 3♀, S. Ávila ( TAMU) . Limón: Río Suzrez at Hwy 36, ca. 17 Km NW Bribri (09º43'36"N, 82º50'21"W; elev. 20 m), 11.vi.2001, 1L, DEB ( DB 01­30 ) ( INBio) .

NICARAGUA: Granada: unnamed creek at Domitila Field Station , ca. 30 km S Granada (11º42'09"N, 85º57'06"W; elev. 80 m), 13­18.vi.2004, DEB ( DB 04­41 ), 12L, 1 slide (#DB04x3001) (8L TAMU, 2L each FAMU, PERC) .

Material Excluded From Type Series: NICARAGUA: Río San Juan: Bartola Field Station , Río San Juan, ca. 3 km SE El Castillo (10º58'22"N, 84º20'24"W; elev. 50 m), 19­24.vi.2004, 1L (immature), DEB ( DB 04­43 ) ( TAMU) . PANAMÁ: Panamá, Capira, Río Capira , tierras bajas, 15­iv­1995, Coll. J. Coronado, 1L ( TAMU) .

Figures

FIGURES 1–9. Cabecar serratus. Figs. 1–6 larval mouthparts. 1, labrum: left, dorsal view; right, ventral view; 2, right mandible; 3, left mandible; 4, hypopharynx; 5, maxilla; 6, labium: left, dorsal; right, ventral view. Figs. 7–9 mature larva. 7, pronotum and mesonotum: dorsal view; 8, foreleg: dorsal view 9, foreclaw.

FIGURES 10–15. Cabecar serratus. Figs. 10–13 mature larva. 10, metaleg: dorsal view; 11, metaleg seta. 12, metaclaw; 13, abdominal gill 2 (operculate gill). Figs. 14–15 male imago. Fig. 14, for wing; Fig. 15, male genitalia, ventral view. Figure 16. Tricorythodes sordidus Allen, male genitalia, ventral view.