Porrorhynchus (Rhomborhynchus) misoolensis Gustafson & Miller, 1835

Gustafson, Grey T. & Miller, Kelly B., 1835, Revision of the Southeast Asian Whirligig Beetle GenusPorrorhynchusLaporte, 1835 (Coleoptera: Gyrinidae: Gyrininae: Dineutini), The Coleopterists Bulletin 1835 (4), pp. 675-714 : 675-714

Porrorhychus (Rhomborhynchus) misoolensis ( Ochs, 1955) , new status

( Figs. 1E , 11M–P , 12M–P , 13E , 15 , 17H )

Dineutus (Rhomborhynchus) depressus misoolensis Ochs 1955: 135 [original description].

Porrorhynchus (Rhomborhynchus) depressus misoolensis: Polhemus 2011: 53 [locality and habitat information].

Type Material Examined. Paratype (♂ pinned, with aedeagus pointed, Fig. 17H ): “ ♂ [white label, typed black ink]// MISOOL Id. (W.)/ 0–75m.

Fakal./ 8.ix–20.x.1948./ M.A. Lieftinck [beige label, typed black ink, except Fakal handwritten in black ink]// Coll./ G.Ochs [white label, typed black ink]// Para-/ typoid [red label with thick black border, typed black ink; underneath handwritten in black ink SMF C 9540]// misoolensis/ Ochs [beige label with black border, handwritten in blue ink,

handwriting appears to be Ochs’]// ” ( SMF); paratype (♀ pinned): Same as previous except with ♀ label and underneath Para-typoid label handwriting reads SMF C 9541, and without misoolensis Ochs label ( SMF) .

Additional Material Examined. INDONESIA: West Papua (" Irian Jaya "): Misool Island: Tama

River, SE of old Fakal village site, 1°51'38.1"S 129°55'24.1"E, 60m, 22.iv.1999, leg. D.A. Polhemus, CL 7110 (4 ex. DAPC) .

Type Locality. Misool Island , West Papua .

Diagnosis. Labrum elongate and in the form of a nearly equilateral triangle. Antenna with six flagellomeres. Dorsally bronzy brown, with pronotal yellow lateral margins broad, completely reaching lateral boundary of pronotum. Yellow lateral margins complete on elytra, extending to elytral apices, never interrupted in basal third by a dark spot; elytra without swelling associated with reception of fore leg in males. Elytra broadest just anteriad mid-length, apices spinose, apicolaterally without sawtooth-like spines, sutural angle produced to a short point, one large parasutural spine, epipleural angle with a large spine ( Fig. 1E ).

Porrorhynchus misoolensis can be distinguished from most other species of the genus in having spinose elytral apices without apicolateral triangular sawtooth-like spines, and from P. depressus in the form of the aedeagus ( Fig. 12M ) and female RT ( Fig. 13E ). See the diagnosis for P. depressus for further details. Distribution can also be used to separate P. misoolensis , as it is only known from Misool Island.

Description. Size: ♂ L: 9.4 – 10.1 mm, W: 5.6–5.8 mm; ♀ L: 9.9–10.1 mm, W 5.6–5.8 mm. Habitus: Smallest member of genus; body form elongate oval, evenly attenuated anteriorly and posteriorly; in lateral view, depressed, weakly humped in scutellar region, depressed posteriorly and anteriorly; in anterior and posterior views, weakly sloped towards lateral margins, lateral margins explanate. Coloration: Dorsally head, pronotum, and elytra bronzy brown; labrum of uniform color, similar to head; pronotum and elytra with yellow lateral margins; elytral margin uniformly yellow, only darkened at epipleural spine; venter yellow; ultimate maxillary palpomere not darkened; fore legs with tibia darker in proximal 1/2, profemora shortly darker apically. Head: Vertex with even covering of lightly impressed, fine punctures, often obscured by strong reticulation, most readily visible in lateral view, separated from nearest puncture by ca. 1.5–2.0X diameter of a puncture; orbital ridge without yellow margin; punctation on frons similar to vertex, sparser, punctures sparsest apicomedially, separated from nearest puncture by ca. 2–3X diameter of a puncture, frontolateral margins very lightly wrinkled, frontoclypeal suture with posterior margin nearly straight, lateral margins shallowly arched, meeting posterior margin at ca. 130° angle; clypeus with punctation most evident at anterior margin, sparsest medially, punctures separated from nearest puncture by ca. 1.5–2.0X diameter of a puncture, becoming more densely spaced anteriorly/laterally; antennal flagellum with 6 complete flagellomeres, ultimate flagellomere ca. 3X longer than penultimate, trapezoidal; labrum in form of equilateral triangle, punctation absent basomedially, strongly present apically, punctation more strongly impressed than on remainder of head, separated from nearest puncture by 1.0–1.5X diameter of a puncture; maxil- lary and labial palpi similar in shape ( Fig. 11O ), both strongly hatchet-form with anterior margin of maxillary palp and ventral margin of labial palp evenly curved, posterior margin of maxillary palp and dorsal margin of labial palp more strongly curved proximally, nearly straight apically, apex of both truncate. Thorax: Pronotum with even covering of fine, weakly impressed punctures, most evident medially, nearly imperceptible laterally, punctures separated from nearest puncture by 1.0–1.5X diameter of a puncture, reticulation less impressed medially, very well-impressed laterally, shallow transverse depression often present medially, lateral marginal depression absent; protibial spine projecting anterolaterally; male protarsi narrow, somewhat convex dorsally, shape as in Fig. 11M , ultimate protarsomere of male ca. 2x as long as wide, penultimate protarsomere slightly larger than previous 3; ultimate protarsomere of female ca. 0.5X length of penultimate; elytra with uniform reticulation, elytral discs with even covering of weakly impressed, fine, nearly imperceptible punctation, distance between nearest punctures on average ca. 5–6X diameter of a puncture, punctures more closely spaced in suture; lateral marginal depression absent, elytral margins evenly sloped, explanate; yellow lateral margin complete, ending apicolaterally at epipleural spine, never interrupted in basal 1/3 by darkly colored spot, males without swelling associated with cavity for reception of fore leg, apicolateral margins of elytra without triangular sawtooth-like spines, epipleural angle produced to spine, elytral apices spinose ( Fig. 1E ), with 1 parasutural spine, sutural angle produced; mesoventral apex shortly acuminate with broad apex; meso- and metacoxae dissimilar, mesocoxae without posteriorly projecting process; metacoxal process without distinct lobes ( Fig. 11N ); male mesotarsal claws as in Fig. 11P , with ventral margin strongly arched, anterior claw not significantly narrowed apically. Genitalia: Aedeagus ( Fig. 12M–O ) with median lobe ca. 5/6 length of parameres, parallel-sided in basal 3/4, then laterally expanded, apically arcuately narrowed towards apex in apical 1/4, apex carinate, narrowly rounded, apex subtruncate in lateral view, median lobe weakly arched dorsally; parameres broad, setose in apical ½; in dorsal view, laterally expanded in apical 1/2, apically narrowly rounded; in lateral view, ventral margin of parameres very weakly curved anteriorly to posteriorly. Female reproductive tract ( Fig. 13E ) with narrow, elongate, tubiform spermatheca; gonocoxae broad, lateral margin pbliquely angled towards apex, apex truncate.

Sexual Dimorphism. No sexual dimorphism appears evident. The only differences are those mentioned in the description of the subgenus.

Variation. Very little variation was observed, but only a small number of individuals were available for study.

Distribution. This species is known only from Misool Island, West Papua ( Fig. 15 ).

Biology. This species has only been collected once after its original description in the 1950s, from an upland forested stream ( Polhemus 2011). The habitat is described in detail by Polhemus (2011) who suggested this species may be influenced by stream water chemistry and substrate characteristics.

Discussion. Porrorhynchus misoolensis was only collected from a single locality during the sampling of many streams on Misool Island by Polhemus in 1999 ( Polhemus 2011). This, coupled with the species’ limited distribution and potential sensitivity to water chemistry, suggests P. misoolensis may be of conservation concern. Further investigations into the species distribution on the island and its sensitivity to water quality and chemistry would be beneficial. We here propose the common name of the Misool snouted whirligig for P. misoolensis .

CONCLUSIONS

A few features unite all the species currently recognized within Porrorhynchus . These features are: 1) an elongate labrum that is at least half as long as wide; 2) a spinose distolateral angle of the protibia; 3) an elongate, tubiform spermatheca associated with a vaginal shield. These, however, could simply be symplesiomorphies as members of the Dineutus subgenus Rhombodineutus Ochs also have elongate labra and elongate spermathecae, and members of Andogyrus Ochs have the protibia with an expanded distolateral angle forming a blunt spine ( Hatch 1926b; Brinck 1983). Members of Porrorhynchus s. str., on the other hand, present at least three potential synapomorphies: 1) the presence of a protrochanteric setose patch in males; 2) loss of the pronotal transverse impressed line; 3) setation of the ventral face of the profemora consisting of two longitudinal lines of clusters of large setae, progressively becoming denser apically. These features separate members of Porrorhynchus s. str. from all other gyrinid genera and may, in fact, represent excellent apomorphies for the true genus Porrorhynchus . Brinck’ s Ceylorhynchus was erected for P. indicans and diagnosed by small setae present at the apicolateral angle of the protibia and differing elytral apices, but these setae are present on many gyrinid species, and the separation of P. indicans from the members of Porrorhynchus s. str. based only on elytral apices seems unjustified given the aforementioned shared features.

Rhomborhynchus , on the other hand, shares numerous features with the genus Dineutus . These are: 1) profemora with setigerous punctures; 2) setation on the ventral face of the profemur composed of small clusters of setae; 3) narrow protibia that is not strongly laterally expanded; 4) median lobe of aedeagus narrowly articulating with parameres. Given these shared features, it is understandable why Ochs (1926, 1955) considered Rhomborhynchus a subgenus of Dineutus . Whether Rhomborhynchus is sister to the rest of Dineutus retaining features from a common ancestor with Porrorhynchus , sister to Porrorhynchus s. str. retaining features from a common ancestor with Dineutus , or forming a grade into Dineutus from Porrorhynchus will need to be clarified via phylogenetic analysis.

Figures

Fig. 1. Porrorhynchus species, dorsal habitus. A) P. marginatus, B) P. landaisi, C) P. indicans, D) P. depressus, E) P. misoolensis. Scale bar = 5 mm.

Fig. 11. Porrorhynchus species. P. depressus from Gulf Province, Papua New Guinea: A) Protarsus, B) Metacoxal apex, C) Maxillary (above) and labial (below) palpi, D) Mesotarsal claw. P. depressus from the Lorentz River, southwestern Irian Jaya: E) Protarsus, F) Metacoxal apex, G) Maxillary (above) and labial (below) palpi, H) Mesotarsal claw. P. depressus from Nabire, western Irian Jaya: I) Protarsus, J) Metacoxal apex, K) Maxillary (above) and labial (below) palpi, L) Mesotarsal claws. P. misoolensis: M) Protarsus, N) Metacoxal apex, O) Maxillary (above) and labial (below) palpi, P) Mesotarsal claws. Scale bars = 0.5 mm.

Fig. 12. Porrorhynchus species. P. depressus from Omo River, Gulf Province, Papua New Guinea: Aedeagus in A) Dorsal view, scale bar = 1 mm, B) Ventral view, C) Lateral view, and D) Dorsal habitus, scale bar = 5 mm. P. depressus from Lorentz River, southwestern Irian Jaya: Aedeagus in E) Dorsal view, scale bar = 1 mm, F) Ventral view, G) Lateral view, and H) Dorsal habitus, scale bar = 5 mm. P. depressus from Nabire, western Irian Jaya: Aedeagus in I) Dorsal view, scale bar = 1 mm, J) Ventral view, K) Lateral view, and L) Dorsal habitus, scale bar = 5 mm. P. misoolensis: Aedeagus in M) Dorsal view, scale bar = 1 mm, N) Ventral view, O) Lateral view, and P) Dorsal habitus, scale bar = 5 mm.

Fig. 13. Porrorhynchus species, female reproductive tract. A) P. landaisi, B) P. indicans, C) P. marginatus, D) P. depressus, E) P. misoolensis. More heavily sclerotized areas indicated in gray. Scale bars = 1 mm.

Fig. 15. Map showing distribution of species in the subgenus Rhomborhynchus. Triangles = P. depressus; circle = P. misoolensis.

Fig. 17. Type specimens. A) Porrorhynchus marginatus, holotype and label, B) Porrorhynchus depressus, holotype, C) Dineutus depressus jamurensis, paratype, D) Porrorhynchus tenuirostris, lectotype and labels, E) Dineutus depressus moszkowskii, holotype, F) Dineutus depressus versteegi, holotype, G) Dineutus marginatus mjobergi, lectotype and labels, H) Dineutus depressus misoolensis, paratype.