Octoglena claraqua, Shelley, Rowland M., Richart, Casey H. & Bogan, Arthur E., 2010

Shelley, Rowland M., Richart, Casey H. & Bogan, Arthur E., 2010, Octoglena claraqua, n. sp. (Polyzoniida: Hirudisomatidae), a new milliped from Idaho, USA; first record of the order from the western interior of North America, Zootaxa 2446, pp. 55-64 : 57-60

Octoglena claraqua , new species

Figs. 1–8

Type specimen. 3 holotype ( NCSM) collected by C.H. Richart, 20 July 2008, 0.4 mi (0.6 km) NW US Forest Service Rd. 720 and 0.7 mi (1.1 km) WNW USFS Rd. 250 & Cedars Recreation site, beside unnamed tributary of North Fork Clearwater River, Clearwater National Forest (N 46° 52' 39.34", W 115° 05' 20.05"), ca. 67 mi (107 km) NE Pierce, Clearwater County, Idaho, USA.

Diagnosis. Prozona transversely banded. Gonopods in situ recumbent, directed anteriad. Anterior gonopod with coxal lobe directed laterad; 5th podomere with sinuate lobe arising mediad from caudal surface and directed distad; ultimate podomere in form of terminal calyx.

Preserved coloration. Head cream-colored; ocelli black, situated in angular gray to blackish band extending just below basalmost ocelli ( Fig. 4 ). Prozona of segments 2-26 with distinct, pinkish-brown, speckled bands ( Fig. 1 ), collum and metaterga 2-5 with additional, scattered, light speckling ( Figs. 1-4 ), remaining metaterga light cream-colored; telson colorless and transparent, revealing underlying paraprocts ( Fig. 5 ); venter uniformly light cream-colored.

Holotype. Length ca. 4.0 mm, maximum width ca. 1.2 mm, W/L ratio 30%; 28 segments including telson, last two legless. Antennae directed sublaterad ( Fig. 4 ), reaching back only to caudal margin of 2nd metatergite, relative lengths of antennomeres 6>3>5>2>4>1>7. Caudal metatergal margins strongly upturned and transparent ( Figs. 1–2 ), revealing pigmented band on underlying prozona; collum semilunar, overhanging epicranium and uppermost ocelli, anterior margin gently convex and flared ( Figs. 3–4 ); anteriolateral tergal corners blunt, caudolateral corners rounded, produced very slightly caudad on segments 13–23, more strongly prolonged on segments 26–27 ( Fig. 5 ); ozopores opening laterad but positioned submarginally on minute elevations visible only in profile, arising on segment 5 and extending to around segment 25. Telson transparent and broadly semilunar, extending caudad well beyond margins of paraprocts, over twice as broad as long but overhanging and extending well beyond margins of paraprocts, expanding laterad for entire breadth of body ( Figs. 1–2 , 5 ); paraprocts small and indistinct, visible through telson; hypoproct minute. Sterna concave. Legs extending through segment 26, pairs 1–4 becoming progressively longer and less crassate, reaching maximum length and consistent thickness on leg pair 5.

Gonopods in situ recumbent ( Figs. 2–3 ), apices directed anteriad, anterior surface facing dorsad, and caudal surface facing ventrad; appearing disproportionately large in relation to overall body-size and rhomboid, completely filling sternal region of body between medial pleural margins, expanding body longitudinally around segments 7–8. Anterior gonopods ( Figs. 6–7 ) upright in relation to sternum, distal podomeres positioned parallel to sternal lobes rather than overhanging them; sternal lobes moderately long, relatively widely separated; coxal lobe apically rounded and expanded, directed laterad, arising behind (caudal to) sternum, origin obscured in anterior view; 5th podomere with long, broad, lightly sinuate process arising around midlength on medial side of caudal surface, directed distomediad and lying subparallel to ultimate podomere; latter in form of calyx with open side facing anteriad, also with hirsute, basal lobe anteriolaterad. 3rd podomere of posterior gonopod with broad, rounded, sublaminate lobe mediad ( Fig. 8 ); ultimate podomere extending distad on anterior side of projection on 5th anterior gonopod podomere, terminating beside ultimate podomere of anterior gonopod, tapering smoothly and subcontinuously to blunt, angled, barbed tip.

Etymology. The species name is a latinization of "clearwater," the name of the Idaho county and drainage in which the holotype was discovered.

Ecology. The holotype was discovered in streamside woody debris in a predominantly Englemann Spruce ( Picea englemannii Parry ex Engelm. ) forest at 3,740 ft (1,140 m) elevation.

Distribution. Known only from the type locality, which is in the northeastern corner of Clearwater Co. and uncommonly remote. It is actually closer to (ca. 36 mi [58 km] SW) Superior, Mineral Co., Montana, from which it is reachable via Diamond and Trout Creek rds., and then USFS 250 after crossing into Idaho over Hoodoo Pass. Cedars USFS Campsite and Recreation Area is at the juncture of USFS Rds. 250 & 720. While it may be restricted to the western part of the Bitterroot Mountains, O. claraqua conceivably occurs east of the crest of the Range in Mineral Co., Montana, ~ 14 mi (22 km) to the east.

Remarks. The smallest representative of the genus, O. claraqua constitutes the first record of order & family from Idaho, the western interior of North America, and the Rocky Mountains in the broad sense.

In situ, the gonopods appear disproportionately large in relation to overall body size ( Figs. 2–3 ); viewed from a directly ventral perspective, they appear rhomboid and distort the body slightly in this region. However, this dramatically large size is primarily an illusion and a function of their recumbent, rather than upright, orientation. It results from the lengthwise orientation of their long, rather than narrow, dimension, the latter occurring in other Western Hemisphere hirudisomatids.

Figures

FIGURES 1 – 4. Octoglena claraqua holotype. 1, lateral view of entire specimen showing color pattern. 2, ventrolateral view of entire specimen showing recumbent gonopod complex. 3, the same of anterior end; ag, anterior gonopods, pg, posterior gonopods. 4, anterior view of head, antennae, and collum.

FIGURES 5 – 8. Octoglena claraqua, somatic and gonopodal features. 5, telson and segments 25 – 27, dashed line denotes the area of the paraprocts and anus; scale line = 0.5 mm. 6, left anterior gonopod and sternum, anterior view. 7, right gonopods, caudal view. 8, right posterior gonopod, sublateral view. 25 – 28, segment numbers. Scale line for fig. 5 = 0.5 mm; line for figs. 6 – 8 = 0.05 mm.