Branneria bonoculus, Shear, William A., 2003

Shear, William A., 2003, Branneria bonoculus, n. sp., a second species in the North American milliped family Branneriidae (Diplopoda: Chordeumatida: Brannerioidea), Zootaxa 233, pp. 1-7 : 3-6

Branneria bonoculus n. sp.

Figs. 1­3

Diagnosis: Distinct from B. carinata , its only congener, in having 28 trunk segments in the male, rather than 26; and in differences in the gonopods and ninth and tenth legs, discussed below.

Holotype: Male from Nevada Co., Arkansas, without further details, collected 25 February, 1977, collector unknown. Deposited in the collection of the Field Museum of Natural History, Chicago, Illinois, USA.

1 Etymology: The species name, a noun in apposition, is a Latin neologism, ‘good eye’ and refers to the better developed ocelli, compared to B. carinata .

Description: Male of head and 28 segments, about 4.0 mm long (specimen broken), 0.4 mm wide. Head subglobose, with eleven round, well­developed, pigmented ocelli in rows in triangular eyepatch. Antennae short, reaching only midpoint of trunk segment 2 when extended, clavate, article 4 nearly twice as wide as article 3. Trunk segments with well­developed paranota, outer segmental seta inserted on posterior angle of paranotum, middle seta on distinct tubercle just above and posterior to paranotum. Metatergal sculpture of short, sharp­edged ridges, irregularly, sparsely distributed, but in a distinct row at posterior margin of segment. Color dark brown, metaterga with symmetrical darker brown patches. Legpairs 3­7 slightly shorter, stouter, than legpairs posterior to legpair 12.

Gonopods ( Fig. 1 ) typical of genus. Sternum (s) bandlike, lacking spiracles. Coxae (c) rounded, somewhat rugose laterally, with two groups of 5 lateral setae, basalmost median setae proximal to coxal midpoint. Angiocoxal process (a) set off by deep constriction, median part about as long as lateral branches; lateral branches flattened, slightly diverging, squared at tips, with subapical setae. Lateral lobes of coxae lamellate, thin, with a few irregular teeth. Colpocoxite with two branches, anteriormost robust, curved, with subdistal tooth, posterior branch flagelliform, looping first anteriorly, then posteriorly between anterior branches.

Legpair 9 ( Fig. 2 ) with separate coxosterna (cxs) bearing coxal lobes from which eversible glands proceed. Prefemora with smooth cuticle, distal median lobe; distal article about 1/5 size of prefemur, bearing 3­5 setae. Legpair 10 ( Fig. 3 ) more robust than legpair 9, sternum (s) separate from coxae (c), coxae evidently fused, anteriorly excavate or depressed, but gland not detected. Prefemora distally with acute tubercles; small distal article with few similar tubercles. Legpair 11 with slightly enlaraged coxae bearing small eversible glands and acute tubercles; telopodites of normal size. Subsequent legpairs unmodified.

Discussion: I compared the single available specimen of Branneria bonoculus sideby­side with males from a large sample of B. carinata taken at Torreya State Park, Liberty Co., Florida, USA, and with other specimens from throughout the range of the latter species. Aside from the immediately obvious difference in segment number, bonoculus was distinctly darker in pigmentation than any carinata specimens­­the Florida collection was almost unpigmented. Nearly all carinata have 9 ocelli on each side of the head, usually rather poorly formed, poorly pigmented and slightly separated from one another, while bonoculus has 11 large, round, well­formed, darkly pigmented and contiguous ocelli. No additional nonsexual differences were evident.

The gonopods, while fundamentally similar, show significant differences (compare Figs. 1 and 4 ). The coxal setae have a different arrangement, with the basalmost median seta in carinata well distal to coxal midlength, while in bonoculus , it is proximal. Both species have 6 setae in the median group, but in bonoculus , the middle pair is displaced; this might be an anomaly of the single specimen. The deep constriction at the base of the angiocoxal process, the stronger fusion of the coxae, and the broader, toothed angiocoxal lobe are all significant characters of bonoculus as opposed to carinata , where the constriction is far less pronounced, the coxae have a suture along the midline, and the angiocoxal lobe is small. The anterior colpocoxal processes are significantly more robust in bonoculus , but the flagelliform posterior branch seems about the same in both species.

Legpair 9 (compare Figs. 2 and 5 ) prefemora are stout, only about 3 times as long as wide in carinata , and about 4­4.5 times as long as wide in bonoculus . The relationship is reversed in the tenth legpair (compare Figs. 3 and 6 ), where bonoculus has stouter prefemora with much more obvious tubercles; the coxae of these legs are more heavily sclerotized in bonoculus and seem fused (or partly so) in the midline; the coxae have obvious glands in carinata , but I could not detect them in bonoculus . Coxae 11 of bonoculus have readily visible glands, but these are perhaps absent in carinata .

Trunk segment numbers are fixed within species in the milliped order Chordeumatida , but range between 26 and 32 through the order. Thirty­two segmented species are found only in the suborder Heterochordeumatidea; the most common number in the order as a whole is 30. Is it not unusual for males to have two fewer segments than females, the most frequent pattern being 28­segmented males and 30­segmented females. Twenty­six segments is uncommon and found only in a relatively few, very small, species. Two cases are known in which the fixed number is not an even number; in both there are 29 trunk segments. Reduction of segment number seems to be adaptive, since lower segment numbers are generally correlated with small size, and, as in the present case, it sometimes happens that species obviously closely related (with similar male gonopods) have different numbers. In the large genus Diplomaragna (Diplomaragnidae) , species are found with 32, 30, 28 and even 26 segments ( Shear, 1990; pers. obs.)

Figures

FIGURES 1 ­ 6. Branneria bonoculus, n. sp., 1 ­ 3. 1, gonopods, anterior view. 2, ninth legpair, anterior view. 3, tenth legpair, anterior view. Branneria carinata (Bollman), 4 ­ 6. 4, gonopods, anterior view. 5, ninth legpair, anterior view. 6, tenth legpair, anterior view. Scale lines = 0.1 mm (100 µ).