Amplaria oedipus Shear, Nosler & Marek, 2022

Shear, William A., Nosler, Philip & Marek, Paul E., 2022, The millipede family Striariidae Bollman, 1893. IV. Amplaria oedipus, n. sp., with a secondary sexual modification of males unique among millipedes (Diplopoda Chordeumatida, Striarioidea), Zootaxa 5099 (1), pp. 137-145 : 139-143

Amplaria oedipus Shear, Nosler & Marek , new species

Figs 1–13 .

Types: Male holotype and female paratype from Cape Mountain , near Florence , 44.0947°, -124.0756°, Lane Co., Oregon, collected 18 September 2021 by Phil Nosler; male paratype from same locality but 44.0954°, -124.9766, collected 25 September 2019 by Phil Nosler .

Parts of male paratype on SEM stub WS36-15. All specimens deposited in California Academy of Sciences .

Diagnosis: This species cannot be confused with any other, due to the unique modification of the tarsi of male legpairs 5 and 6, which are enormously swollen and pyriform ( Figs 3, 6, 7 ).

Etymology: The species epithet is a noun in apposition, a Greek proper name. Oedipus is a well-known figure from Greek mythology and the subject of two tragedies by Sophocles. The name Oedipus means “swollen foot” and is therefore appropriate for this unusual species.

Description: Male holotype. Body with 30 rings (including telson). Length, about 12 mm, width 1.2 mm at midbody. Ocularium with 12 or 13 ommatidia. Labrum (lab, Fig. 1 ) with acute spines (lh, Fig. 1 ) at distal corners. Mandibular stipes (ms, Fig. 1 ) lacking projections, rimmed with rounded teeth. Collum white, with 10 low crests, sixth crest on each side vaguely noticeable. Metazonite ornamentation (Fig. 2) typical of the family, with 12 crests, prominent and equal, wider spacing between crests 2 and 3, and 4 and 5 on each side. Rings with two longitudinal bands of purplish brown pigment; crests 2 and 3 of each side within these pigmented bands thereby making crests appear with darker pigment. Segmental setae short, distally with a brush of small spinules. Telson (tel, Fig. 2) slightly elongated, 3-lobed. Cerotegument lacking in all specimens so far examined.

Legpair 1 white, reduced, smallest of all legs ( Fig. 1 ), needle-like setae lacking, but femora with flattened specialized setae. Tarsi of legpair 1 (t1, Fig. 1 ) with comb setae. Remaining legpairs with purplish brown pigment. Legpair 2 ( Figs 1 , 4 ) with vasa deferentia (vd, Fig. 4 ) opening from unmodified coxae (cx2, Fig. 4 ); with rounded, bulging trochanters (tr2, Fig. 4 ) with short processes bearing modified setae (trp, Fig. 4 ); and with enlarged, flattened prefemora (pf2, Fig. 4 ). Legpair 3 ( Figs 3, 5 ) with short, curved coxal flasks (cf, Fig. 5 ) distally with curled setae; and with telopodites not enlarged but femora flattened, lower surface with evenly scattered small tubercles ( Fig. 3 ). Postcoxal bars of ring 3 long, distally expanded, meeting or crossing in midline. Legpairs 4–7 ( Fig. 3 ) much enlarged, with flattened femora; legpairs 5 and 6 with greatly swollen pyriform tarsi (t5, t6, Figs 3, 6, 7 ) about 0.5 mm long and 0.4 mm in diameter, tapering proximally to articulation with tibiae and tapering distally at tarsungulum ( Fig. 7 ), but nearly spherical in distal view ( Fig. 6 ). Legpair 7 without coxal lobes covering bases of gonopods ( Fig. 3 ).

Gonopods ( Figs 8–10 , 12, 13 ) with structure typical of Amplaria . Anterior angiocoxites (aac, Figs 8, 10 , 12, 13 ) slightly curved, distally hook-like, with small, bifurcate posterior distal process ( Fig. 9 ). Posterior angiocoxites (pac, Figs 8–10 , 12, 13 ) about half the length of the anterior angiocoxites, long, projecting anterior branch sheaths at least 3 flagellocoxites (fc, Figs 8 , 13 ). Posterior lobes of colpocoxites (pcc, Figs 8 , 13 ) with finely spiculate surface. Lateral lobes of colpocoxite (lcc) large. Ninth legpair ( Fig. 11 ) with mesally hooked coxal process (cp, Fig. 11 ), telopodite setose, flattened, mesally with recess receiving coxal process. Telopodites fitting into shallow depressions in ventrolateral margins of seventh diplotergite. Tenth leg coxae with coxal glands.

Female paratype. Similar to male but with smaller collum, less projecting pygidium and lacking the greatly inflated tarsi on the 5th and 6th legpairs, and other male secondary sexual modifications.

Distribution: Known only from Cape Mountain, Lane Co., Oregon.

Notes: Collections were made by hand in early fall to late spring. Most searches were made along the main trail to the peak of Cape Mountain (accessed from the parking lot at Dry Lake Horse Camp). All specimens were collected from the vicinity of the peak. Litter and soil were examined, as well as the undersides of logs, rocks, and bark. Specimens were fixed in 90% isopropanol and preserved in 70-80% ethanol.

The habitat at this location is a Sitka Spruce ( Picea sitchensis (Bong.) Carrière ) forest. In Oregon, this is a unique ecosystem found only in very close proximity to the Pacific coast, where the climate is mild and wet (Franklin and Dyrness 1988); Cape Mountain lies approximately 5 km from the coast. Sitka Spruce is the dominant conifer in this habitat, and is supplemented by Western Red Cedar ( Thuja plicata Donn ex D. Don ) and Red Alder ( Alnus rubra Bong. ) in disturbed areas. The undergrowth consists of dense Salal ( Gaultheria shallon Pursh ), Western Sword-fern ( Polystichum munitum (Kaulf.) C. Presl ), Salmonberry ( Rubus spectabilis Pursh ), Red Elderberry ( Sambucus racemosa Linnaeus ), Evergreen Huckleberry ( Vaccinium ovatum Pursh ), and Red Huckleberry ( Vaccinium parvifolium Sm. in Rees).

Amplaria oedipu s was always found at or near the litter surface. The male paratype was found underneath a small, broken branch which also supported platydesmid and rhiscosomid millipedes. The male holotype and female paratype were found in leaf litter. Amplaria oedipus was found in places rich with other chordeumatidan families, including Caseyidae , Tingupidae , and Conotylidae .

When the first male was collected by PN and sent to WS for identification we suspected the strange tarsi might have been due to a parasite, such as a nematode or a fly larva. However, dissection of one of the tarsi revealed neither, just amorphous tissue. Also, why would a parasitic attack be limited to just those tarsi? Another consideration was that a random mutation may have occurred in the single male. The collection by PN of another male with the exact same greatly inflated tarsi on the 5th and 6th legpairs spoke against both the parasite and mutation hypotheses. We therefore think that the evidence at hand supports our conclusion that the modifications are normal for the mature males of this species. In our experience, such a tarsal condition is not known from any other species of the class Diplopoda, though enlarged other podomeres (usually the prefemora) are not unusual. Aside from the enlarged tarsi, A. oedipus is a typical species of Amplaria .

The unique nature of this modification recalls the eastern North American species Pseudotremia peponocranium Shear, 2011 (Cleidogonidae) which differs from all other members of its genus in having a large, swollen, quadrate projection on the front of the head in both males and females ( Shear 2011: 15, figs 34, 35).

A single male and two female Amplaria of another, undescribed species were collected at a lower elevation on Cape Mountain (44.0910°N, - 124.0737°W). The gonopods of this species, to be described later, are similar but distinct from those of A. oedipus and the male lacks the enlarged tarsi.

Figures

FIGURES 1 and 2. Amplaria oedipus n. sp., male paratype. Fig. 1. Head and anterior legs, ventral view; lab, labrum; lh, labral hook; ms, mandibular stipes; pf1, prefemur of first leg; pf2, prefemur of second leg; t1, tarsus of first leg. Fig. 2. Rings 26–29 and telson; numerals, ring numbers; c (numerals), crest numbers of right side of ring 26; tel, telson.

FIGURES 3–7. Amplaria oedipus, n. sp., male paratype. Fig. 3. Legpairs 3–7, ventral view; cx3, third leg coxa; pf(numeral), prefemora of legs 4-7; t(numeral), greatly inflated tarsi of legs 5, 6. Fig. 4. Bases of legpair 2, ventral view; cx2, coxa of second leg; pf2, prefemur of leg 2; tr2, trochanter of second leg; trp, trochanteral process; vd, opening of vas deferens. Fig. 5. Bases of legpair 3; cf, coxal flask of third leg; cx3, coxa of third leg; s3, sternum of third leg. Fig. 6. Greatly inflated tarsus of left fifth leg, distal view; t5, tarsus of fifth leg. Fig. 7. Greatly inflated tarsus of right sixth leg, lateral view; t6, tarsus of sixth leg.

FIGURES 8–11. Amplaria oedipus, n. sp., male paratype. Fig. 8. Gonopods, posterior view; aac, anterior angiocoxite; cx, gonopod coxa; fc, flagellocoxite; lcc, lateral lobe of colpocoxite; pac, posterior angiocoxite; pcc, posterior lobe of colpocoxite. The lateral lobe of the colpocoxite has collapsed due to drying for SEM. Fig. 9. Tip of left anterior angiocoxite, mesal view. Fig. 10. Tips of right anterior and posterior angiocoxites, posterior view; aac, anterior angiocoxite; fc, flagellocoxite; pac, posterior angiocoxite. Fig. 11. Left leg 9, anterior view; cp, coxal process; cx9, coxa of leg 9.

FIGURES 12, 13. Amplaria oedipus, n. sp., male holotype. Fig. 12. Right gonopod, lateral view; aac, anterior angiocoxite; pac, posterior angiocoxite; lcc, lateral lobe of colpocoxite. Fig. 13. Right gonopod, mesal view; aac, anterior angiocoxite; fc, flagellocoxite; pcc, posterior lobe of colpocoxite; pac, posterior angiocoxite. Without scale.