Illacme socal Marek & Shear, 2023

Marek, Paul E., Hall, Charity L., Lee, Cedric, Bailey, James, Berger, Matt C., Kasson, Matt T. & Shear, William, 2023, A new species of Illacme from southern California (Siphonophorida, Siphonorhinidae), ZooKeys 1167, pp. 265-291 : 265

publication ID	https://dx.doi.org/10.3897/zookeys.1167.102537
publication LSID	lsid:zoobank.org:pub:D97DDFD1-9B48-4432-BE92-46E4743C44EA
persistent identifier	https://treatment.plazi.org/id/BE9ACD34-40AB-414F-B8D8-AF3ED0952ABA
taxon LSID	lsid:zoobank.org:act:BE9ACD34-40AB-414F-B8D8-AF3ED0952ABA
treatment provided by	ZooKeys by Pensoft
scientific name	Illacme socal Marek & Shear
status	sp. nov.

Treatment

Illacme socal Marek & Shear sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4

Illacme "Santa Ana" Marek et al. 2021: 3.

Type material.

Holotype: United States - California • ♂; Orange County, Lake Forest, Whiting Ranch Wilderness Park, junction of Serrano and Line Shack roads; 33.67943°N, - 117.64629°W, elev. 272.8 m; 21 December 2018; 13:28; P. Marek, C. Hall leg.; VTEC, MPE04621. Paratypes: United States - California • 8 ♂, 11 ♀; same collection data as for holotype; VTEC, MPE04622, MPE04963-4977; VMNH, MPE04624; UCDC, MPE04625. Non-type material: United States - California • 4 ♂, 5 ♀; Orange County, Lake Forest, Whiting Ranch Wilderness Park, junction of Serrano Road and Live Oak Trail; 33.679406°N, - 117.647208°W, elev. 268 m; 18 January 2022; 16:41; M. Berger leg.; VTEC, MPE05265-5274.

Diagnosis.

Adult males of I. socal sp. nov. are distinct from I. plenipes and I. tobini based on the combination of: Metazonites slightly wider than prozonites, with faintly enlarged paranota (Suppl. material 5: fig. S17), not subequal in width as in I. plenipes nor noticeably wider as in I. tobini . Ozopore peritreme with two large backwards projecting spines (sp, Suppl. material 5: fig. S20) as in I. plenipes , not lacking two large spines as in I. tobini . Ozopore ringed with ca. 14 setae. Ozopores situated inside (mediad) lateral margin, oriented dorsally (Suppl. material 5: fig. S17) as in I. plenipes , not dorsolaterally and near lateral margin as in I. tobini . Metazonite posterior margin (limbus) lined with anchor-shaped, posteriorly projecting spines as in I. plenipes (an, Suppl. material 5: figs S17, S20); spines not quadrate-shaped as in I. tobini . Posterior margin of metazonite straight as in I. plenipes , not sinuate with anteriorly curved paramedial margins as in I. tobini (Suppl. material 5: fig. S17). Telson densely covered with irregularly oriented and unevenly distributed stout spines on lateral surface only (Suppl. material 6: fig. S22) as in I. tobini ; telson not covered with stout spines on all surfaces nor with posterior margin lined with posterodorsally oriented anchor-shaped spikes as in I. plenipes . Hypoproct with> 2 setae present arranged in a setal row as in I. plenipes (Suppl. material 6: fig. S22), not as in I. tobini with two setae. Anterior gonopodal apex (podomere 7) with four spines (+ 1 tarsungulum) (Fig. 3A View Figure 3 ; Suppl. materials 6, 7: figs S23-S27), not three spines (+ 1 tarsungulum) as in I. plenipes nor spinose with eight spines (+ 1 tarsungulum) as in I. tobini . Anterior gonopodal podomere 3 with two long setae as in I. tobini (Fig. 3A View Figure 3 ), not ringed with six setae as in I. plenipes . Posterior gonopodal apex (podomere 7) comprising a bundle of five styliform articles, with one article (the tarsungulum) spike-shaped (i-v, Fig. 3B View Figure 3 ; Suppl. material 7: figs S25-S27), not bundle of three styliform articles as in I. plenipes nor four styliform articles as in I. tobini . The differential diagnosis of I. socal sp. nov., I. tobini and I. plenipes is summarized in Table 1 View Table 1 , and a comparison of measurements between these species for a male individual with an equivalent number of rings shown in Table 2 View Table 2 .

Nucleotide site substitutions. COI: A (36, 48, 51, 57, 67, 70, 75, 84, 85, 135, 138, 153, 156, 165, 181, 195, 198, 213, 243, 246, 280, 291, 294, 297, 312, 321, 366, 390, 447, 471, 486, 519, 522), C (18, 33, 55, 132, 134, 162, 172, 180, 201, 207, 240, 252, 259, 273, 276, 327, 333, 360, 361, 403, 414, 417, 429, 435, 464, 493, 505, 517, 523, 525), G (32, 74, 97, 100, 117, 120, 216, 264, 287, 292, 300, 433, 454, 501), T (25, 30, 54, 81, 96, 102, 105, 114, 147, 177, 222, 258, 262, 282, 303, 318, 369, 372, 378, 384, 393, 396, 409, 420, 423, 450, 459, 468, 469, 483, 504, 556, 559, 561, 570, 576).

Description of holotype.

(♂) (Fig. 1 View Figure 1 ). Counts and measurements: p = 102. a = 1. l = 398. (102 + 1 + T). BL = 18.93. HW = 0.31. HL = 0.39. ISW = 0.20. AW = 0.10. CW = 0.40. W1 = 0.50. L1 = 0.12. H1 = 0.40. AS1 = 0.43. A7W = 0.04. P7W = 0.03. Head pear-shaped, tapered anteriorly to round point at a 130° angle from antennal sockets; occiput gradually curved medially towards occipital foramen (Suppl. materials 1, 9: figs S1, S2, S32, S34). Head covered with long slender, erect setae (Fig. 2 View Figure 2 ; Suppl. materials 1, 9: figs S1-S3, S32). Gnathochilarium and labrum closely appressed, tapered anteriorly to round point (Suppl. materials 1, 3, 9: figs S1, S3, S10-S12, S32). Labrum with anteromedial tooth-lined orifice (to, Fig. 4 View Figure 4 ; Suppl. materialS 3,4: figs S9, S13, S14). Labral surface without noticeable pores (Fig. 4 View Figure 4 ). (However, the apparent lack of labral pores may be a result of specimen preparation for microscopy. Labral pores are present in I. plenipes and I. tobini . A few pores may be visible in Fig. 4A View Figure 4 ). Shelf-like carina projecting dorsally from labrum-epistome margin (sh, Fig. 4 View Figure 4 ; Suppl. material 4: figs S13, S15). Gnathochilarium and head capsule noticeably separate, with thin gap visible between (gp, Suppl. material 3: fig. S10). Gnathochilarium thin plate-like, occupying nearly entire ventral surface of head (Suppl. material 3: fig. S10). Gnathochilarium tightly appressed to ventral surface of head capsule, leaving a small gap anteriorly between labrum, gnathochilarial stipes. Gnathochilarium with sclerites: stipes (st), mentum (me), postmentum (pm), lamellae linguales (ll), cardines (cd) (cd, ll, me, pm, st, Suppl. material 3: fig. S10). Gnathochilarial cardo (mistakenly homologized with the mandibular cardo in Marek et al. 2016) noticeable between head capsule, gnathochilarial stipes (cd, Suppl. material 3: fig. S10). Stipes of gnathochilarium with inner, outer palps; outer, inner palps with 2, 3 setae, respectively (ip, op, Fig. 4 View Figure 4 ; Suppl. materials 3, 4: figs S10, S13). Lamellae linguales with subapical palps (lp, Suppl. material 3: fig. S10). Mandibles not externally visible (Fig. 4 View Figure 4 ; Suppl. materials 1, 3: figs S1, S10). Mandible spear shaped, ca. 1/2 length of gnathochilarium (Fig. 4 View Figure 4 ; Suppl. materials 3, 4: figs S11, S15). Mandible with pectinate lamella and four or five flabellate external teeth (md, et, pl, Suppl. material 4: figs S13-S16). Molar plate absent. Mandibular pectinate lamella with numerous rows of jagged ventrally projecting serrulae, nested in groove of endochilarial frontal body (Fig. 4 View Figure 4 ; Suppl. material 4: figs S13-S16). Endochilarium with V-shaped frontal body. Endochilarium with fringed lobes ( ‘spatulae’ sensu Silvestri, 1903) that protrude distally through gnathochilarial stipes and lamellae linguales (fl, Fig. 4 View Figure 4 ; Suppl. material 4: figs S13, S14). Antennae sub-geniculate, elbowed between antennomeres 3 and 4 (Figs 1 View Figure 1 , 2 View Figure 2 ; Suppl. materials 1, 10, 11: figs S1-S4; S36, S42). Antennae comprising eight antennomeres, 5 and 6 enlarged. Five sensillum types: four apical cones (AS) oriented in a trapezoidal cluster on eighth antennomere, with longitudinally grooved outer surface and circular pores apically (as, Fig. 2 View Figure 2 ; Suppl. material 2: figs S6-S8). Chaetiform sensilla (CS) widely spaced on antennomeres 1-7, each sensillum with one or two barbules (cs, Fig. 2 View Figure 2 ; Suppl. materials 1, 2: figs S1-S8). Trichoid sensilla (TS) oriented apically encircling antennomeres 6, 7, lacking barbules (ts, Fig. 2 View Figure 2 ; Suppl. material 2: figs S5, S6). Small basiconic sensilla (Bs2) in rows of six and seven oriented apical dorsally (retrolaterally) on antennomeres 5 and 6; smooth, capsule-shaped, 1/2 length of chaetiform sensillum (b2, Fig. 2 View Figure 2 ; Suppl. material 2: figs S5, S6). Spiniform basiconic sensilla (Bs3) in row of 4, oriented apical dorsally on antennomere 7 (on longitudinal axis with Bs2 on antennomeres 5, 6); sensilla tips facing apical cones; each sensillum with ca. 3 barbules encircling tip (b3, Fig. 2 View Figure 2 ; Suppl. material 2: figs S6, S7). Two auxiliary spiniform basiconic sensilla, each on distal rim of antennomere 7 oriented 120° from row of four (Suppl. material 2: fig. S6). Antennae extend posteriorly to middle of tergite 3. Relative antennomere lengths 6>2>5>3>4>1>7>8. Collum not concealing head, with straight anteromedial edge, gradually tapering laterally (Suppl. materials 1, 11: figs S1, S40-S42). Lateral margin of collum rounded, with thickened scaly carina (Suppl. materials 1, 3: figs S4, S10). This carina repeated serially on lateral tergal and pleural margins (absent from telson). Lateral tergal and pleural carinae jagged, saw-like (potentially interlocking), pronounced on midbody rings (Fig. 1 View Figure 1 , Suppl. material 5: fig. S18). Metazonites slightly wider than prozonites, with faintly enlarged paranota (Suppl. materials 5, 11: figs S17, S39, S40). Metazonites slightly arched (Suppl. material 9: fig. S32). Metazonite dorsally covered with long, slender setae (Fig. 1 View Figure 1 ; Suppl. material 11: figs S40, S41). Tergal setae hollow; tipped with translucent silk-like exudate, exudate sometimes tangled with neighboring setae (ex, Suppl. material 9: fig. S35). Metazonite posterior margin (limbus) lined with anchor-shaped posteriorly projecting spines (an, Suppl. material 5: figs S17, S20). With row of conical spines anterior to limbus on ozoporiferous rings only (Suppl. material 5: figs S17, S20). Limbal anchor-shaped spikes alternating in size (large, small-sometimes large, small, small, large) along margin. Ozopores oriented dorsally, located near limbus (Suppl. material 5: fig. S17). Ozopores absent from collum, tergites 2-4, telson. Ozopores elevated faintly on peritremata (porosteles absent), with two large backwards projecting spines, encircled with ca. 14 robust setae (sp, Suppl. material 5: fig. S20). Row of stout flat tubercles along anterior margin of metazonite; tubercles absent medially. Posterior half of body with rings more convex (Suppl. material 10: fig. S37), posterior-most tergites covered with a greater density of long, slender setae (Suppl. material 5: fig. S18). Apodous ring without visible sternum, pleurites contiguous in midline. Apodous tergite densely setose, with unevenly distributed spikes localized to posterolateral corner; posterior margin lined with posteriorly oriented anchor-shaped spikes (Fig. 3A View Figure 3 ; Suppl. material 6: fig. S22). Telson covered with dorsally oriented stout spines on lateral surface only; without anchor-shaped spikes on margin (Suppl. material 6: fig. S22). Prozonite highly sculptured, with 2-4 rows of discoidal flat tubercles (Suppl. material 5: fig. S20). Tubercles in two shape classes: posterior prozonal tubercles button-shaped protuberant (tb); anterior tubercles flush (tf) with surface anteriorly (tb, tf, Suppl. material 5: fig. S20). Pleurites quadrate, flat, with jagged scaly lateral, posterior, medial margins (Fig. 1 View Figure 1 ). Pleurite medial margin broad, with scaly raised carina (Fig. 1 View Figure 1 ). Pleurites plate-like, large, composing 4/5 of ventral ring area. Pleural medial margins overlapping lateral sternal margins, covering spiracles (Fig. 1 View Figure 1 ). Sternites heart-shaped, wider anteriorly. Anterior, posterior sternites free, separate from pleurites (Suppl. material 5: fig. S19). Sternum with prominent midline triangular ridge projecting ventrally, tapering to a point anteriorly (rd, Suppl. material 5: fig. S19). Sternum with spiracles and legs oriented posteroventrally (Fig. 1 View Figure 1 ; Suppl. material 5: fig. S19). Spiracles circular, orifice open, hollow; oriented (above) dorsal to legs (Suppl. material 5: fig. S19). Tergites, pleurites, sternites separated by arthrodial membrane (Suppl. materials 5, 6: figs S18, S19, S22). Arthrodial membrane between tergites, pleurites wider posteriorly, pleated, thereby allowing telescoping body rings. Telson, paraprocts covered with long slender erect setae (Suppl. materials 5, 6: figs S18, S19, S22). Setae on epiproct margin have inflated bases (potentially glandular in nature). Paraprocts quarter-spherical, anterior margins faintly scaly (Suppl. material 6: fig. S22). Hypoproct small, ca. 1/8 area of paraproct, with four posterior projecting setae. Legs (postgonopodal) with seven podomeres (relative lengths denoted by numbers; 1 longest, 7 shortest): coxa (6), trochanter (7), prefemur (2), femur (3), postfemur (5), tibia (4), and tarsus (1). Legs with sparse setae, appearance similar to chaetiform sensilla with one or two barbules. Coxae nearly contiguous medially, separated by narrow sternal ridge. Coxa (postgonopodal legs) with large posteroventrally oriented D-shaped opening for eversible sac (Fig. 1 View Figure 1 ; es, Suppl. material 5: fig. S19). Eversible sacs membranous, distended slightly from aperture (Fig. 1 View Figure 1 ). Tarsus with pincer-like claw, dorsal claw arcuate; ventral accessory claw thinner, arcuate, 1/2 length of dorsal claw (Suppl. materials 5, 6: figs S18, S22). Second leg pair with posteriorly oriented coxal gonapophyses; rounded, protuberant. Ninth, tenth leg pairs modified into gonopods, each comprising seven podomeres (Fig. 3 View Figure 3 ; Suppl. materials 6, 7: figs S23-S27). Anterior gonopod, ninth leg pair, robust, thicker than posterior gonopod, tenth leg pair (Fig. 3A View Figure 3 ; Suppl. material 7: fig. S25). Anterior gonopodal apex (podomere 7) spade-shaped; in repose cupped around flagelliform posterior gonopodal apex (podomere 7). Anterior gonopodal podomere 7 with four spines + 1 tarsungulum (Fig. 3A View Figure 3 ; Suppl. materials 6, 7: figs S23-S27). Anterior gonopodal podomere 3 with two setae. Posterior gonopodal podomere 7 deeply divided, comprising a bundle of five styliform articles, with one these articles (the tarsungulum) spike-shaped (i - v, Fig. 3A View Figure 3 ; Suppl. material 7: figs S25-S27). Four dorsal-most, longest articles laminate distally, recurving laterally, with denticulate posterior margins (i - iv, Fig. 3B View Figure 3 ; Suppl. material 7: figs S25-S27). Ventral-most, fifth article spike-like (v, Fig. 3B View Figure 3 ). Accessory seta located proximal to fifth spike-like article at base of podomere (s, Fig. 3B View Figure 3 ). Triangle-shaped sterna present between left and right gonopods of ninth and tenth leg pairs, thicker between posterior gonopods. Supplementary micrographs of I. socal sp. nov. are archived in the Dryad Data Repository at: https://doi.org/10.5061/dryad.x95x69pq7.

Description of largest paratype.

(♀) VTEC (MPE04622) - Counts and measurements: p = 118. a = 1. l = 462. (118 + 1 + T). HW = 0.32. HL = 0.38. ISW = 0.21. AW = 0.10. CW = 0.40. W1 = 0.52. L1 = 0.18. H1 = 0.39. AS1 = 0.38. BL = 22.47. Morphology similar to male holotype. In combination with its counts and measurements, the following structures of female paratype differ from male holotype. Head chevron-shaped, tapered anteriorly to round point at a 120° angle anterior from antennal sockets (Fig. 1 View Figure 1 ; Suppl. material 11: figs S36, S39); occipital area posterior from antennal sockets nearly straight, faintly curved medially towards occipital foramen (Suppl. material 11: fig. S41). Cyphopods large, area 1/6 the ring area in its widest cross-section; almond-shaped, bivalvular, narrow apex oriented ventrally.

Variation.

There is negligible variation in coloration between live specimens. Female specimens are generally larger in size (greater head, ring width) and have more rings and legs. The predominant source of variation between specimens is ring and leg counts (Tables 2 View Table 2 , 3 View Table 3 ). Females have a maximum of 125 rings (486 legs maximum) with a median of 94, and males a maximum of 104 rings (402 legs maximum) with a median of 73. The rings of I. socal sp. nov. (males and females) are uniform in length, width, and height along the trunk, but are slightly taller and more convex in posterior rings.

Ecology.

Illacme socal sp. nov. individuals were encountered during the day in a California live oak woodland habitat surrounded by chaparral shrubland (Fig. 5 View Figure 5 ). One female individual was found beneath a dead oak log, and the others were encountered beneath the humus layer and embedded within the underlying soil matrix (Suppl. material 8: figs S28-S31). Co-occurring dominant flora included California live-oak ( Quercus agrifolia ), California sagebrush ( Artemisia californica ), California broom ( Acmispon glaber ), hollyleaf redberry ( Rhamnus ilicifolia ), Pacific poison-oak ( Toxicodendron diversilobum ), and Coastal cholla ( Cylindropuntia prolifera ). Other invertebrates encountered included centipedes ( Arenophilus iugans Chamberlin, 1944, Taiyuna isantus (Chamberlin, 1909), Oabius Chamberlin, 1916), beetles ( Eleodes osculans , Apsena sp.), and arachnids ( Hubbardia sp., Cicurina sp.). Between the collection of the type material by PEM in 2018 and nontype material by MCB in 2022, the Silverado fire (26 October-7 November 2020) burned ca. 12,500 acres including portions of Whiting Ranch Wilderness Park. The impact of this fire on the I. socal sp. nov. population remains unclear, but given their efficient burrowing locomotion (see behavior below), this species likely minimizes fire risk by staying in deeper soils with higher soil moisture.

Behavior.

When uncovered, individuals were observed spiraling downward into the soil cavity via a corkscrew-like pattern. Filmed in the laboratory, and within the soil from its microhabitat, the burrowing locomotion of a female I. socal sp. nov. was slow (100 µm /s), undulatory, and continuous (MPE04624, Suppl. material 12: https://vimeo.com/823446011?share=copy). The sinuous locomotory movement of the millipede appeared to follow a path of low resistance and track the topography within the soil matrix. While burrowing, a single orientation was not continually maintained, and the individual repeatedly turned and continued motion several times in different planes. While passing through a narrow junction, I. socal sp. nov. appeared to squeeze through the crevice by reduction of its body height by ca. 1/2 (Suppl. material 12: https://vimeo.com/823446011?share=copy, at 34 s). After squeezing into the interstice, and through cephalic nodding and dorso-ventral arching of the trunk, the millipede forcibly enlarged the interstice. The body rings did not appear to telescope into one another while passing through narrow junctions. Moving within the soil matrix, the millipede appeared to be positively thigmotactic to contact with the soil. The millipede appeared to navigate by aid of its large antennae, and detection of interstitial voids seemed to be mediated by these appendages. The antennae moved rapidly, and the left and right antennae, each equally and continually, tapped on the soil grains. As it walked, the millipede was observed asymmetrically extending one antenna into the soil lacunae ahead as if the sole appendage was used as a probe by the blind millipede to survey ahead of itself in the confined subterranean space (Suppl. material 12: https://vimeo.com/823446011?share=copy, at 30 s).

Distribution.

Only known from its type locality at Whiting Ranch Wilderness Park. An observation by CL from Los Angeles County at Eaton Canyon Natural Area in Pasadena, California, appears consistent with I. socal sp. nov. in morphological features. This millipede, a juvenile and of uncertain species identity due to lack of species-diagnostic gonopods, was observed on 10 February 2021; iNaturalist, observation: 69384055.

Etymology.

The species name refers to its type locality in Southern California, commonly shortened to SoCal.