Nyctimystes intercastellus, Kraus, Fred, 2012

Kraus, Fred, 2012, Identity of Nyctimystes cheesmani (Anura: Hylidae), with description of two new related species, Zootaxa 3493, pp. 1-26 : 14-17

Nyctimystes intercastellus sp. nov.

Fig. 1 E, F

Holotype. BPBM 17938 (field tag FK 7188), adult male, collected by F. Kraus along stream SE of Sewa Bay, 10.0406˚ S, 150.9826˚ E, 120 m, Normanby Island, Milne Bay Province, Papua New Guinea, 27 January 2003.

Paratypes (n = 68). Papua New Guinea: Milne Bay Province: Fergusson Island, E slope Oya Tabu, 9.4576˚ S, 150.7888˚ E, 960 m, 18–23 August 2002 ( BPBM 16481–96, PNGNM 24129–32), Awavula River, W of Saibutu, 9.4710˚ S, 150.5410˚ E, 200 m, 7–8 September 2002 ( BPBM 16497–509, PNGNM 24133, 24141), Normanby Island, stream SE of Sewa Bay, 10.0406˚ S, 150.9826˚ E, 120 m, 27–30 January 2003 ( BPBM 17937, 17939–50, 17958, PNGNM 24134–39), 10.0394˚ S, 150.9822˚ E, 110 m, 29 January 2003 ( BPBM 17951–56), 10.0413˚ S, 150.9828˚ E, 110 m, 30 January 2003 ( BPBM 17957), Wamula, Sugunaki River, 26 July 1989 (AMS 132110–11, 132118, 132125–27, 132143).

Additional specimens. Papua New Guinea: Milne Bay Province: Normanby Island, S end Sewa Bay, 10.0315˚ S, 150.9803˚ E, 122 m ( BPBM 37765), 10.0304˚ S, 150.9812˚ E, 60 m ( BPBM 37766–70), Goodenough Island (AMS R125287–89).

Diagnosis. Nyctimystes intercastellus is unique in its combination of medium body size (male SV = 36.6–47.7 mm, female SV = 42.7–55.5 mm); presence of a small tubercle on heel; webbing on hand extending as far as the top of the penultimate tubercle on fourth finger; tympanum exposed; palpebral reticulum well-developed, largely oriented vertically but with many horizontal cross-connections; snout relatively broad (EN/IN = 0.86–1.19); iris dark brown in adults, pale tan in juveniles; rear of thighs brown with caramel-colored or tan or gray barring or flecking; males with vocal slits and sac; and call a set of 1–6 slightly pulsed, relatively long (0.188– 0.320 s) croaks delivered relatively rapidly (1.96–2.29 calls/s), clustered in no apparent pattern, and having a dominant frequency of 1.96–2.46 Hz.

Comparisons with other species. Nyctimystes intercastellus differs from N. avocalis , N. disruptus , N. oktediensis , N. papua , N. trachydermis , and N. tyleri in having (vs. lacking) vocal slits in males; from N. foricula , N. granti , N. gularis , N. humeralis , N. kubori , N. kuduki , N. montanus , N. narinosus , N. persimilis , and N. zweifeli in having (vs. lacking) a distinct tubercle on the heel; from N. obsoletus in having an exposed tympanum (hidden in N. obsoletus ); from N. pulcher in its smaller size (female SV to 84 mm, male SV to 65 mm in N. pulcher ) and small tubercle (vs. large lappet) on heel; from N. fluviatilis in lacking (vs. having) a row of pale-colored tubercles on outer edge of tarsus, having a thinner palpebral reticulum, and lacking bright orange on rear of thighs (present in N. fluviatilis ); from N. perimetri in its smaller size (male SV to 61 mm, female SV to 76 mm in N. perimetri ) and shorter snout (EN/IN = 1.23–1.56 in N. perimetri ); from N. semipalmatus in having the rear of thighs barred or mottled with brown or blue gray (uniformly bright orange in N. semipalmatus ), and a brown dorsum without dense black spotting (light tan or gray with many rounded black spots in N. semipalmatus ); and from N. daymani in its greater size (male SV to 42 mm, female SV to 48 mm in N. daymani ) and shorter snout (EN/IN = 1.17–1.39 in N. daymani ). From N. cheesmani the new species differs in its dark-brown iris in adults (light brown in N. cheesmani ), more extensive hand webbing (reaching no farther than base of penultimate tubercle on fourth finger in N. cheesmani ), palpebral reticulum oriented more vertically (more obliquely in N. cheesmani ) and with more horizontal cross-connections, irregular call structure (call a regular train of notes in N. cheesmani ), more rapid calling rate (1.03–1.36 calls/s in N. cheesmani ), and higher dominant frequency of the call (1.84–1.96 Hz in N. cheesmani ). From N. bivocalis , N. intercastellus differs in its shorter snout (EN/IN = 1.04–1.58 in N. bivocalis ), absence of sexually dimorphic color pattern, palpebral reticulum oriented more vertically (more obliquely in N. bivocalis ) and with more horizontal cross-connections, irregular call structure of 1–6 slightly pulsed notes/call (calls consisting of unpulsed paired notes in N. bivocalis ), longer notes (0.076– 0.106 s in N. bivocalis ), more rapid calling rate (1.05–1.44 calls/s in N. bivocalis ), and higher dominant frequency of call (1.56–1.72 Hz in N. bivocalis ).

Description of holotype. An adult male with right-lateral incision. Vomeropalatines with two patches of teeth (6 on right side, 5 on left) between internal nares. Vocal slits and sac present. Head moderately wide (HW/SV = 0.35), as wide as long (HL/SV = 0.35, HL/HW = 1.0); loreal region oblique; canthus rostralis rounded, concave; nostrils closer to tip of snout than to eyes; internarial distance slightly less than distance from external naris to eye (EN/IN = 1.05, IN/SV = 0.094, EN/SV = 0.099); snout rounded when viewed from the side or from above; eyes of moderate size (EY/SV = 0.12), not especially protuberant, eyelid only slightly less than width of interorbital distance; tympanic ring distinct but top margin covered by supratympanic skin fold, horizontal diameter less than half width of eye (TY/EY = 0.31). Supratympanic fold extends from behind eye to above forearm insertion. Skin of dorsal surfaces finely granular; ventral surfaces of body and thighs coarsely granular, smooth under arms and tibiae. Fingers slightly more than one-half webbed, I 2.5–2.5 II 1.75–2.75 III 2.25– 2 IV; relative lengths 3>4>2>1; tips flattened into discs bearing circum-marginal grooves; discs approximately 1.5 times width of penultimate phalanges on F2–F4 but barely wider than penultimate phalanx on F1; single subarticular tubercle present at base of each phalanx, the penultimate and antepenultimate tubercles circular and very prominently raised; each metacarpal with series of 2–4 small, raised tubercles; raised, circular outer metacarpal tubercle present, inner a long, low oval. First finger with a triangular nuptial pad of fine, light-brown dermal asperities, whose long base extends from center of inner metacarpal tubercle to penultimate phalangeal tubercle; nuptial pad approximately twice area of first finger disc. Toes well webbed, I 1– 1 II 1– 1 III 1–1.5 IV 1.5– 1 V; relative lengths 4>5=3>2>1; tips flattened into discs with circum-marginal grooves; discs slightly wider than penultimate phalanges; inner metatarsal tubercle a prominent, short oval; outer absent. Hind legs moderately long (TL/SV = 0.53), with a small tubercle at the heel.

In preservative, dorsal ground color medium gray with few obscure, scattered dark-gray flecks; rear of thighs medium gray with medium-brown blotches; front of thighs pale gray; face medium gray. Venter dirty cream with brown punctations scattered throughout. Series of low white tubercles along outer margin of forearm. Hands and feet, including webbing, gray or gray brown. Iris dark brown. Lower eyelid with thick black upper margin, a palpebral reticulum consisting of many silver or pale-brown vertical lines with several horizontal crossconnections, and a lower half that is uniformly gray like the face.

Measurements (in mm). —SV = 42.4, TL = 23.5, HW = 14.7, HL = 14.7, IN = 4.0, EN = 4.2, SN = 6.9, EY = 5.2, TY = 1.6.

Variation. Sexual differences are not obvious, except that females are larger than males ( Table 7 ). Otherwise, mensural variation among adults is not remarkable. Juveniles, however, show larger values of all mensural features relative to SV than do adults ( Table 7 ). Juvenile values of EN/IN are, conversely, smaller than those for adults.

The heel tubercle is small but always obvious and almost always tipped with white. Hand webbing reaches to anywhere between the base and top of the penultimate tubercles of F4 and F2. Series of tubercles along the metacarpals are evident in most specimens but not all, the variation apparently being a preservation artifact. Tubercles on the hands are generally small, circular, and well raised. The third and fifth toes are generally subequal in length. The palpebral reticulum runs vertically without a very oblique angle, and it has several to many horizontal cross-connections; these lines vary from rather sparse to dense and in color from silver to pale brown. Males have vocal slits and a nuptial pad of fine, light-brown dermal asperities in approximately an L shape, with the main body of the pad lying between and dorsal to the penultimate phalangeal tubercle and inner metacarpal tubercle, and with a short ventral tail extending posteriorly along the dorsal margin of the inner metacarpal tubercle.

Males are typically gray brown, either uniformly so or flecked or mottled with black or dark gray brown; some females are the same. One male has a few pale-tan flecks; another male and one immature specimen have small beige blotches above the sacrum and on the shanks. Eight females are pale orange brown with black spots or punctations (n = 2) or mottled with darker brown (n = 3). Juveniles are pale orange brown or tan mottled with brown. Venters are white with fine brown stippling, giving an overall impression of dirty white; juveniles have brighter white venters. Frogs with dorsal mottling or flecking usually have the rear of thighs orange brown or tan or pale gray brown irregularly barred with darker orange brown; frogs that are uniformly brown above are also typically uniformly brown on backs of thighs. Rear of thighs of the smallest juveniles are yellow brown, with those of older juveniles turning to caramel orange. The frogs from Normanby Island are more uniformly gray brown (males) or pale orange brown (females), with little obvious blotching, mottling, or spotting. These pattern elements are more common on the frogs from Fergusson Island. All adults have dark-brown irises, but all juveniles have pale-tan irises, so an ontogenetic change clearly takes place.

Color in life. Field notes for BPBM 16481 noted the dorsum to be chocolate brown ( Fig. 1 E), the ventrum to be dirty white with a slight lavender wash posteriorly, a white fringe along the forearms, the iris brown, and the palpebral reticulum gold. For specimens BPBM 17942, 17950, and 17958, the dorsum was mottled dark and light orange-brown, with the webbing of the same color or varying to bright orange. The chin, throat, and chest of these animals was white, changing to pale orange or orange-brown on the abdomen and under the limbs. The palpebral reticulum of each was white. In contrast, BPBM 17937–17941 and 17943 had the dorsum and webbing uniform olive-brown, the venter white with a dark-purple wash (darker under legs), and the palpebral reticulum bronze; BPBM 17944 was similar to these but with a pale violet cast. A color image of BPBM 37765 shows a pale tan animal with a few scattered gray flecks, which are likely scar tissue, and some yellow on the webbing of the foot ( Fig. 1 F). This pale color pattern was typical of animals resting during the daytime.

Call. The call of Nyctimystes intercastellus consists of short, unmodulated, slightly pulsed croaks ( Figs. 3 C, 7C) usually delivered in clusters of 3–6 notes/call, but with single notes frequently interspersed among the longer calls (Figs. 7A, C, 8). The number of notes/call varies in no apparent pattern as the frog calls, but most calls have a middling number of notes, usually three, four, or five ( Fig. 8 ). Calls vary from 0.19– 3.60 s, depending on the number of notes/call, and intervals between calls are longer, varying from 0.81– 20.68 s overall and with average intervals between calls varying little (4.86– 5.09 s) among the three frogs recorded by me ( Table 8 ). Note duration is relatively short (0.188– 0.320 s) and is approximately equal to inter-note length for calls consisting of multi-note clusters, although notes average of slightly shorter duration than do intervals between notes within multi-note calls ( Table 8 ). For multi-note calls, note length usually shortens progressively within the sequence; BPBM 17949 had more exceptions to this rule than did the other two recorded frogs. Similarly, interval length between subsequent notes in multi-note calls is usually shortened sequentially, except that for most multi-note calls interval length between the last two notes increases from that of the penultimate interval. Waveforms of the first note or two in multi-note calls are distinctly bimodal, with low amplitude at the beginning of the note and higher amplitude in its second half; later notes in the sequence are of similar amplitude throughout ( Fig. 3 C). Dominant frequency of notes varied little, with averages among the three frogs ranging from 2040–2310 Hz and overall variation among notes ranging from 1950–2460 Hz (Fig. 7B, Table 8 ).

Etymology. The name is a masculine singular Latin compound adjective meaning “between the castles” and is a direct translation of “D’Entrecasteaux”, the name of the archipelago to which this species is limited.

Range. Known from Fergusson, Goodenough, and Normanby islands of the D’Entrecasteaux Archipelago ( Fig. 5 , triangles). It does not appear to occur on the adjacent mainland of New Guinea nor on the larger islands of the Louisiade Archipelago, so it is almost certainly endemic to the D’Entrecasteaux islands.

Ecological notes. Animals were common along fast-moving streams at elevations ranging from 120– 960 m. The upper-elevation stream was shallow and on a wide (ca. 10 m), smooth, rock bed, but the stream itself was typically only 1–3 m wide. This stream had a series of narrow runs and a few small pools, with many large boulders present in sections. Lowland streams were shallow, fast-moving, and very wide (ca. 15–40 m). The upland site on Oya Tabu was well-developed small-crowned lowland hill forest ( Paijmans, 1975, 1976), with canopy at approximately 20–25 m and emergents to 30+ m. The lowland sites on Normanby Island were welldeveloped lowland rainforest with canopy of approximately 35 m and relatively dense understory. The Awavulu River site on western Fergusson Island was in a heavily disturbed lowland area of secondary scrub and open vegetation.

Figures

FIGURE 1. Portraits in life of (A) Nyctimystes cheesmani, BPBM 18293, Fane, Central Province; (B) N. cheesmani, BPBM 18294, Fane, Central Province; (C) male N. bivocalis, BPBM 15206, Cloudy Mts., Milne Bay Province; (D) female N. bivocalis, BPBM 15209, Cloudy Mts., Milne Bay Province; (E) N. intercastellus, BPBM 16481, Fergusson Is., Milne Bay Province; (F) N. intercastellus, BPBM 37765, Normanby Is., Milne Bay Province.

FIGURE 3. Expanded waveforms and spectrograms showing note structure for (A) Nyctimystes cheesmani from Fane, Central Province (uncaptured), (B) N. bivocalis (BPBM 15202) from Cloudy Mts., Milne Bay Province, and (C) N. intercastellus (BPBM 17938) from Normanby Island, Milne Bay Province.

FIGURE 5. Map of the Southeastern Peninsula of New Guinea showing localities for Nyctimystes cheesmani (star), N. bivocalis (circles), and N. intercastellus (triangles). Type localities are solid symbols; additional localities are open symbols.

FIGURE 8. Number of notes / call for three specimens of Nyctimystes intercastellus. (Top) Summary numbers across all three specimens; (Bottom) individual variation for BPBM 17937 (black bars), BPBM 17938 (gray bars), and BPBM 17949 (open bars).

Tables

TABLE 7. Mensural variation among adults and juveniles of Nyctimystes intercastellus.

Character SV (mm)	mean 43.1	Males (n = 46) SD range 0.3668 36.6–47.7	Females (n = 11) mean SD range 48.4 1.4676 42.7–55.5	Juveniles (n = 10) mean SD range 21.0 0.9362 17.3–25.8
TL/SV	0.53	0.0023 0.50–0.58	0.55 0.0058 0.50–0.57	0.58 0.0042 0.57–0.60
EN/SV	0.098	0.0006 0.090–0.107	0.100 0.0012 0.095–0.106	0.107 0.0013 0.100–0.113
IN/SV	0.093	0.0005 0.085–0.101	0.090 0.0014 0.081–0.096	0.113 0.0018 0.105–0.119
SN/SV	0.16	0.0009 0.15–0.17	0.15 0.0023 0.14–0.16	0.17 0.0025 0.15–0.18
TY/SV	0.042	0.0005 0.032–0.051	0.044 0.0007 0.040–0.047	0.044 0.0015 0.034–0.051
EY/SV	0.12	0.0012 0.11–0.14	0.11 0.0019 0.10–0.12	0.14 0.0015 0.13–0.14
HW/SV	0.35	0.0017 0.33–0.39	0.35 0.0047 0.33–0.38	0.39 0.0031 0.37–0.40
HL/SV	0.34	0.0018 0.33–0.38	0.33 0.0021 0.32–0.35	0.37 0.0036 0.34–0.48
EN/IN	1.06	0.0063 1.00–1.15	1.12 0.0148 1.05–1.19	0.95 0.0147 0.86–1.00
HL/HW	0.98	0.0032 0.94–1.02	0.97 0.0085 0.90–0.99	0.96 0.0075 0.92–1.00

TABLE 8. Call data for three specimens of Nyctimystes intercastellus from Normanby Island. Numbers for call parameters are mean ± SD (range).

Character	BPBM 17937	BPBM 17938	BPBM 17949
Temperature (C)	25.6	25.8	26.0
Number of calls	19	16	20
Number of notes	48	47	55