Eukoenenia draco (Peyerimhoff 1906)

Mayoral, J. G. & Barranco, P., 2013, Rediscovery of the troglobious palpigrade Eukoenenia draco (Peyerimhoff 1906) (Palpigradi: Eukoeneniidae), with notes on the adaptations to a cave-dwelling life, Zootaxa 3635 (2), pp. 174-184 : 175-181

Eukoenenia draco (Peyerimhoff 1906)

( Figs. 1–12 )

Kaenenia [sic] draco Peyerimhoff 1906: 300 –302, figs 1–4; Peyerimhoff 1908: 193. Eukoenenia draco Harvey 2003: 154 (full synonymy).

Material examined. 1 ♀, Coves des Pirata, Mallorca, Spain, 10 June 2006, UTM: 4373310N 31525880E, M. Vadell leg.; this specimen was captured 60 meters from the entrance, on rotten wood soaked in water, at 23.4 °C and 81% relative humidity. 1 ♀, Cova des Pas de Vallgornera (Llucmajor, Mallorca), Spain, 11 April 2009, M. Vadell leg.; 3 ♀, Cova des Pas de Vallgornera (Lucmajor, Mallorca), 16 October 2010, M. Vadell leg.; 1 ♂, Cova des Pas de Vallgornera (Lucmajor, Mallorca), 25 April 2009, M. Vadell leg.; 1 imm., C type, Cova des Pas de Vallgornera (Lucmajor, Mallorca), 11 April 2009, M. Vadell leg.

Description of female. Prosoma: Frontal organ with 2 expanded, granulate branches over 2.3 times longer than wide ( Fig. 1 ). Lateral organ with 8–9 blades, each granulate and 6 times longer than wide. Dorsal shield short, rounded, almost as wide as long, with 10 + 10 setae. Metapeltidium with 3 + 3 setae (t1, t2, t3) with lengths t1=28, t2=163 and t3= 102 ( Fig. 2 ). Medial setae (t1) shorter and thinner than middle setae (t2), latter being the thickest and longest. Chelicera with 9 teeth on each finger and 6 dorsal and 1 ventral setae. Nine to eleven deuto-tritosternal setae. Chaetotaxy of coxae of pedipalpus and legs I–IV: 18, 15, 16, 14, and 11 setae ( Figs. 3–7 ). Coxae II and III with 6 thickened setae, arranged in line; coxae IV with 5 thickened setae. Basitarsus 3 of leg I very slender ( Fig. 8 ), 6 times longer than broad, with 4 setae: stiff seta (r) thick, shorter than the segment, and inserted slightly in front of hind edge. Basitarsus IV very long, with 7 setae (2 esd, 2 esp, gla, grt and r), and with a faint suture approximately at the middle of the segment ( Fig. 9 ). Stiff seta r much shorter than tergal edge (t/r=3.15) and inserted in distal half, slightly beyond middle of segment (t/er=1.77). Both esp setae inserted proximally in first third, followed by gla and grt, inserted approximately at same level before the middle line, and esd inserted at the beginning of last third. Ta3 of the Pedipalp (Pta3) with 2 long forked setae, arranged in line and with branches of unequal length (distal one with branches 11/25 μm long and proximal 8/11 μm); ta3 of Leg I (Ita3) with 5 bifurcate setae, arranged in 4 transverse rows, from distal to proximal (2+1+1+1); these setae shorter than those on Pta3, with branches of equal length (approximately 13 μm). One bifurcated seta inserted near distal end of Ita2, Ibta4, Ibta1 and Ibta2. Leg I with 7 trichobothria in usual positions. Total length of pedipalp 1712–1875 μm; total length of leg I 2638–2816 μm; total length of leg IV 1818–1985 μm.

Opisthosoma: Tergites II–VI with 3+3 dorsal setae each, 2 pairs of setae (t1, t3) between slender a seta (s1) (one specimen with 3+2 on tergite II); tergite VII–VIII with 2+2 setae (t1, t3), without (s1); setae slightly longer than those on previous tergites. Sternite III with 2+2 setae. Setae of sternites IV–VI variable ( Fig. 10 ): sternite IV, 13–14 setae, three specimens (2+5+4+2) and the other two (2+5+5+2); sternite V, 10–14 setae, each specimen with different formula, (2+5+5+2), (2+5+4+2), (2+4+5+2), (2+4+4+2) and (2+3+3+2); sternite VI with 10–14 setae, two specimens (2+5+5+2), one (2+5+4+2), another (2+3+3+2), and the other (2+3+4+2). Sternite VII, with 6 setae. Sternite VIII with 6 setae (3+3) (one specimen with 2+3). Segments IX–XI with 8 setae each (one specimen with 9 setae on segment XI).

Genitalia ( Fig. 11 ): first lobe broad and with rounded looking aspect, wider at the median level; distal margin with a clear medial deep cleft separating the two sides. First lobe carries 11+11 setae in 5 transverse rows. First row with 4 long setae arranged in an arc (2+2), 1.1 times longer than the 2+2 setae of second row, inserted on the outer edges of the lobe. Setae of third row (2+2) shorter and closer to the medial axis of the lobe. Fourth row with 2 setae (1+1) inserted next to medial cleavage of lobe. Fifth and last row (4+4, a1–a4) inserted on posterior edge of the two sides of lobe, setae of different sizes, a2<a1<a3=a4. Second lobe with a medial indentation that separates the two triangular sides, each carrying a pair of distal setae (x, y) of similar length (proximal seta z missing). Two groups of six lateral refringent bodies and two small peduncle-like structures located proximally of genital lobe (viewed under first lobe). Their functions are unknown.

Description of male. Overall aspect as for female (except for sternal setation). Lateral organs, with 8 blades each. Twelve deuto-tritosternal setae. Dorsal chaetotaxy as for female. Sternites IV–VI with a pair of s setae on each side (s1, s2), and 22, 22, and 19 setae between those setae on each sternite, respectively ( Fig. 10 ). Basitarsus 3–4 leg I, and bta leg IV identical to those of female. Total length of the pedipalp 1630; total length of leg I 2682; total length of leg IV 1867.

Genitalia ( Fig. 12 ): 3 pairs of lobes, with a total of 42 setae. First lobe long, broad and butterfly-shaped due to a deep medial cleavage on both apical and distal borders; 11+11 setae in 4 rows: first row 2 + 2 setae, second 3 + 3, third with two pairs of fusules 2 + 2, and fourth row with 4 + 4 setae. Fusules long, close to each other, parallel, not very expanded at the base, and not borne on protuberances; similar in length and reaching past distal margin of second lobe. Second lobe clearly overreaching the first, end rounded, with a thin blade-shaped structure projected distally from the inner side of each lobe, 5 + 5 setae (a, b, c, cʹ, d). Third lobe with a single, large, pointed apical ending, 3 + 3 setae (x, y, z).

Remarks. The above description of Eukoenenia draco is based on all the available specimens. The measurements given are for the female from Coves des Pirata, chosen because of its proximity to the type locality; measurements for all the specimens are presented in Table 1 .

Eukoenenia draco (Peyerimhoff 1906) was described from a single female, which is currently lost. The holotype has been searched for in the following institutions, to no avail: Museo Nacional de Ciencias Naturales, Madrid (Dr Javier Sánchez Almazán), Museo de Ciencias Naturales de Barcelona (Dr Oleguer Escolà), Museum of Natural History, Geneva (Dr Peter J. Schwendinger), Zoological Museum, University of Copenhagen (Drs Alexey Solodovnikov & Nikolaj Scharff), Muséum national d’Histoire naturelle, Paris (Dr Mark Judson) and the Institutul de Speologie “Emil Racovitza”, Cluj (Dr Oana T. Moldovan).

The original description by Peyerimhoff (1906), while appropriate at the time, is wholly incomplete at present. It does not offer any information about the pedipalps, leg IV or the structure and setae of the genitalia (Condé 1951). Also, we do not have any measurements for the type specimen, except for the total length, which is almost twice that of an average palpigrade.

The specimens of E. draco reported in this study were not captured at the type locality of Coves del Drac. However, Coves des Pirata is very close, within the same municipality, Manacor, and only 4.2 Km from Coves des Drac. The other specimens are from Cova des Pas de Vallgornera, which is further West, on the other side of the island, 43.4 Km from Coves del Drac and 39.7 Km from Coves des Pirata. Several attempts have been made to capture E. draco in Coves del Drac, but they have been unsuccessful (Mateo Vadell, pers. comm.).

Eukoenenia draco E. zariquieyi C. Pirata Cova des Pas de Vallgornera C. Salitre PA 110409 -1 PA 161010 -3 PA 161010 -2 PA 161010 -1 PA 250409 -1

The specimens captured from these two caves, apart from each other on the island, belong to the same species, sharing the same characters, chaetotaxy and morphometric data. The chaetotaxy of these specimens corresponds to that described by Peyerimhoff in 1906 for E. draco , but we found high variability in characters frequently used to separate species, even for specimens collected within the same cave, e.g. the number of lateral organs and the deuto-tritosternal setae, amongst others (see last section). We found 9–11 deuto-tritosternal setae in the specimens captured in Cova des Pas de Vallgornera and Coves des Pirate; Peyerimhoff (1906) reported 11 setae for the specimen from Coves del Drac. Similarly, the number of lateral organs for the new material is 8–9, and 9 for the type specimen.

Peyerimhoff (1906) only offered comments about length to width ratios of some segments, the single quantitative measurement given being that of the total length of the type: 2.8 mm (without flagellum). That makes this specimen the largest palpigrade ever known (Condé 1984b). Peyerimhoff (1906) reported the length/width ratios of the tibia of the pedipalpus and of leg I to be around 8. However, he did not state whether he used the maximum, minimum or any other width of the segment to calculate this ratio. Using his figure 3 of leg I, we digitally enlarged the image and measured its total length, maximum and minimal width, as well as the width at the middle of the segment. The ratio varied considerably due to the shape of the tibia: it was 5.4 when the maximal width was used, 8.9 for the minimal width, and 5.9 when the width was measured at the middle of the segment. Clearly, the closest of these numbers to that reported by Peyerimhoff (8 times) is the ratio obtained when the minimal width of tibia is used, at the distal edge of the segment. This is surprising since a priori one would expect Peyerimhoff to have used the maximum width to calculate this ratio. In order to compare the new specimens with the type, we calculated this ratio using the width at the distal border of tibia (minimum) for the specimens from Coves des Pirata and for another specimen from Cova des Pas de Vallgornera. The ratios obtained were 8.2 and 8.5, respectively. We did the same for the tibia of the palp, obtaining ratios of 8.0 and 8.8, respectively. These numbers are very similar to those reported by Peyerimhoff (1906). A second ratio was reported by Peyerimhoff (1906), namely that the length of Ibta3 was double that of Ibta4. This ratio ranges from 1.7–2.0 for the specimens from Coves des Pirata and Cova des Pas de Vallgornera.

In summary, the new specimens are very similar to the type reported from Coves del Drac by Peyerimhoff (1906), except for the total length of the body (2.8 vs. 1.7–2.3 mm). We do not have an explanation for this discrepancy, but we cannot ignore the similarities regarding all other characters.

Figures

FIGURE 10. Eukoenenia draco. Representation of setal variability on sternites IV – VII for the specimens studied and for type specimen (top-left from Peyerimhoff 1906). Specimen number and sex indicated above each figure. Number of lateral organs (Lat. Org.) and number of deuto-tritosternal setae (Deut. setae) also reported under each specimen. Nomenclature of setae shown for type specimen. See Material and Methods for abbreviations.

FIGURES 1 – 7. Eukoenenia draco. 1, Frontal organ, dorsal view. 2, Metapeltidial setae. 3, Pedipalp coxa. 4, Coxa I. 5, Coxa II. 6, Coxa III. 7, Coxa IV. Scale bars 100 µm (Fig. 1 to same scale as Fig. 2). See Material and Methods for abbreviations.

FIGURES 8 – 9. Eukoenenia draco. 8, Basitarsus 3 – 4, leg I. 9, Basitarsus, leg IV. Scale bar 100 µm. See Material and Methods for abbreviations.

FIGURES 11 – 12. Eukoenenia draco, genitalia. 11, female. 12, male. Scale bar 100 µm. See Material and Methods for abbreviations.

Tables

TABLE 1. Measurements (in micrometres) and ratios for Eukoenenia draco and E. zariquieyi (data for latter extracted from Condé 1951).

Ƥ	Ƥ	Ƥ	Ƥ	Ƥ	3	Ƥ
L 1710	–	2010	2209	2356	–	1250
B 480	–	473	504	541	510	–
Pcx 242	231	220	252	247	226	–
Ptc 352	315	347	336	347	279	–
Pfe 252	242	247	231	315	252	–
Pti 347	342	341	320	352	310	94
Pbta1 142	132	125	121	131	121	33.5
Pbta2 168	158	148	158	173	158	47.5
Pta1 95	99	90	100	110	95	29
Pta2 95	95	90	89	95	89	29
Pta3 110	110	105	105	105	100	37
Icx 310	289	310	298	315	290	–
Itc 378	352	394	368	379	341	–
Ife 300	252	269	252	278	279	–
Ipa 368	336	347	331	373	347	–
Iti 378	368	378	363	383	368	94
Ibta1+2 290	311	336	305	326	300	75
Ibta3 190	184	182	179	200	195	45.5
Ibta4 95	105	103	105	105	105	28.5
Ita1 90	95	93	95	95	105	25
Ita2 85	95	90	84	89	89	25
Ita3 265	263	260	258	273	263	78
IVcx 194	173	200	174	210	189	–
IVtc 210	163	215	216	206	210	–
IVfe 331	290	315	326	337	331	–
IVpa 289	263	273	263	279	263	–
IVti 362	336	341	331	357	331	78
IVbta 347	331	326	310	337	315	78
IVta1 110	120	112	116	116	116	27.5
IVta2 142	142	138	131	142	142	42
a 33	30	–	28	27	29	–
er 203	190	–	178	165	168	–
grt 115	152	155	143	142	147	–
gla 200	180	185	175	189	179	–
r 115	117	113	105	110	110	–
t/r 2.96	2.87	2.88	3.15	3.25	3.01	–
t/er 1.70	1.74	–	1.74	2.04	1.87	–
gla/grt 1.74	1.18	1.19	1.22	1.33	1.22	–
B/bta 1.33	–	1.45	1.52	1.52	1.54	–
bta/ti 0.95	1.02	0.96	1.07	1.06	1.05	1.0