Nemesia maltensis, Cassar & Mifsud & Decae, 2022

Cassar, Thomas, Mifsud, David & Decae, Arthur E., 2022, The Nemesia trapdoor spider fauna of the Maltese archipelago, with the description of two new species (Araneae, Mygalomorphae, Nemesiidae), European Journal of Taxonomy 806 (1), pp. 90-112 : 101-106

Nemesia maltensis sp. nov.

urn:lsid:zoobank.org:act:BB791B03-F14E-4D15-9338-EE2E02244C4A

Figs 54–73

Diagnosis

Nemesia maltensis groups out with a species-complex that is common in the central and eastern Mediterranean Basin ( Decae 2012). In this species-complex the palpal organ of males has striae (fine ribs) on the proximal embolus ( Figs 59–62 ), and females have tube shaped, tripartite spermathecae in which the median part is folded and twisted ( Fig. 69 ). Within this species-complex, N. maltensis fits in a central Mediterranean subgroup that has informally been named the maculatipes group ( Decae et al. 2015). Species in this subgroup, such as N. maculatipes Ausserer, 1871 (Sardinia) , N. meridionalis (Costa, 1835) (southern Italy), N. sanzoi Fage, 1917 (Sicily) and N. pannonica Herman, 1879 ( Serbia) have conspicuous dark coloured patches (maculae) on legs and/or the external proximal article of the PLS ( Figs 58 , 64–65, 67 ). Within the maculatipes group N. maltensis keys out with N. meridionalis on grounds of a similar morphology of the distal embolus in males being ornamented with a short row of tiny denticles ( Fig. 63 cf. Isaia & Decae 2012: fig. 4). This character is not known from any other Nemesia species. Males of N. maltensis can be distinguished from those of N. meridionalis by the absence of an abrupt narrowing of the distal embolus ( Figs 59–62 cf. Isaia & Decae 2012: fig. 3), females of N. maltensis can be distinguished from those of N. meridionalis by the relatively flat profile of the carapace (lateral view Fig. 65 ), lack of sharply defined light coloured spigot fields on the PMS and PLS ( Fig. 68 cf. Isaia & Decae 2012: fig. 5), and absence of a strong colour contrast between the labium and the sternum and the indistinct central division of the labial furrow ( Fig. 66 cf. Isaia & Decae 2012: figs 7–8).

Etymology

The name refers to Malta, the largest island in the Maltese Archipelago and the only Mediterranean island where the species is currently known to occur.

Type material

Holotype MALTA • ♂; Buskett ; 8–13 Sep. 2020; 35.856° N, 14.396° E; T. Cassar leg.; (no. TC.004); NHMR.

Paratypes MALTA • 4 ♂♂; same collection data as for holotype; (no. TC.005 to TC.008); NHMR • 2 ♂♂; same collection data as for holotype; (no. TC.009, TC.010); NHMW • 2 ♀♀; same collection data as for holotype; 14 Mar. 2021; (no. TC.012, TC.013); NHMR .

Description

Male holotype (no. TC-004, NHMR)

PRESERVATION AND CONDITION. Specimen 6 months preserved in 70% ethanol, in good condition ( Fig. 54 ), right bulb detached for study ( Figs 59–63 ).

GENERAL COLORATION. Carapace yellowish with dark flanks of cephalic part and dark margin ( Fig. 55 ), chelicerae brown, darker than carapace with dorsal lighter coloured patch, opisthosoma dorsal anterior dark greyish-brown, further light coloured with dark, irregular chevrons and a dark cardiac line ( Fig. 54 ), opisthosoma ventral uniform creamy white, palps and legs lighter coloured than body in dorsal view and ventrally lighter coloured than dorsally, sternum and ventral coxae creamy white, labium conspicuously darker than other ventral parts.

CARAPACE. Longer than wide (CW/CL 0.8), covered with very fine silvery pubescence, curved bristles concentrated along the margins and posterior on the thoracic part, longitudinal row on the crest of the cephalic part and few forwardly projecting bristles on clypeus. Cephalic not elevated, thoracic part bulging slightly up from the fovea before sloping down to the posterior margin ( Fig. 55 ).

EYES. Ocular-tubercle dome-shaped, clypeus narrow sloping down from eyes, eye-group rectangular, twice as wide as long (EL/PR 0.51), AME less than their diameter apart (dis.AME/dia.AME 0.87), dis. ALE–PLE less than ½ dia.ALE (ALE–PLE/ALE 0.44).

CHELICERAE. Rastellum with few strong teeth on the apical prolateral corner of chelicerae, prolateral row of furrow teeth, fangs sharp, bent, ventral un-serrated ridge.

VENTRAL PROSOMA. Maxillae rounded distal lobe, few spiky cuspules on proximo-anterior margin. Labium: wider than long (LW/LL 0.7), cuspules absent, labial furrow narrow. Sternum: longer than wide (SW/SL 0.8) three pairs round sigilla, posteriors sub-marginal, evenly covered with bristles.

PALPS. Cymbium with distal group of spines, tibia with PTR strongly develop ( Fig. 56 ), proximally inflated (TibW/PTib 0.6), patella spineless, femur longer than tibia (PFem/PTib 1.6) with group of slender spines dorsally on distal half of the article. Palpal organ, proximal bulbous part pyriform extending distally into a slender curved embolus. Embolus curved, distally gradually tapering to a sharp, bevelled tip. Striae on proximal embolus, few tiny denticles just proximal of the embolus tip ( Figs 59–63 ).

LEGS. All tarsi with fine ventral scopulae. Leg: I: metatarsus and tibia modified, metatarsus curved, lateral longitudinal rows of spines over the length of the article, CF with dense brush of short bristles, tibia distally widened, TA reduced ( Fig. 57 cf Fig. 29 ), TS smoothly upward curved ( Fig. 57 ), spines present on all articles proximal of tarsus, patella with two prolateral spines. Legs I–III; tarsi without spines, other articles with numerous spines, maculae vague, most prominent on prolateral femur (apical) and patella (central). Leg IV, tibia> femur> metatarsus (Fem4/Met4 = 1.02, Tib4/Met4 = 1.07). Leg formula: 4123. PTC on all tarsi with ventrally two parallel combs of small teeth (genus character), ATC smooth.

OPISTHOSOMA. Ovoid, anterior narrowing with numerous forward directed bristles, dorsal bristles are backward directed, Spinnerets: PMS knob-shaped, spigots apically concentrated, PLS proximal article with external macula ( Fig. 58 ), as long as medial + distal articles, spigots spread over ventral proximal and medial articles and on apical distal article.

MEASUREMENTS. TBL = 12.3; CL = 5.0; CW = 3.8; CP = 3.0; AR = 0.83; PR = 0.83; EL = 0.42; dia.ALE = 0.25; dia.PLE 0.15; dia.AME = 0.15; dia.PME = 0.12; dis.AME–AME = 0.13; dis.ALE–PLE = 0.11; SL = 2.6; SW = 1.9; LL = 0.6; LW = 0.8; Palp = 4.9 (0.7 + 1.2 + 1.1 + 1.9); Leg I = 13.2 (2.0 + 2.6 + 2.6 + 2.4 + 3.6); Leg II = 12.5 (2.0 + 2.5 + 2.4 + 2.1 + 3.5); Leg III = 11.9 (2.0 + 3.0 + 2.1 + 1.7 + 3.1); Leg IV = 16.8 (2.3 + 3.9 + 4.2 + 2.4 + 4.0); BuL = 1.12; BuW = 0.39; EmL = 0.51.

VARIATION MALES (n = 7). TBL = 8.7–12.3 (av. 10.1, sd. 1.2); CL = 3.8–5.0 (av. 4.4, sd. 0.4); CW = 2.8–3.8 (av. 3.3, sd. 0.3); CP = 2.1–3.0 (av. 2.5, sd. 0.3); AR = 0.67–0.83 (av. 0.74, sd. 0.05); PR = 0.69– 0.83 (av. 0.76, sd. 0.05); EL = 0.36–0.44 (av. 0.40, sd. 0.03); dia.ALE = 0.20–0.25 (av. 0.22, sd. 0.02); dia.PLE = 0.14–0.18 (av. 0.17, sd. 0.02); dia.AME = 0.13–0.15 (av. 0.14, sd. 0.01); dia.PME = 0.11– 0.14 (av. 0.13, sd. 0.01); dis.AME–AME = 0.08–0.14 (av. 0.11, sd. 0.02); dis.ALE–PLE = 0.04–0.11 (av. 0.07, sd. 0.02); SL = 1.9–2.6 (av. 2.2, sd. 0.2); SW = 1.5–1.9 (av. 1.7, sd. 0.1); LL = 0.3–0.6 (av. 0.4, sd. 0.1); LW = 0.6–0.8 (av. 0.7, sd. 0.1); Palp = 4.0–4.9 (av. 4.6, sd. 0.3); Leg I = 10.4–13.0 (av. 11.7, sd. 0.9); Leg II = 9.5–12.5 (av. 11.0, sd. 1.0); Leg III = 9.0–11.8 (av. 10.3, sd. 0.9); Leg IV = 13.5–16.8 (av. 15.1, sd. 1.2); Bul = 0.96–1.12 (av. 1.06, sd. 0.06); BuW = 0.31–0.39 (av. 0.36, sd. 0.03); EmL = 0.47–0.52 (av. 0.52, sd. 0.02).

Female paratype (no. TC-012, NHMR)

Note. The females available for description are small and might not be reproductive adults, the spermathecae of the here described paratype are however sufficiently developed for study. Specimens, 6 months preserved in 70% ethanol, in perfect condition.

GENERAL COLORATION. Carapace cephalic part has wide light brown crest-zone and is generally darker in colour than thoracic part, black margin prominent ( Fig. 64 ), chelicerae bicoloured brown, slightly darker than carapace, abdomen dorsal as in male, palps and legs generally as in male, but dorsal femora lighter coloured and with prominent maculae ( Figs 64–65, 67 ), sternum and labium slightly darker coloured than ventral coxae.

CARAPACE. Longer than wide (CW/CL 0.7), sparsely covered with very fine black pubescence, bristles centrally in longitudinal row on crest-zone. Cephalic part only slightly elevated and gradually sloping down over the thoracic part to the posterior margin ( Fig. 65 ).

EYES. Ocular-tubercle as in male, eye-group rectangular, twice as wide as long (EL/PR 0.53), AME less than their diameter apart (dis.AME/dia.AME 0.92), dis.ALE–PLE less than ½ dia.ALE (ALE–PLE/ ALE 0.42).

CHELICERAE. Stronger developed than in male with distinct rastellum, prolateral row of furrow teeth with six conical teeth, fangs sharp, bent, ventral un-serrated ridge.

VENTRAL PROSOMA. Maxillae small rounded distal lobe, few knobby cuspules on proximo-anterior margin. Labium: twice as wide as long (LW/LL 2.3), cuspules absent, labial furrow centrally divided ( Fig. 66 ). Sternum: longer than wide (SW/SL 0.7), sigilla not distinguished.

PALPS. Femur and patella spineless, tibia ventral and prolateral sharp distally pointing spines and dorsal long parallel rows of trichobothria, tarsus, distally pointed, ventral half fully scopulate with group of sharp distally pointing spines, dorsal row trichobothria in central part of article, palpal claw with short proximal row of teeth.

LEGS. All femora with external maculae ( Figs 64–65 ). Anterior legs with ventro-prolateral scopulae extending from tip of tarsus to distal patella, ventral spines on tibia and metatarsus. Posterior legs with dense groups of spiny bristles prolateral on distal femur and dorsal patella. Leg III, patella with three prolateral spines ( Fig. 67 ) and one retrolateral spine. Leg IV patella spineless, tibia> femur> metatarsus (Fem4/Met4 1,1, Tib4/Met4 1,3). Leg formula: 4123. PTC and ATC as in male.

OPISTHOSOMA. Generally as in male, anterior bristle group less distinct, spinnerets without sharply defined spigot-fields ( Fig. 68 ). Spermathecae, tripartite, tube shaped, proximal part with dense concentration of pigmented cells, proximally widest, median part folded and twisted ( Fig. 69 ), distal part digitiform with few pigmented cells.

MEASUREMENTS. TBL = 9.7; CL = 3.9; CW = 2.9; CP = 2.3; AR = 0.71; PR = 0.74; EL = 0.39; dia.ALE = 0.18; dia.PLE 0.13; dia.AME = 0.10; dia.PME = 0.10; dis.AME–AME = 0.10; dis.ALE–PLE = 0.05; SL = 1.7; SW = 1.3; LL = 0.3; LW = 0.6; Palp = 5.1 (1.1 + 1.1 + 1.1 + 1.8); Leg I = 8.3 (1.0 + 1.3 + 1.6 + 1.8 + 2.6); Leg II = 7.4 (1.0 + 1.3 + 1.4 + 1.5 + 2.2); Leg III = 7.1 (1.1 + 1.6 + 1.1 + 1.3 + 2.0); Leg IV = 11.3 (1.1 + 2.4 + 3.1 + 2.0 + 2.7).

VARIATION FEMALE (n = 2). TBL = 9.2, 9.7; CL = 3.4, 3.9; CW = 2.3, 2.9; CP = 2.0, 2.3; AR = 0.62, 0.71; PR = 0.61, 0.74; EL = 0.33, 0.39; dia.ALE = 0.18, 0.19; dia.PLE = 0.13, 0.16; dia.AME = 0.10, 0.12; dia.PME = 0.10; dis.AME–AME = 0.10, 0.11; dis.ALE–PLE = 0.05, 0.08; SL = 1.7, 2.1; SW = 1.3, 1.5; LL = 0.3, 0.4; LW = 0.6, 0.8; Palp = 4.2, 5.1; Leg I = 6.7, 8.3; Leg II = 6.3, 7.4; Leg III = 5.9, 7.1; Leg IV = 9.6, 11.3.

Observations

In the field ( Fig. 70 ), the burrows of this species appeared to be completely lidless, with the burrow entrance opening at the ground surface directly ( Fig. 72 ). The wall of the burrow is lined with almost imperceptibly thin strands of silk from the inside; but the burrow walls derive most of their structural integrity from the compaction of the soil around them ( Fig. 71 ). In captivity, once soil was moistened, a female constructed a bifurcated burrow with two shafts opening at the soil surface with no lids ( Fig. 73 ), joining together into one shaft deeper into the soil. Females were collected from burrows some 15 cm deep in the soil, congregated at the edge of a small boulder embedded in deep soil in a wooded area populated by trees of Laurus nobilis L., Olea europaea , Rhamnus alaternus L. and Pinus halepensis Mill. Burrow entrances always appeared at the soil surface at the edge of the boulder or, in one instance, at the base of the thick stems of an Acanthus mollis L. plant nearby. Males were collected in pitfall traps after several heavy rainfall events which occurred in September – the so called “first rains” which bring an end to the dry season.

Figures

Figs 54–63. Nemesia maltensis sp. nov. holotype, ♂ (TC.004, NHMR). 54. Dorsal habitus (note distinct dark flanks of cephalic part). 55. Prosoma in lateral view (note dark margin of the carapace and cephalic part not elevated). 56. Dorso-distal right palp (note strong development of PTR). 57. Prolateral left metatarsus and distal tibia leg I (note CF with dense brush of short bristles, short TA and smoothly curved TS). 58. Spinnerets, lateral view showing macula (MAC) on external proximal article of PLS. 59–63. Right palpal organ in four different positions rotated clock-wise by 90°. 59. Ventral view. 60. Prolateral view. 61. Dorsal view. 62. Retrolateral view. 63. Embolus tip at high magnification, note short row of tiny denticles (den) and bevelled tip.

Figs 64–69. Nemesia maltensis sp. nov. paratype, ♀ (TC.012, NHMR). 64. Dorsal habitus, note maculae on external femora I & II (m). 65. Left lateral habitus, note numerous maculae on legs arrow indications (m) and the low carapace profile (lp). 66. Ventral anterior prosoma, note indistinct central division (cd) in labial furrow. 67. Prolateral patella III, note three spines (sp) in a row. 68. Ventral spinnerets, note absence of distinct light coloured spigot fields. 69. Spermathecae, ventral view, note median part of the receptacles being folded and twisted (ft).

Figs 70–73. Nemesia maltensis sp. nov. observations. 70. Natural habitat. 71. Borrow top cut open, note virtual absence of a silk lining of the burrow shaft and the compacted soil from which the burrow walls derive most of their structural integrity. 72. Natural burrow entrance flush with the soil surface, note absence of trapdoor. 73. Two surface openings of the bifurcated burrow seen in an observation container.

Figs 27–35. Nemesia arboricola Pocock, 1903, ♂ reference specimen (TD.4, NHMR). 27. Dorsal habitus. 28. Prosoma lateral, note slight elevation of the cephalic part, ocular process and gradual posterior slope of thoracic part. 29. Metatarsus and tibia leg I, note tibial apophysis (TA), tibia spur (TS), clasper field (CF). 30. Prolateral patella III with single spine (SS). 31–34. Right palpal organ in four different positions rotated clock-wise by 90°. 31. Ventral view, 32. Prolateral view. 33. Dorsal view. 34. Retrolateral view. 35. Embolus tip at high magnification, note slightly scooped tip.