Nemesia cominensis, 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 : 106-110

Nemesia cominensis sp. nov.

urn:lsid:zoobank.org:act:1194AF54-FEB0-4E94-BA86-708827BB2F1B

Figs 74–94

Diagnosis

Nemesia cominensis females can be distinguished from all known Nemesia species by its general light colour ( Figs 74–75 ) and the elongated, wiggly, tube-shaped spermathecal receptacles without a clear

differentiation in proximal, medial and distal parts ( Figs 79 , 87 ). It further differs from N. maltensis in the absence of maculae on legs ( Fig. 75 ) and the elevated cephalic part ( Fig. 75 ).

Etymology

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

Type material

Holotype MALTA • ♀; Comino Island ; 36.012° N, 14.337° E; 11 Sep. 2020; T. Cassar leg.; (no. TC.002); NHMR:

Additional material

MALTA • 1 ♀ subadult; same collection data as for holotype; (no. TC.001); NHMR • 1 ♂ subadult; same collection data as for holotype; 17 Sep. 2020; (no. TC.003); NHMR .

Description

Female holotype (no. TC-002, NHMR) GENERAL COLORATION. General appearance as a relatively light-coloured Nemesia species ( Fig. 74 ). carapace cephalic part with wide orange-brown crest zone and light grey flanks, thoracic part light yellow with vague grey folia pattern, chelicerae dark brown, distally darkest, palps and legs crème-coloured with dorsal yellow zones, sternum light yellow, labium and maxillae light brown, opisthosoma dorsal

creme-colour with light grey pattern of blotches and chevrons, ventral orange-brown zone between epigastric furrow and light-coloured spinnerets.

CARAPACE. Longer than wide (CW/CL 0.8), sparsely covered with very fine black pubescence, bristles centrally in longitudinal row on crest-zone and around the eyes. Cephalic part elevated; fovea only weakly recurved. Eyes: eye-group almost twice as wide as long (EL/PR 0.48), PR slightly wider than AR (PR/AR 1.03), AME slightly more than their diameter apart (dis.AME/dia.AME 1.10), distance ALE–PLE less than ½ dia.ALE (ALE–PLE/ALE 0.44).

CHELICERAE. Strong, rastellum triangular group of strong teeth placed apically, prolateral row of 6 conical furrow teeth, retrolateral furrow scopula, field of tiny denticles at furrow bottom, fang proximally hooked, very fine serrations on fang keel ( Fig. 76 ).

VENTRAL PROSOMA. Distal maxillae lobe reduced, three cuspules on proximo-anterior margin, labium: almost twice as wide as long (LW/LL 1.9), cuspules absent, labial furrow centrally divided. Sternum: longer than wide (SW/SL 0.8), with three pairs of light brown sub-marginal sigilla.

PALPS. Femur and patella spineless, tibia two ventro-lateral rows of sharp distally pointing spines and dorsal long parallel rows of trichobothria, tarsus ventral half fully scopulate with group of sharp distally pointing spines, dorsal trichobothria in V-formation, palpal claw with short proximal row of four teeth.

LEGS. Maculae absent ( Fig. 75 ). Leg I ventro-prolateral scopulae extending to distal tibia, row of three ventro-prolateral metatarsal spines, spines on other articles spineless. Leg II scopula restricted to tarsus and metatarsus, spines and spiny bristles stronger developed than on leg I. Posterior legs with dense groups of spiny bristles prolateral on distal femur and dorsal patella. Leg III, patella with two prolateral spines ( Fig. 77 ) retrolateral spines absent. Leg IV patella spineless, tibia> femur> metatarsus (Fem4/ Met4 1,1; Tib4/Met4 1,2). Leg formula: 4132. PTC and ATC identical to the ones of N. maltensis sp. nov.

OPISTHOSOMA. Ovoid, anterior narrowing ( Fig. 74 ), spinnerets without maculae or sharply defined spigot-fields, PMS digitiform ( Fig. 78 ). Spermathecae, tube shaped, wavy, wiggly structures without much differentiation ( Fig. 79 ).

MEASUREMENTS. TBL = 20.5; CL = 7.0; CW = 5.8; CP = 4.4; AR = 1.23; PR = 1.27; EL = 0.61; dia.ALE = 0.32; dia.PLE 0.25; dia.AME = 0.20; dia.PME = 0.14; dis.AME–AME = 0.22; dis.ALE–PLE = 0.14; SL = 4.0; SW = 3.1; LL = 0.7; LW = 1.4; Palp = 10.3 (2.3 + 2.2 + 2.1 + 3.7); Leg I = 15.3 (1.8 + 2.6 + 3.1 + 3.1 + 4.7); Leg II = 13.0 (1.6 + 2.5 + 2.7 + 2.9 + 3.3); Leg III = 14.0 (1.6 + 2.5 + 2.7 + 2.9 + 4.3); Leg IV = 20.9 (2.0 + 4.6 + 5.5 + 3.6 + 5.2).

VARIATION FEMALE (n = 2). TBL = 14.5, 20.5; CL = 6.0, 7.0; CW = 4.9, 5.8; CP = 3.7, 4.4; AR = 1.12, 1.23; PR = 1.19, 1.27; EL = 0.55, 0.61; dia.ALE = 0.21, 0.32; dia.PLE = 0.20, 0.25; dia.AME = 0.16, 0.20; dia.PME = 0.13, 0.14; dis.AME–AME = 0.19, 0.22; dis.ALE–PLE = 0.14, 0.20; SL = 3.3, 4.0; SW = 2.6, 3.1; LL = 0.7; LW = 1.3, 1.4; Palp = 8.5, 10.3; Leg I = 12.6, 15.3; Leg II = 11.5, 13.0; Leg III = 11.3, 14.0; Leg IV = 17.8, 20.9.

Sub-adult male (no. TC-003, NHMR)

As in all species of Nemesia , sub-adult spiders are, except for their small size, similar to adult females in general appearance and somatic characters. Males and females of Nemesia can be distinguished in juveniles by internally checking the presence of spermathecae that are already detectable in small juvenile and sub-adult females ( Fig. 87 cf. Fig. 88 ). Sub-adult males overlap in general body size with young females, but can be distinguished on the shape of the palp-tarsus that is slightly swollen ( Figs 82, 84 cf. 81, 83) and the absence of a vulva structure in the epigastric furrow ( Fig. 85 cf. 86).

Observations

Nemesia cominensis constructs a thin, flimsy wafer-door lid to its burrow ( Fig. 90 ), which is partly concealed by a thin layer of loose soil particles on top ( Fig. 89 ). Nemesia cominensis captures its prey in the usual trapdoor spider fashion by laying in ambush under a cracked open trapdoor, launching a flash attack on small animals that wander within reach of the spider ( Figs 91–94 ). Burrows are constructed in the ground in deep soil, with the door flush with the flat ground surface, and may be unbranched (single shaft) or bifurcated (two shafts joining to become one at the bottom, in a Y shape). During the aestivation period, the burrows have no lids whatsoever, and the burrow entrances are instead concealed and obstructed by up to about 2 cm of soil; they are also completely devoid of any silk lining. When the soil is moistened, the spiders resume their door-making and hunting; the first few millimetres of the burrow entrance are lined with a very thin layer of silk to which the door is attached, but the rest of the burrow still remains without silk lining. It is not known how deep the burrow shafts are in nature during the active period; in captivity an active burrow was constructed which reached 8 cm in depth but this was restricted by the size of the flower-pot; on location some spiders were found residing in aestivation burrows up to some 15 cm deep into the soil. Recently hatched spiders have been found after digging up aestivation burrows belonging to mature individuals, so it is assumed that the young are retained within the maternal burrow and disperse afterwards, taking up residence in close proximity (the sampled population was localized and dense). So far, this species has only been found to construct its burrows in relatively deep soil at the bottom of a shallow valley on the island of Comino, from which all of the aforementioned observations have been made. The difficulty in locating specimens may doubtless obscure the true distribution and ecological preferences of this newly described species from the Maltese Islands.

Figures

Figs 74–79. Nemesia cominensis sp. nov. holotype, ♀ (TC.002, NHMR). 74. Dorsal habitus. 75. Lateral habitus, note the elevated cephalic part or high carapace profile (hp). 76. Chelicerae in ventro-lateral view, note the hooked fangs and the finely serrated fang-keel (arrow indication).77. Prolateral patella III, not the two spines in line (sp). 78. Spinnerets ventral view, note the digitiform PMS. 79. Spermathecae with elongated, wavy, wiggly, tube-shaped receptacles.

Figs 80–88.Nemesia cominensis sp. nov. sub-adult, ♂ (no. TC.003, NHMR) vs sub-adult, ♀ (no. TC.001, NHMR). 80. Dorsal habitus sub-adult male, note the similarity in general appearance with the adult female holotype (Fig. 74). 81. Sub-adult female, palp tarsus, prolateral, note the slightly conical, normal female shape of the article (nt). 82. Sub-adult male, palp tarsus, prolateral, note the slightly swollen shape of the article (sst). 83. Similar as 81, but ventral view. 84. Similar as 82, but ventral view. 85. Epigastric furrow in sub-adult female, note the vulva structure (sf). 86. Epigastric furrow in sub-adult male, note the absence of a vulva structure (cf). 87. Genital zone sub-adult female with cuticle removed, note the presence of spermathecae (spe). 88. Idem sub-adult male, note the absence of spermathecae.

Figs 89–94. Nemesia cominensis sp. nov. observations. 89. Thin wafer-type trapdoor cracked open (a). 90. Opened trapdoor (b). 91. Closed trapdoor (c). 92. Flash-attack by spider as a reaction on subtle movements near the trapdoor (d). 93. Spider retreats after attack (e). 94. Trapdoor remains ajar after retreat (f).