Kryptochroma Machado, 2021

Machado, Miguel, Viecelli, Rafaela, Guzati, Catherine, Grismado, Cristian J. & Teixeira, Renato A., 2021, Kryptochroma: a new genus of bark-dwelling crab spiders (Araneae, Thomisidae), European Journal of Taxonomy 778, pp. 26-70 : 29-32

Kryptochroma Machado gen. nov.

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Type species

Stephanopis pentacantha Mello-Leitão, 1929 . Designated here.

Diagnosis

The species of Kryptochroma gen. nov. resemble some of those of Epicadus [e.g., Epicadus caudatus ( Mello-Leitão, 1929) and Epicadus tuberculatus (Petrunkevitch, 1910) ] by their cryptic bark-dwelling habitus with predominant brown or reddish-brown body coloration, and those of Epicadinus , especially by their small size (varying from approximately three millimeters of the total body length for males and nine to females) and spiny habitus (body covered by many setae and rugose teguments, and opisthosoma bearing stout conical projections) ( Fig. 2A–D ). However, they can be easily recognized and distinguished from Epicadus , Epicadinus and other genera of Stephanopinae by the presence of a pair of ventral macrosetae on their anterior patellae (I and II) ( Fig. 1D ), sensorial pits (three to five trichobothria surrounded by a small group of duster-shaped setae) on dorsal tibial depressions preceded by a strong plumose macroseta ( Fig. 1C ), and a pair of circular taints on the posterior slope of the prosoma ( Figs 3A , 4A , 7A ). Differently from Epicadinus , the species of Kryptochroma gen. nov. have five opisthosomal projections instead of three, and short leaf-shaped setae covering their entire body instead of long needle-shaped ones ( Fig. 1A–B ). Females present a flat epigynal plate, short copulatory ducts and a single pair of oval spermathecae ( Fig. 10C–F ); the male palp bears a pear-shaped tegulum with a short and fixed embolus, and a single tipped, stout and conical RTA ( Fig. 11C–F ).

Etymology

The name of the genus is a combination of the Greek words ‘ kryptos ’ (κρυπτός) and ‘ chroma ’ (χρῶμα), which respectively mean ‘hidden’ and ‘color’. The name is a reference to the general color pattern of these spiders, which is associated to their cryptic behavior. Gender feminine.

Description

PROSOMA. Granular surfaced due to the presence of spherical setae sockets ( Fig. 1A–B ); slightly longer than wide, pear-shaped and usually covered with organic particles.ALE almost two times as large as AME, prosoma coloration shows a gradient of brown and dark-yellow shades (predominantly reddish brown in Kryptochroma hilaris Machado & Teixeira gen. et sp. nov.), lighter on the posterior slope, where there is a pair of rounded spots close to the anterior border of the opisthosoma ( Figs 3A , 4A , 7A ); in some cases the individual has a yellow longitudinal line between the MS and PME ( Figs 3A , 5A , 7A , 9A ). Anterior eye row strongly recurved, AME close to each other, and posterior eye row procurved ( Fig. 11A–B ). Clypeus with a central pair of serrated macrosetae ( Fig. 1A ). Sternum scutiform, slightly longer than wide in females and as long as wide in males, with brush-shaped setae. Carapace with a conical medianposterior projection pointing backwards (except for K. hilaris gen. et sp. nov. and K. parahybana (Mello- Leitão, 1929) gen. et comb. nov., which have just an obtuse and slight elevation on the top of the thoracic area); opisthosoma short with five stout projections (two lateral pairs and one single and larger terminal projection), anal region and spinneret ring area projected backwards. Mouthparts: chelicerae with five equal-sized teeth; three on the promarginal row and two on the retromarginal. Labium truncated, slightly wider than long. Endites truncated, longer than wide, with scarce promarginal scopula.

LEGS. Anterior femora enlarged and bearing many conical setiferous tubercles, legs I and II stouter and longer than legs III and IV, femora I and II with dorsal and dorsolateral stout macrosetae in conical sockets. Tibia I and II with five pairs of ventral macrosetae, metatarsi I and II with three ventral and one dorso-distal pair ( Fig. 1E ). Tarsal claws curved, pectinated, unequal in number of teeth (mesial claw with numerous thin teeth and ectal having three stout ones); subungueal tufts scarce, with brush-shaped setae ( Fig. 3B ).

OPISTHOSOMA. Five short conical projections (two dorsolateral consecutive pairs, and a single caudal one), straight or slightly concave anterior border and rough surfaced, covered by leaf-shaped setae ( Fig. 1B ). Anal region and spinneret ring projected backwards, elongated.

GENITALIA. Palpus with cymbium and tegulum pear-shaped, without apophyses; RTA single tipped, stout and presenting grooves at the apex ( Figs 8D , 11D, 13D). The internal morphology of female genitalia is very conservative, presenting a single pair of reniform spermathecae without any accessory glands or coiled ducts ( Figs 3D , 4D , 7D , 10D , 12D, 16D); in ventral view the copulatory openings are excavated in relation to the rest of the surface of the genital area, separated by a septum and located close to the edges of the posterior margin of the epigynal plate ( Figs 10C , 12C, 16C).

Composition

Nine species distributed within the Neotropical Region: Kryptochroma gigas Machado & Viecelli gen. et sp. nov., Kryptochroma hilaris Machado & Teixeira gen. et sp. nov., Kryptochroma macrostyla (Mello- Leitão, 1929) gen. et comb. nov., Kryptochroma parahybana ( Mello-Leitão, 1929) gen. et comb. nov., Kryptochroma pentacantha ( Mello-Leitão, 1929) gen. et comb. nov., Kryptochroma quadrata Machado & Viecelli gen. et sp. nov., Kryptochroma quinquetuberculata ( Taczanowski, 1872) gen. et comb. nov., Kryptochroma renipalpis ( Mello-Leitão, 1929) comb. nov. and Kryptochroma septata Machado & Teixeira gen. et sp. nov.

Distribution

Brazil (Amazonas, Bahia, Espírito Santo, Minas Gerais, Pará, Paraíba, Paraná, Pernambuco, Roraima, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo) and French Guiana (Cayenne, Maripasoula, Saint-Élie and Saül) ( Figs 9 , 18).

Variations

Each one of the color variations documented here (from greyish-green to dark-yellow or predominantly reddish-brown), as well as the stained (e.g., opisthosoma of K. septata sp. nov. – Fig. 16A ) and striped patterns (e.g., prosoma of the specimen in the Fig. 2A ) were observed in all species. Therefore, since all species of Kryptochroma gen. nov. can present any combination of tegument hue, is it virtually impossible to identify them solely based on their color.

Figures

Fig. 2. A–D. Color variations of live specimens of Kryptochroma Machado gen. nov. Photo credits: Thiago Carvalho.

Fig. 1. Scanning electron microscopy of a male of Kryptochroma pentacantha (Mello-Leitão, 1929) gen. et comb. nov. (MCTP 7362). A. Prosoma, frontal view. B. Detail of a leaf-shaped setae and its spherical socket. C. Sensorial pit preceeded by a plumose macrosetae on tibia I. D. Pair of ventral macrosetae on patella I. E. Metatarsal macrosetae. F. Tarsal claw and detail of setae tuft.

Fig. 3. Female of Kryptochroma gigas Machado & Viecelli gen. et sp. nov. Holotype (UFMG 4734). A. Habitus, dorsal view (arrows indicate the pair of circular taints on the posterior slope of the prosoma). B. Front. C, E. Epigynal plate, ventral view. D, F. Spermathecae, dorsal view.

Fig.4.Female ofKryptochromahilaris Machado&Teixeira gen. etsp. nov.Holotype (MPEG13322). A. Habitus, dorsal view (arrows indicate the pair of circular taints on the posterior slope of the prosoma. B. Front. C, E. Epigynal plate, ventral view. D, F. Spermathecae, dorsal view.

Fig. 7. Female of Kryptochroma parahybana (Mello-Leitão, 1929) gen. et comb. nov. (MPEG 30339) A. Habitus, dorsal view (arrows indicate the pair of circular taints on the posterior slope of the prosoma). B. Front. C, E. Epigynal plate, ventral view. D, F. Spermathecae, dorsal view.

Fig. 10. Female of Kryptochroma pentacantha (Mello-Leitão, 1929) gen. et comb. nov. (MCTP 38671) A. Habitus, dorsal view. B. Front. C, E. Epigynal plate, ventral view, D, F. Spermathecae, dorsal view.

Fig. 11. Male of Kryptochroma pentacantha (Mello-Leitão, 1929) gen. et comb. nov. (MCTP 25762). A. Habitus, dorsal view. B. Front. C–F. Left male palp. C, E. Ventral view. D, F. Retrolateral view.

Fig. 5. Male of Kryptochroma hilaris Machado & Teixeira gen. et sp. nov. (MPEG 13239). A. Habitus, dorsal view. B. Front. C–F. Left male palp. C, E. Ventral view. D, F. Retrolateral view.

Fig. 9. Distribution records of species of Kryptochroma Machado gen. nov.

Fig. 8. Male of Kryptochroma parahybana (Mello-Leitão, 1929) gen. et comb. nov. (MPEG 9069). A. Habitus, dorsal view. B. Front. C–F. Left male palp. C, E. Ventral view. D, F. Retrolateral view.

Fig. 16. Kryptochroma septata Machado & Teixeira gen. et sp. nov., holotype, ♀ (UFMG 18269). A. Habitus, dorsal view. B. Front. C, E. Epigynal plate, ventral view. D, F. Spermathecae, dorsal view.