Salina beta

Soto-Adames, Felipe N., 2010, Review of the New World species of Salina (Collembola: Paronellidae) with bidentate mucro, including a key to all New World members of Salina, Zootaxa 2333, pp. 26-40 : 28-29

Salina beta species group

Fourth antennal segment with apical papilla. Eyes ( Fig. 2 ) A, B, E, F subequal, eyes C, D smaller, eyes G and H smallest; with 1 macro- and 2 microsetae in eyepatch ( Fig.1 ). Ant. 1 with variable number of dorsal macrosetae according to the species. Dorsal head macrochaetotaxy as in Fig. 2 ; macrosetae marked with arrows are smaller than others in some individuals of S. wolcotti and S. bidentata ; these macrosetae also apparently absent in S. ventricolor . Prelabral setae always ciliate and either 2 or 4, according to species; labrum with 5, 5, 4 smooth setae, internal pair on distal row enlarged, weakly spine-like ( Fig. 3 ); labral papillae 2+2 smooth mounds. Subapical seta of outer maxillary lobe acuminate, smooth and shorter than apical seta; sublobular plate with three seta-like processes. Labial palps with five proximal setae; hypostomal seta (H of Fjellberg 1999) spine-like, h1 and h2 apically curved. Labial palp papillae A and C without guard setae; papillae B and D, with 5 and 4 guards, respectively; papilla E ( Fig. 4 ) with two guards (apparently e1 and e2), lateral appendage blunt and not reaching tip of papilla. Labial triangle setae as MEL1–3, A1–4, all smooth. Most setae along cephalic groove (column CG) long acuminate and ciliate, in some species short smooth setae present between ciliate setae ( Fig. 5 ), number of setae variable between and within species, individuals often with asymmetric number of setae; medial postlabial column (PLM) always with 2 long, ciliate acuminate setae, posterior seta inserted between setae CG1–2; external postlabial column (PLE) with variable number of setae, but column not well organized, often making it difficult to determine if a particular setae should be counted as part of column or not. Tergal macrochaetotaxy of Th. 2–Abd. 2 variable; Abd. 3 with 2 macrosetae typical for genus. Abd. 4 with at least 8 inner and 8–9 outer macrosetae, 2–3 marginal mesosetae, and 0–7 posterior microsetae arranged as in Fig. 9 , individuals of some species with supplementary macrosetae often asymmetrically distributed (e.g., Fig. 32 ). Abd. 4 with 2 bothriotricha, presumably homologous to those in all Entomobryoidea ( Fig. 9 setae a and b), and three other bothriotrichalike setae distributed as in Fig. 9 . Bothriotricha-like setae shorter than normal bothriotricha ( Fig. 10 ) and without differentiated sockets, but inserted in the same relative position in all individuals examined. Inner face of femoral base of all legs with 4 pegs. Foot complex typical for genus: tenent hair thick, ciliate and strongly spatulate; unguiculus strongly truncate; unguis with short outer and lateral teeth, small paired inner teeth and 1–2 inconspicuous distal unpaired teeth. Anterior face of collophore with 3–4 distal macrosetae and variable number of microsetae according to species; number of lateral setae variable; posterior face with 1–6 paired and 0–3 unpaired microsetae. Distal manubrial plate with 3+3 ciliate setae, without pseudopores. Distal dental vesicle elongate, subequal to mucro ( Fig. 8 a); mucro with 2 large upturned teeth, and 1 short, dorso-basal denticle, additional supplementary teeth present or absent according to species.

Remarks: The diagnostic character of the beta species group is the presence of a rectangular mucro, with the two largest teeth pointing dorsally instead of posteriorly and a short dorsal tooth basal to the large subapical tooth. Currently the beta group comprises four named species and one new species described here. An undescribed species from Panama, with two inner macrosetae on Abd. 2, was represented by a single individual, insufficient material for a proper description. Salina montana ( Imms, 1912) and S. choudhurii Mitra, 1973 from India may have tridentate mucrones somewhat similar to members of the beta group although it is difficult to judge from Imms’ (1912) and Mitra’s (1973) drawings. Both Indian species have reduced chaetotaxy on Th. 2–3, with pattern similar to that in the beta group, but the chaetotaxy of Abd. 3, and Abd. 4 (at least in choudhurii ) are different to that in New World species. A more detailed study of the Indian forms will be needed to decide if they are part of the S. beta lineage.

The four species in the genus Pseudosalina Mitra, 1974, are endemic to the Indian subcontinent and all have bidentate mucrones. However, in Pseudosalina, the mucronal structure is similar to that in species with square mucrones (cf. Figs. 6 and 8 a–b), albeit with reduced number of teeth, and not to members of the beta group. Many other features distinguish Pseudosalina from members of the beta group, in particular, all Pseudosalina have a very abundant chaetotaxy, with at least eight inner macrosetae on Abd. 2.

The mucronal type characteristic of the beta group defines a group endemic to the Americas (but see comment above). All members of the beta group described so far are restricted to the area delimited in the north by Southern USA (California and Florida), in the east by the Lesser Antilles and in the south by Panama. This distribution suggests that the group might have originated in Central America. However, Salina in general has been poorly studied and sampled in the Americas and more extensive collections in Central and South America are likely to produce new records of members of the beta group.

Figures

FIGURES 1 – 12. 1 – 4 Salina wolcotti; 1. Detail of left eye patch; 2. Dorsal head chaetotaxy, arrow heads point at variable macrosetae (see text); 3. Prelabral and labral chaetotaxy, arrows point at spine-like setae; 4. Labial papilla E; 5. Postlabial chaetotaxy in S. thibaudi n. sp., circles represent ciliate microsetae similar to seta PLE 2 illlustrated, CG = Cephalic Groove column, PLM and PLE = Post Labial Medial and External columns, respectively; 6 – 8. Mucro and distal dental vesicle: 6. S. tristani; 7. S. banski; 8 a. S. wolcotti; 8 b. Pseudosalina nigrocephala (after Mitra 1974); 9. Chaetotaxy of left side of Abd. 4 in S. wolcotti, large circles represent macrosetae, small circles near posterior margin are mesosetae, dots are posterior setae, dotted lines join macrosetae present in all species in the beta group; 10. Relative length of Abd. 4 bothriotricha and bothriotricha-like setae in S. wolcotti, letters refer to position in Fig. 9; 11. S. ventricolor colour pattern (after Gruia 1983); 12. S. wolcotti, colour pattern (after Folsom 1927)

FIGURES 25 – 33. All figures show left aspect; arrowheads identify macrosetae absent or reduced in some individuals. 25 – 26 Salina beta; 25. Schematic distribution of macrosetae on Th. 2 – Abd. 2; 26. Th. 2; 27 – 33 S. thibaudi n. sp.; 27. Ant. 1; 28. Schematic distribution of macrosetae on Th. 2 – Abd. 2; 29. Th. 2; 30. Th. 3, setae 1 b, 2 b and 5 b are absent in most individuals examined; 31. Abd. 1; 32. Abd. 4, circles are macrosetae, dots are posterior setae; 33. Posterior chaetotaxy of collophore.