Texanobathynella cf. bowmani

Camacho, A. I., Mas-Peinado, P., Hutchins, B. T., Schwartz, B. F., Dorda, B. A., Casado, A. & Rey, I., 2021, New stygofauna from Texas, USA: three new species of Parabathynellidae (Crustacea: Bathynellacea), Journal of Natural History 55 (15 - 16), pp. 979-1007 : 999-1002

Texanobathynella cf. bowmani

Material examined ( Table 1)

Three specimens studied ( Tables 1 and 2): one female from Live Oak Creek , Crocket County, Texas USA ( WGS 84 30.74220ºN, − 101,6739ºE, 655 m amsl) ( MNCN 20.04 /19739 slide and MNCN / ADN 54641 DNA extract) (coll. 23 March 2015, sample 150713-H2, B. Hutchins and A. Swink); one female from Finnegan Spring, Devil’s River , Val Verde County , Texas, USA ( WGS84 29.90016, −100.99801, 405 m amsl) ( MNCN 20.04 /19741 slide and MNCN / ADN 54643 DNA extract) (coll. 25 February 2010); and one male from Schumann House Well, Comal County ( WGS84 29.75961, −98.19680, 310 m amsl) ( MNCN 20.04 /19740 slide and MNCN / ADN 54642 DNA extract) (both coll. 17 February 2008, R. J. Gibson) .

These three specimens, despite coming from three different locations, show only very small differences from the original description of the species (see Table 3). Similar number of teeth on labrum (12), but only six main teeth in our specimens vs 10 in type material, two smaller ones on each side and a bicuspidate tooth at either end; Md pars molaris with fewer teeth; exopod of ThVII 3-segmented (vs exopod, 2-segmented in the original description); first segment of female ThVIII with two teeth (vs only one); sympod of uropod of one of our specimens with seven spines instead of eight; furca of one specimen with seven spines instead of six. We consider the studied specimens to correspond to T. bowmani and that the few differences found fall within normal population variability.

Taxonomic remarks. A comparison between the species of the genus Texanobathynella is shown in Table 3. The type species, T. bowmani , T. sachi from California and the two new Texans species share the display of 6-segmented AI, but it is 7-segmented in T. aaronswinki sp. nov. Texanobathynella coloradoensis sp. nov. has six teeth on the pars incisiva and six also on the pars molaris of Md, whereas the most frequent formula in the genus is four or five teeth on the pars incisiva and six or eight on the pars molaris. The two new species have fewer setae on MxII than T. sachi . The latter is unique in the display of an unsegmented exopod of ThI, the other species having a 2-segmented exopod on this thoracopod; furthermore, the number of setae on the endopod is different in each species, being highest in T. aaronswinki sp. nov. Thoracopod exopod segmentation is also variable across species, being 3-segmented in ThII– VII of T. coloradoensis sp. nov., ThII– VI of T. bowmani, ThII – V of T. aaronswinki sp. nov., and ThII–IV of T. sachi . The third segment of the endopod of ThII– VII is naked in the Texan species, but displays one seta in all Ths in T. sachi . Female ThVIII has four teeth in T. aaronswinki sp. nov., two in T. sachi and only one in T. bowmani , whereas the state in T. coloradoensis sp. nov. is unknown. Male ThVIII is very similar in all species. Only the Californian species, T. sachi , retains the first pleopod. The largest number of spines on the sympod of the uropod is found in the new species T. aaronswinki sp. nov. (6–10), whereas eight is the most frequent number in the other species, and in all cases the distal spine is larger than the rest. The two new species have only two setae on the exopod of the uropod, whereas the other two species display three or four. Texanobathynella coloradoensis sp. nov. has seven spines on the furcal rami, whereas the other species have six. In all species, the anal operculum does not protrude.

Molecular results

Phylogenetic analysis. The concatenated COI-18S alignment includes 28 sequences of 1843 bp. Best-fit models identified by JModelTest were COI TPM 1uf + I + G and 18S TrNef + I, according to the AIC and BIC. The 18S uncorrected sequence divergence estimates among genera of Parathynellidae were consistent with those of previous studies (Camacho, Mas-Peinado, Iepure, et al. 2021; Camacho, Mas-Peinado, Ranga Reddy, et al. 2021). For 18S, the sequence divergence was 0.9–2.4% between the ‘ Iberobathynella group’ and Texanobathynella species , 0.6% between Parabathynella and Montanabathynella , and 0.1–2.5% within the ‘ Iberobathynella group’.

ML (bootstrap support, BS) and BI (posterior probabilities, PP) phylogenetic analyses recovered similar topologies, supporting two major clades: the ‘ Iberobathynella group’ ( Iberobathynella and Paraiberobathynella ) ( BS = 74, PP = 0.97) and all Texanobathynella species ( BS = 100, PP = 1). Parabathynella sp. and Montanabathynella pecosensis sp. nov. were recovered as a sister clade ( BS = 88). The ‘ Iberobathynella group’ ( BS = 98, PP = 1) included four phylogroups, with the Spanish I. andalusica Camacho, 2007 and I. celiana Camacho, 2003 forming a basal phylogroup. Two phylogroups were well supported in both analyses; one of them ( BS = 95, PP = 1) included four species of Iberobathynella from Asturias, Lugo and Cantabria ( Spain), whereas the other ( BS = 85, PP = 1) included at least two species from Cantabria and Burgos ( Spain). However, the third phylogroup clustered together species of Iberobathynella and Paraiberobathynella , indicating the need to expand the sampling within the ‘ Iberobathynella group’ in order to understand its actual diversity, taxonomic position and phylogenetic relationships.