Lurchibates, Goldschmidt & Fu, 2011

Goldschmidt, Tom, Nishikawa, Kanto, Hiruta, Shimpei F., Pfingstl, Tobias, Jiang, Jian-Ping & Shimano, Satoshi, 2021, Systematics, distribution and morphology of the newt parasitic water mites of the subgenus Lurchibates Goldschmidt & Fu, 2011 (Acari, Hydrachnidia Hygrobatidae, Hygrobates Koch, 1837), including the description of four new species and a key to all so far known species, Zootaxa 4985 (1), pp. 1-36 : 15-21

Annotations to the subgenus Lurchibates

Comparison Hygrobates (Lurchibates) to Hygrobates (s. str.)

The most obvious character separating Lurchibates from other subgenera of Hygrobates , beside the life-style as newt parasites, are the by far larger, stronger and overall more massive mouthparts ( Figs. 46, 47 ). In contrast, the morphology of the idiosoma and the legs does not show any specific modifications ( Figs. 45 vs. 48).

Sexual dimorphism in Lurchibates

As mentioned before ( Goldschmidt & Fu 2011, Goldschmidt et al. 2020), sexual dimorphism in the subgenus Lurchibates mainly refers to the shape of the coxal field (the basal width of Cx-I in general is larger in females), thus the main difference is found in the shape of the genital field (following the general pattern of Hygrobates ) ( Figs. 51 vs. 52): In males the acetabular plates are fused forming a single wing-like, dumbbell- or apple-shaped genital plate ( Fig. 51 ); in females the acetabular plates are always separated, not connected with the pre- and post-genital sclerites, flanking the genital opening (in some species shifted to posterior), their shape varies from kidney- to crescent-shaped ( Fig. 52 ).

Furthermore females are generally larger than males and show a wider variation in size: E.g. the idiosoma length in H. (L.) aloisii in the type series varies from 948–1134 in males and 1488–1932 in females (in the present study from 756–852 in males, 864–1320 in females). In H. (L.) macrochela sp. nov. the idiosoma length varies from 660–924 in males and 882–1536 in females.

The size differences of males vs. females are again intensified by an enormous increase of size in ovigerous females: H. (L.) aloisii (present study), 864–1260 (non-ovigerous females) vs. 1320 (ovigerous female); H. (L.) macrochela sp. nov., 882–1104 (non- ovigerous females) vs. 1284–1536 (ovigerous females) ( Figs. 52, 53 ). The so far studied specimens of most species included as well several ovigerous females, however the number of eggs per specimen is rather variable within the species. Based on the current data no differences between the species are visible in this respect. The number of eggs per ovigerous female varies overall between one and 100 (average 38, median 42). Whereas the egg size not varies much, neither between nor among species (overall diameter 140–165).

The sexual dimorphism documented in H. (L.) intermedius , idiosoma L 900 (males) vs. 1824 (female), is probably strongly biased by the fact, that the only female used in the study was an ovigerous specimen ( Goldschmidt et al. 2020).

Additional information to the so far known species of Lurchibates

So far the only records of the subgenus Lurchibates have been the species descriptions. Consequently any information on the morphological variability was exclusively based upon the type series of the respective species. In the present study ( Goldschmidt et al. 2020, present paper), besides the seven new species, further specimens of three out of four already known species were found: H. (L.) forcipifer , H. (L.) ancistrophorus and H. (L.) aloisii . Therefore, we are providing some additional measurement data for these species (see Tab. 2 , appendix): The new measurement data for the males of H. (L.) forcipifer and the single female of H. (L.) ancistrophorus are mostly within the already known range, just the male genital field of H. (L.) forcipifer is slightly smaller in the present study ( Tab. 2 , appendix). Yet the measurements of the three males and four females of H. (L.) aloisii are greatly extending the known size range of that species, the specimens of the present study (males as well as females) are clearly smaller than the ones of the type series ( Tab. 2 , appendix).

Distribution of the so far known species of Lurchibates

The genus Lurchibates seems to be limited to SE-Asia, the distribution of the individual species could be derived from the distribution pattern of their respective hosts ( Fig. 54 ).

Relationship among Lurchibates species based on morphometric analysis

In order to confirm and visualize the separation of the so far known species of Hygrobates (Lurchibates) , and to get an idea of phylogenetic relationships among the species, a character matrix was analyzed.

Principal Component Analysis (PCA) based on raw data results in an ordination of individuals showing most species grouped together ( Fig. 55 ) whereas there are as well certain overlaps between all species when the first two principal axes are plotted, except for ancistrophorus which is placed distant from all others. The first three components account for 79.2% of total variation (PC1 58.1, PC2 15.1, PC3 6.0). Highest loadings on PC1 showed the variables W of Cx-III and Cx-IV (one side) with 0.221 and P1-dorsal length with 0.296. On PC 2 the variables Ac-1 width, Ac-2 width and Ac-3 width showed the highest loadings with 0.367, 0.394 and 0.482 respectively. The variables Ac-2 length, P-5 length and P-2 height showed the highest loadings on PC3 with values of 0.366, 0.394 and 0.378. Variation explained by PC1 is related to size and shows that size contributes considerably to species separation.

PCA on size corrected data results in larger overlaps between the species, whereas individuals are scattered on two distinctly separated “groups”: The first group with macrochela , robustipalpis , intermedius and malosimilis and the second group including ancistrophorus , pilosus , aloisii , incognitus and forcipifer . Lurchibates salamandrarum is clearly isolated in this analysis, by far separated from remaining individuals ( Fig. 56 ). The first three components account for 74.1% of total variation (PC1 40.1, PC2 20.8, PC3 13.2). Highest loadings were shown in the variable width of coxa I+II.

Non metric Multidimensional Scaling (NMDS) on raw data shows a clear morphometric distinction between all species, again with certain overlaps but with a stress of 0.1004 ( Fig. 57 ).

Figures

FIGURE 54. Map of East Asia showing the distribution of the host newts of the genera Laotriton, Pachytriton and Paramesotriton.

FIGURE 55. Graph showing results of Principle Component Analysis (PCA) on raw data of ten different species of Hygrobates (Lurchibates). Different colors refer to different species.

FIGURE 56. Scatterplot showing results of Principle Component Analysis (PCA) on size corrected data of ten different species of Hygrobates (Lurchibates).

FIGURE 57. Graph highlighting results of a Non Metric Multidimensional Scaling (NMDS) performed on raw data of ten different species of Hygrobates (Lurchibates).

FIGURES 45–47. Hygrobates (Lurchibates) macrochela sp. nov., female, Fig. 45. ventral view of idiosoma, legs and gnathosoma; Fig. 46. palp; Fig. 47. chelicera. FIGURES 48–50. Fig. Hygrobates (s. str.) fluviatilis – group 48. Hygrobates (s. str.) marezaensis, female, ventral view of idiosoma, legs and gnathosoma. Fig. 49. Hygrobates (s. str.) c.f. arenarius, female, palp. Fig. 50. Hygrobates (s. str.) c.f. arenarius, female, chelicera.

FIGURES 51–53. Hygrobates (Lurchibates) macrochela sp. nov., Fig. 51. male, ventral view of idiosoma, legs (left IV-leg missing) and gnathosoma (left palp missing); Fig. 52. female, ventral view of idiosoma, legs and gnathosoma; Fig. 53. ovigerous female, ventral view of idiosoma (filled with eggs) and gnathosoma (appendages missing); scale bar = 1 mm.