Vagabundia sci, Valdecasas, Antonio G., 2008

Valdecasas, Antonio G., 2008, Confocal microscopy applied to water mite taxonomy with the description of a new genus of Axonopsinae (Acari, Parasitengona, Hydrachnidia) from Central America, Zootaxa 1820, pp. 41-48 : 43-47

Vagabundia sci n. sp.

Figs 1–10

Male. Body rectangular. Length of dorsal shield 440, width 335. Three pairs of glandularia on the dorsal shield with postocularia located close to the first pair. Length of the ventral shield up to the tip of the first coxae 510, width 350. First three pairs of coxae projecting beyond the anterior end of the ventral shield ( Figs. 1 , 6 ). First coxae pointed, the second and third more or less rounded. Suture line between first and second coxae converging and continues in a straight line up to the posterior line of the fourth coxa. Suture line between second and third as well as third and fourth coxae incomplete. A longitudinal ridge at both sides and parallel to median suture line. Rounded projections covering the insertions of the fourth legs. A ridge present on each side extending anterolaterally and posterolaterally from processes in the IV-coxae. Genital field obliterated. There are four pairs of genital acetabula, one acetabula on the right side is reduced. Two pairs of small glandularia placed close together laterally near posterior end of fourth coxae. One of these glandularia on left side is reduced. Palps with a single dorsal seta on P-II and one ventral seta on P-IV ( Fig. 10 ). Dorsal length of palp segments: P-I: 28; P-II 49; P-III 22; P-IV 72; P-V 31. Length of capitulum: 188. Length of chelicera: 225. II-Leg with morphological dimorphism of distal segments ( Fig. 7 ). Length of dorsal segments of second leg: II-Leg-2: 35; II-Leg-3: 45; II-Leg-4: 45; II-Leg-5: 165; II-Leg-6: 195. IV-Leg with strong dimorphism in the third and fourth segments ( Figs 3 , 8 ). Length of dorsal segments of fourth leg: IV-Leg- 2: 150; IV-Leg-3: 185; IV-Leg-4: 68; IV-Leg-5: 145; IV-Leg-6: 112.

Type material. Holotype: Male, 8-viii-1994, Rio Escondido, immediately above waterfall, Coiba Island, Panama. Dissected and on a permanent slides embedded in glycerine jelly.

Etymology. Vagabundia comes from the Spanish word ‘vagabundo’ that means ‘wanderer’. It is a feminine substantive; s ci refers to Science Citation Index. We pointed out some time ago ( Valdecasas et al. 2000) that the popularity of the Science Citation Index ( SCI ) as a measure of ‘good’ science has been damaging to basic taxonomic work. Despite statements to the contrary that SCI is not adequate to evaluate taxonomic production ( Krell 2000), it is used routinely to evaluate taxonomists and prioritize research grant proposals. As with everything in life, SCI had a beginning and will have an end. Before it becomes history, I dedicate this species to this sociological tool that has done more harm than good to taxonomic work and the basic study of biodiversity. Young biologists avoid the ‘taxonomic trap’ or becoming taxonomic specialists ( Agnarsson & Kuntner 2007) due to the low citation rate of strictly discovery-oriented and interpretative taxonomic publications. Lack of recognition of the value of these publications, makes it difficult for authors to obtain grants or stable professional positions.

Habitat. Interstitial habitat as sampled by the Karaman-Chappuis method.

Discussion.

On the morphology of the Axonopsella-like mites Axonopsella -like mites belong to the subfamily Axonopsinae, having entire dorsal shields that may or may not be fused. As reviewed by Cook (1974), the body is dorsal-ventrally flattened and the eyes lie beneath the integument. The coxae are fused with the ventral shield and the capitulum is not fused with the coxae. Tips of the first three pairs of coxae are rounded or, rarely, somewhat pointed. The fourth coxae have large pointed or rounded projections partially covering the insertion of IV-legs. Genital acetabula vary from four pairs to several. The gonopore is terminal and wide in females, subterminal or ventral in males. Suture line of fourth coxae of females are more or less developed. Setae on capitulum are typically small. Sexual dimorphisms in IV-leg-4 is present in males. Male II-leg can be with or without sexual dimorphism.

Discussion of the eight genera described is limited by the fact that some of them are known only from the female specimens, and some species are temporarily assigned to a genus pending male description, and therefore subject to revision. Vagabundia sci n.sp known only from the male contributes to this temporary lack of definition of the group ‘ Axonopsella -like’ mites. Table 1 summarizes the main characteristics differentiating species of the genera, while taking the limitations mentioned into account. Adelaxonopsella , although not considered by Cook as Axonopsella -like, ‘seems to have some affinities’ ( Cook, 1974: 329-330) with this group of species, and is included in the table for the sake of completeness. The long pointed capitulum, the dimorphism of the II-Leg and especially the IV-Leg are characters that clearly differentiate Vagabundia n. gen. from all other genera.

Vagabundia n. gen. Axonopsella Polyaxonopsella Submiraxona

Kown from Male Male and female Female Male and female The adequacy of describing a new genus and species from a single specimen is debatable, although this is not an uncommon practice. Many taxa have only parts of their body or incomplete specimens available for study. What is an accepted practice in paleontology should be equally accepted in neontology. This is not to say that taxa should be described from single specimens if it can be avoided, but if the only specimen available differs enough from currently described species, there is no compelling reason that this information should not be presented to fellow specialists.

On CLSM

The specimen on which this interpretation is based had been in Koenike´s fluid for over 10 years, and no special treatment was applied before the confocal study. It was embedded in glycerine jelly prior to the microscopy study, as explained in Material and Methods section. The CLSM provides images with realism similar to that provided by the ESEM, and the processing of the slices for EDF are much more efficient in CLSM than in bright field microscopy. Figures 3 and 4 are provided to show that based on optical slicing images taken of the same specimen at the same time with the same microscope and objective, the resolution and discrimination of CLSM is far superior to that of the bright field EDF. This opens a potential avenue for a renewed study of the type specimens and other material of water mites that are stored in microscopic slides in museum and zoological collections around the world (see a partial list in www.watermite.org), something that cannot be said for ESEM. If it is shown that those mites respond to an exciting laser, then it would be possible to restudy structures and morphologies to obtain a more realistic 3D view of the animal.

Although stacks of images taken with CLSM are amenable to rotation as a solid volume in the three-space axis and, as such, are able to provide angles of view not possible with the microscope, it demands high memory and processing capacity from computer systems. An alternative to imaging structures that may not be visible in the 3D composition is to process partial EDF for sets of optical slices. Figure 11 provides one set of bright field microscopy and CLSM EDF taken with 100 consecutive optical slices of the fourth leg. It can be seen that CLSM better resolves structures that are collinear in the Z axis than bright field microscopy. For example, see the square structure overhanging the strong boomerang shape in Fig 11 . In this sense, it is also important to check for structures that are shaded through EDF processing, and a correct drawing could complement the 2D summary image. CLSM seems to be, as well, the adequate technique to avoid the problem mentioned by Cook (1986: 211):’to be able to see many of the ventral structures…it was necessary to remove the dorsal shield (which is generally fused with the ventral shield) destroying or at least distorting the relationships of these posterior structures to each other.’

Figures

FIGURE 11. Bright field microscopy (left) and confocal (right) EDF images built with set of 100 consecutive optical slices. Step between optical slices 0.2 µm.

FIGURES 1 – 4. Vagabundia sci n. sp. (holotype). 1, ventral shield, CLSM; 2, dorsal shield, CLSM; 3, fourth leg EDF with bright field microscopy; 4, fourth leg EDF with confocal slicing.

FIGURES 5 – 10. Vagabundia sci n. sp. (holotype). 5, dorsal shield; 6, ventral shield; 7, II-Leg 2 - 6; 8, IV-Leg 2 - 6; 9, capitulum, lateral view; 10, right palp, lateral view.

Tables

TABLE 1. Main morphological differences among the eight previously described ‘ Axonopsella - like’ mites and Vagabundia n. gen.

Coxae extending beyond Yes anterior end of body	No	No	No (or only tips of 1rst coxae)
Pairs of genital acetabula 4	4	6	5 to many
Male II-Leg dimorphism Yes	Yes	-	No
Male IV-Leg dimorphism Yes	Yes	-	Yes
Tips of 1st coxae Pointed	Rounded	Rounded	Rounded
Tips of 2nd and 3rd coxae Rounded	Rounded	Rounded	Rounded