Neumania ( Neumania ) navina ( Cook 1967 )

Zawal, Andrzej, Springer, Monika & Górecka, Ewa, 2025, Description of the larva of Neumania (Neumania) navina (Cook, 1967) (Acari: Hydrachnidia: Unionicolidae) with some taxonomical remarks, Zootaxa 5717 (2), pp. 297-300 : 297-299

Neumania ( Neumania) navina ( Cook 1967)

Material examined. One reared larva. From the two females collected, just one female laid seven eggs, and only one larva hatched. The duration of the embryonic period was 20 days.

Diagnosis. Dorsal plate oval, elongated (L/W ratio 1.45) anteriorly and posteriorly convex, antero-lateral indents very small, almost invisible, setae Mh1–Mh4 connected with dorsal plate; tmas invisible CIII with big spine posteriorly; excretory pore plate broad and convex anteriorly, narrow posteriorly, excretory pore located posteriorly; P-5 with three long and four short simple setae.

Description. Idiosoma flat, dorsal plate in unengorged larvae covering almost the whole dorsum, oval, elongated (L/ W ratio 1.4), anteriorly and posteriorly convex, antero-lateral indents very small, almost invisible, dorsal plate with slightly elongate and punctuate scale-like patterns. Setae Lp1, Lp2, Mh1, and Mh2 on the dorsal plate thin and approximately equal in length. Setae Mh1–Mh4 inserted at the edge of the dorsal plate, Lh1–Lh3 thin and situated in the soft membrane ( Fig. 1B , 2B ). Coxal plates moderately large and elongate, CpII–III completely connected to each other, seam invisible, tmas invisible CpIII with big spine medio-posteriorly. Setae C1–C3 medium long, setae C4 1.5 times longer. Setae V4 very long, well-thickened, and located on small tubercles. Setae V1–V3 relatively long ( Fig. 1A , 2A ). Excretory pore plate pentagonal with borders slightly convex, almost as long as wide (L/W ratio 1.07), broad and convex anteriorly, narrow posteriorly, excretory pore located posteriorly ( Fig. 1D ). Setae E1 and E2 long, relatively thick, located anteriorly to excretory pore, and projecting far beyond posterior margin of excretory pore plate; distance between E2 about 1.5 time longer than distance between E1 ( Fig. 1D ).

Pedipalps very short and stocky ( Fig. 1C ); P-2 small with convex dorsal margin, dorsal seta invisible; P-3 large with convex dorsal margin, thick and long latero-proximal seta, fine dorsodistal seta; P-4 with two unequal setae (long and short) and very large dorsodistal claw; P-5 small, with single solenidium, three long and four short simple setae.

Numbers and setae arrangement on leg segments as shown in Fig. 1 (G–I). Total number of leg setae, excluding eupathidia, as follows (specialized setae indicated in parentheses): I-Leg—1–5: 1, 7, 3, 8 (s), 7 (s, eu); II-Leg—1–5: 1, 7, 5, 11 (s), 8 (s, eu); III-Leg—1–5: 1, 5, 5, 10 (s), 7 (eu). Eupathidium setae relatively long, thin, and setose. Lateral claws and empodial claw nearly equal in length, but lateral claws less heavy than empodial claw ( Fig. 1E–G ).

Measurements. Idiosoma L 190, W 139; dorsal plate L 190, W 131; medial margin L: CpI 67, CpII+III 65; distance: Mp1–Mp1 47, Lp1–Lp1 49, Lp2–Lp2 87, Mp2–Mp2 38, Mh1–Mp2 25, Mp1–Lp1 7, Mp1–Lp2 32, Mp1–Mp2 33, Mp2– Mh1 43, C1–C2 48, C1–CpI medial margin 11, C4–CpIII medial margin 28, Expp L 15, W 14; Exp–Expp posterior margin 5, E1–Expp anterior margin 3; E2–Expp posterior margin 9; pedipalp segments (PII–PIII) L: 7, 19; PIV claw L 22; seta on P-3 L 65; leg segments L: I-Leg—1–5: 17, 23, 22, 34, 44; II-Leg—1–5: 17, 25, 27, 32, 50; III-Leg—1–5: 27, 27, 31, 39, 69.

Remarks

The larva of Neumania navina differs in some aspects from others of the genus Neumania or even from the whole family Unionicolidae : the dorsal plate is generally similar to the Unionicolidae , but antero-lateral indents are very small, almost invisible, and the anterior edge is convex, whereas the dorsal plate overall is more oval. Setae Mh1–Mh4 are located on the dorsal plate, which distinguishes the larva of N. navina from all other known Unionicolidae larvae. CpIII with tmas invisible and with the big spine on the medio-posterior corner are also different from other larvae of the family Unionicolidae . The excretory pore plate broad and slightly convex anteriorly is bringing the larva closer to the larva of Neumania imitata ( Tuzovskij 2012) , but the excretory pore located posterior to the centre of the excretory pore plate, is distinguishing it from N. imitata . This last character state refers to this feature in the Unionicola genus and, in this case, shows that the character indicated by Vajnštejn (1980) as differentiating the genera Unionicola and Neumania does not apply. The eupathidia on I–III legs refer to N. figuralis ( Tuzovskij 2012) , but there is only one solenidium on one segment, which is unique for the whole Unionicolidae family, as well as the number of setae on some segments. These significant differences between N. navina and the larvae of the family Unionicolidae described so far from Europe and North America ( Prasad & Cook 1972; Vajnštejn 1980; Tuzovskij 2012) indicate a significant long and distinct evolution of the Asian species of Unionicolidae .

The separation of particular superfamilies and families of water mites occurred around 170—140 million years ago in Laurasia ( Dabert et al. 2016). At that time, the main, most widely distributed genera, such as Neumania and Unionicola , were distinguished, which is reflected in the basic morphological differences of their adults. Later, evolution occurred in isolated areas of individual continental plates, including the Indian subcontinent, which led to the separation of further subfamilies, e.g., Encentridophorinae ( Smit 2020), and further differentiation of the genera Neumania and Unionicola . Hence, the morphological features of the Neumania navina larva deviate from the characteristic patterns of the genera Neumania and Unionicola and do not confirm the features previously indicated as differentiating these genera ( Vajnštejn 1980).

Figures

FIGURE 1. Neumania navina larva.A—ventral side; B—dorsal side; C—pedipalp; D—excretory pore plate; E—leg I; F—leg II; G—leg III. Scale bars = 50 μm.

FIGURE 2. Neumania navina larva. A—photograph of ventral side; B—photograph of dorsal side. Scale bars = 100 μm.