Ilyocryptus silvaeducensis subsp. paraensis Kotov & Elmoor-Loureiro 2008, subsp. nov.

Ilyocryptus silvaeducensis paraensis subsp. nov.

Figure 4

Undescribed subspesies of I. silvaeducensis in Kotov and Štifter, 2005a: p. 8, Figs 35–76; Kotov and Štifter, 2006: p. 125, Fig. 62N.

Etymology. This subspecies is named after the state of Brazil where it was found, Pará.

Type locality. Lake Batata, Porto Trombetas (01°30'0.00''S, 56°19'30.34''W), Município de Oriximiná, Pará, Brazil. The type series was collected in xii.1988 by R.L. Bozelli.

Type material. Holotype. A juvenile parthenogenetic female, MNRJ 21505. The label of holotype is: " Ilyocryptus silvaeducensis paraensis subsp. nov., 1 parth. ♀ from Lake Batata, Pará, Brazil, HOLOTYPE ". Paratypes. 2 juvenile females, MGU Ml 76.

Short description. Adult parthenogenetic female. See Kotov and Štifter (2005a).

Juvenile female. General: In lateral view body triangular-ovoid, relative height of juveniles small for the genus (body height/body length = 0.66–0.70 in juveniles), maximum height in posterior half (Figure 4A). Dorsal margin straight, postero-dorsal angle expressed. In anterior view, body compressed laterally, with distinct, sharp dorsal keel (Figure 4B), but we do not know, is this characteristic of adults also? Molting incomplete, but first instar female has no previous exuvia on valves and head shield (Figure 4A). Reticulation on head shield and valves very fine.

Head small, its ventral margin in posterior part with a low basis for antennae I (Figure 4C).

Valves subovoid. Numerous setae along free margin, five anteriormost setae protruding sparsely and very long (this is a juvenile character, in adults these setae significantly shorter), followed with a bunch of 5–7 closely located setae, which are only somewhat longer that following setae, the first seta in bunch directed posteriorly. Setae in middle of ventral margin with long setules, setae in postero-ventral region not longer that the former. Each seta at posterior margin basally with series of spine-like setules along one its side (Figures 4E–D).

Postabdomen relatively short, height maximal in middle. Preanal margin approximately as long as postanal one (this is a juvenile character, in adults preanal margin shorter), with a row of 5–6 regularly located, straight teeth, which are predominantly or exclusively doubled, 1–2 distalmost teeth small (Figure 4F–G). Rare denticles near preanal teeth (a juvenile character, in adults these are absent). Few denticles on lateral faces of postabdomen basally. Anus small, 7–9 spinules on its internal wall (Figure 4H). A row of relatively short paired spines starts on anal margin and continues up to distal boundary of preanal margin. Large lateral setae longer than paired spines, the proximalmost lateral seta located on distal portion of preanal margin, several lateral setae present at anal margin. On the distal part of postabdomen, the row of lateral setae fluently transits into the group of 4–7 middle-sized setae, the latter, more distally, – into group of rudimentary setae.

Postabdominal claw slightly bent. Few denticles on claw ventrally. Distalmost spine on base of postabdominal claw slightly longer than proximal one. Long setules on claw base ventrally.

Postabdominal seta longer than postabdomen, its distal segment with long, sparse hairs (Figure 4A).

Antenna I of medium length for Ilyocryptus, bases of antennae I not compressed against each other. Proximal segment with a well-expressed finger-like projection and low hillocks; distal segment without ridges and denticles, distal end with concentric row of small hillocks. Nine relatively short aesthetascs, two of them longer than the rest.

Antenna II relatively short, coxal part with two sensory setae of greatly differing size (Figure 4I). Distal burrowing spine short, reaching only the distal end of basal segment. Antennal branches massive, on all segments, there are well-developed denticles around distal segment ends, and groups of similar denticles in middle part. Swimming setae 0-0-0-3/1-1-3, spines 0-1-0-1/0-0-1. Apical swimming setae asymmetrically armed with minute setules (Figure 4J). Lateral swimming setae armed along one side with setules on type of apical setae, and along another side with remarkably longer setules (Figure 4K). Apical spine on exopod longer than spine on endopod. Spine on second segment of exopod longer than half of third segment.

Limbs. Typical of the genus.

Ephippial female, male. Unknown.

Size. Juvenile females from type locality 0.29–0.31 mm, holotype 0.31 mm. Maximum size is greatly underestimated due to absence of adults in our sample.

Distribution. At this moment, the taxon is known only from two localities in northern portion of Brazil: (1) Lake Batata, Porto Trombetas, Pará and (2) a small, shallow pool near Lagoa da Colher, the eastern border of the Lençóis Maranhenses dune field, Maranhão. Probably, this is a rare species in Brazil.

Differential diagnosis. Ilyocryptus silvaeducensis paraensis subsp. nov. differs from two other known subspecies in: (1) presence of several lateral setae at anal margin; (2) relatively short distal burrowing spine, not protruding beyond the distal end of basal segment of antenna II; (3) specially thick segments of branches of antenna II (Kotov & Štifter 2005 a, 2006).

Comments. Only three juvenile females were found, and one of them was designated as the holotype. I. silvaeducensis silvaeducensis occurs only in North Europe, the Nearctic zone is populated by a separate subspecies I. silvaeducensis chengalathi. Here we establish a new Neotropical subspecies. So, subspecies of I. silvaeducensis conform to main biogeographical zones. Kotov and Štifter (2005a) found that Brazilian subspecies (un-named at that time) is more distant from European and North American subspecies, which are closest congeners. African (Kotov 2000) and Australian (Sars 1896) silvaeducensis -like populations must be specially examined in the future.