Reidnitocrella borutzkyi, Karanovic & Hancock, 2009

Karanovic, Tomislav & Hancock, Peter, 2009, On the diagnostic characters of the genus Stygonitocrella (Copepoda, Harpacticoida), with descriptions of seven new species from Australian subterranean waters 2324, Zootaxa 2324 (1), pp. 1-85 : 39-41

Reidnitocrella borutzkyi sp. nov.

Synonymy. Nitocrella tianschanica sp. nov. [partim.] – Borutzky 1972: p. 111, figs 7/11–7/16.

[non] Nitocrella tianschanica sp. nov. – Borutzky 1972: p. 111, figs 7/1–7/15.

Type material (not examined). Holotype, adult female dissected on one slide ( Borutzky, 1972) from a well (sample no 9) near the Biological Station in Cholpon-Ata city, 1,606 m a.s. l., Lake Issyk-Kul, Kyrgyzstan, 11 July 1961, leg. A. Yankovskaya & T. Kac, 42°05’N 77°05’E.

Other material (also not examined). Three adult males (one dissected on one slide; Borutzky 1972) from interstitial of Lake Issyk-Kul (Karaman-Chappuis pit no 16; sample no 34), near the Biological Station in Cholpon-Ata city, 1,606 m a.s.l., Kyrgyzstan, 14 August 1961, leg. A. Yankovskaya & T. Kac, 42°05’N 77°05’E .

Redescription. FEMALE (HOLOTYPE). Total body length more than 0.5 mm. Habitus cylindrical, slender, without distinct demarcation between prosome and urosome. Free pedigerous somites without pronounced lateral or dorsal expansions. Integument not strongly chitinized and without cuticular windows. Cephalothorax with completely incorporated first pedigerous somite. Surface of cephalic shield and tergites of three free pedigerous somites ornamented only with large sensilla. Hyaline fringe of all prosomites narrow and smooth. Genital double-somite without visible suture and only slightly wider at anterior part; hyaline fringe finely serrated both ventrally and dorsally. Genital field with single large copulatory pore, sclerotized wide copulatory duct and two small seminal receptacles. Single small genital aperture covered by fused reduced sixth legs, represents 70% of somite width. Third and fourth free urosomites without rows of small spinules. Anal somite ornamented with pair of large dorsal sensilla and posterior ventral row of spinules, those near inner corner of caudal rami especially large. Anal operculum small and convex, unornamented, not reaching to posterior end of anal somite, represents 50% of somite's width. Anal sinus smooth.

Caudal rami short and cylindical, clearly convergent, with space between them more than one ramus width, about twice as long as wide; armed with seven armature elements (three lateral, one dorsal and three apical). Ornamentation consists of several spinules at base of dorsal and distal lateral seta. Dorsal seta smooth, inserted posteriorly and close to inner margin, 1.8 times as long as caudal ramus, probably biarticulate at its base. Proximal and distal lateral setae smooth and of about same length as dorsal seta; proximal seta arising somewhat dorsolaterally at midlength; distal lateral seta arising close to posterior margin. Inner apical seta smooth, about 1.4 times as long as ramus. Both principal setae bipinnate; inner one twice as long as outer principal seta.

Antennula eight-segmented, slender. Long and relatively slender aesthetasc on fourth segment reaches beyond tip of appendage for length of last two segments combined and fused basally with large subapical seta; much smaller and even more slender apical aesthetasc on eighth segment fused basally to two apical setae. Seta on first segment unipinnate, all other setae smooth.

Antenna composed of coxa, basis, two-segmented endopod and one-segmented exopod. Exopod small, armed with three setae.

Labrum and paragnaths unknown.

Mandibula with uniramous palp, comprising basis and one-segmented endopod. Basis unarmed and unornamented, 1.5 times as long as wide and 1.2 times as long as endopod. Endopod slender and unornamented, about twice as long as wide, armed with four slender and smooth apical setae.

Maxillula, maxilla and maxilliped unknown.

All swimming legs with three-segmented exopod; endopod of first leg three-segmented, that of second and third legs two-segmented, while endopod of fourth swimming leg one-segmented. Armature formula of swimming legs as follows (inner/outer element; inner/terminal/outer element):

Exopod Endopod

Segments 1 2 3 1 2 3

First leg 0/1 1/1 0/2/2 1/0 0/0 1/1/1

Second leg 0/1 1/1 0/2/2 1/0 1/1/0 -

Third leg 0/1 1/1 0/2/2 0/0 1/1/0 -

Fourth leg 0/1 1/1 2/2/2 0/1/0 - -

Basis of each leg armed with outer spine or seta. All exopodal and endopodal segments ornamented with strong spinules along outer margin and on outer distal corner. All exopodal segments of about same length. First endopodal segment of first swimming leg large, about 2.4 times as long as wide and about as long as first two exopodal segments combined; endopod significantly longer than exopod. Endopod of second and third swimming legs reaching to midlength of second exopodal segment, while that of fourth leg half as long as first exopodal segment. All setae on each ramus (except minute inner seta on third endopodal segment of first leg) strong and some also spiniform. Apical armature element(s) on first leg geniculate.

Fifth leg biramous but baseoendopod fused medially together and to somite. Endopodal lobe not recognizable, without armature or ornamentation. Basal outer seta slender and smooth, arising from very long setophore. Exopod a distinct segment, quadriform, small, 1.5 times as long as its maximum width, unornamented and armed with three slender smooth setae; length ratio of exopodal setae slightly different between left and right legs, although all setae on each side of similar length and longer than segment.

Sixth legs completely fused together, indistinct, forming simple operculum covering single gonopore, without ornamentation but each armed with single minute seta.

MALE FROM SAMPLE 34. Habitus, ornamentation of prosomites and caudal rami similar to female. Hyaline fringe of all somites smooth.

Antennula strongly geniculate, with geniculation between seventh and eighth segments, unornamented. Very long and broad aesthetasc present on apical acrothek of fifth segment (homologous to aesthetasc on fourth segment in female).

Antenna, labrum, mandibula, maxillula, maxilla, maxilliped, second swimming leg, and fourth swimming leg similar to female.

First swimming leg with inner spine on basis modified, inflated distally.

Third swimming leg with first endopodal segment armed with inner seta and second segment with significantly shorter inner apical seta than in female.

Fifth leg similar to female.

Sixth legs unknown.

Variability. The first endopodal segment of the third swimming leg can be with or without an inner seta, but at present this is known only as sexual dimorphism.

Etymology. The species name is dedicated to late Dr E.V. Borutzky, who first described these specimens as part of normal interspecific variability of Nitocrella tianschanica Borutzky, 1972 . The name is a noun in the genitive singular.

Remarks. Reidnitocrella borutzkyi sp. nov. differs from Reidnitocrella tianschanica ( Borutzky, 1972) comb. nov., in its larger size, naked abdominal somites, two-segmented endopod of the third leg, armed penultimate endopodal segment of the second leg and shorter innermost seta on the fifth leg exopod. Borutzky (1972) noted that (translated from Russian) “The female specimen from the well near the Biological station (sample no 9) somewhat differs from the above described by its larger size and a narrower fifth leg exopod.”, but did not recognize it as a separate species. Given the differences observed and considering the fact that all the specimens studied by Borutzky (1972) come from a very small area, it is quite clear that he was dealing with at least two different species of Stygonitocrella s. l., but was confused by their very similar (quite reduced) fifth legs. Unfortunately his descriptions lack many details, especially in the mouth appendages, so it is not possible to compare them more closely.

The new species differs from Reidnitocrella djirgalanica ( Borutzky 1978) comb. nov. by having two armature elements on the ultimate endopodal segment of the third leg (only one in R. djirgalanica ), like the other two species in this genus, but also by having a distinct exopodal segment of the fifth leg (the fifth leg is apparently absent in R. djirgalanica ). Unfortunately, the description of R. djirgalanica is also incomplete and lacks drawings ( Borutzky 1978). The new species differs from Reidnitocrella pseudotianschanica ( Sterba, 1973) comb. nov. by its two-segmented endopod of the third leg (one-segmented in R. pseudotianschanica ), having three setae on the fifth leg exopod (only two in R. pseudotianschanica ) and by other small details in the ornamentation of the abdominal somites and caudal rami (see Sterba 1973).