Typhlotanais aequiremis ( Lilljeborg, 1864 )

Błażewicz-Paszkowycz, Magdalena, 2007, Figure 6. Typhlotanais Compactus, Female A In Family Nototanaidae Sieg, 1976 And Typhlotanaidae Sieg, 1984, Zootaxa 1598, pp. 1-141 : 29-34

Typhlotanais aequiremis ( Lilljeborg, 1864)

( Figs 13–15 )

Tanais aequiremis: Lilljeborg (1864) 1864: 12 , 21; Lilljeborg (1865) 1: 14, 25; Gerstaecker (1888) 5(1): 540; Sieg (1980a) 537: 11–12.

Tanais aequiremis: G.O. Sars (1866) 15: 122.

Tanais depressus: G.O. Sars (1866) 15: 121–122; G.O. Sars (1871 (1872)) 275, 285; G.O. Sars (1877) 2: 246; G.O. Sars, (1882a) 7: 34; Gerstaecker (1888) 5(2): 540; G.O. Sars (1896): 21–22; Norman (1899) 3: 340; Sieg (1980a) 537: 11– 12.

Typhlotanais aequiremis: G.O. Sars (1882a) 7: 34–35; G.O. Sars ((1882)1883): 14; G.O. Sars (1896): 21–22; Norman (1899) 3: 340; Norman (1905) 16: 78–95; Hansen (1909) 1909: 229; Hansen (1913) 3(3): 56; Grieg (1914): 105; Stephensen (1937) 2(24): 19; Stephensen (1943) 121(10): 73; Stephensen (1948) 53: 164–165.

Typhlotanais aequiremis: Zirwas (1911) 12: 105; Nierstrasz (1913) 32(a): 35; Nierstrasz & Schuurmans Stekhoven (1930) 10: 162–164; Stephensen (1932) 6: 349; Stephensen (1937) 3(27): 23; Greve (1965b) 1(27): 5; Greve (1965c) 20: 15; Greve (1965a) 20: 44, 50, 53; Greve (1965d) 38: 142; Greve (1967) 29: 295–297; Greve (1968) 36: 77–78, 82; Kudinova-Pasternak (1969) 48: 1737; Lang (1970) 23: 267–270, 288; Morino (1971) 18(5): 349; Brattegard & Vader (1972) 49: 36; Greve (1972) 48: 35; Sieg (1980a) 537: 12; Holdich & Jones (1983a) 60–61; Holdich & Jones (1983b) 17: 158, 170–172, 176, 178, 180. Hassack & Holdich (1987) 16(3): 223, 226–227, 229.

Typhlotanais aeqviremis: Kudinova-Pasternak (1966) 45: 528.

Typhlotanais aequiremis: Wallace (1919) 18: 7–8. Lang (1970) 23: 270.

? Typhlotanais aequiremis: Lang (1957) 52: 2.

Material examined: 32 females, CRU 3887 , (one female dissected on slides), Norway, material determined by G.O. Sars , 1898; three females, CRU 3888 , Norway, material determined by G.O. Sars , 1898.

Diagnosis: As for the genus.

Complementary description: Female 3.5 mm ( Fig. 13A, B ) body long, 7.5 times as long as wide; carapace smooth, 1.3 times as long as wide, lateral margins slightly rounded; rostrum pointed; pereonites smooth, all wider than long; pereonite-1 shortest, twice as wide as long; pereonites 2, 4 and 5 subequal, 1.5 times as long as pereonite-1; pereonite-3 longest; pereonite-6 slightly longer than pereonite-1. Pleon about as long as carapace, pleonites 1–5 similar in size; pleotelson rounded.

Antennule ( Fig. 14A ): Article-1 slender, about four times as long as wide, with two groups of pinnate and simple setae along article; article-2 with three simple setae distally; article-3 four times as long as article-2, with five apical setae.

Antenna ( Fig. 14B ): Article-2 as long as wide, twice as long as article-3, both naked; article-4 four times as long as article-5, with two simple and three pinnate setae distally; article-5 with one simple seta distally; article-6 very short, with six terminal setae.

Mouth parts: Labrum ( Fig. 14C ) hood-shaped, with minute setae. Mandible ( Figs 14D,E ) molar welldeveloped, longer than incisor with regular, blunt teeth; incisor blunt, crenulated; lacinia mobilis well-developed, crenulated. Maxillule ( Fig. 14F ) endite with nine apical spiniform setae, palp with two terminal setae. Both lobes of labium ( Fig. 14G ) poorly separated and sparsely setose distally. Epignath ( Fig. 14I ) curved, simple distally. Maxilliped ( Fig. 14H ): coxa reduced; basis fused, heart-shaped, as long as wide, with short seta; endite with two simple setae and two tubercles distally; palp article-1 unarmed; article-2 wedge-shaped, with three setae (one robust) on inner margin and one minute seta on outer margin; article-3 trapezoidal, with four weakly-serrated setae on inner margin; article-4 slender, with one simple seta on outer margin and five weakly-serrated distal setae (one broken off).

Cheliped ( Fig. 15A ): Basis slightly rounded, twice as long as wide; merus wedge shaped, with one seta ventrally; carpus with two long and one short setae ventrally and two setae dorsally; propodus with distal seta on inner side; fixed finger (propodus projection) tipped with strong spine, with three setae on well-calcified inner margin and two setae ventrally; dactylus slightly curved with one short, rod seta proximally on dorsal margin.

Pereopod-1 ( Fig. 15B ): Slender (walking type); coxa with one seta; basis as long as merus, carpus and half of propodus combined, with eight short simple setae dorsally and two setae ventrally; ischium short, with one seta; merus shorter than carpus with two simple setae ventro-distally and two setae dorso-distally; carpus with two setae ventro-distally and five setae on dorsal margin; propodus a little longer than carpus, with two setae distally; dactylus half as long as unguis; both slightly shorter than propodus.

Pereopod-2 ( Fig. 15C ): Slender (walking type); coxa with one seta; basis slightly shorter than rest of articles combined, with three minute setae proximally on dorsal margin and two short setae on ventral margin; ischium with simple seta; merus a little shorter than carpus, with three simple setae distally; carpus slightly longer than merus, with four simple setae and one spiniform distally; propodus a little longer than merus and carpus combined length, with spiniform seta ventrally and two setae dorsally; dactylus half as long as unguis, with one simple seta.

Pereopod-3 ( Fig. 15D ): Similar to pereopod-2, but basis with only one seta.

Pereopod-4 ( Fig. 15E ): Clinging type; basis robust, less than twice as long as wide, with two setae ventrally and one seta dorsally; ischium with two setae; merus with two spiniform setae ventrally; carpus with prickly tubercles of moderate size distal hooks and one setae dorso-distally; propodus with two ventro-distal spiniform setae and one dorso-distal seta as long as dactylus; unguis bifid tipped, half as long as dactylus; both almost as long as propodus.

Pereopod-5 similar to pereopod-4.

Pereopod-6 ( Fig. 15F ): Similar to pereopod-5, but propodus with three dorso-distal setae.

Pleopod ( Fig. 15G ): Basal article naked; exopod with one seta on inner margin and fourteen plumose setae on outer margin; endopod with eighteen plumose setae on outer margin; no clear gap between proximal seta and other setae.

Uropods ( Fig. 15H ): Basal article as long as wide; both rami one-articled (see comment in generic diagnosis); exopod 0.7 times as long as endopod, with one strong seta and one regular seta distally; endopod tipped by one strong, four regular and one pinnate setae.

Distribution: North Sea, The Skagerrak, Sweden, Norwegian south and west coast up far north of Tromso, Spitsbergen, British waters, western and eastern Iceland, at the depth 22–430 m ( Holdich and Jones, 1983a).

Remarks: Pragmatically, all typhlotanaids with prickly tubercles (i.e. all except Obesutanaids and Hamatipedis) can be divided into short body (length: width ratio <5) and long body forms (length: width ratio>6). The first group includes species of two morpho-groups—the ‘ eximus ’ group, i.e. T. penicillatus , T. eximus , T. spinipes and Typhlotanais sp. A (present work), and the ‘ cornutus ’ group, i.e. T. cornutus , T. crassus , T. andeepae n. sp., and T. adipatus sensu Tzareva —as well as Larsenotanais amabilis n. sp. and three species incertae sedis T. parvus , T. grahami and T. solidus .

Typhlotanais aequiremis , at present the only member of Typhlotanais sensu stricto, is representative of the long form (length: width ratio>6) with pereonites wider than long or square, but never longer than wide. The smooth cuticle covering the pereonites distinguishes Typhlotanais sensu stricto from Peraeospinosus and the ‘ plicatus ’ group. The first pereonite that is shorter than the carapace allows immediate distinction from Pulcherella n. gen and Hamatipeda n. gen., while the unarmed pleotelson allows distinction from members of the ‘ spinicauda ’ group. T. sensu stricto is distinguished from members of genus Typhlamia n. gen. by having the antennule shorter than the carapace, and from species presently combined in the ‘ trispinosus ’ group— T. trispinosus Hansen, 1913 and T. tenuicornis G.O. Sars, 1882 —by the lack of teeth on the second and third antennal articles.

Mouthparts are conservative in their morphology within the family, although some variability occurs in the character of the molar and the ornamentation of the maxilliped endites. The mandible molar of the type species is armed by a row of blunt and regular teeth. The same blunt and regular molar teeth occur in members of Pulcherella , Torquella and Typhlamia , although they are less densely arranged. The short seta on the maxilliped basis distinguishes T. aequiremis from the genera above. In addition, the distal edges of the maxilliped endites are armed with two setae and two tubercles of regular size. Tubercles of similar character occur gener- ally in most typhlotanaids, although they are clearly smaller in Peraeospinosus , and especially large in T. inaequipes Hansen, 1913 and T. williamsae Dojiri & Sieg, 1997 ( Typhlotanais sensu lato).

Unique characters of T. aequiremis are the relatively numerous setae on the dorsal margin of the basis (eight) and carpus (five) of pereopod-1. The presence of spiniform setae on the carpus of the second and third pereopods is a character shared by T. aequiremis and most typhlotanaids (including the genera Peraeospinosus , Torquella , Typhlamia ), but they absent in Pulcherella , T. parvus and T. grahami (see remarks under Typhlotanais s. str In T. aequiremis the prickly tubercles are well embossed but relatively small (not longer half of carpus), in the ‘ spinicauda ’ group they are large (as long as carpus), in Pulcherella they are large but almost flat, in Peraeospinosus and Torquella they are surrounded by a row of spines, while in Typhlamia they are minute.

The gap between the most proximal and the other setae on the pleopods is so small in T. aequiremis that the pleopod setation in this species is considered to be continuous. The uni-articled uropod rami of T. aequiremis is a rather common character among typhlotanaids and thus far has been observed in most members of Peraeospinosus , Typhlotanais adipatus (both sensu Tzareva and sensu Sieg ), T. crassus Dojiri & Sieg, 1997 , T. finmarchicus G.O. Sars 1882 , and in the ‘ plicatus ’ group. Articulation of the uropod is a convenient character unless the articles are partially fused (semi-fused). The fusion line is often difficult to observe under the light microscope, and may become even less clear in adult and in preadult stages (pers. obs.).

Typhlotanais aequiremis can be distinguished by various characters from those species not included to any of proposed morpho-groups. Most difficult for comparison at the moment is the poorly-described T. simplex , of which type material is not available for study. T. brachyurus Beddard, 1886 and T. longicephala Kudinova-Pasternak 1970 can be immediately distinguished: the first species has pereonite-1 just as long as the carapace, while the second has an extremely long carapace that is about twice as long as wide. The relatively large ventral gap between the distal edge of the cheliped basis and pereonite-1 allows the distinction of T. mixtus from T. aequiremis . The same large gap probably exists in T. plebejus Hansen, 1913 , but because its cheliped distal edge is distally expanded, this gap is not visible. Further comparison of T. plebejus with the type species is not possible owing to the insufficiency of material available for study (the holotype only). Details of the first three pairs of pereopods allows the distinction of three other Typhlotanais sensu lato species from T. aequiremis : these details are large spines on the merus of pereopod- 3 in T. proctagon Tattersall, 1904 , the long setae on the carpus of pereopods-1 and – 2 in T. inermis Hansen, 1913 , and the long seta far exceeding the unguis on the propodus of pereopods 4-6 in T. kussakini Kudinova-Pasternak, 1970 .

Six other species— T. assimilis G.O. Sars, 1882 , T. compactus Kudinova-Pasternak, 1966 , T. finmarchicus G.O. Sars, 1882 , T. inaequipes Hansen, 1913 T. profundus Hansen, 1913 , T. williamsae Dojiri & Sieg, 1997 – share a similar body habitus with T. aequiremis . Two of them, T. inaequipes and T. williamsae , can be distinguished by their large tubercles on the maxilliped endites and long setae (just reaching the distal edge of the endites) on the maxilliped basis. Except for T. profundus , all the other species share with T. aequiremis the characters of prickly tubercles, small spiniform setae on the carpus of the second and third pair of pereopods, the relatively short distal seta on the propodus of the fourth and fifth pereopods, and the short setae on the maxilliped basis. Apart from that, T. compactus has numerous setae on the basis, merus and carpus of the first pereopod.

According to observations by Hassack & Holdich (1987), tubes made by non-ovigerous females of T. aequiremis are incrusted mostly by sand grains, with a higher sand concentration towards the anterior part of tube. The posterior part of the tube is sac-like and is made of a mucous lining which can adjust to pleon. The anterior part of tube is open to allow the animal to emerge from the tube, for example for grazing for food particles.

Figures

FIGURE 13. Typhlotanais aequiremis, female. A), dorsal view; B) lateral view; C) carapace ventral side. Scale 1 mm.

FIGURE 14. Typhlotanais aequiremis, female. A) Antennule; B) Antenna; C) Labrum; D) Left mandible; E) Right mandible; F) Maxillule; G) Labium; H) Maxilliped; I) epignath. Scale: A, B = 0.1 mm; C-I = 0.01 mm.

FIGURE 15. Typhlotanais aequiremis. A) Cheliped; B) Pereopod-1; C) Pereopod-2; D) Pereopod-3; E) Pereopod-4; F) Pereopod-6; G) Pleopod; H) Uropod. Scale = 0.1 mm.