Review of the genus Chauliopleona Dojiri and Sieg, 1997 (Crustacea, Peracarida, Tanaidacea) and description of three new species

The tanaidacean genus Chauliopleona Dojiri and Sieg, 1997 is reviewed. A generic diagnosis is given and the type species Chauliopleona dentata Dojiri and Sieg, 1997 is redescribed. Three species, Leptognathia armataHansen, 1913, L. amdrupii Hansen, 1913 and L. hastata Hansen, 1913 are placed into this genus. Three new species, one from the Angola Basin, one from the deep sea of the tropical East Pacific and one from Antarctica are described. A key for the genus is provided.

Pacific Ocean (Menzies and Mohr 1962;Kudinova-Pasternak 1965, 1970, 1973 and from the Beagle Channel (Schmidt 1999). The discovery of tanaids with a pleonal spur from the deep Angola Basin, from the deep sea of the East Pacific Ocean, and from Antarctica has led to their comparison with other known tanaids with this feature. The results are given in the present work.

Material and methods
The material examined came from different expeditions; station data are given in Table I. The dissections were made in glycerine under a Großfeld dissecting microscope TS from Leitz. All drawings were made using a Leitz Dialux microscope with camera lucida.
The holotype and the type series of the new species are deposited in the Zoological Museum Hamburg (ZMH). The types of L. armata, L. hastata and L. amdrupii are deposited in the Zoological Museum Copenhagen (ZMC) and the paratype of C. dentata is deposited at the moment in the reference collection of Jü rgen Sieg in the Naturkundemuseum Berlin and will be sent to the Santa Barbara Museum of Natural History (SBMNH). The terminology used in this work follows Larsen (2003). The classification follows Gutu and Sieg (1999); the more recent classification of Larsen and Wilson (2002) considered the genus Chauliopleona as incertae sedis because of its incomplete description.
Length is measured from the tip of the cephalothorax to the tip of the pleotelson.

Description
Body cylindrical, long and slender, about seven times as long as broad. Cephalothorax oval or triangular. Eyes and eyelobes absent. Pereon composed of six free pereonites, pereonite 2 longest. Pleon composed of five free pleonites and a pleotelson. Pleonite 5 with a backwarddirected ventral apophysis. Antennule composed of four articles. Antenna composed of six articles. Labrum hood-like with marginal setules. Mandible well calcified, molar process not pointed, turned downward, bearing about 10 pointed spinules. Maxilla rectangular. Maxillule endite with seven or eight terminal spines. Maxilliped basis fused, endites not fused. Cheliped attached laterally by a sidepiece, carpus common with a carpal shield. Pereopods 1-3 with coxa, pereopods 4-6 lacking coxa. Pereopod 1, merus with one spiniform seta and a row of ventral spines or spinules on propodus. Dactylus of pereopods 4-6 with a ventral groove bordered by spinules, unguis short and pointed. Pleopods biramous. Uropods biramous, exopod shorter than endopod, both composed of two articles each.

Remarks
Chauliopleona is very easy to distinguish from other genera because of its posteriorly directed ventral apophysis on pleonite 5. The genus Portaratrum Guerrero-Kommritz, 2003 and the species Leptognathia tuberculata Hansen, 1913 do possess a ventral spiniform process on pleonite 5, but this is directed downwards and is not as long as in the species of Chauliopleona. The insertion of the cheliped in L. tuberculata is a typical Leptognathia insertion and that of Portaratrum resembles that of Metagathotanais Bird and Holdich, 1988. The genus Scoloura Sieg and Dojiri, 1991 has a posteriorly directed lateral spiniform process on each side of the pleotelson.
Akanthophoreus Sieg, 1986 is a very similar genus in many characters but has no ventral posteriorly directed spiniform process on any pleonite or pleotelson.

Diagnosis
Cheliped dactylus with dorsal crenulation, carpal shield poorly developed. Basal article of uropod with three distal setae.
Antennule (Figure 1d). Article 1 longest with one simple and three feathered setae. Article 2 with one long and two simple setae. Article 3 shortest with one simple and two feathered setae. Article 4 with six terminal simple setae.
Antenna (Figure 1e). Article 1 very short. Article 2 as long as broad with one simple thin seta. Article 3 short with one simple seta. Article 4 longest with one short and two long setae as long as article 5. Article 5 with one long terminal seta. Article 6 with four terminal simple setae.
Labrum (Figure 1i). Hood-like with fine marginal setules. Figure 1j). Well calcified and sclerotized on incisive margins, molar process developed, slender, bearing about 10 distal spinules. Figure 1l). Endite naked with two large setulated, five large simple and one small terminal spines. Palp with one long terminal seta. Figure 1m). Rectangular, with one row of setules distally.  Labium (Figure 1k). Composed of two triangular lobes, with one small terminal seta. Figure 1n). Endites with a blunt spine and a simple seta. Palp article 1 naked. Article 2 with one long outer and three curved inner setae. Article 3 with two inner setae. Article 4 with two long and two short inner setae and one short outer seta.
Cheliped (Figures 1f, 15g). Basis shorter than carpus, divided unequally by sclerite. Merus with one simple ventral seta. Carpus about 1.7 times as long as broad, with one simple ventral and one small dorsal seta. Carpal shield developed. Propodus with two ventral setae. Fixed finger with three small teeth, cutting edge with one short and two long setae near articulation of finger. Dactylus with crenulations along dorsal margin.
Pereopod 1 (Figure 2a). Coxa with seta. Basis longer than three following articles together. Ischium with one small simple seta. Merus bearing one pinnate spiniform seta. Carpus with one row of ventral spinules and two spiniform setae. Propodus with one ventral row of spinules and curved rows of minute setules, one short dorsal spine and one short spiniform seta. Dactylus short, about half unguis length. Unguis pointed.
Pereopod 2 ( Figure 2b). Coxa with seta. Basis longer than three succeeding articles together. Ischium with one small simple seta. Merus with one spiniform seta. Carpus with three spiniform setae. Propodus with one ventral row of spinules and one short spiniform terminal seta. Dactylus and unguis as in pereopod 1.
Pereopod 4 ( Figure 2d). Basis longer than three succeeding articles together. Ischium with simple seta. Merus with two short strong simple setae. Carpus smooth with two strong simple setae. Propodus with one ventral row of small spinules, with three distal long simple strong setae. Dactylus with ventral groove bordered by proximally directed spinules. Unguis short and pointed.

Pleopods (
Uropods (Figure 1g). Basal article with three small setae near insertion of endopod. Exopod shorter than article 1 of endopod, composed of two articles: article 1 with one simple thin seta, article 2 with one short and one long terminal setae. Endopod composed of two articles: article 1 with one simple and two feathered setae, article 2 with two short feathered and four long simple setae.

Remarks
As C. dentata is currently defined, the distribution is disjunct. It can be found in the Magellan Strait, Beagle Channel and on the coasts of California.
The material examined from the Beagle Channel shows no significant difference from the type material from California. More material from the west coast of South America is needed to clarify whether this species has a such a wide geographical distribution or if there are two different populations, one in California and one in the Beagle Channel. Some features that were described in the original paper could not be seen in the type material. The armature of the antennule and the uropod varies from individual to individual. The feathered setae are not always present.
Cheliped (Figures 3f, 15e). Basis as long as carpus, divided unequally by sclerite. Merus triangular in shape with one ventral simple seta. Carpus 2.2 times as long as wide. One ventral and one dorsal simple seta. Carpal shield very weak or absent. Fixed finger with four small teeth, three dorsal and two ventral setae. Dactylus smooth.
Pereopod 1 (Figure 4g). Coxa without seta. Basis longer than the three following articles together, with two simple setae. Ischium short, naked. Merus with one spiniform seta. Carpus with two serrated strong setae and a row of spines ventrally. Propodus with about seven short spines ventrally and one short terminal spine, one spiniform terminal and one simple setae. Dactylus about as long as unguis. Unguis pointed.
Pereopod 2 ( Figure 4h). As pereopod 1, basis with one simple seta, ischium with one seta, merus with one short and one long spiniform pinnate seta. Carpus with about four small spines, one long spiniform pinnate and two short spiniform setae.
Pereopod 4 (Figure 4j). Basis longer than three following articles, with two simple setae. Ischium with one simple seta. Merus with two spiniform pinnate setae. Carpus with two long spiniform pinnate and one short spiniform setae and a mid-ventral row of spinules. Propodus with a mid-ventral row of spinules and three very sharp spiniform setae. Dactylus long with a mid-ventral groove bordered by proximally directed spinules. Unguis short and pointed. Uropods (Figure 3h). Basal article naked. Exopod very short, less than 50% of article 1 of endopod. Article 1 as long as 2, each with one long terminal simple seta. Endopod article 1 with one long feathered and one short simple seta. Article 2 with four long simple setae.

Remarks
The redescription is based on the type specimen of Hansen (1913) and one specimen from south Greenland. Most of the drawings are from the specimen from south Greenland (ZMH K-40228).

Diagnosis
Cephalothorax long, about 1.6 times as long as broad. Cheliped propodus and dactylus smooth and slender, carpal shield well developed and rounded.
Uropods (Figure 5h). Basal article rhomboid. Exopod shorter than half of article 1 of endopod. Exopod of two subequal articles: article 1 with a simple terminal seta, article 2 with a long simple terminal seta. Endopod composed of two equally long articles: article 1 with one short simple terminal seta, article 2 with three long terminal simple setae.

Remarks
For this species only the type material was available so that no dissection was possible to study mouthparts. This species is only present in the North Atlantic Ocean.

Diagnosis
Cheliped well developed, strong, carpal shield well developed with proximal ventral lobes, chela strong.
Antennule (Figure 7d). Article 1 longest, with one distal simple seta. Article 2 as long as 4 with simple terminal seta. Article 3 shortest with simple seta. Article 4 with three long simple setae, one short simple seta and one aesthetasc.  Antenna (Figure 7e). Article 1 very short. Article 2 square, with one simple seta. Article 3 with small terminal simple seta. Article 4 with three small simple setae. Article 5 with simple long terminal seta. Article 6 with three long simple setae, one short simple seta and one aesthetasc.
Labium (Figure 8f). Composed of two pentagonal lobes. Cheliped (Figures 7f, 15b). Basis as long as carpus, 50% of basis proximal to attachment. Merus triangular, with one simple seta. Carpus about 1.1 times as long as broad. Carpal shield very well developed. One rounded protuberance near insertion of propodus, two lobes under carpal shield, and one ventral and one dorsal simple seta. Propodus twice as long as broad, with four teeth on fixed finger and two ventral and three dorsal setae. Two dorsal blunt lobes on top of finger insertion. Dactylus curved with three small ventral teeth, smooth.
Pereopod 1 (Figure 8h). Coxa without seta. Basis with one simple seta. Ischium with one simple seta. Merus with one long spiniform pinnate seta. Carpus with one long spiniform seta and about six ventral spinules. Propodus with about 24 small ventral spinules and one short spiniform seta. Dactylus short, about as long as unguis. Unguis pointed.
Pereopod 2 ( Figure 8i). As pereopod 1 except basis naked, merus with one spiniform seta. Carpus with three fine ventral spines and one long spiniform pinnate and two short simple setae. Propodus with about 15 small ventral spinules and one short spiniform seta.
Pereopod 4 (Figure 8k). Basis with one feathered and two small simple setae. Ischium with two simple setae. Merus triangular with two long spiniform seta. Carpus with three long spiniform setae. Propodus with three long spiniform terminal setae. Dactylus with ventral groove bordered by very fine proximally directed spinules. Unguis short and pointed.
Uropods (Figure 7h). Basal article rectangular. Exopod shorter than article 1 of endopod, composed of two articles: article 1 with one short terminal simple seta, article 2 with one long simple terminal seta. Endopod of two articles equal in length: article 1 naked, article 2 with four terminal simple setae.

Remarks
This description is based on the type material and on animals from north Greenland. This species can be easily differentiated from C. armata by the form of the carpal shield which is very pronounced, as well as the chela, which is stronger and heavier in C. hastata. This is a valid species, and no synonym of C. armata or C. amdrupii. Chauliopleona hastata can be found in very cold waters from north Greenland, C. armata only in waters from south Greenland or Iceland in depths between 188 and 1373 m.

Diagnosis
Cheliped merus with one ventral rounded protuberance with one simple seta on it.
Antennule (Figure 9d). Article 1 with three small short and one long simple setae. Article 2 with one long terminal seta. Article 3 with three small lateral and two terminal setae. Article 4 with one short and four long terminal setae.
Antenna (Figure 9e). Article 1 short. Article 2 as long as wide, with one small distal seta. Article 3 with long simple seta. Article 4 longest, with one small lateral and one short and two long terminal setae. Article 5 about half length of 4, with one terminal simple seta. Article 6 very short, with four terminal setae, two long and two short. Labrum (Figure 10b). Hood-like with fine marginal setules.
Maxilliped (Figure 10h). Endites with one short spiniform seta. Palp article 1 naked. Article 2 with one outer spiniform seta. Article 3 with four inner setae. Article 4 with three inner and three terminal setae.
Cheliped (Figures 9f, 15d). Basis as long as carpus. Merus triangular with one ventral rounded protuberance at mid-length, with one simple seta on top of it. Carpus about 1.5 times as long as broad with one ventral seta at mid-length. Carpal shield developed. Fixed finger with four teeth on inner margin, two ventral and three laterodorsal simple setae. Dactylus smooth with no special features.
Pereopod 1 (Figure 10i). Coxa without seta. Basis longer than three following articles together, with one simple seta at mid-length. Ischium with one small simple seta. Merus with one spiniform seta as long as carpus. Carpus with two rows of small setules and two terminal spiniform setae. Propodus with row of about 15 spinules, two small terminal spiniform setae. Unguis as long as dactylus.
Pereopod 2 (Figure 10j). Coxa without seta. Basis longer than the three following articles together, with one simple seta. Ischium with a small simple seta. Merus with one long terminal spiniform seta. Carpus with row of setules ventrally and three terminal spiniform and one simple setae. Propodus with one terminal spiniform seta and row of setules ventrally and around insertion of dactylus. Unguis pointed, about half as long as dactylus.
Pereopod 6 ( Figure 10n). As pereopod 4, except basis with one simple and one setulose setae, carpus with three long and one short spiniform setae, propodus with four spiniform setae.
Uropods (Figure 10a). Basis rectangular naked. Exopod as long as basis, composed of two articles: article 1 with one long seta, article 2 with two terminal setae, one very long. Endopod article 1 with small terminal seta, article 2 with one short and four long terminal setae.

Etymology
The species is named after Diana Amft.

Remarks
This species resembles C. armata. It differs from the latter in the shape of the cephalothorax and the cheliped (see Figure 15a, d).
Chauliopleona paradoxa n. sp. (Figures 11, 12  Antennule (Figure 11d). Article 1 longest with two small and one long simple setae. Article 2 with one long and one short simple setae. Article 3 with a simple seta. Article 4 with four long and one short simple terminal setae. Antenna (Figure 11e). Article 1 short, naked. Article 2 with one simple dorsodistal seta. Article 3 with one long simple dorsodistal seta. Article 4 longest with two long simple setae distally. Article 5 with one terminal seta. Article 6 shortest with two short and three long simple setae.
Labrum (Figure 11i). Hood-like, with a row of long setules laterally and short setules distally.
Maxillule (Figure 11l). Endite with setules, with five long setulose and two long simple spines and one short terminal one. Palp with two distal setae.
Labium (Figure 11k). Composed of two triangular lobes with one distal seta.
Cheliped (Figures 11f, 15f). Posterior part of basis tapering distally. Merus with one simple seta. Carpus 1.6 times as long as broad, with one ventral simple seta and two dorsal simple setae, one rounded protuberance near attachment of propodus. Carpal shield well developed. Propodus twice as long as broad with two or three teeth on fixed finger, three dorsal and two ventral simple setae. Dactylus with a fine crenulated dorsal border.
Pereopod 1 (Figure 12a). Coxa without setae. Basis naked. Ischium with one simple seta. Merus with one long spiniform seta. Carpus with two long spiniform setae and ventral row of spinules. Propodus with one short terminal spiniform seta and many small spinules ventrally. Dactylus short, about half the length of unguis. Unguis pointed.
Pleopods (Figure 11g). Endopod with one long simple seta at attachment to basis and seven simple setae distally. Exopod with six distal simple setae.
Uropods (Figure 11h). Basal article long, naked. Exopod shorter than article 1 of endopod, of two articles: article 1 longest, with a lateral simple seta, article 2 with one short and one long simple terminal seta. Endopod article 1 with two small simple terminal setae, article 2 with four long and one short simple terminal setae.

Etymology
The name refers to the fact that this species is a 'strange' C. hastata with some highly variable characters making it difficult to identify.

Remarks
This species has a very wide morphological variability. The posteriorly directed ventral apophysis is very variable and may be very small to very large. The same can be recognized in other characters, such as dentition of the fixed finger of the chela, that varies from one to three teeth. The crenulation on the finger is in some individuals very weak and in others very prominent.

Etymology
This species is named after Jö rg Nickel, a colleague and friend.

Remarks
The C. armata reported from the South Pacific, Indian Ocean and Antarctic waters by Kudinova-Pasternak (1986) are probably C. nickeli n. sp. or a closely similar species. Material from the reference collection of Jü rgen Sieg from Kerguelen Island are close to C. nickeli n. sp., unfortunately they are not in good enough condition to make a description. The material of Vanhö ffen (1914) referred to Leptognathia sp., could not be found for comparison but it is very probable that it belongs to C. nickeli n. sp.

Discussion
Chauliopleona is very easy to distighuish from other taxa because of its posteriorly directed ventral apophysis on pleonite 5. This apophysis is very variable among all the studied material. In some individuals it reaches to the junction of pleonite 5 to the pleotelson, in some to the mid-length of the pleotelson, and in others it can be very large, surpassing the length of the pleotelson. In some individuals it is not very well developed, and in two specimens of C. nickeli it was directed downwards. The distribution of the genus is very wide in the Atlantic Ocean, from Greenland to the Antarctic, and in the East Pacific Ocean from California to the Magellan Strait.
The species of Chauliopleona are similar in their morphology, leading many authors in the past to doubt the validity of some species. Hansen (1913), in his original description of Leptognatia armata, L. hastata and L. amdrupii, refers to this problem. Kudinova-Pasternak (1965, 1986 synonymized L. hastata with L. armata and did not recognize the Antarctic form as a new species. Unfortunately the material examined by Kudinova-Pasternak could not be obtained for comparison. It is not clear to which Chauliopleona species the specimens mentioned by Menzies and Mohr (1962) belong. Their drawings are not good enough to identify the animal, although it may be a preparatory male because five articles are shown on the antennule. C. armata was until now only known from south Greenland and the North Atlantic Ocean. The presence of this species in the North Pacific is doubtful and it is posible that the animals reported belong to C. dentata or to a new, undescribed species.
The absence of males, and mancas, in the material studied cannot be satisfactorily explained. Preparatory males of these species were described by Dojiri and Sieg (1997) and are characterized by having five articles in the antennule. The most probable explanation is that the male to female ratio is very low. Future studies may resolve this problem.