Chalaraspidum alatum ( Willemoes-Suhm, 1874 )

Richter, Stefan, 2003, The mouthparts of two lophogastrids, Chalaraspidum alatum and Pseudochalaraspidum hanseni (Lophogastrida, Peracarida, Malacostraca), including some remarks on the monophyly of the Lophogastrida, Journal of Natural History 37 (23), pp. 2773-2786 : 2776-2781

Chalaraspidum alatum ( Willemoes-Suhm, 1874)

Chalaraspis alata Willemoes-Suhm, 1874: XX.

Chalaraspis alata: Willemoes-Suhm, 1876: 592.

Chalaraspis alata: G.O. Sars, 1885: 51, figures 1–2 .

Chalaraspidum [ alatum ] Willemoes-Suhm, 1895: 521.

Eclytaspis alata: Faxon, 1895: 219.

Chalaraspidum alatum (in partem): W. M. Tattersall, 1951: 14–15.

Chalaraspidum alatum: O. S. Tattersall, 1955: 27–30 , figure 1A–E .

Parachalaraspis vitjazi: Birstein and Chindonova, 1958: 261–265 , figures 1–2 .

Chalaraspidum alatum: Birstein and Chindonova, 1962: 59–61 , figure 1 .

Chalaraspidum alatum: Mauchline and Murano, 1977: 51 (list).

Distribution. one female, 40 mm: ‘Challenger’ South Pacific: 50 ° 1 ∞ S 123 ° 4 ∞ E [Willemoes-Suhm, Sars]; one specimen, 38 mm: ‘Albatross 1906’ Japan, St. 4919: 30 ° 34 ∞ N 129 ° 19 ∞ 30 ◊ E [W. M. Tattersall]; one specimen, 37 mm: ‘Albatross 1906’ Japan, St. 4960: 32 ° 34 ∞ N 132 ° 21 ∞ 45 ◊ E [W. M. Tattersall]; one female, 28 mm: ‘Discovery’ West of Cape Town, St. 101: 33 ° 50 ∞ to 34 ° 13 ∞ S 16 ° 04 ∞ to 15 ° 49 ∞ E [O. S. Tattersall]; one female, 38 mm: ‘Discovery’ about 1000 miles west of Cape Peninsula, St. 253: 35 ° 06 ∞ 00 ◊ S 2 ° 19 ∞ 00 ◊ E [O. S. Tattersall]; one female, 34 mm: 29 ° 55 ∞ N 137 ° 01 ∞ E [ Birstein and Chindonova, 1958]; one specimen, 14 mm: 38 ° 03 ∞ N 143 ° 55 ∞ E [ Birstein and Chindonova, 1958]; one specimen, 20 mm: 33 ° 30 ∞ N 149 ° 33 ∞ E [ Birstein and Chindonova, 1958]; one male, 12 mm: ‘Ob 1955–1958’: St. 441: 32 ° 25 ∞ S 75 ° 42 ∞ W [ Birstein and Chindonova, 1962]; one specimen: ‘Dana II (1921–1922)’, St. 1208-IV: 6 ° 48 ∞ N 80 ° 33 ∞ W; 16 January 1922 [ZMUC, CRU-3682; new record as the following]; one specimen: ‘Tethys’, St. 19: 10,150 N 147,133 W [SIO 60-243]; four specimens: ‘Tethys’, St. 15: 0,150 S 138,850 W [SIO 60-235]; one specimen: ‘Tethys’, St. 5: 18,733 N 124,400 W [SIO 60-209]; one specimen: ‘Tethys’, St. 18: 7,433 N 144,483 W [SIO 60-244]; two specimens: ‘Tethys’, St. 28: 26,233 N 141,583 W [SIO 60-280]; three specimens: ‘Tethys’, St. 27: 25,350 N 144,750 W [SIO 60-278]; one specimen: ‘Tethys’, St. 25: 23,383 N 151,067 W [SIO 60-275]; one specimen: ‘Easttropic’, St. 4: 08,31 N 110,11 W [SIO 55-229]; one specimen: ‘Northern Holiday’, St. 7: 40,37 N 143,25 W [SIO H51-357].

Pseudochalaraspidum hanseni Birstein and Chindonova, 1962 Pseudochalaraspidum hanseni Birstein and Chindonova, 1962: 61 .

Chalaraspis alata: Hansen, 1912: 182–183, figures 1 a–l .

Chalaraspis alata: Fage, 1939: 68–76, figures 1 –7.

Chalaraspis alata: Fage, 1941: 4–9, figures 1 –8.

Chalaraspidum alatum (in partem): Tattersall, 1951: 14–15.

Chalaraspidum alatum: Banner, 1954: 5–7 .

Pseudochalaraspidum hanseni: Mauchline and Murano, 1977: 73 (list).

Distribution. one male, 35 mm: ‘Albatross 1904–1905’, St. 4719: 6 ° 29.9 ∞ S 101 ° 16.8 ∞ W [Hansen]; one specimen: ‘Albatross 1904–1905’, St. 4675: 12 ° 54 ∞ S 78 ° 33 ∞ W [Hansen]; two specimens: ‘Albatross 1904–1905’, St. 4672: 13 ° 11 ∞ 30 ◊ S 78 ° 18 ∞ W [Hansen]; one specimen (very young): ‘Albatross 1904–1905’, St. 4665: 11 ° 45 ∞ S 86 ° 05.2 ∞ W [Hansen]; one female: ‘Dana 1928–1930’, St. 3550-VI: 7 ° 10 ∞ N 78 ° 15 ∞ W [Fage]; one male, 56 mm: ‘Dana 1928–1930’, St. 3731-XIV: 14 ° 37 ∞ N 119 ° 52 ∞ W [Fage]; one specimen: ‘Dana 1928–1930’, St. 3766-XVIII: 1 ° 13 ∞ S 138 ° 42 ∞ E [Fage]; one male, 35 mm: ‘Dana 1928–1930’, St. 3768-III: 1 ° 20 ∞ S 138 ° 42 ∞ E [Fage]; one specimen, 32 mm: ‘Albatross’, St. 4334: Point Loma Lt.Ho., N. 33 ° 30 ∞ E, 13,6 miles [Tattersall]; one female, 45 mm: ‘Hancock Foundation’, St. 2081-51: 27 ° 29 ∞ 33 ◊ N 115 ° 03 ∞ 02 ◊ W [Banner]; one female?, 28 mm: ‘Hancock Foundation’, St. 2081-51: 27 ° 29 ∞ 33 ◊ N 115 ° 03 ∞ 02 ◊ W [Banner]; one female, 40 mm: ‘Hancock Foundation’, St. 2084-51: 33 ° 04 ∞ 10 ◊ N 119 ° 06 ∞ 39 ◊ W [Banner]; one male?, 21 mm: ‘Hancock Foundation’, St. 2084-51: 33 ° 04 ∞ 10 ◊ N 119 ° 06 ∞ 39 ◊ W [Banner]: one specimen: ‘Dana (1921–1922)’, 16 January 1922, St. 1208-IV: 6 ° 48 ∞ N 80 ° 33 ∞ W [ZMUC, CRU-3681; new record as the following]; one specimen: ‘Shellback’, St. 1: 17,800 N 124,117W [SIO H52-309]; one specimen: ‘Southern Ca and Baja Ca Trawls’ (‘SCBCT’): 28,51 N 118,11 W [SIO 56-76]; one specimen: ‘SCBCT’: 32,39 N 117,37 W [SIO H51-392]; one specimen: ‘SCBCT’: 25,52 N 114,40 W [SIO H51-91]; one specimen: ‘Easttropic’, St. 1: 24,41 N 121,43 W [SIO 55-204]; one specimen: ‘Tethys’:, 12,117 N 148,583 W St. 20 [SIO 60-245]; two specimens: ‘SCBCT’: 28,53 N 118,12 W [SIO 57-212]; one specimen: ‘SCBCT’: 28,52 N 118,13 W [SIO 57-43]; one specimen: ‘SCBCT’: 29,12 N 118,13 W [SIO 57-213]; one specimen: ‘Tethys’, St. 4: 21,550 N 123,033 W [SIO 60-207]; one specimen: ‘SCBCT’: 32,44 N 117,40 W [SIO H53-225]; one specimen: ‘SCBCT’: 32,33 N 117,35 W [SIO H53-223]; one specimen: ‘SCBCT’: 28,50 N 118,11 W [SIO 56-79]; one specimen: ‘Capricorn’, St. 41: 00,04 N 169,00 E [SIO 60-130]; one specimen: ‘SCBCT’: 32,43 N 117,37 W [SIO H51-397]; one specimen: ‘Northern Holiday’, St. 2: 40,27 N 131,06 W [H51-352]; one specimen: ‘Tethys’, St. 3: 24,217 N 121,600 W [SIO 60-206]; one specimen: ‘SCBCT’: 32,39 N 117,37 W [SIO H51-392]; two specimens: ‘Midpac’, St. 29: 10,25 N 135,55 W [SIO 52-082]; one specimen: ‘Tethys’, St. 9: 7,783 N 129,617 W [SIO 60-218]; one specimen: ‘Monsoon’, St. 4: 10,10 S 115,17 E [SIO 61-32]; one specimen: ‘SCBCT’: 32,58 N 118,25 W [SIO H50-287]; three specimens: ‘SCBCT’: 32,12 N 117,12 W [SIO 57-96].

Mouthparts of Chalaraspidum alatum and Pseudochalaraspidum hanseni

For a better understanding of the morphological and functional correlation between the different mouthparts, two figures showing the mouthparts of Lophogaster subglaber are also included ( figure 1A,B ). The general arrangement of the mouthparts is identical in the three species. However, the detailed description will be restricted to Chalaraspidum alatum and Pseudochalaraspidum hanseni . Each of the mouthparts will be described for both species together.

The labrum of C. alatum ( figure 2A,B ) and P. hanseni ( figure 4A ) has a triangular shape, with an anterior pointed tip and a rounded posterior edge. At the posterior edge, a tooth-like structure is separated from the rest of the labrum by a distinct suture ( figure 2A ). This tooth-like structure ends in both species in a rounded hook, the tip of which is orientated towards the left mandible (compare with figure 1B ). This hook shows a particular armature which is different in both species. In C. alatum the armature is of comb-like appearance, each comb consisting of about five to eight teeth ( figure 2B ). In P. hanseni , the ‘combs’ consist of only two to three teeth ( figure 4A ).

The mandibles consist of a three-segmented palp and the protopodal part with the biting edge. The distal segment of the palp carries on its ventral margin a single row of fine feathered setae of more or less equal length ( figure 4B ). These setae occupy about the distal two thirds of the last segment. In addition to this row of setae, some (about 11–12 in C. alatum and about seven to eight in P. hanseni ) longer setae are found on the inner surface of the distal segment, more concentrated to the proximal part of the row of setae. The tip of the distal segment has one long seta ( figure 4B ). In both species, the biting edges of left ( figures 2C,D ; 4C,D ) and right mandible ( figures 2E,F ; 4E,F ) are different. The edge of the left mandible is divided into an incisor and a molar process, between the two processes, in the centre of the edge, a lacinia mobilis is present. The incisor process has a semicircular shape and carries five teeth, the four distal teeth are more or less pointed, the most proximal one is rounded and of semicircular shape. The molar processes are different between the two species. In C. alatum ( figure 2C,D ) the molar process is well developed, consisting of about 12–14 semicircular arranged scaly ridges. A bush of long cuticular hairs is located at the proximal tip of the mandible, close to the oesophagus. In P. hanseni ( figure 4C,D ) the molar process is more or less reduced. Between molar process, or more precisely cusp c (terminology after Manton, 1928), and the incisor process, the crown shaped lacinia mobilis is located. The lacinia is orientated parallel to the mandibular edge. The suture between lacinia and the main body of the edge is very distinct in C. alatum ( figure 2D ) but more indistinct in P. hanseni ( figure 4D ). In the right mandible the incisor process is T-shaped in both species. The distal part carrying four pointed teeth is orientated at a right angle to the remaining mandible edge, the proximal part carries two teeth, the most proximal one having been called cusp b by Manton (1928). The molar processes are similar to those of the left mandible in both species. In C. alatum ( figure 2E,F ) the molar process is well developed and on the anterior surface a row of strong spine-like projections extends from the proximal tip of the mandible to cusp c. In P. hanseni ( figure 4E,F ), the molar process is reduced, remnants of the row of projections can be discovered. The cuticular hairs of the proximal mandible tip are present also on the right mandibles. On the right mandible a lacinia mobilis is missing in both species. The centre of the mandible edge is filled with cusps b and c. The two cusps are separated by a deep notch in C. alatum ( figure 2F , arrow). This notch is indistinct in P. hanseni ( figure 4F ).

In common with the mandibles, the right and left paragnath are also very different in both species ( figure 4G ). The right paragnath is more or less of ‘normal’ flap-like shape although it might be in some respects stronger than in, for example, mysids. The left paragnath ( figures 1A ; 2G,H ; 4G,H ) is much stronger than the right one and sculptured in a particular way, anterior and posterior part are separated like two steps of a staircase with the anterior part as the lower step. The surface of the anterior part corresponds to the semicircular incisor process of the left mandible ( figures 2G,H ; 4G,H ). The median edge of this anterior part of the paragnath possesses several protrusions, carrying different cuticular outgrowths, which fit with the posterior face of the left mandible like lock and key (compare also with figure 1A ).

The maxillula ( figures 3A,B ; 5A,B ) consists of a bipartite protopod and two endites (here called outer and an inner endite), a maxillular palp is missing in both species. The outer endite carries 12 cuspidate robust setae on its tip in C. alatum ( figure 3B ) and 11 in P. hanseni ( figure 5B ). These cuspidate setae possess a stronger basis in C. alatum in comparison to P. hanseni . On the surface of the outer endite one single seta is located more or less in a central position in both species. The shape of the inner endite differs slightly between the two species (compare figure 3A and 5A ). In both species, three long setae with their origins at the tip of the inner endite reach into the direction of the mouth (compare also with figures 1A,B ), some shorter setae have their origin on the surface close to the tip. In addition, some cuticular hairs are present on the more proximal part of the surface and one longer seta is located on the median edge of the inner endite in C. alatum ( figure 3A ). These cuticular outgrowths are missing in P. hanseni ( figure 5A ).

The maxilla ( figures 3C ; 5C ) consists in both species of a protopod (potential divisions of the protopod could not be clearly seen), an exopod, a small palp (endopod) and two endites (the proximal one is here called endite 1, the distal one is called endite 2). The margin of the exopod carries long plumose setae. The palp is two-segmented in C. alatum ( figure 3C ), only one segment is present in P. hanseni ( figure 5C ). On the distal segment of the palp several setae are present in C. alatum whereas in P. hanseni the single segment carries only two distal setae and one more proximal one. The two endites are similar in both species. However, in C. alatum the distal setae of the endite 2 are separated into two groups, which is not the case in P. hanseni .

The maxilliped ( figures 3D ; 5D ) consists of a strong protopod, a pentapartite endopod and a blade-shaped exopod. The protopod consists of the fused coxa and basis and is of more or less rectangular shape. Its outer margin carries a thin but extended epipodite (not shown in the figures). The endopod is five-segmented, consisting of ischium, merus, carpus, propodus and dactylus. The dactylus ends in a strong cuspidate seta in both species. Another correspondence between the two species is that the endopod carries three cuspidate setae on the inner margin of the propodus and one on the inner margin of the carpus. However, one of the studied specimens of P. hanseni possesses four cuspidate setae on the propodus edge. The exopod is of blade-like shape in both species. Its margin carries plumose setae.

Figures

FIG. 1. Lophogaster subglaber. (A) Left part of the mouthparts shown from the median food channel. Anterior is left, ventral is up. The morphological correlation between mandible (with lacinia mobilis, lm) and paragnath (pg) can be seen. The strong endopod of the maxilliped (mxp) covers the maxillula with outer (oe) and inner endite. The maxilla cannot be seen. (B) Right part of the mouthparts shown from the median food channel. Anterior is right, ventral is up. The mandible is located between labrum (lbr) and paragnath (pg). The hook of the labrum tooth (lt) is orientated medially. The molar process of the mandible is close to the oesophagus (oe). A few longer setae of the inner endite (ie) of the maxillula reach into the food channel.

FIG. 2. Chalaraspidum alatum [SIO 60-243]. (A) Posterior end of the labrum (posterior is up), ventral view. Labrum tooth (lt) with ‘hook’. (B) Armature of the ‘hook’. (C) Left mandible, view on the edge with incisor process (ip), lacinia mobilis (lm), cusp c (cc) and molar process (mp). (D) Left mandible, posterior view. (E) Right mandible, view on the edge. (F) Right mandible, anterior view. Between incisor and molar process, cusps b (cb) and c (cc). There is a notch between the two cusps (arrow). (G) Left paragnath, anterior view, ventral is up, right paragnath (rp) on the right side. (H) Left paragnath, ventral view, anterior is up; maxillula (mx 1) posterior of paragnath.

FIG. 4. Pseudochalaraspidum hanseni [SIO 56-76]. (A) Posterior end of the labrum (posterior is up), ventral view. Armature of the ‘hook’. (B) Distal segment of the right mandibular palp with row of fine feathered setae of equal length on the ventral margin and some additional setae on the inner surface. (C) Left mandible, view on the edge with incisor process (ip), lacinia mobilis (lm), cusp c (cc) and the reduced molar process (mp). (D) Left mandible, posterior view. (E) Right mandible, view on the edge. (F) Right mandible, anterior view. Between incisor and molar process, cusps b (cb) and c (cc). The notch between the two cusps (arrow) is indistinct. (G) Paragnaths, anterior view, ventral is up. The left paragnath (lp) is sculptured, the right paragnath (rp) of more ‘normal’ shape. (H) Left paragnath, ventral view, anterior is up; maxillula (mx 1) posterior of paragnath.

FIG. 3. Chalaraspidum alatum [SIO 60-243]. (A) Maxillula, posterior view, with paragnaths (pg) in the background. Notice the single seta on the surface of the outer endite (oe). (B) Magnification of the strong cuspidate setae of the outer endites. (C) Left Maxilla, ventral (posterior) view. The two-segmented palp (p) is located between exopod (ex) and the two endites (en1, en2). (D) Right maxilliped, ventral (posterior) view. The protopod (pp) consisting of the fused coxa and basis carries the five-segmented endopod (ep) and the exopod (ex). The epipodite is removed.

FIG. 5. Pseudochalaraspidum hanseni. (A) Maxillula [SIO 56-76], posterior view, with paragnaths (pg) in the background. On the surface of the outer endite (oe) a single seta is present. (B) Magnification of the strong cuspidate setae of the outer endites. (C) Right Maxilla [SIO 56-76], ventral (posterior) view. Between exopod (ex) and the two endites (en1, en2) the one-segmented palp (p). (D) Left maxilliped [USNM 82422], ventral (posterior) view. The protopod (pp) consisting of the fused coxa and basis carries the five-segmented endopod (ep) and the exopod (ex). The epipodite is removed.