Meterythrops intermedius, Fukuoka & Murano, 2006
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publication ID |
https://doi.org/ 10.1080/00222930600956858 |
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persistent identifier |
https://treatment.plazi.org/id/860DB34F-2717-D52C-CDB1-1EC4FE57FC2C |
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treatment provided by |
Carolina |
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scientific name |
Meterythrops intermedius |
| status |
sp. nov. |
Meterythrops intermedius sp. nov.
( Figures 8 View Figure 8 , 9 View Figure 9 , 12G View Figure 12 )
Material examined
Holotype: NSMT-Cr 16758, male (18.3 mm), dissected, S139A, Shelikof Strait , Alaska, sledge, date unknown . Paratypes: NSMT-Cr 16759, one female (13.3 mm), dissected, data same as holotype; NMST-Cr 16760, one male (17.8 mm) and two females (14.4 and 14.5 mm), data same as holotype .
Description
Body robust, constricted between thorax and abdomen. Thoracic somites without sternal processes. Anterior four abdominal somites gradually decreasing in length, fifth somite subequal with fourth, sixth somite 1.5–1.6 times as long as fifth; in male first to fourth somites with small, blunt, papilliform process along ventral median line, these processes gradually becoming smaller posteriorly.
Carapace produced anteriorly into rounded rostral plate, extending to or slightly beyond base of antennular peduncle; anterolateral corner pointed; posterior margin emarginate, leaving last thoracic somite exposed dorsally ( Figure 8A, B View Figure 8 ).
Eyes as long as broad, not depressed dorsoventrally; cornea occupying half of eye; eyestalk with papilla on dorsal surface ( Figure 8A, B View Figure 8 ).
Antennular peduncle more robust in male than in female, distal segment slightly longer than combined length of proximal two segments, 1.1 times as long as broad in male, and 1.3 times as long as broad in female, with well-developed appendix masculina in male ( Figure 8A, B View Figure 8 ).
Antennal scale extending beyond apex of antennular peduncle by one-fourth of its length, 3.3 times as long as broad, with suture near apex; lateral margin smooth, terminating in strong spiniform process; apical lobe occupying one-fourth of entire length of scale, 1.2 times as long as broad at base, three to four times longer than lateral terminal process ( Figure 8 View Figure 8 A–C). Antennal peduncle extending to distal two-fifths of scale in male and distal four-ninths in female ( Figure 8C View Figure 8 ). Antennal sympod with spiniform process at lateral distal angle ( Figure 8C View Figure 8 ).
Labrum without frontal spiniform process.
Mandibular palp: second segment armed with numerous setae on lateral margin; third segment half to four-sevenths of second segment in length ( Figure 8D View Figure 8 ).
Maxillule: lateral lobe armed with 13 strong spines on distal margin and with four long setae on ventral surface, small lobe present in middle of lateral margin ( Figure 8E View Figure 8 ).
Maxilla: second segment of endopod twice as long as broad, armed with long setae on margin; exopod extending to distal margin of proximal endopodal segment ( Figure 8F View Figure 8 ).
Endopod of first thoracopod short, robust; dactylus with strong terminal claw ( Figure 8G View Figure 8 ). Endopod of second thoracopod long; merus 5.3–6 times as long as broad; carpopropodus five-sevenths of merus in length; dactylus with strong terminal claw ( Figure 8H View Figure 8 ). Endopod of third to eighth thoracopods with three-subsegmented carpopropodus, middle subsegment separated from proximal one by oblique articulation and from distal one by transverse articulation ( Figure 9A View Figure 9 ). Exopod of thoracopods with 14- to 16-segmented flagellum; basal plate with blunt lobule at lateral distal corner ( Figures 8G View Figure 8 , 9A View Figure 9 ).
Penis 2.6 times as long as broad in lateral view, armed with about six short setae on posterolateral margin, distally bilobed, anterior lobe overreaching apex of posterior one, posterior lobe armed with 10 long, mesially curved setae ( Figure 9B View Figure 9 ).
Female with tuft of setae on coxa of sixth thoracopod and with developed oostegite on seventh and eighth thoracopods; oostegite on seventh thoracopod with small lobe.
All pleopods of male developed, biramous ( Figure 9 View Figure 9 C–E). First pleopod with endopod reduced to unsegmented lobe and with exopod 14-segmented ( Figure 9C View Figure 9 ). Second to fourth pleopods with 12-segmented endopod and 13-segmented exopod slightly shorter than endopod ( Figure 9D View Figure 9 ). Endopod of fifth pleopod nine-segmented, ultimate and penultimate segments lengthened, penultimate segment 2.7 times as long as broad, ultimate segment 3.4 times as long as broad, armed on distal end with two long, modified setae, mesial seta slightly longer than lateral one, these setae thicker than other normal setae, and furnished densely with setules on distal two-fifths except for distal tenth naked ( Figure 9E, F View Figure 9 ). Exopod of fifth pleopod 10-segmented, shorter than endopod, ultimate segment armed with normal plumose seta and long, modified seta, latter seta thicker, 1.7 times longer than former, spinulated on distal third except for distal tenth naked ( Figure 9E View Figure 9 ). Pseudobranchial lobe of male pleopods rectangular ( Figure 9 View Figure 9 C–E). All female pleopods reduced to unsegmented single lobe, increasing in length towards posterior pair ( Figure 9 View Figure 9 G–I).
Endopod of uropod overreaching distal end of telson for one-fourth of its length, armed on mesial ventral margin from statocyst region to distal third with 12–18 small spines, which become sparser posteriorly ( Figure 9J, K View Figure 9 ). Exopod of uropod 1.4 times as long as endopod ( Figure 9J View Figure 9 ).
Telson elongated triangular with narrowly truncated apex, 1.3 times as long as last abdominal somite, 1.8–1.9 times as long as maximum width; lateral margin slightly concave in proximal half and almost straight in distal half, without spines throughout but serrated barely on distal third; apex armed with median pair of plumose setae and two pairs of spines, mesial pair 1.3–1.4 times as long as lateral pair ( Figure 9J View Figure 9 ).
Etymology
The specific name is derived from the Latin intermedius referring to the intermediate size of the eyes between M. microphthalmus and M. robustus .
Remarks
Meterythrops intermedius is similar to M. microphthalmus and M. robustus by possessing an elongated triangular telson and a uropodal endopod with a row of spines on the mesial ventral margin. However, M. intermedius is distinguished from M. microphthalmus as follows. (1) The eyes of M. intermedius are larger than those of M. microphthalmus . (2) The apical lobe of the antennal scale in M. intermedius is one-fourth the length of the scale and 1.2 times longer than it is broad, whereas in M. microphthalmus it is three-sevenths of the scale in length and twice longer than it is broad at the base. (3) The lateral lobe of the maxillule bears four setae on the ventral surface in M. intermedius compared to three setae in M. microphthalmus . (4) The mesial margin of the uropodal endopod is armed with 12–18 spines from the statocyst region to the distal third in M. intermedius , compared to 22–28 spines from the statocyst region to the distal fourth in M. microphthalmus . Meterythrops intermedius differs from M. robustus by having eyes that are not flattened and a smaller number of spines on the uropodal endopod (12–18 in M. intermedius and 22–37 in M. robustus ).
Banner (1948) reported an intermediate form between M. robustus and M. microphthalmus in the size and shape of the eyes in Meterythrops specimens collected from the northeastern Pacific. The eye characters in M. intermedius most likely correspond to those of Banner’s intermediate form.
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