Research Article |
Corresponding author: Rony Huys ( rjh@nhm.ac.uk ) Academic editor: Kai Horst George
© 2017 Fang-hong Mu, Rony Huys.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Mu F-h, Huys R (2017) New Mesopsyllus species from the Bohai Sea, China, re-evaluation of the validity of Vibriopsyllus Kornev & Chertoprud, 2008 and proposal of Sympodella gen. n. (Copepoda, Harpacticoida, Canthocamptidae). ZooKeys 718: 1-33. https://doi.org/10.3897/zookeys.718.13700
|
Two new species of the genus Mesopsyllus Por, 1960 (Canthocamptidae) are described from the Bohai Sea, eastern China. Mesopsyllus dimorphus sp. n. and M. spiniferus sp. n. differ from their congeners by the presence of two instead of three outer spines on P2–P3 exp-3. They can be differentiated from each other by (1) number of inner setae on P3–P4 enp-2; (2) anterior margin of antennulary segment 7 of male; (3) ornamentation of male abdomen; (4) sexual dimorphism on P2 endopod and P3–P4 exp-3; and (5) differences in length of setae on male P5. Some observations in the original description of M. atargatis Por, 1960 are reinterpreted and the type material of M. secundus (Wells, 1965) is re-examined. Comparison between the type species of Vibriopsyllus Kornev & Chertoprud, 2008 and the four known species of Mesopsyllus shows the former as a junior subjective synonym of the latter. Consequently, Vibriopsyllus curviseta Kornev & Chertoprud, 2008 is formally transferred to Mesopsyllus as M. curvisetus (Kornev & Chertoprud, 2008), comb. n. A key to species and an updated generic diagnosis of Mesopsyllus are presented.
The taxonomic status of the genus Carolinicola Huys & Thistle, 1989 is re-evaluated. The characters of its type species, C. trisetosa (Coull, 1973), indicate that the latter (and – by inference – the genus Carolinicola) should remain in the Danielsseniinae. Carolinicola galapagoensis Mielke, 1997 is fixed as the type species of a new genus Sympodella gen. n. and placed in the Hemimesochrinae (Canthocamptidae) as the putative sistertaxon of Pusillargillus Huys & Thistle, 1989. The relationships and potential synonymy of the genera Pyrocletodes Coull, 1973, Perucamptus Huys & Thistle, 1989 and Isthmiocaris George & Schminke, 2003 are briefly discussed.
Carolinicola , Hemimesochrinae , Isthmiocaris , Mesopsyllus dimorphus sp. n., M. spiniferus sp. n., Perucamptus , Pyrocletodes , Sympodella gen. n.
Specimens were collected during 1998–1999 from the central region and the strait of the Bohai Sea (Fig.
All drawings were prepared using a camera lucida on a Zeiss Axioskop differential interference contrast microscope. The terminology for body and appendage morphology follows that of Huys and Boxshall (1991) and
Rostrum not defined at base; triangular. Antennule 6-segmented in ♀, with aesthetasc on segments 4 and 6; 8-segmented, haplocer with geniculation between segments 6 and 7 in ♂; with enlarged modified spines on segments 2–3 and 6 in ♀, and segments 2–4 in ♂. Antenna with one abexopodal seta on allobasis; exopod 1-segmented, with 2–3 setae. Mandibular palp with short basis (with one seta), 1-segmented endopod (with four setae) and vestigial unisetose exopod. Maxillule with rami incorporated into basis. Maxilla with two endites on syncoxa; endopod discrete. Maxilliped with well developed seta on syncoxa. Swimming legs of ♀ with 3-segmented exopods and 3- (typical condition in P1) or 2-segmented endopods (P2–P4, unusual condition in P1). Setal formulae of P1–P4 as follows:
Thoracopod | Exopod | Endopod |
P1 | 0.1.022 | 1.1.111 or 1.111 |
P2 | 0.1.12[2–3] | 1.[1–2]21 |
P3 | 0.1.22[2–3] | 1.[1–2]21 (♀) or 1.1+apo.020 (♂) |
P4 | 0.1.[1–2]2[2–3] | 1.[1–2]21 |
Inner seta of P1 enp-1 short, not recurved backwardly and dorsally; outer spine of P1 exp-1 not enlarged; outer exopodal spines of P1–P4 sparsely bipinnate, in P2–P4 without elongate pinnules in proximal half. P2 endopod occasionally with sexual dimorphism (inner seta of enp-1 distinctly shorter in ♀; enp-2 with additional inner seta in ♀). P3 endopod 3-segmented in ♂; enp-2 with inner seta and slender terminal apophysis; enp-3 with two apical setae. P4 enp-1 and sometimes enp-2 and exp-3 with slight sexual dimorphism (setal lengths). P4 exp-3 occasionally sexually dimorphic (length of proximal inner seta). P5 with discrete exopod and baseoendopod; exopod small, with 3–5 and 4–5 elements in ♀ and ♂, respectively; endopodal lobe with four and two elements in ♀ and ♂, respectively. Sixth pair of legs asymmetrical in ♂, unarmed. Caudal ramus short, with six setae.
Mesopsyllus atargatis Por, 1960 (by monotypy).
Mesopsyllus secundus (Wells, 1965), M. curvisetus (Kornev & Chertoprud, 2008), comb. n., M. dimorphus sp. n., M. spiniferus sp. n.
Eastern China, Strait of the Bohai Sea, sampling locality D5 (38°15'N, 121°15'E); 37.0 m depth; very fine sand (Fig.
Material examined. Holotype: adult ♂ dissected on 13 slides (
Location and environmental characteristics of sampling stations in the Bohai Sea (Md = median grain size).
Station | Lattitude / Longitude | Depth (m) | Sediment type | Md |
---|---|---|---|---|
A1 | 37°44'N, 121°35'E | 20.5 | coarse silt | 5.42 |
A2 | 38°00'N, 121°35'E | 42.8 | sandy silt | 5.4 |
A4 | 38°25'N, 121°35'E | 50.8 | very fine sand | 3.87 |
C4 | 38°00'N, 121°15'E | 23.8 | sandy silt | 5.19 |
D3 | 38°15'N, 119°44'E | 22.9 | coarse silt | 5.73 |
D4 | 38°15'N, 120°15'E | 24.3 | silty sand | 4.96 |
D5 | 38°15'N, 121°15'E | 37.0 | very fine sand | 3.94 |
E3 | 38°30'N, 119°30'E | 26.0 | clayey silt | 7.63 |
Body length 220–280 µm (n = 3, mean = 250 µm). Body slightly tapering posteriorly as in ♀ (compare Fig.
Body ornamentation (Fig.
Mesopsyllus dimorphus sp. n.: A urosome ♂, dorsal B urosome ♂, lateral C urosome ♂, ventral D caudal ramus ♂, ventral (inset showing spinules around base of seta II) E P5 ♂, anterior F rostrum ♂, dorsal G P5 ♀, anterior (minute setae on exopod and endopodal lobe indicated by arrow) H anal operculum ♀. [Caudal rami in A–C not drawn at full length]. A–F based on holotype (
Rostrum (Fig.
Antennule (Fig.
Mesopsyllus dimorphus sp. n.: A antennule ♂ (armature omitted), ventral B antennule ♂ (disarticulated), ventral C antennule ♀ (armature omitted), ventral D antennule ♀ (disarticulated), ventral A–B based on holotype (
Antenna (Fig.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Swimming legs with 3-segmented exopods and 3- (P1, P3) or 2-segmented endopods (P2, P4).
Mesopsyllus dimorphus sp. n. (♂): A antenna (abexopodal seta on allobasis indicated by arrow) B mandible (with palp disarticulated) C maxillule (with palp disarticulated) D maxilla E maxilliped (vestigial seta on endopod indicated by arrow). All drawings based on holotype (
P1 (Fig.
P2 (Fig.
Mesopsyllus dimorphus sp. n.: A P1 ♂, anterior (outer basal seta indicated by arrow in inset) B P2 ♂, anterior (outer basal seta indicated by arrow) C P2 endopod ♀, anterior (vestigial setae along inner margin and hook-like process along outer margin indicated by arrows) A–B based on holotype (
P3 (Fig.
P4 (Fig.
Mesopsyllus dimorphus sp. n.: A P3 ♂, anterior B P4 ♂, anterior C P3 endopod ♀, anterior (vestigial seta indicated by arrow) D P3 exp-3 ♀ (apical and outer elements not drawn at full length), anterior E P4 endopod and distal portion of basis ♀, anterior F P4 exp-3 ♀ (apical and outer elements not drawn at full length), anterior A–B based on holotype (
P5 (Fig.
P6 (Fig.
Caudal ramus (Fig.
Body length 240–330 µm (n = 10, mean = 292 µm). General body shape (Fig.
Urosome (Fig.
Antennule (Fig.
P2 (Fig.
P3 (Fig.
P4 (Fig.
Seta and spine formulae of P1–P4 as follows:
Thoracopod | Exopod | Endopod |
P1 | 0.1.022 | 1.1.111 |
P2 | 0.1.122 | 1.121 (1.221) |
P3 | 0.1.222 | 1.1+apo.020 (1.121) |
P4 | 0.1.222 | 1.121 |
Formulae in parentheses denote female condition.
P5 (Fig.
One female specimen shows an asymmetrical armature pattern on P4 exp-3, having one inner seta on one side and two on the other.
The species name is derived from the Greek dis, meaning twice, and morphe, meaning form, and alludes to the sexual dimorphism on P2–P4.
Eastern China, strait of Bohai Sea, sampling locality C4 (38°00'N, 121°15'E); 23.8 m depth; sandy silt (Fig.
Holotype: adult ♂ dissected on 16 slides (
Since the new species is very similar to M. dimorphus its description is largely restricted to those features which are different.
Body length 280–320 µm (n = 2, mean = 300 µm). Body covered with pattern of minute pimples (not figured). Urosomal ornamentation (Fig.
Antennae, mouthparts, P6, caudal rami and rostrum as in M. dimorphus.
Antennule (Fig.
P1 with different spinular ornamentation on coxa, as figured for ♀ (Fig.
P2 (Fig.
Mesopsyllus spiniferus sp. n.: A antennule ♂, distal five segments, showing modified elements on segments 6–7 (armature elements on other segments omitted or not drawn at full length), ventral B antennule ♂, distal three segments, showing modified elements on segments 6–7 (elements on segment 8 omitted), anterior C P2 ♂, anterior D P1 ♀, anterior A–C based on holotype (
P3 (Fig.
P4 (Fig.
Seta and spine formula of P1–P4 as follows:
Thoracopod | Exopod | Endopod |
P1 | 0.1.022 | 1.1.111 |
P2 | 0.1.122 | 1.221 |
P3 | 0.1.222 | 1.1+apo.020 (1.221) |
P4 | 0.1.222 | 1.221 |
Formulae in parentheses denote female condition.
P5 (Fig.
Body length 340–350 µm (n = 2, mean = 345 µm). Body covered with pattern of minute pimples (not figured). Sexual dimorphism in antennule, P3–P5, and urosomal segmentation and ornamentation.
Antennule, P5, and urosomal segmentation and ornamentation as in M. dimorphus.
P3 (Fig.
P4 (Fig.
Mesopsyllus spiniferus sp. n.: A P3 ♂, anterior B P4 ♂, anterior C P3 endopod ♀, anterior (vestigial seta on enp-1 indicated by arrow) D P4 endopod ♀ (reduced seta on enp-1 indicated by arrow; setae on enp-2 not drawn at full length), anterior E P5 ♂, anterior (minute setae on exopod and endopodal lobe indicated by arrow) A–B, E based on holotype (
Both female specimens display right-left asymmetrical setal formulae on one pair of swimming legs. In the first specimen P3 enp-2 displays only one inner seta on one side and two on the other; in the second specimen P4 exp-3 exhibits one inner seta on one side but two on the other. The male holotype is aberrant in leg 1 with one side represented by a single segment with two distal setae and one outer spine (compare typical condition observed in dissected ♀ paratype: Fig.
The species name alludes to the two spiniform elements on segment 7 of the male antennule.
Antennulary characters (# = number of segments; ae = segment on which proximal aesthetasc is located; sp = presence/absence of enlarged spinulose spines on segments 2–3) and P1–P5 armature formulae of species of Mesopsyllus Por, 1960 (M.) and related genera (Ba. = Bathycamptus Huys & Thistle, 1989; Bo. = Boreolimella Huys & Thistle, 1989; Ha. = Hanikraia Huys, 2009; He. = Hemimesochra Sars, 1920; Ps. = Psammocamptus Mielke, 1975; Pu. = Pusillargillus Huys & Thistle, 1989; S. = Sympodella gen. n.; ? = condition unknown).
A1 ♀ | P1 | P2 | P3 | P4 | P5 ♀ | P5 ♂ | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
# | ae | sp | exp | enp | exp | enp | exp | enp | exp | enp | rami | exp | benp | exp | benp | |
M. atargatis | 6 | 4 | + | 0.1.022a | 1.1.111 | 0.1.123 | 1.121b | 0.1.223 | 1.121 | 0.1.123c | 1.121 | free | 3 | 4d | ? | ? |
M. curvisetus | 6 | 4 | + | 0.1.022 | 1.1.111e | 0.1.123 | 1?.221f | 0.1.223 | 1.221 | 0.1.222 | 1.121 | free | 4 | 4 | 5 | 2 |
M. dimorphus | 6 | 4 | + | 0.1.022 | 1.1.111 | 0.1.122 | 1.221 | 0.1.222 | 1.121 | 0.1.222 | 1.121 | free | 3 | 4 | 4 | 2 |
M. secundus | 6 | 4 | + | 0.1.022g | 1.111h | 0.1.123i | 1.121 | 0.1.223 | 1.121 | 0.1.223 | 1.121 | free | 5 | 4 | 4 | 2 |
M. spiniferus | 6 | 4 | + | 0.1.022 | 1.1.111 | 0.1.122 | 1.221 | 0.1.222 | 1.221 | 0.1.222 | 1.221 | free | 3 | 4 | 4 | 2 |
Ba. minutus | ? | ? | + | 0.1.022 | 1.1.111 | 0.1.122 | 1.121 | 0.1.222 | ? | 0.1.222 | ? | ? | ? | ? | 5 | 2 |
Ba. eckmani | 7 | 4 | + | 0.1.022 | 1.1.111 | 0.1.122 | 1.121 | 0.1.223 | 1.121 | 0.1.223 | 1.121 | fused | 4 | 4 | 5 | 2 |
Ps. axi | (7)j | 4 | + | 0.1.022k | 1.1.111k | 0.0.022 | (1).111l | 0.0.122 | (1).121l | 0.(1).122l | 1.121 | fused | 3 | 4 | 4 | 2 |
Ps. galapagoensis | 7 | 4 | + | 0.1.022 | 1.1.111 | 0.1.122 | 1.111 | 1.1.122 | 1.121 | 0.1.122 | 1.121 | fused | 3 | 4 | 4 | 2 |
He. clavularis | 5 | 3 | + | 0.0.022m | 1.111 | 0.1.123 | 1.221 | 0.1.223 | 1.321 | unknownn | unknownn | fusedo | 4 | 4 | ? | ? |
Bo. dubia | 5p | 3 | + | 0.1.022q | 1.211q | 0.1.122 | 1.121 | 0.1.122 | 1.121 | 0.1.122 | 1.121 | fused | 4 | 4 | ? | ? |
Bo. nympha | 5 | 3 | + | 0.1.022 | 1.211r | 0.1.122 | 1.221 | 0.1.222 | 1.221 | 0.1.222 | 1.221 | fused | 4 | 4 | ? | ? |
Ha. derketo | 6s | 3 | – | 0.0.022m | 1.1.111 | 0.1.123t | 1.1.111 | 0.1.223t | 1.1.121 | 0.1.223 | 1.221 | free | 4 | 4 | ? | ? |
Pu. nixe | 5 | 3 | – | 0.1.022 | 1.211 | 0.1.122 | 1.221 | 0.1.222 | 1.221 | 0.1.222 | 1.221 | free | 5 | 4 | 5 | 2 |
S. galapagoensis | 6 | 3 | – | 0.1.022m | 1.1.111 | 0.1.122 | 1.111 | 0.1.222 | 1.121 | 0.1.222 | 1.121 | fused | 5 | 4 | 6 | 2 |
The two Chinese species described herein, M. dimorphus and M. spiniferus, differ from their congeners by the presence of two instead of three outer spines on P2–P3 exp-3. They can be differentiated from each other by the following combination of characters: (1) number of inner setae on P3–P4 enp-2 (one in M. dimorphus, two in M. spiniferus); (2) anterior margin of antennulary segment 7 of male (with two spiniform elements in M. spiniferus; with three conical elements in M. dimorphus); (3) ornamentation of male urosome (second abdominal somite with paired dorsal spinular patches in M. spiniferus; absent in M. dimorphus); (4) presence/absence of sexual dimorphism on P2 endopod, P3–P4 exp-3 (present in M. dimorphus; absent in M. spiniferus); and (5) differences in length of setae on male P5.
The genus Mesopsyllus is so far restricted to the Northern Hemisphere.
Caution must be exercised while attempting to identify species since some original descriptions contain inaccuracies and anomalous setation patterns in legs 1–5 are known to exist in some species so that observations based on a single specimen may not always reveal the usual (typical) condition. Members of the genus Mesopsyllus are typically small to very small and most original descriptions were based on very few specimens (Table
Body length (in μm) and number of specimens (#) used in original descriptions of Mesopsyllus species.
Species | ♀ (μm) | ♂ (μm) | # ♀♀ | # ♂♂ |
---|---|---|---|---|
M. atargatis | 470 | ? | 4 | ? |
M. secundus | 400 | 340 | 1 | 1 |
M. dimorphus | 240–330 | 220–280 | 11 | 3 |
M. spiniferus | 340–350 | 280–320 | 2 | 2 |
M. curvisetus | 405 | not given | 1 | 1 |
1 | Rostrum with setulose anterior margin; P2 enp-2 with one inner seta; P4 exp-3 with three outer spines | 2 |
– | Rostrum with smooth anterior margin; P2 enp-2 with two inner setae; P4 exp-3 with two outer spines | 3 |
2 | P1 endopod 3-segmented; P4 exp-3 with one inner seta | M. atargatis Por, 1960 |
– | P1 endopod 2-segmented; P4 exp-3 with two inner setae | M. secundus (Wells, 1965) |
3 | P2–P3 exp-3 with two outer spines; P5 ♀ exopod with three elements; P5 ♂ exopod with four elements | 4 |
– | P2–P3 exp-3 with three outer spines; P5 ♀ exopod with four elements; P5 ♂ exopod with five elements | M. curvisetus (Kornev & Chertoprud, 2008), comb. n. |
4 | P3–P4 enp-2 ♀ with one inner seta; P2 endopod and P3–P4 exp-3 displaying sexual dimorphism as illustrated in Fig. |
M. dimorphus sp. n. |
– | P3–P4 enp-2 ♀ with two inner setae; P2 endopod and P3–P4 exp-3 without such sexual dimorphism; second abdominal somite with paired dorsal spinular patches in ♂ | M. spiniferus sp. n. |
Based on irreconcilable differences in the morphology of the rostrum, antenna, mandible and caudal rami,
Rostrum defined at base; triangular. Antennule 6-segmented in ♀, with aesthetasc on segments 3 and 6; 9-segmented, haplocer with geniculation between segments 7 and 8 in ♂; without enlarged modified spines in both sexes. Antenna with two abexopodal setae on allobasis; exopod 1-segmented, with three setae. Mandibular palp with elongate basis (with one seta), 1-segmented endopod (with four setae) and vestigial unisetose exopod. Maxillule with rami incorporated into basis. Maxilla with two endites on syncoxa; endopod fused to allobasis. Maxilliped with well developed seta on syncoxa. Swimming legs of ♀ with 3-segmented exopods and 3- (P1) or 2-segmented endopods (P2–P4); armature formulae as in Table
Carolinicola galapagoensis Mielke, 1997 = Sympodella galapagoensis (Mielke, 1997) (by original designation).
The name is derived from the Greek syn, sym, meaning together, and pous (genitive podos), meaning foot, and refers to the fused condition of leg 5 in both sexes. Gender: feminine.
Salient characters of members of Pyrocletodes Coull, 1973b, Perucamptus Huys & Thisle, 1989 and Isthmiocaris George & Schminke, 2003. [A1 ♀: number of segments and position of aesthetasc (ae); A2exp = number of setae on antennary exopod; P3 enp: apo = apophysis; P5: b = outer basal setae, sp = spine(s); –– = absent].
Species | sex | A1 ♀ | A2 | P1 | P2 | P3 | P4 | P5 | ||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
exp | exp | enp | exp | enp | exp | enp | exp | enp | ||||
Pyrocletodes desuramus | ♀ | 5 (ae on 3) | 2 | 0.1.022 | 1.020 | 0.1.122 | –– | 0.1.122 | –– | 0.1.122 | –– | b + 2 |
Pyrocletodes coulli | ♀ | 5 (ae on 3) | 3 | 0.0.021 | 1.020 | 0.1.122 | –– | 0.1.122 | –– | 0.1.122 | –– | b + 2 |
Perucamptus rapiens | ?† | 5 (ae on 3) | 3 | 0.0.022 | 1.121 | 0.1.122 | 0.121 | 0.1.122 | 0.020 | 0.1.122 | –– | b+2 + 2 |
Isthmiocaris longitelson | ♀ | 6 (ae on 4) | 3 | 0.021 | 010 | 0.020 | –– | 0.1.021 | –– | 0.021 | –– | 1 |
♂ | 3 | 0.021 | 010 | 0.021 | –– | 0.1.021 | 0.apo.020 | 0.0.021 | 0.021 | b + 2 + sp | ||
Isthmiocaris laurae | ♀ | 6 (ae on 3) | 3 | 0.0.022 | 0.011 | 0.0.022 | 020 | 0.0.022 | 020 | 0.0.022 | 010 | b + 2 |
♂ | 3 | 0.0.022 | 0.021 | 0.1.122 | 1.321 | 0.1.222 | 1.apo.020 | 0.1.222 | 0.221 | b + 5 + 2sp | ||
CV♀ | ? | ? | 0.0.022 | 0.021 | 0.0.022 | 0.020 | 0.0.022 | 0.020 | 0.0.022 | 010 | ? | |
CV♂ | ? | ? | 0.0.022 | 0.021 | 0.1.122 | 0.121 | 0.1.122 | 0.0.021 | 0.1.022 | 0.011 | ? |
The present work was carried out under a Royal Society Royal Fellowship awarded to F.-h. Mu and also funded jointly by the National Science Foundation of China (41576153; 41106122; 40906063) and National Science Foundation of Shandong Province (ZR2010CM013). Dr Kate Shalaeva (AKT Solutions Ltd, Rayleigh, U.K.) is gratefully acknowledged for her help in translating