Mesochra huysi Suárez-Morales & Fuentes-Reinés 2015
- Dataset
- A new species of Mesochra (Copepoda: Harpacticoida: Canthocamptidae) from a coastal system of northern Colombia with a key to the American species
- Rank
- SPECIES
- Published in
- Suárez-Morales, Eduardo, Fuentes-Reinés, Juan M. (2015): A new species of Mesochra (Copepoda: Harpacticoida: Canthocamptidae) from a coastal system of northern Colombia with a key to the American species. Journal of Natural History 49 (45): 2969-2982, DOI: 10.1080/00222933.2015.1085604
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Hexanauplia
- order
- Harpacticoida
- family
- Canthocamptidae
- genus
- Mesochra
- species
- Mesochra huysi
description
(Figures 1 – 4)
description
Description of female Body fusiform, slightly tapering posteriorly (Figure 1 A). Habitus in dorsal view as in Figure 1 A, in lateral view as in Figure 1 B. Total body length, measured from tip of rostrum to posterior margin of caudal rami ranging from 336 to 403 μm (average 374 μm, n = 10; holotype: 336 μm). Rostrum distinct, flat in dorsal view, subtriangular, with rounded tip in lateral view. Dorsal surface of cephalosome and free prosomites with incised hyaline frill. Transverse row of microspinules on dorsal surface of first three pedigerous free somites, fourth free somite without dorsal spinulation. Genital double-somite with vestigial suture visible in ventral view, first genital somite with row of small spinules on mid-dorsal surface and posterior frill; second genital somite with transverse row of spinules and weak frill along posterior margin on dorsal surface (Figure 1 A); lateral and ventral margins with larger set of spinules (Figures 1 B, 4 D). First and second free urosomites with mid-dorsal row of minute spinules and row of spinules along posterior margin, spinules increasing in size laterally and ventrally (Figure 4 D). Anal somite with separate transverse rows of minute spinules on mid-dorsal surface, distal margin with short row of spinules along insertion of caudal rami. Anal operculum rounded, ornamented with slender spinules (Figure 4 F). Caudal rami (Figure 4 F) subquadrate, with six setae, with spinules along ventral surface. Seta II with accompanying spinules, and about as long as caudal rami, seta III 1.2 times as long as seta II, seta V about 4.2 times longer than seta IV and seta VII as long as seta II. Antennule. 6 - segmented, with distal row of 8 – 9 spinules on first segment. Aesthetasc on third segment reaching well beyond last segment, this segment with small outer spine (Figure 1 C). Armature formula as follows: 1 (0), 2 (8), 3 (7 + 1 ae), 4 (1), 5 (1), 6 (9 + ae). Antenna. Allobasis with two short setae, one proximal and one on subdistal position. Exopod short, cylindrical, 1 - segmented, with three unequally long terminal setae, middle setae being longest. Endopod 1 - segmented, inner margin with row of spinules on proximal 1 / 3 of segment, lateral armature represented by two subequal spines plus two outer spinules distally. Distal margin with five setal elements, two spines, two geniculate setae and one stout seta furnished with spinules (Figure 2 A). Mandible. Gnathobase with strong, wide teeth and one plumose dorsal seta, basis elongate, armed with one basipodal seta and row of long spinules. Endopodal lobe armed with four setae (Figure 2 B). Maxillule. Praecoxal arthrite with two setae. Distal margin with five strong curved claws and four setal elements. Coxa and basis partially fused; coxal endite with two slender setae. Basis with one seta. Endopodal and exopodal rami fused to basis, each represented by four and four setae, respectively (Figure 2 C). Maxilla. Syncoxa ornamented with row of minute spinules, with two endites, each with three setal elements, two of them wide-based, spinulated, the other slender. Basis forming strong claw with one slender seta. Endopod represented by three slender setae (Figure 2 D). Maxilliped. Syncoxa furnished with subdistal row of spinules, with inner distal plumose seta reaching half-length of basis. Basal segment robust, ornamented with longitudinal row of long spinules from proximal margin to distal 1 / 3 of segment; distal outer margin with row of small spinules. Endopod represented by weakly curved claw with an accompanying proximal seta (Figure 2 E). P 1 (Figure 3 A). Protopod ornamented with row of spinules along posterior margin, coxa with proximal rows of minute spinules, additional rows also along outer and posterior margins. Basis with curved row of spinules on middle surface; segment with strong spinules along distal margin, particularly near insertion of endopod; with outer and inner spine, latter stout, straight, reaching about 1 / 3 of ENP 1. ENP 2 - segmented, longer than EXP, first segment reaching well beyond length of EXP, about 7 times as long as wide, inner seta on first segment inserted almost at the half of segment; second segment ornamented with outer row of spinules, armed with three elements, inner subdistal one shorter than segment. EXP 3 - segmented, reaching beyond insertion of inner seta on ENP 1, EXP 1 and EXP 2 without inner setae, third segment with four elements, two of them geniculate. P 2 (Figure 3 B). Coxa and basis with weaker ornamentation than in P 1. Basis with slender outer basipodal seta. ENP 2 - segmented, shorter than EXP, not reaching midlength of EXP 3. ENP 1 with outer seta, without inner seta, ENP 2 with five setal elements. EXP 3 - segmented, EXP 1 without inner seta, EXP 2 with short inner seta, EXP 3 with five elements. P 3 (Figure 3 C). Coxa and basis with weaker ornamentation than in P 1, as in P 2. Basis with slender outer basipodal seta. ENP 2 - segmented, barely reaching distal end of EXP 2; ENP 1 with outer seta, without inner seta; ENP 2 with five elements. EXP 3 - segmented, EXP 1 and EXP 2 without inner setae, third segment with six elements. P 4 (Figure 3 D). Coxa and basis with weaker ornamentation than in P 1, as in P 2 and P 3. Basis with slender outer basipodal seta. ENP 2 - segmented, short, reaching only proximal 1 / 3 of EXP 1; ENP 1 with inner seta, without outer seta; ENP 2 with five setal elements. EXP 3 - segmented, EXP 1 with inner seta, third segment with six elements, one of them a thickened pectinate seta (arrowed in Figure 3 D). P 5 (Figure 4 C). Baseoendopod with single seta. EXP rounded, shorter than endopodal lobe, with five elements, inner middle distal seta longer than inner distal spine. Endopodal lobe armed with five elements (Figure 4 E). Setal formula (Arabic numerals = setae, Roman numerals = spines) of P 1 – P 4 as in Table 1. P 6 (Figure 1 D) vestigial, represented by small crescent-shaped lobe (Figure 1 D), with one short seta. Description of male Habitus resembling that of female except for narrower prosome and urosome (Figure 4 D). Smaller than female, total body length, measured from tip of rostrum to posterior margin of caudal rami ranging from 263 to 315 μm (average 289 μm, n = 5; holotype: 263 μm). Somitic ornamentation as in female. Urosomites 1 – 3 with ventral row of large spinule along posterior margin (Figure 4 D) which are coarser than those along the dorsal surface. Row of spinules along ventral margin of preanal somite with discontinuous row of spinules, as opposed to female, with continuous such row. Anal somite as in female, with smaller spinules on ventral surface and along insertion of caudal rami. Armature of caudal rami as in female. Antennule. Geniculate, 8 - segmented (Figure 4 A). Mouthparts, P 1, P 2, and P 4 as in female. P 3 (Figure 4 B). Coxa and basis with weaker ornamentation than in female P 1, as in female P 2. Basis with slender outer basipodal seta. ENP 3 - segmented, shorter than EXP, reaching proximal 1 / 4 of EXP 3; ENP 1 unarmed, ENP 2 without inner seta but with inner sinuous apophysis reaching apical margin of ENP 3; ENP 3 with two distal setae and a single claw-like or flame-shaped (Gómez and Fiers 1997) element (arrowed in Figure 4 B). EXP 3 - segmented, EXP 1 and EXP 2 with strong, long outer spine. EXP 2 ornamented with noticeably strong, wide-based spinules (double arrow in Figure 4 B). EXP 3 with 6 setal elements, two of them on inner margin (Figure 4 B). P 5 (Figure 4 C). Baseoendopod with cluster of spinules at point of insertion of seta. EXP rounded, reaching slightly beyond distal margin of endopodal lobe, with six setal elements, middle seta being longest. Endopodal lobe ornamented with few small spinules along inner and outer margins, armed with two spines of unequal length.
discussion
Remarks Mesochra huysi sp. nov. most closely resembles M. parva Thomson, 1946, M. pacifica Gómez and Fiers, 1997, and M. pseudoparva Gómez and Fiers, 1997; they share an identical armature formula of P 1 – P 4. The female fifth leg armature, with five setal elements on the fifth leg EXP also resembles that of M. parva (Hamond 1971, fig. 13), M. pacifica (Gómez and Fiers, 1997, fig. 5 b) and M. pseudoparva (Gómez and Fiers 1997, fig. 11 b). However, M. huysi sp. nov. can be separated from these species when comparing the insertion of the inner seta P 1 ENP 1. It is at the same level of the distal margin of P 1 EXP 3 in both M. parva (Hamond 1971, fig. 14) and M. pseudoparva (Gómez and Fiers 1997, fig. 10 a), it is inserted beyond the distal end of P 1 EXP 3, in the distal 1 / 3 of the ENP 1 in M. pacifica (Gómez and Fiers 1997, fig. 4 a), while in M. huysi this seta is at the level of half the length of P 1 EXP 3 (Figure 3 A). Also, the length / width ratio of the P 1 ENP 1 is different in these species: is similar in both M. parva (from Hamond 1971, fig. 14) and M. pseudoparva (from Gómez and Fiers 1997, fig. 10 a), 6.0 in M. pacifica (from Gómez and Fiers 1997, fig. 4 a) and 5.0 in the new species, M. huysi. The length ratio of the inner seta of P 1 ENP 2 / length of P 1 ENP 2 reveals some additional differences among these species. The seta is short, only about half as long as the second endopodal segment in both M. parva (Hamond 1971, fig. 14) and M. huysi (Figure 3 A) but it is as long as the second endopodal segment in M. pacifica (Gómez and Fiers 1997, fig. 4 a) and it is longest, 1.3 longer than the P 1 ENP 2, in M. pseudoparva (Gómez and Fiers 1997, fig. 10 a). In addition, the distal end of P 3 ENP reaches the proximal 1 / 3 of P 3 EXP 3 in M. parva (Hamond 1971, fig. 16) while in M. pseudoparva (Gómez and Fiers 1997, fig. 10 d), M. huysi (Figure 3 C), and M. pacifica (Gómez and Fiers 1997, fig. 4 c), the ENP reaches the distal margin of P 3 EXP 2. The P 4 ENP reaches the distal margin of P 4 EXP 2 in M. parva (Hamond 1971, fig. 17), half of EXP 2, almost reaching the insertion of the inner seta of EXP 2 in M. pseudoparva (Gómez and Fiers 1997, fig. 11 a), and the proximal 1 / 3 of P 4 EXP 2 in both M. huysi (Figure 3 D) and M. pacifica (Gómez and Fiers 1997, fig. 5 a). The anal operculum is naked in M. parva (Hamond 1971, fig. 6) and M. pseudoparva (Gómez and Fiers 1997, fig. 8 a) whereas it is furnished with fine spinules in both M. huysi (Figures 1 A, 4 F) and also in M. pacifica (Gómez and Fiers 1997, fig. 6 a, b). The male of M. huysi sp. nov. differs from the male of its congeners M. pseudoparva, M. pacifica and M. parva by the features of the outer spinules on the first and second segments of P 3 EXP; such spinules are remarkably strong in M. huysi while in the other three species, M. parva (Hamond 1971, fig. 20), M. pacifica (Gómez and Fiers 1997, fig. 7 b) and M. pseudoparva (Gómez and Fiers 1997, fig. 13 a) these elements are slender, regular spinules. The apophysis of P 3 ENP 2 differs among these species. This structure does not reach the distal end of P 3 ENP 3 in M. pseudoparva (Gómez and Fiers 1997, fig. 13 a), M. pacifica (Gómez and Fiers 1997, fig. 7 b) and M. huysi (Figure 4 B) but in M. parva it is clearly shorter, not reaching the midlength of P 3 ENP 3 (Hamond 1971, fig. 20). The claw-like or flame-shaped elements in P 3 ENP 3 are unreported or absent in both M. parva (Hamond 1971, fig. 20) and M. pacifica (Gómez and Fiers 1997, fig. 7 b), but one is present in M. huysi (arrowed in Figure 4 B) and two in M. pseudoparva (Gómez and Fiers 1997, fig. 13 a, b). As mentioned by Gómez and Fiers (1997), these structures are likely to be overlooked by its size and position in some cases or even confused with other setal elements; their homologies or function cannot be established yet. The male P 5 EXP has six setal elements in M. huysi, M. pseudoparva (Gómez and Fiers 1997, fig. 13 c) and M. pacifica (Gómez and Fiers 1997, fig. 7 c), while only five are present in M. parva (Hamond 1971, fig. 21). Following Wells’ (2007) key, our specimens are grouped among several species of Mesochra (key KG 33) (M. sewelli Lang, 1948, M. meridionalis Sars, 1905, M. pseudoparva, M. parva, M. wolskii Jakubisiak, 1933, M. lindbergi Petkovski, 1964, M. rostrata Gurney, 1927 and M. aestuarii Gurney, 1921) by its possession of a combination of characters including the segmentation of P 1 rami, the number of segments on P 2 ENP and P 4 ENP, and the number of setae on the EXP 3 of P 2 – P 4. The new species is then compared (KG 33 / 2) with M. pacifica and M. suifunensis Borutsky, 1952, both sharing the same ornamentation of the anal operculum, armature of ENP 2 of P 2 – P 4 and armature of male and female fifth legs. Mesochra suifunensis clearly differs from the new species, M. huysi, in the lack of inner seta on ENP 1 of P 2 and P 3; these setae are present in the new species. Also, the male of M. suifunensis lacks an apophysis in the P 3, which is present in M. huysi. Therefore, the unique combination of characters of these specimens from Colombia appears to be enough evidence to consider them as belonging to a new species of Mesochra.
distribution
Distribution and ecology Hamond (1971) recognized 31 valid species of Mesochra and presented a key based on Lang’ s (1948) work. Fiers and Rutledge (1990) recognized, apart from Mielke’ s (1974) Mesochra sp., 34 valid species. Gómez and Fiers (1997) added M. pacifica and M. pseudoparva. The number of species increased with the addition of three species from Iceland (Gómez and Steinarsdóttir 2007), and one from South Korea (Lee and Chang 2008). Gaviria-Melo et al. (2013) recognized up to 45 species of Mesochra; hence, with the addition of this new species from Colombia, the number of species in the genus rises to 46. Overall, from the valid species of Mesochra, only about 25 % of them have been recorded in the Americas, Brazil harbouring the highest number of species of this genus (Reid 1998). According to Fiers and Rutledge’ s (1990) and to our comparative analysis, only 11 species (M. lindbergi Petkovski, 1964, M. dulcicula Jakobi, 1956, M. suifunensis Borutsky, 1952, M. meridionalis Sars, 1905, M. aestuari Gurney, 1921, M. wolskii Jakubisiak, 1933, M. rostrata Gurney, 1927, M. sewelli Lang, 1948, M. parva Thomson, 1946, M. pacifica Gómez & Fiers, 1997, and M. pseudoparva Gómez & Fiers, 1997 have a 2 - segmented P 1 ENP combined with a 222 spine formula (number of spines on the ultimate exopodal segment of P 2 – P 4). The new species M. huysi can be assigned to this group. Only four species of this group (M. dulcicula, M. pacifica, M. pseudoparva and the new species, M. huysi) are known to be distributed in the Americas. There are only 10 species of the genus known from the continent (Gómez and Fiers 1997; Suárez-Morales et al. 2006; Sarmento and Parrera Santos 2012; Gómez and Morales-Serna 2014), a figure that reaches 11 with the addition of the new species. Only two of these species of Mesochra have been known from the Caribbean, the nominal M. pygmaea (Claus, 1863) from Barbados (Coull 1970), which is probably a species complex (Wells 2007), and a Mesochra sp. from the Mexican Caribbean coast (Suárez-Morales et al. 2006). This is the third record of a species of this genus from the Caribbean. Mesochra huysi is currently known from a single locality, Laguna Navío Quebrado (Colombia). It was found in the limnetic region associated to a salinity of 28 psu. This large (surface area = 10.7 km 2) and shallow (depth range = 30 – 110 cm) lagoonal system has a temperature ranging between 28 and 31 ° C, and pH values were 7.8 – 8.3. This is the same kind of lagoonal environment from which its closest congeners, C. pacifica, C. parva and C. pseudoparva (Hamond 1971; Gómez and Fiers 1997) have been collected. Currently, up to 14 species of Harpacticoida have been recorded in this water body (Fuentes-Reinés and Suárez-Morales 2014).
etymology
Etymology The new species is named after Dr Rony Huys (Natural History Museum, London, UK), for his outstanding contributions to the taxonomic knowledge of the Harpacticoida.
materials_examined
Material examined Female holotype (UARC 390), male allotype (UARC 391), from shallow plankton samples, Laguna Navío Quebrado, Colombia (11 ° 25 ʹ N, 73 ° 05 ʹ W), partially dissected, semi-permanent slides. Paratypes: one female, one male, plus two undissected females and two males, ethanol-preserved, vial (UARC 392). Three adult females and two adult males, dissected, mounted in slides, same locality, and collector (ECOCHZ- 09325). Additional material: 5 adult females, 5 adult males in author’ s (JF-R) personal collection; these specimens are available for consultation upon request. Type locality Laguna Navío Quebrado, La Guajira, Colombia (11 ° 25 ʹ N, 73 ° 05 ʹ W).