Mamilloecia mamillata (Müller, 1906) Graves, 2012

Graves, Carol, 2012, Mamilloecia indica (Halocyprididae: Ostracoda) a new genus and species from the Northwest Indian Ocean, Journal of Natural History 46 (9 - 10), pp. 517-556 : 544-551

publication ID	https://doi.org/ 10.1080/00222933.2011.649017
DOI	https://doi.org/10.5281/zenodo.10536939
persistent identifier	https://treatment.plazi.org/id/0E4C87B1-FF9A-C16A-865A-6BF2AE1FFE79
treatment provided by	Felipe
scientific name	Mamilloecia mamillata (Müller, 1906)
status	comb. nov.

Treatment

Mamilloecia mamillata (Müller, 1906) View in CoL comb. nov.

( Figures 12–16 View Figure 12 View Figure 13 View Figure 14 View Figure 15 View Figure 16 )

Conchoecia mamillata Müller, 1906: 60 View in CoL , pls 16, 1–9; 35, 8, Müller 1906: 66. (Südpolar), Müller, 19–12, Granata and Caporiacco, 1949: 30, Iles, 1953: 269, Rudjakov, 1962: 175, fig. 1a–e, Deevey, 1968: 36, fig. 12d–f, Deevey and Brooks, 1980: 66, figs 11e–h; 12a; 13b,e–j, Angel, 1981: 559, fig. 194.

Paraconchoecia mamillata View in CoL (part) Poulsen, 1973: 42–43, fig. 16a–j.

Material

The material was collected from Discovery station 9022 (see above). Permanent preparations of dissected specimens used to prepare the illustrations in this paper have been deposited in the collections of the Natural History Museum, London: registration number NHMUK 2011 View Materials 1637 for the female on slides and NHMUK 2011.1638 View Materials for the male on slides. The 53 females and 40 males that were measured are retained in 80% industrial methylated ethanol registration numbers NHMUK 2011.1639 View Materials – 1648 View Materials .

Description

A full description is merited here as the species has not been comprehensively illustrated and it is being transferred to the new genus of Mamilloecia . The morphological

characters of the carapaces and internal structures of both sexes are listed in Tables 5–12, together with comparative data for the other species described here.

Description of female

Carapace ( Figure 12A–C View Figure 12 ). Mean length 1.75 ± 0.03 mm (n = 53). Carapace of exemplar specimen ( Table 5) length 1.74 mm; height 0.68 m; breadth 0.56 mm. Height: length ratio 39.1%CL, breadth: length ratio 32.2%CL. In lateral view carapace faintly sculpted with parallel lines running at approximately 45 ◦ to ventral surface. Carapace elongate, maximum height posterior to mid-length. Ventral margin curving smoothly into posterior margin. On posterior margin of right carapace tubercular bulge with asymmetric gland. Posterior dorsal corner of right valve furnished with small pointed spine. Posterior dorsal corner of left valve furnished with blunt process and opening of asymmetric gland.

Frontal organ ( Table 5; Figure 12D View Figure 12 ). Frontal organ stem slender, almost straight and longer than limb of first antenna. Capitulum with rounded end and bare dorsal surface, distal end of ventral surface covered in small spinules. Total length 34.9%CL, much longer than first antenna.

First antenna ( Table 6; Figure 12D View Figure 12 ). Five-segmented. Limb length 16.8%CL. Third segment with dorsal seta 5.8%CL. Fifth segment with five unequal setae; a-seta 16.7%CL; b-seta 17.8%CL; c-seta 17.2%CL; d-seta 16.7%CL; e-seta 26.1%CL with long hairs.

Second antenna ( Table 6; Figure 12E View Figure 12 ). Protopodite 32.3%CL. First exopodite segment about half length of protopodite. Most swimming setae similar in length to protopodite, all but shortest two setae have long hairs distally. Endopodite ( Figure 12F View Figure 12 ) a-seta short, pointed bare; b-seta pointed with hairs; no c-, d- or e-setae; f- and g- setae respectively 20.8%CL and 23.9%CL; h-seta 17.0%CL; i-seta 19.7%CL; j-seta 18.7%CL.

Mandible ( Table 7; Figure 13A–C View Figure 13 ). Coxale toothed edge of pars incisiva with 10 large blunt teeth. Distal tooth list with two large and about 15 small pointed teeth. Proximal tooth list slightly narrower with two large teeth and about 18 small pointed teeth. Outer margin of toothed edge of basal endite with two large dagger-shaped teeth, second with rounded tip, one pointed tooth and five subserrate teeth. Exopodite represented by moderately long plumose seta inserted on outer margin of basis. First endopodite segment with plumose dorsal seta and four finely spinose ventral setae. Second segment with two ventral and three dorsal setae, all finely spinose. Third segment with seven spinose terminal setae; one very long and robust.

Maxilla ( Table 7; Figure 13D View Figure 13 ). Basal segment with six anterior, one lateral and four posterior setae. Distal segment comparatively short and wide with five bare terminal claw setae, posteriormost longest.

Fifth limb ( Table 8; Figure 13E View Figure 13 ). Ventrally basale with one plumose and five spinose setae, laterally one plumose and two bare setae, dorsally one long seta. First segment with two ventral setae and one dorsal seta. Second segment with three unequal, curved terminal claw setae; middle claw longest 5.6%CL.

Sixth limb ( Table 8; Figure 13F View Figure 13 ). Basale with five plumose ventral setae, laterally one plumose seta and one bare seta dorsally. First endopodite segment with one ventral spinose seta. Second segment with one spinose seta ventrally and one dorsally. Third segment with three unequal spinose, terminal claw setae; middle claw longest 10.5%CL.

Caudal furca ( Table 8; Figure 13G View Figure 13 ). Eight pairs of claw setae diminishing in size dorsally; longest claw 9.3%CL.

Description of male

Carapace ( Figure 14A–C View Figure 14 ). Mean length 1.69 ± 0.04 mm (n = 40). Carapace of exemplar specimen ( Table 9) length 1.72 mm; height 0.64 mm; breadth 0.62 mm. Height: length ratio 37.2%CL, breadth: length ratio 36.0%CL. In lateral view carapace faintly sculpted as in female, maximum height posterior to mid-length. Ventral margin curving smoothly into posterior margin. On posterior margin of right valve tubercular bulge containing asymmetric gland. Posterior dorsal corner of right valve furnished with small pointed spine. Posterior dorsal corner of left valve furnished with blunt process on which asymmetric gland opens.

Frontal organ ( Table 9; Figure 14D View Figure 14 ). Frontal organ stem straight and similar in length to limb of first antenna. Capitulum long, with bulbous distal end. Dorsal surface bare, but proximal ventral surface covered in small spinules. Total length 43.3%CL, much longer than first antenna,

First antenna ( Table 10; Figure 14D View Figure 14 ). Five-segmented. Limb length 37.1%CL. Third segment with dorsal seta 5.7%CL. Fifth segment with five unequal setae; a-seta 24.1%CL; b-seta 38.4%CL; c-seta 11.6%CL; d-seta with short fine hairs 38.4%CL; e-seta 40.7%CL with long hairs.

Second antenna ( Table 10; Figure 14E View Figure 14 ). Protopodite 42.2%CL. First exopodite segment about one-third length of protopodite. All swimming setae shorter than protopodite, all but shortest two setae have long hairs distally. Endopodite a-seta short, pointed, bare; b-seta pointed with hairs; c-, d- and e-setae all very short; f- and g-setae respectively 35.8%CL and 33.7%CL; h-seta short 11.6%CL; i-seta 12.9%CL; j-seta 12.4%CL. Right endopodite ( Figure 15B View Figure 15 ) with elongated clasping organ in form of hook with long proximal shank and very long curved end piece 6.8%CL. Left endopodite ( Figure 15A View Figure 15 ) ‘hook’ much shorter and curved 4.3%CL.

Mandible, maxilla and fifth limb ( Tables 11, 12; Figures 15C–F View Figure 15 , 16A View Figure 16 ). Structure and arrangement of setae for mandible, maxilla and fifth limb as for female.

Sixth limb ( Table 12; Figure 16B View Figure 16 ). Basale with five plumose setae ventrally, one laterally and one bare dorsal exopodal seta. First endopodite segment with one ventral seta. Second endopodite segment with single seta both ventrally and dorsally. Third segment with three terminal setae; two very long, evenly curved ventrally with long hairs 23.0%CL and one much shorter seta 3.8%CL.

Caudal furca ( Table 12; Figure 16C View Figure 16 ). Structure and arrangement of furcal claws similar to female. Longest claw 14.2%CL.

Intromittent organ ( Table 12; Figure 16C View Figure 16 ). Male copulatory appendage exceptionally long, 29.7%CL, with two oblique muscles.

Remarks

The carapace shape ( Figures 7 View Figure 7 , 9 View Figure 9 , 12 View Figure 12 , 14 View Figure 14 ) and measurements ( Tables 5–12) of the two species of Mamilloecia differ significantly. The maximum height of the carapace in both sexes of M. mamillata is posterior to mid-length, whereas in both sexes of M. indica it is anterior. The tubercle of both sexes of M. mamillata is pointed and positioned about two-thirds of the way along the posterior margin nearer to the posterior dorsal corner, but in M. indica it is rounded and positioned at about mid-height. In M. mamillata there is not such a significant difference in length between males and females as in M. indica .

The principal component analysis for both the Atlantic form and the Oman form of Mamilloecia females ( Table 3) produced an eigenvalue of 2.479 that translated to ∼ 50% variation between individuals. For males ( Table 3) an eigenvalue of 3.090 translated to ∼ 62% variation between individuals. The component matrix ( Table 4) shows the weightings allocated to each of the variables for the extracted factors. For the females, the results from the component matrix suggest that the best contrast between individuals is obtained by comparing length of rostrum to posterior dorsal corner with length of posterior dorsal corner to below tubercle, i.e. individuals that are longer from rostrum to posterior dorsal corner are shorter from posterior dorsal corner to below tubercle and vice versa. For the males ( Table 4), the results suggest that the best contrast between individuals is obtained by comparing the length from rostrum to posterior dorsal corner with height, i.e. individuals that are longer from rostrum to posterior dorsal corner show the greatest height and vice versa. The x -axis for the scatterplots for each sex ( Figures 17 View Figure 17 , 18 View Figure 18 ) is derived from the weighted scores of component 1 and the y -axis is derived from the weighted scores of component 2. Hence, the morphological data on axis 1 correlate with length and those on axis 2 correlate with shape. Both plots show distinct separation of forms, although there is a little overlap. The principal component analysis of the morphometric characters of the carapace ( Figures 17 View Figure 17 , 18 View Figure 18 ) provides strong evidence supporting the inference that the two forms are distinct species. The Oman form is here recognized as a new species, M. indica . In both sexes the length of the frontal organ and length of the first antenna is significantly longer in M. indica , but most setae of the first antenna are longer in M. mamillata ( Tables 6, 10). In the male both right and left clasper shank lengths are significantly longer in M. indica ( Table 10).