Pycnogonum cesairei, Sabroux & Hassanin & Corbari, 2022

Sabroux, Romain, Hassanin, Alexandre & Corbari, Laure, 2022, Sea spiders (Arthropoda: Pycnogonida) collected during the Madibenthos Expedition from Martinique shallow waters, European Journal of Taxonomy 851 (1), pp. 1-141 : 107-109

Pycnogonum cesairei sp. nov.

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Fig. 28

Pycnogonum sp. 1 – Sabroux et al. 2019b: 1531, tab. 1, fig. 3.

Material examined

Holotype MARTINIQUE • ♂; Grand’Rivière ; 14°52ʹ N, 61°11.7ʹ W; depth 6 m; 3 Oct. 2016; st. AB556; MNHN- IU-2016-10338/ MK411029 .

Etymology

Latinized name, 2 nd decl. (masc.), genitive singular. Named after the Martinique poet Aimé Césaire.

Description (holotype, ♂, MNHN-IU-2016-10338)

BODY. Trunk completely segmented, stout, reticulated. Dorsomedian tubercles on 1 st to 3 rd segments, rounded, very granulous, carrying small setae. Ocular tubercle slightly higher than dorsomedian tubercles, rounded, carrying four pigmented eyes. Lateral processes shorter than wide, separated by a narrow space all along their length, with bead at their distal margin and one spine on posterior side.

PROBOScIS. About as long as distance from 1 st to 3 rd trunk segments, gently bent downward, tapering, truncated, very granular getting smoother at its tip, with four rows of spines (2 lateral, 2 dorsolateral) on proximal half, each separated at regular distance.

ABDOMEN. Trapezoidal and angulous dorsally, larger at tip than base.

CHELIFORE. Absent.

PALP. Absent.

OvIGER. 8-articled, cuticle reticulated. 1 st article shortest, about as long as wide, fused with 2 nd. 2 nd article larger than 1 st, as long as wide. 3 rd article shorter than 2 nd, about as long as wide, with distal blunt spine on inner surface. 4 th and 5 th articles subequal and longest, 5 th carrying a blunt distal spine on inner surface. 6 th, 7 th and 8 th articles subequal, about 0.8 times as long as 4 th or 5 th. 6 th and 7 th articles with blunt distal spine on inner surface, 8 th article with 3 blunt spines on distal half. Terminal claw as long as 8 th article.

LEGS. Stout, cuticle reticulated. Coxa 1 very wide dorsally, wider than long, with large bead at distal margin carrying some tiny spines, forming low dorsodistal tubercle on 4 th leg. Coxa 2 wider than long, bearing several tiny spines, with white coxal pellicula on dorsal surface. Coxa 3 smaller than 1 or 2, bearing some tiny normal spines. Femur and tibia 1 subequal; femur about 1.4 times as long as wide, dorsally granulated on distal half; on ventral and dorsal surface, several blunt or slightly bifurcated spines mounted on tiny tubercles, plus tiny normal spines; dorsal side of distal margin forming short rounded spurs. Tibia 1 about 1.6 times as long as wide, with dorsal surface granulous, bearing a few blunt spines ventrally, mounted on small tubercles, and tiny normal spines dorsally. Tibia 2 short, less than half as long as femur or tibia 1, about as long as wide, with many blunt or slightly bifurcated spines distally on ventral surface, longer blunt spine distally on dorsal surface. Tarsus shortest, with spines on ventral side. Propodus about 0.9 times as long as femur or tibia 1 and twice as long as tibia 2, 3 times as long as wide, straight except for most proximal part, which is bent with strong angle marked dorsally; spines of sole simple or slightly bifurcated at tip. Main claw about half as long as propodus. No auxiliary claw.

MEASUREMENTS (mm). Trunk 1.52; abdomen 0.49; proboscis 1.18; coxa 1 0.28; coxa 2 0.29; coxa 3 0.26; femur 0.49; tibia 1 0.53; tibia 2 0.24; tarsus 0.14; propodus 0.47; main claw 0.209.

Sexual dimorphism

No female currently available.

Individual variability

No other material available.

Remarks

Pycnogonum cesairei sp. nov. differs from most other species of the genus by the following combination of characters: the cuticula is strongly reticulated; the proboscis is conical, bent forward; there is no tubercle on coxa 1 (except on the fourth legs); the tibia 2 is very short, about as long as wide, and shorter than the propodus. Three other species of Pycnogonum share these characters: P. tesselatum Stock, 1968 from Pakistan, which has, however, a proboscis broader at the tip and a rounded abdomen ( Stock 1968a; George et al. 2020); P. clarki Staples, 2002 from Australia, which differs from P. cesairei by its more rounded dorsal tubercles, a more deeply incised dichotomy of propodus spines, the presence of a bulge on the posterodorsal end of the abdomen, the presence of tubercles on the lateral processes of the fourth trunk segment and no bifurcated spine on the legs ( Staples 2002); and P. madagascariensis Bouvier, 1911 from Madagascar. For this latter species, we reexamined the syntypes of Bouvier (1911a): the proboscis of P. madagascariensis is barrel-shaped ( Arnaud 1971), the tibia 2 of P. madagascariensis is shorter than wide, while tibia 2 is about as long as wide in P. cesairei , and the abdomen of P. madagascariensis presents a distinctive posterodorsal bulge (visible in Arnaud 1971) with two distal rounded tips lateral to the anus, both characters not being present in P. cesairei . It also seems that none of these species have an angulous propodus, in contrast to P. cesairei .

However, the closest species to Pycnogonum cesairei sp. nov. may well be P. calculum Bamber, 1995 from the Falkland Islands, which also presents a rather angulous propodus, has a proboscis of the same size, has the same body proportions and carries blunt spines. The coloration indicated by Bamber (light brown culticle with yellowish reticulation; Bamber 1995b) also corresponds to that observed on the specimen from Martinique. However, P. calculum is described with a small rounded dorsomedian tubercle on the fourth trunk segment, which is absent in P. cesairei , as well as on all lateral processes, while P. cesairei only carries one on coxa 1 of the fourth leg.

In Caribbean waters, the new species can be mistaken at first glance with Pycnogonum reticulatum Hedgpeth, 1948 , for which we could examine the holotype of Hedgpeth (1948), but the two species are readily distinguished by the wider proboscis and longer tibiae 2 of P. reticulatum .

The single sampled specimen was collected on the northern coast of Martinique.

Distribution

Only known from Martinique.

Depth range

6 m.

Figures

Fig. 28. Pycnogonum cesairei sp. nov., holotype, ♂, MNHN-IU-2016-10338. A. Body, dorsal view. B. Body, lateral view (same scale as A). C. Third leg. D. Oviger. E. Close-up of six terminal segments of oviger.