Penicillicaris sewelli, Huys, Rony & Mu, Fanghong, 2021

Huys, Rony & Mu, Fanghong, 2021, Johnwellsia, a new intertidal genus of Parastenheliidae (Copepoda, Harpacticoida) from the Taiwan Strait, China, including a review of the family and key to genera, Zootaxa 5051 (1), pp. 236-318 : 300-301

Penicillicaris sewelli sp. nov.

urn:lsid:zoobank.org:act:5F142B2D-CDF6-4109-AA29-3B93121663FC

Microthalestris littoralis Sars, 1911 f . penicillata sensu Sewell (1940)

Microthalestris littoralis Sars, 1911 f . penicillata sensu Vervoort (1964)

The second form reported by Sewell (1940: 193) is only known from the female. Although the author claimed that his Indian Ocean form was identical with Willey’s (1935) Atlantic forma penicillata we consider it more likely that it is conspecific with Vervoort’s (1964) material from Ifalik Atoll in the Pacific which also includes the male.

Original description. Sewell (1940): 193–195; Text-fig. 27A–J (♀ only).

Additional description. Vervoort (1964): 177, 181–184, 189; Figs 64c, 66c, 67, 68d, 70a–g.

Type material. The female specimen illustrated by Sewell (1940: Text-fig. 27A–J) is here designated as the holotype of P. sewelli sp. nov. ( ICZN Arts 16.4 and 72.5.6). The species can be differentiated by the characters mentioned in the diagnosis below and those discussed and illustrated by Sewell (1940) ( ICZN Art. 13.1).

Type locality. Maldive archipelago, Addu Atoll ; seaweed washings .

Differential diagnosis. Penicillicaris . Body length 520–600 μm in ♀, 420 μm in ♂. Antennule 8-segmented in ♀. Antenna with 2-segmented exopod bearing two setae on exp-1 and two lateral and three apical elements on exp-2. Mandible with two setae on basis; exopod 1-segmented, with two setae. Maxillipedal syncoxa unarmed; basis with one seta on palmar margin. P1 exp-3 with two penicillate spines, one geniculate seta and one short nongeniculate seta. P1 enp-1 about 1.15 times length of exopod. Armature pattern of ♀ P2–P4:

P3 endopod ♂ 3-segmented, with apophysis on enp-3, armature pattern [1.1.02 + apo]. P 5 ♀ exopod about three times as long as maximum width; inner margin and proximal two-thirds of outer margin parallel; with six elements. P5 endopodal lobe ♀ extending to about proximal third of exopodal length. P5 exopod ♂ 1-segmented, elongate–oval; with seven elements. P5 endopodal lobe ♂ well developed, trapezoidal, extending slightly beyond insertion point of proximal inner seta of exopod; with two elements. Caudal ramus setae IV– V of ♀ inflated near base (forcipate type) .

Etymology. The species is dedicated to Robert Beresford Seymour Sewell, leader of the John Murray Expedition (1933–1934) to the Indian Ocean, during which it was collected.

Notes. Sewell (1940: Text-fig. 27G) illustrates an inner seta in the proximal quarter of P1 exp-2 but this, in addition to the alleged absence of the short seta on both exp-3 and enp-2 of this limb, must be based on observational errors. Vervoort (1964) misinterpreted the exopod as the endopod in both sexes in his text (pp. 182, 194) and illustration (Fig. 70b); the inner seta on exp-2 was almost certainly overlooked. According to Sewell (1940: Textfig. 27H) P2 exp-1 lacks an inner seta but Vervoort shows a small inner element which is included in the armature formula here. The only significant difference between the Maldivian and Pacific populations appears to be the armature of the antennary exopod. According to Sewell (1940) the proximal segment has one minute and one long seta, and the distal segment has two lateral and three distal setae. Vervoort’s (1964: 70 g) illustration of the antenna appears to indicate that the proximal segment has two long setae and the distal segment only one lateral in addition to the three distal ones. It is conceivable that this discrepancy is the result of an incorrectly observed segment boundary, causing the proximal inner seta of exp-2 to erroneously originate from exp-1, combined with the oversight of the minute proximal element on exp-1. In addition to the type locality in the Maldives, the species has also been recorded from the Caroline Islands ( Federated States of Micronesia).