Clausidium sarii Sepahvand et Kihara, 2018

Ahmed, Quratulan, Ali, Qadeer Mohammad, Marin, Ivan N., Mubarak, Shumaila & Baloch, Ateeqa, 2025, First record of Clausidium sarii (Copepoda: Clausidiidae) from the coastal waters of Pakistan, with the first description of the male and a new host, Arthropoda Selecta 34 (1), pp. 41-50 : 45

Clausidium sarii Sepahvand et Kihara, 2018

Figs 4–7 .

PV 2-segmented and uniramous. Exopodal segment is elongated, with 2 pinnate setae along the outer margin, 1 small or vestigial naked subterminal seta and 1 long terminal pinnate apical seta. PVI with 2 setae.

ADULT MALE ( Figs 6 , 7 ). Body cyclopiform in shape. Mean body length measured from frontal margin of cephalothorax to posterior length of urosomal segment about 1.5–1.9 mm (10 specimens measured). Thoracic somite I fused with the cephalothorax. Thoracic somite VI broader than long, posteriorly formed bilobed and not completely covered thoracic somite V. Prosome longer than urosome. Labrum expanded and broader than wider. Antenna I, antenna II, mandible, maxilla I and maxilla II are similar as in ♀♀. Maxilliped is modified for prehension with a large basal segment; lobe formed near inner edge of distal border of segment 1; segment 2 armed with a moveable process/claw with 3 blunt teeth. Abdomen with 4 segments: 1 genital segment, 2 abdominal segments and 1 anal somite. Anal somite clearly distinct from caudal rami on ventral side. Caudal furca as similar as in ♀♀. PI biramous as in ♀♀; endopodal segment 2 have 1 large pectinate stout seta and 2 small setae in replacement of blade like process and blunt median process as observed in PI female. 2 sucking disks present, with smaller distal disc have a bifurcate element. Armature formula for exopod I–0; I–0; III–2–2. PpII–IV have only 1 inner seta on endopodal segment 2.

Armature formula of PpII–IV as follows:

PV is uniramous and shorter than PV in ♀♀. Exopodal segment with 4 well developed setae: 2 along the outer margin, 1 subterminal seta and 1 long terminal pinnate apical seta. PVI with 1 seta present on genital segment.

HABITAT. The species was found living in the brachial cavity of the ghost shrimp Corallianassa martensi Miers, 1884 ( Axiidea : Callichiridae ), which represents a new host recorded for the species. Totally, 84 specimens were extracted from left and 39 specimens from right brachial cavity of the collected ghost shrimp. Previously, the species was recorded from the large chelipeds of the ghost shrimp Neocallichirus natalensis (Barnard, 1947) ( Axiidea : Callichiridae ) [ Sepahvand et al., 2018].

DISTRIBUTION. Gulf of Oman, Chabahar, Iran (type locality) and Pakistan (present study).

REMARKS. The species has been previously known by a single holotype ♀ [ Sepahvand et al., 2018]. The species could be referred to C. sarii by the specific distinguishing morphological features of free exopodal segment of PV, which is elongated and about 5 times longer than wide; the presence of 3 well developed and 1 vestigial seta on exopodal segment of PV in ♀♀, similar as illustrated by Sepahvand et al. [2018].

Figures

Fig. 4. Symbiotic copepod Clausidium sarii, ♀; A — habitus; B — antenna I; C — antenna II; D — labrum; E — mandible; F — maxillule; G — maxilla; H — maxilliped. Рис. 4. СимбиотическаЯ копепода Clausidium sarii, ♀; А — обЩий вид; B — антенна I; C — антенна II; D — нижнЯЯ губа (лабрум); E — мандибула; F — максиллула; G — максилла; Y — максиллипеда.

Fig. 5. Symbiotic copepod Clausidium sarii, ♀; A — anal somite (ventral); B — PI; C — PII; D — PIII; E — PIV; F — PV. Рис.5. СимбиотическаЯ копепода Clausidium sarii, ♀; А — анальный сомит (вентральный); B — PI; C — PII; D — PIII; Е — PIV; F — PV.

Fig. 6. Symbiotic copepod Clausidium sarii, ♂: A — habitus; B — antenna I; C — antenna II; D — labrum; E — mandible; F — maxilla; G — maxilliped. Рис. 6. СимбиотическаЯ копепода Clausidium sarii, ♂: А — обЩий вид; B — антенна I; C — антенна II; D — нижнЯЯ губа (лабрум); Е — мандибула; F — максилла; G — максиллипеда.

Fig. 7. Symbiotic copepod Clausidium sarii, ♂: A — PI; B — PII; C — PV. Рис. 7. СимбиотическаЯ копепода Clausidium sarii, ♂: А — PI; B — PII; C — PIII.